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  • Lectin-stimulated cellular iron uptake and toxin generation in the freshwater cyanobacterium Microcystis aeruginosa
    Harmful Algae (IF 4.138) Pub Date : 2019-02-01
    Tomoko Takaara, Shiori Sasaki, Manabu Fujii, Hiroaki Ito, Yoshifumi Masago, Tatsuo Omura
    更新日期:2019-02-05
  • Application of Bayesian network including Microcystis morphospecies for microcystin risk assessment in three cyanobacterial bloom-plagued lakes, China
    Harmful Algae (IF 4.138) Pub Date : 2019-01-25
    Kun Shan, Mingsheng Shang, Botian Zhou, Lin Li, Xiaoxiao Wang, Hong Yang, Lirong Song

    Microcystis spp., which occur as colonies of different sizes under natural conditions, have expanded in temperate and tropical freshwater ecosystems and caused seriously environmental and ecological problems. In the current study, a Bayesian network (BN) framework was developed to access the probability of microcystins (MCs) risk in large shallow eutrophic lakes in China, namely, Taihu Lake, Chaohu Lake, and Dianchi Lake. By means of a knowledge-supported way, physicochemical factors, Microcystis morphospecies, and MCs were integrated into different network structures. The sensitive analysis illustrated that Microcystis aeruginosa biomass was overall the best predictor of MCs risk, and its high biomass relied on the combined condition that water temperature exceeded 24 °C and total phosphorus was above 0.2 mg/L. Simulated scenarios suggested that the probability of hazardous MCs (≥1.0 μg/L) was higher under interactive effect of temperature increase and nutrients (nitrogen and phosphorus) imbalance than that of warming alone. Likewise, data-driven model development using a naïve Bayes classifier and equal frequency discretization resulted in a substantial technical performance (CCI = 0.83, K = 0.60), but the performance significantly decreased when model excluded species-specific biomasses from input variables (CCI = 0.76, K = 0.40). The BN framework provided a useful screening tool to evaluate cyanotoxin in three studied lakes in China, and it can also be used in other lakes suffering from cyanobacterial blooms dominated by Microcystis.

    更新日期:2019-01-28
  • Ecological meta-analysis of bloom-forming planktonic Cyanobacteria in Argentina
    Harmful Algae (IF 4.138) Pub Date : 2019-01-18
    Inés O'Farrell, Carolina Motta, Marina Forastier, Wanda Polla, Silvia Otaño, Norma Meichtry, Melina Devercelli, Ruben Lombardo

    The aim of the present research was to summarize the main reasons that explain the distribution of harmful blooms of cyanobacteria in Argentina. It is a large territory with climates ranging from humid tropical to cold temperate. We performed a meta-analysis of the published data and information in technical reports published from 1945 to 2015, and included additional data from personal non-published studies. A total of 122 water bodies affected by planktonic cyanobacterial blooms were recorded and geo-referenced. The analysis showed that blooms, defined as events exceeding 5000 cells/mL, occurred in different types of water bodies, including shallow lakes, rivers, streams, reservoirs, estuaries and storage facilities. Maximum bloom abundance and species and ecological strategies (dispersive, scum-forming, nitrogen fixer) responsible for each event were related to the geographic and climatologic characteristics and type and origin of water bodies. The Puna and the Andean Patagonia eco-regions were mostly free of blooms. The most impaired aquatic systems were shallow lakes and reservoirs (46.7 and 24.6%, respectively). Deep lakes had no reports of blooms and rivers were mainly affected at the regulated reaches, with intensities generally decreasing downstream the dams. Besides, 74.3% of the blooms reported in Argentina exceeded WHO Alert Level 2 for drinking and bathing waters (100,000 cells/mL). Thirty-nine species, identified by Komárek’s polyphasic approach to taxonomy, were responsible for the blooms. Microcystis aeruginosa, Dolichospermum spiroides, Dolichospermum circinale, Raphidiopsis mediterranea and Cylindrospermopsis raciborskii were frequently found participating in either mixed or single species blooms. The species distribution was associated with the eco-region and aquatic system typologies and affected by seasonality and climatological and geographic variables. The eco-strategies of cyanobacterial species showed stronger associations with the qualitative and quantitative indicators used in the meta-analysis, and appeared as useful tools for management measures.

    更新日期:2019-01-23
  • High antioxidant capability interacts with respiration to mediate two Alexandrium species growth exploitation of photoperiods and light intensities
    Harmful Algae (IF 4.138) Pub Date : 2019-01-04
    Hui Wang, Bowen Zhang, Xingyu Song, Xiaohui Jian, Chengxi Tang, Douglas A. Campbell, Qiang Lin, Gang Li

    Light drives phytoplankton photosynthesis, so phytoplankton in their living habitats must exploit variable light levels and exposure durations, depending upon seasons, latitudes, depths and mixing events. Comparative growth, physiology and biochemical compositions were explored for the small Alexnadrium minutum (˜40 μm3 biovolume) and large Alexandrium catenella (˜9300 μm3 biovolume), globally wide spread coastal toxic red tide dinoflagellates, responding to a matrix of photoperiods (Light:Dark, 8:16, 16:8 and 24:0) and growth light irradiances. Smaller A. minutum grew faster under shorter photoperiods across growth light levels, while larger A. catenella grew fastest under longer photoperiods at the lowest applied light level. Photosystem II function responded largely to the instantaneous growth light level across photoperiod lengths, while the cell biovolume-based respiration, antioxidant capacity as well as cell composition responded more to photoperiod duration than to light level. These complex photophysiological responses resolved into linear correlations between growth rate versus cellular antioxidant activity and versus dark respiration, indicating that respiration energizes cellular antioxidant systems to benefit the growth of the cells. These results show the growth responses of Alexandrium species to light levels across photoperiods vary with species, and possibly with cell size. Together with previous results this puts a note of caution on meta-analytical extrapolations of physiological responses to light intensity derived from studies applying different photoperiods to different taxa, because different taxa show differential, even opposite growth responses to photoperiods and light intensities.

    更新日期:2019-01-06
  • Effects of warming and eutrophication on coastal phytoplankton production
    Harmful Algae (IF 4.138) Pub Date : 2019-01-03
    Kyung Ha Lee, Hae Jin Jeong, Kitack Lee, Peter J.S. Franks, Kyeong Ah Seong, Sung Yeon Lee, Moo Joon Lee, Se Hyeon Jang, Eric Potvin, An Suk Lim, Eun Young Yoon, Yeong Du Yoo, Nam Seon Kang, Kwang Young Kim

    Phytoplankton production in coastal waters influences seafood production and human health and can lead to harmful algal blooms. Water temperature and eutrophication are critical factors affecting phytoplankton production, although the combined effects of warming and nutrient changes on phytoplankton production in coastal waters are not well understood. To address this, phytoplankton production changes in natural waters were investigated using samples collected over eight months, and under 64 different initial conditions, established by combining four different water temperatures (i.e., ambient T, +2, +4, and + 6 °C), and two different nutrient conditions (i.e., non-enriched and enriched). Under the non-enriched conditions, the effect of warming on phytoplankton production was significantly positive in some months, significantly negative in others, or had no effect. However, under enriched conditions, warming affected phytoplankton production positively in all months except one, when the salinity was as low as 6.5. These results suggest that nutrient conditions can alter the effects of warming on phytoplankton production. Of several parameters, the ratio of initial nitrate concentration to chlorophyll a concentration [NCCA, μM (μg L−1)−1] was one of the most critical factors determining the directionality of the warming effects. In laboratory experiments, when NCCA in the ambient or nutrient-enriched waters was ≥1.2, warming increased or did not change phytoplankton production with one exception; however, when NCCA was <1.2, warming did not change or decreased production. In the time series data obtained from the coastal waters of four target countries, when NCCA was 1.5 or more, warming increased phytoplankton production, whereas when NCCA was lower than 1.5, warming lowered phytoplankton production, Thus, it is suggested that NCCA could be used as an index for predicting future phytoplankton production changes in coastal waters.

    更新日期:2019-01-04
  • Spatial and temporal variability of biomass and composition of green tides in Ireland
    Harmful Algae (IF 4.138) Pub Date : 2019-01-03
    Ricardo Bermejo, Svenja Heesch, Michéal Mac Monagail, Moya O'Donnell, Eve Daly, Robert J. Wilkes, Liam Morrison

    Although nutrient enrichment of estuarine and coastal waters is considered a key factor for the development of green tides, the extent, distribution, and species composition of blooms vary among systems of similar nutrient loading, which compromises our ability to predict these events based on information about nutrient status alone. Additional factors may play a role in the control and development of macroalgal blooms. The identification of relevant scales of variation is a necessary prerequisite before explanatory models can be proposed and tested. In this study spatial and temporal patterns of biomass distribution were assessed for two Ulva morphologies in two Irish estuaries heavily affected by green tides (wet biomass >1 kg m−2 during the peak bloom). Moreover, using genetic markers, the species composition of these green tides was assessed. Results revealed that these blooms were multi-specific, with Ulva prolifera, U. compressa and U.rigida the most frequent species. The species U. prolifera and U. compressa usually showed a tubular morphology, while U. rigida was mainly laminar. A seasonal succession common to both estuaries was also identified, with the bloom dominated by tubular species during spring and early summer, and co-dominated by tubular and laminar morphologies during late summer and autumn. Moreover, tubular and laminar morphologies exhibited different distribution patterns, with tubular morphologies varying at bigger spatial scales and higher biomass than the laminar. As tubular and laminar morphologies exhibited different distribution patterns, varying tubular morphologies along bigger spatial scales with higher biomass levels than the laminar. Considering that tubular morphologies were usually anchored to the sediment, while laminar Ulva were usually observed free-floating, these differences could explain a differential influence by water motion. An important annual and decadal variability in biomass levels of Ulva was observed, in the case of the Tolka estuary a noticeable increase over the last two decades. These findings should be considered for the development of management and monitoring strategies since the different habitat of laminar and tubular morphologies (anchored vs. free-floating) may play an important role in the balance of nutrients and biomass in the estuary, or determine the response to pollutant exposure. Furthermore, the presence of different species with different ecological requirements could favour the duration and extension of the bloom though temporal and spatial successions.

    更新日期:2019-01-04
  • Reduced forms of nitrogen are a driver of non-nitrogen-fixing harmful cyanobacterial blooms and toxicity in Lake Erie
    Harmful Algae (IF 4.138) Pub Date : 2019-01-02
    Silvia E. Newell, Timothy W. Davis, Thomas H. Johengen, Duane Gossiaux, Ashley Burtner, Danna Palladino, Mark J. McCarthy

    Western Lake Erie (WLE) experiences anthropogenic eutrophication and annual, toxic cyanobacterial blooms of non-nitrogen (N) fixing Microcystis. Numerous studies have shown that bloom biomass is correlated with an increased proportion of soluble reactive phosphorus loading from the Maumee River. Long term monitoring shows that the proportion of the annual Maumee River N load of non-nitrate N, or total Kjeldahl nitrogen (TKN), has also increased significantly (Spearman's ρ = 0.68, p = 0.001) over the last few decades and is also significantly correlated to cyanobacterial bloom biomass (Spearman's ρ = 0.64, p = 0.003). The ratio of chemically reduced N to oxidized N (TKN:NO3) concentrations was also compared to extracted chlorophyll and phycocyanin concentrations from all weekly sampling stations within WLE from 2009 to 2015. Both chlorophyll (Spearman's ρ = 0.657, p < 0.0001) and phycocyanin (Spearman's ρ = 0.714, p < 0.0001) were significantly correlated with TKN:NO3. This correlation between the increasing fraction of chemically reduced N from the Maumee River and increasing bloom biomass demonstrates the urgent need to control N loading, in addition to current P load reductions, to WLE and similar systems impacted by non-N-fixing, toxin-producing cyanobacteria.

    更新日期:2019-01-03
  • Differential expression of phosphorus acquisition genes in response to phosphorus stress in two Raphidiopsis raciborskii strains
    Harmful Algae (IF 4.138) Pub Date : 2018-12-30
    Anusuya Willis, Ann W. Chuang, Sonya Dyhrman, Michele A. Burford

    The cyanobacterium Raphidiopsis raciborskii is a nuisance in freshwater ecosystems. Strains vary in their physiological responses to environmental drivers, thus a greater understanding of the magnitude of strain variation is required to characterize the species. In this study, two strains of R. raciborskii isolated from a tropical Australian water reservoir were grown with and without phosphorus (P) to determine any relative response to P stress. The strains had the same growth rates and under P free conditions, cells grew at the same rate as P replete conditions until day 9 when cell growth ceased. There was no difference in the alkaline phosphatase activity per cell for the P replete and P free conditions, but the level of activity per cell was greater in CS-505 than CS-506. P acquisition genes were identified from the sequenced genomes; both strains contained the same genes, but with differences in copy number of phoA (7 and 6), phnK (3 and 1) and phnH (2 and 1) between CS-505 and CS-506 (respectively). The expression of P acquisition genes under P stress was measured throughout the experiment and shown to vary in magnitude and timing across strains, and in P replete versus P free cultures. In strain CS-505, upregulation of the pstS1 and phoA genes occurred late in the growth phase and into senescence. These genes are involved in phosphate uptake and use of various forms of organic P. For strain CS-506, there was upregulation of the phosphate uptake gene, pit, and organic P utilization genes, phoA, phoU, phnD and phnK, commencing late in the growth phase. Our study shows that despite the fact that these two strains were isolated from the same waterbody, they differed markedly in their gene expression response to P free conditions. This capacity of R. raciborskii to vary in strain responses to P conditions gives the organism flexibility in responding to environmental change, particularly P stress conditions.

    更新日期:2019-01-01
  • Biodiversity and dynamics of cyanobacterial communities during blooms in temperate lake (Harsha Lake, Ohio, USA)
    Harmful Algae (IF 4.138) Pub Date : 2018-12-29
    Bo Zhu, Huansheng Cao, Gaoyang Li, Wei Du, Guangyu Xu, Jorge Santo Domingo, Haiwei Gu, Ning Xu, Shunshan Duan, Jingrang Lu

    Cyanobacterial blooms are intensifying global ecological hazards. The fine structure and dynamics of bloom community are critical to understanding bloom development but little understood. Here, the questions whether dominant bloomers have high diversity and whether dominant OTUs (operational taxonomical units) compete with one another were addressed. 16S rRNA gene amplicons from an annual bloom at five locations in Harsha Lake (Ohio, USA) showed cyanobacteria were the dominant phylum, and co-existing major bacterial phyla included Proteobacteria, Bacteroidetes, Actinoacteria, and Verrucomicrobia. On the genus level, the initial dominance by Dolichospermum in June yielded to Planktothrix in July, which were replaced by Microcystis and Cylindrospermopsis in August throughout the bloom. Based on the number of verified unique OTUs (a within-genus biodiversity metric), dominant genera tended to have high within-genus diversity. For example, Dolichospermum had 57 unique OTUs, Planktothrix had 36, Microcystis had 12, and Cylindrospermopsis had 4 unique OTUs. Interestingly, these different OTUs showed different dynamics and association with other OTUs. First, no between-OTU competitions were observed during the bloom cycle, and dominant OTUs were abundant throughout the bloom. Such biodiversity of OTUs and their dynamics were verified in Microcystis aeruginosa with two microcystin synthetase genes (mcyA and mcyG): the relative abundance of both genes varied during the bloom based on quantitative PCR. Two Dolichospermum circinale OTUs and one P. rubescens OTU were most abundant and persistently present throughout the entire bloom. Second, these OTUs differed in the OTUs they were associated with. Third, these OTUs tended to have different levels of association with the environmental factors, even they belonged to the same genera. These findings suggest the structure and dynamics of a cyanobacterial bloom community is complex, with only few OTUs dominating the bloom. Thus, high-resolution molecular characterization will be necessary to understand bloom development.

    更新日期:2019-01-01
  • Two novel azaspiracids from Azadinium poporum, and a comprehensive compilation of azaspiracids produced by Amphidomataceae, (Dinophyceae)
    Harmful Algae (IF 4.138) Pub Date : 2018-12-27
    Bernd Krock, Urban Tillmann, Jan Tebben, Nicole Trefault, Haifeng Gu

    Two novel azaspiracids (AZA) with a molecular mass of 869 Da were found in Pacific strains of Azadinium poporum and characterized by tandem mass spectrometry and high resolution mass spectrometry (HRMS). One compound, AZA-42, was found in Az. poporum strains AZFC25 and AZFC26, both isolated from the South China Sea. AZA-42 belongs to the 360-type AZA that in comparison to AZA-1 has an additional double bond in the F–I ring system of AZA comprising C28-C40. The other compound, AZA-62, was detected in Az. poporum strain 1D5 isolated off Chañaral, Northern Chile. Mass spectral data indicate that AZA-62 is a variant of AZA-11 with an additional double bond in the C1-C9 region of AZA. In addition to the description of the two novel AZA, a comprehensive list of all AZA known to be produced by species of the genera Azadinium and Amphidoma comprising 26 AZA variants is presented.

    更新日期:2019-01-01
  • Spatial-temporal survey of Microcystis oligopeptide chemotypes in reservoirs with dissimilar waterbody features and their relation to genetic variation
    Harmful Algae (IF 4.138) Pub Date : 2018-12-11
    M.Á. Lezcano, R. Agha, S. Cirés, A. Quesada

    The ability of cyanobacteria to produce toxins and other secondary metabolites is patchily distributed in natural populations, enabling the use of cellular oligopeptide compositions as markers to classify strains into ecologically-relevant chemotypical subpopulations. The composition and spatiotemporal distribution of Microcystis chemotypes within and among waterbodies was studied at different time scales by analyzing (i) Microcystis strains isolated between 1998 and 2007 from different Spanish reservoirs and (ii) individual Microcystis aeruginosa colonies collected from pelagic and littoral habitats in Valmayor reservoir (Spain) during a bloom. No agreement between chemotypes and both morphotypes and genotypes (based on cpcBA-IGS, 16S–23S rRNA ITS and mcyB genes) was found, suggesting that oligopeptide profiles in individual strains evolve independently across morphospecies and phylogenetic genotypes, and that the diversity of microcystin variants produced cannot be explained by mcyB gene variations alone. The presence of identical chemotypes in spatially-distant reservoirs with dissimilar trophic state, lithology or depth indicate that waterbody characteristics and geographical boundaries weakly affect chemotype composition and distribution. At smaller spatiotemporal scales (i.e. during bloom), M. aeruginosa populations showed high number of chemotypes, as well as marked differences in chemotype composition and relative abundance among the littoral and pelagic habitats. This indicates that the factors influencing chemotype composition, relative abundance and dynamics operate at short spatial and temporal scales, and supports emerging hypotheses about interactions with antagonistic microorganisms as possible drivers for widespread chemical polymorphisms in cyanobacteria.

    更新日期:2018-12-12
  • Distribution of Karlodinium veneficum in the coastal region of Xiangshan Bay in the East China Sea, as detected by a real-time quantitative PCR assay of ribosomal ITS sequence
    Harmful Algae (IF 4.138) Pub Date : 2018-12-11
    Hai-Long Huang, Qian-Wen Shao, Xiao-Juan Zhu, Jie Luo, Ran Meng, Cheng-Xu Zhou, Peng Zhu, Yi-Feng Zhu, Xiao-Jun Yan

    Athecate dinoflagellate Karlodinium veneficum is a universal toxic species possessing karlotoxins recognized especially as ichthyotoxic as well as cytotoxic and hemolytic. Blooms of K. veneficum, both single-species or accompanied with other species, occurred more frequently worldwide in recent years, including the coastal region of China. Normally, K. veneficum present in relatively low abundance in phytoplankton communities in estuary regions. Being small and difficult to identify with light microscopy, it has been ignored for a long time till its blooming and toxins being confirmed. How it presents in background level and what is its relationship with critical geological and hydrological environment factors are basically not clear. In this study, the paper reports the application of a real-time quantitative PCR (qPCR) method to investigate the abundance and distribution of K. veneficum in the coastal waters of Xiangshan Bay in the East China Sea (ECS), a typical bay area of harmful algae blooms and heavily affected by anthropogenic activities. The real-time qPCR assay came out being an efficient method at detecting even low cell densities of K. veneficum of different genotypes. A total of 38 field samples of surface (0.5 m) and bottom water (9–100 m in depth) were analyzed and 12 samples were found positive for K. veneficum. At least 3 genotypes of K. veneficum present in this region. Temperatures in sites of K. veneficum positive ranged from 21.7 to 23.4 °C, and salinity levels were between 21.1 and 26.3. The K. veneficum distributed quite extensively in the waters of Xiangshan Bay, cell abundance varied from a low of 4 cells/L to a maximum of 170 cells/L. Most of the samples containing K. veneficum were collected from bottom water in different sites. At three of the 19 sampling sites, K. veneficum was detected in both surface and bottom water samples. Especially at sampling site near Beilun port, where the water is typically muddy with low transparency, relative high cell numbers of K. veneficum were found in both surface and bottom waters. Mixotrophy and vertical migration of K. veneficum could be important eco-physiological factors to consider in terms of understanding these distribution characteristics. The ideal conditions for K. veneficum growth and aggregation in this area still needs further study.

    更新日期:2018-12-12
  • Science meets policy: A framework for determining impairment designation criteria for large waterbodies affected by cyanobacterial harmful algal blooms
    Harmful Algae (IF 4.138) Pub Date : 2018-12-10
    Timothy W. Davis, Richard Stumpf, George S. Bullerjahn, Robert Michael L. McKay, Justin D. Chaffin, Thomas B. Bridgeman, Christopher Winslow

    Toxic cyanobacterial harmful algal blooms (cyanoHABs) are one of the most significant threats to the security of Earth’s surface freshwaters. In the United States, the Federal Water Pollution Control Act of 1972 (i.e., the Clean Water Act) requires that states report any waterbody that fails to meet applicable water quality standards. The problem is that for fresh waters impacted by cyanoHABs, no scientifically-based framework exists for making this designation. This study describes the development of a data-based framework using the Ohio waters of western Lake Erie as an exemplar for large lakes impacted by cyanoHABs. To address this designation for Ohio’s open waters, the Ohio Environmental Protection Agency (EPA) assembled a group of academic, state and federal scientists to develop a framework that would determine the criteria for Ohio EPA to consider in deciding on a recreation use impairment designation due to cyanoHAB presence. Typically, the metrics are derived from on-lake monitoring programs, but for large, dynamic lakes such as Lake Erie, using criteria based on discrete samples is problematic. However, significant advances in remote sensing allows for the estimation of cyanoHAB biomass of an entire lake. Through multiple years of validation, we developed a framework to determine lake-specific criteria for designating a waterbody as impaired by cyanoHABs on an annual basis. While the criteria reported in this manuscript are specific to Ohio’s open waters, the framework used to determine them can be applied to any large lake where long-term monitoring data and satellite imagery are available.

    更新日期:2018-12-11
  • Initial evidence of functional siRNA machinery in dinoflagellates
    Harmful Algae (IF 4.138) Pub Date : 2018-12-01
    Chao Zhang, Senjie Lin

    Dinoflagellates are a major group of protists widely distributed in the aquatic environments. Many species in this lineage are able to form harmful algal blooms (HAB), some even producing toxins, making this phylum the most important contributors of HAB in the marine ecosystem. Despite the ecological importance, the molecular mechanisms underpinning the basic biology and HAB formation of dinoflagellates are poorly understood. While the high-throughput sequencing studies have documented a large and growing number of genes in dinoflagellates, their functions remained to be experimentally proven using a functional genetic tool. Unfortunately, no such tool is yet available. This study was aimed to adopt the RNA interference (RNAi) gene-silencing tool for dinoflagellate research, and to investigate the potential effects of RNAi-based silencing of proton-pump rhodopsin and CO2-fixing enzyme Rubisco encoding genes in dinoflagellates. It was found that RNAi treatment caused a significant decrease in growth rate in both species. Compared with the non- endogenous target (GFP-siRNA) and the blank control, RNAi treatments also suppressed the expression of the target genes. These results constitute the first experimental evidence of the existence and operation of siRNA in two species of dinoflagellates, present initial evidence that dinoflagellate rhodopsins are functional as a supplemental energy acquisition mechanism, and provide technical information for future functional genetic research on dinoflagellates.

    更新日期:2018-12-02
  • Ammonium recycling supports toxic Planktothrix blooms in Sandusky Bay, Lake Erie: Evidence from stable isotope and metatranscriptome data
    Harmful Algae (IF 4.138) Pub Date : 2018-12-01
    Justyna J. Hampel, Mark J. McCarthy, Michelle Neudeck, George S. Bullerjahn, Robert Michael L. McKay, Silvia E. Newell

    Sandusky Bay, Lake Erie, receives high nutrient loadings (nitrogen and phosphorus) from the Sandusky River, which drains an agricultural watershed. Eutrophication and cyanobacterial harmful algal blooms (cyanoHABs) persist throughout summer. Planktothrix agardhii is the dominant bloom-forming species and the main producer of microcystins in Sandusky Bay. Non-N2 fixing cyanobacteria, such as Planktothrix and Microcystis, thrive on chemically reduced forms of nitrogen, such as ammonium (NH4+) and urea. Ammonium regeneration and potential uptake rates and total microbial community demand for NH4+ were quantified in Sandusky Bay. Potential NH4+ uptake rates in the light increased from June to August at all stations. Dark uptake rates also increased seasonally and, by the end of August, were on par with light uptake rates. Regeneration rates followed a similar pattern and were significantly higher in August than June. Ammonium uptake kinetics during a Planktothrix-dominated bloom in Sandusky Bay and a Microcystis-dominated bloom in Maumee Bay were also compared. The highest half saturation constant (Km) in Sandusky Bay was measured in June and decreased throughout the season. In contrast, Km values in Maumee Bay were lowest at the beginning of summer and increased in October. A significant increase in Vmax in Sandusky Bay was observed between July and the end of August, reflective of intense competition for depleted NH4+. Metatranscriptome results from Sandusky Bay show a shift from cyanophycin synthetase (luxury NH4+ uptake; cphA1) expression in early summer to cyanophycinase (intracellular N mobilization; cphB/cphA2) expression in August, supporting the interpretation that the microbial community is nitrogen-starved in late summer. Combined, our results show that, in late summer, when nitrogen concentrations are low, cyanoHABs in Sandusky Bay rely on regenerated NH4+ to support growth and toxin production. Increased dark NH4+ uptake late in summer suggests an important heterotrophic contribution to NH4+ depletion in the phycosphere. Kinetic experiments in the two bays suggest a competitive advantage for Planktothrix over Microcystis in Sandusky Bay due to its higher affinity for NH4+ at low concentrations.

    更新日期:2018-12-02
  • Devastating farmed abalone mortalities attributed to yessotoxin-producing dinoflagellates
    Harmful Algae (IF 4.138) Pub Date : 2018-11-30
    Grant C. Pitcher, Charles J. Foord, Brett M. Macey, Lisa Mansfield, Anna Mouton, Marie E. Smith, Steven J. Osmond, Lynndal van der Molen

    A large dinoflagellate bloom in Walker Bay (South Africa) in January 2017 impacted 3 land-based abalone farms resulting in the death of several million animals. Satellite-derived images of Chl-a from the Ocean and Land Colour Imager (OLCI) on board the European Space Agency Sentinel-3 A showed bloom initiation in late December 2016 and dispersal in mid-February 2017. The bloom was dominated by two dinoflagellate species identified by light microscopy as Gonyaulax spinifera (Claparède & Lachmann) Diesing, 1866 and Lingulodinium polyedrum (Stein) Dodge, 1989. These morphologically based identifications were confirmed by phylogenetic analysis using partial sequences of the large subunit rDNA of both dinoflagellates. The appearance of yessotoxins (YTX) in abalone clearly coincided with increases in dinoflagellate concentrations. Yessotoxins in both the plankton and abalone were dominated by the two analogues homo-YTX and 45-hydroxy-YTX. The absence of toxins in a clonal culture of L. polyedrum implicated G. spinifera as the likely source of YTX. Toxin concentrations were found to be highest in the gills which showed the most significant pathology, including severe, generalized disruption of the gill epithelium characterized by degeneration and necrosis of epithelial cells accompanied by a modest inflammatory response. Some farms undertook pre-emptive or emergency harvesting to reduce financial losses.

    更新日期:2018-11-30
  • Spatio-temporal dynamics and biotic substrate preferences of benthic dinoflagellates in the Lesser Antilles, Caribbean sea
    Harmful Algae (IF 4.138) Pub Date : 2018-11-28
    Aurélie Boisnoir, Pierre-Yves Pascal, Sébastien Cordonnier, Rodolphe Lemée

    Epibenthic dinoflagellates were monitored monthly over an 18 month period in Guadeloupe and Martinique (Lesser Antilles, Caribbean Sea). These islands are located in the second most affected ciguatera fish poisoning (CFP) region of the world. Guadeloupe presented five times more total epibenthic dinoflagellates and two times less abundant Gambierdiscus spp. compared to Martinique, although the area of frequent CFP outbreaks covers Guadeloupe and not Martinique. Results did not show any clear seasonal variations of benthic dinoflagellates abundances. Temperature and salinity were not driving parameters in the evolution of total benthic dinoflagellate abundances. Preferential associations were found between macrophyte species and epibenthic dinoflagellates. The Phaeophyceae Dictyota spp. hosted the highest abundances of total epibenthic dinoflagellates, composed mainly of Ostrepsis and Prorocentrum genera. The seagrass Halophila stipulacea hosted the highest abundances of Gambierdiscus spp. and Sinophysis spp. whilst the highest abundance of Coolia was determined on Galaxaura spp. The pelagic Sargassum spp. hosted the lowest abundances of benthic dinoflagellates including the genus Gambierdiscus.

    更新日期:2018-11-28
  • Effects of ocean acidification and solar ultraviolet radiation on physiology and toxicity of dinoflagellate Karenia mikimotoi
    Harmful Algae (IF 4.138) Pub Date : 2018-11-28
    Xinjie Wang, Xinqian Feng, Yang Zhuang, Jianghuan Lu, Yang Wang, Rodrigo J. Gonçalves, Xi Li, Yongliang Lou, Wanchun Guan

    A batch culture experiment was conducted to study the interactive effects of ocean acidification (OA) and solar ultraviolet radiation (UVR, 280–400 nm) on the harmful dinoflagellate Karenia mikimotoi. Cells were incubated in 7-days trials under four treatments. Physiological (growth, pigments, UVabc) and toxicity (hemolytic activity and its toxicity to zebrafish embryos) response variables were measured in four treatments, representing two factorial combinations of CO2 (400 and 1000 μatm) and solar irradiance (with or without UVR). Toxic species K. mikimotoi showed sustained growth in all treatments, and there was not statistically significant difference among four treatments. Cell pigment content decreased, but UVabc and hemolytic activity increased in all HC treatments and PAB conditions. The toxicity to zebrafish embryos of K. mikimotoi was not significantly different among four treatments. All HC and UVR conditions and the combinations of HC*UVR (HC-PAB) positively affected the UVabc, hemolytic activity in comparison to the LC*P (LC-P) treatment, and negatively affected the pigments. Ocean acidification (OA) was probably the main factor that affected the chlorophyll-a (Chl-a) and UVabc, but UVR was the main factor that affected the carotenoid (Caro) and hemolytic activity. There were no significant interactive effects of OA*UVR on growth, toxicity to zebrafish embryos. If these results are extrapolated to the natural environment, it can be hypothesized that this strain (DP-C32) of K. mikimotoi cells have the efficient mechanisms to endure the combination of ocean acidification and solar UVR. It is assumed that this toxic strain could form harmful bloom and enlarge the threatening to coastal communities, marine animals, even human health under future conditions.

    更新日期:2018-11-28
  • A-, B- and C-type prymnesins are clade specific compounds and chemotaxonomic markers in Prymnesium parvum
    Harmful Algae (IF 4.138) Pub Date : 2018-11-28
    Sofie Bjørnholt Binzer, Daniel Killerup Svenssen, Niels Daugbjerg, Catharina Alves-de-Souza, Ernani Pinto, Per Juel Hansen, Thomas Ostenfeld Larsen, Elisabeth Varga

    Harmful blooms formed by planktonic microalgae (HABs) in both freshwater and coastal waters regularly lead to severe mortalities of fish and invertebrates causing substantial economic losses of marine products worldwide. The mixotrophic haptophyte Prymnesium parvum is one of the most important microalgae associated with fish kills. Here 26 strains of P. parvum with a wide geographical distribution were screened for the production of prymnesins, the suspected causative allelochemical toxins. All investigated strains produced prymnesins, indicating that the toxins play an important role for the organism. The prymnesins can be classified into three types based on the length of the carbon backbone of the compound and each algal strain produced only one of these types. Biogeographical mapping of the prymnesin distribution indicated a global distribution of each type. In addition, phylogenetic analyses based on internal transcribed spacer (ITS) sequences revealed monophyletic origin of all prymnesin types and clades could therefore be defined based on the toxic compound. It might be that evolution of new species within the P. parvum species complex is driven by changes in toxin type or that they are a result of it. Such a correlation between chemotype and phylotype has never been documented before for a harmful microalga. Chemotaxonomy and ITS-type classification may thus be used to further delimit the P. parvum species complex.

    更新日期:2018-11-28
  • Cryptic diversity within the Scytonema complex: Characterization of the paralytic shellfish toxin producer Heterosyctonema crispum, and the establishment of the family Heteroscytonemataceae (Cyanobacteria/Nostocales)
    Harmful Algae (IF 4.138) Pub Date : 2018-11-23
    Barbara C. Sendall, Glenn B. McGregor

    Strains of the freshwater filamentous, benthic cyanobacterium Scytonema crispum Agardh isolated from six sites in subtropical south-east Queensland were characterised using a combination of phenotypic and genetic traits. Morphologically, the strains were consistent with the description of Scytonemataceae sensu stricto, and the description of Scytonema crispum. However, phylogenetic analysis of the 16S rRNA gene, the 16S-23S rRNA operon, and the nifH gene revealed that these strains and three others from outside Australia formed a monophyletic clade distinct from Scytonema and other species in the Scytonemataceae. Collectively, this data suggests this group is sufficiently evolutionarily distinct to be placed in a new family, Heteroscytonemataceae fam. nov. Accordingly, the taxon previously known as S. crispum has been transferred to a new genus Heteroscytonema gen nov., as H. crispum. Some strains of H. crispum exhibited facultative production of paralytic shellfish toxins (PSTs). The concentration of PSTs produced by individual strains varied widely, from 2.7 μg g−1 to 171.3 μg g−1, and included C toxins, decarbamoyl saxitoxin (dcSTX), gonyautoxins (GTX2, GTX3 and GTX5), saxitoxin (STX) and uncharacterised PSTs. The majority of the Australian strains produced dcSTX as the dominant saxitoxin analogue, a significant finding given that dcSTX has approximately half the relative toxicity of STX. The PST profile varied within and between Australian strains of H. crispum and in strains collected from New Zealand and the United States. The sxtA gene, one of the determinants for the production of PSTs, was present in all strains in which PSTs were detected. The discovery of PST-producing H. crispum in the headwaters of a major drinking water reservoir presents a serious risk for potential human and animal exposure to these neurotoxic compounds and further highlights the importance of monitoring benthic cyanobacteria populations for potentially toxigenic species.

    更新日期:2018-11-26
  • Gambierdiscus jejuensis sp. nov., an epiphytic dinoflagellate from the waters of Jeju Island, Korea, effect of temperature on the growth, and its global distribution
    Harmful Algae (IF 4.138) Pub Date : 2018-11-23
    Se Hyeon Jang, Hae Jin Jeong, Yeong Du Yoo

    The genus Gambierdiscus produces ciguatera toxins, which has led to extensive studies of this genus. Epiphytic dinoflagellate cells were isolated from coralline macroalgae collected from the coastal waters of Jeju Island, Korea, and two clonal cultures were established. The morphology of these cells was examined using light and scanning electron microscopy, and the sequences of the small subunit (SSU), large subunit (LSU), and internal transcribed spacer (ITS) region of rDNA were determined. The phylogenetic trees based on SSU, LSU (D1-D3), and LSU (D8-D10) rDNA showed the two Korean isolates forming a clade with unidentified strains named Gambierdiscus sp. type 2. This clade showed a clear divergence from the two closest clades containing of the G. caribaeus and G. carpenteri strains. Morphologically, the Korean isolates had an anteroposteriorly compressed cell shape having a smooth theca ornamentation. Growth of the Korean isolates ceased when water temperatures were <20 °C or >30 °C with an optimum at 26 °C. This temperature preference may account for why Gambierdiscus sp. type 2 has only been isolated from the temperate waters of Korea and Japan. However, the two most closely related species G. caribaeus and G. carpenteri have broader temperature ranges tolerating as high as 34–36 °C and are globally distributed. Based on these results, the Korean isolates are proposed as a new species in the genus Gambierdiscus and named Gambierdiscus jejuensis sp. nov. Furthermore, it is suggested that the unidentified strains belonging to the Gambierdiscus sp. type 2 be transferred to the new species, G. jejuensis.

    更新日期:2018-11-24
  • Role of temperature and nutrients on the growth and toxin production of Prorocentrum hoffmannianum (Dinophyceae) from the Florida Keys
    Harmful Algae (IF 4.138) Pub Date : 2018-11-20
    Stefano Accoroni, Martina Ceci, Luciana Tartaglione, Tiziana Romagnoli, Alessandra Campanelli, Mauro Marini, Sonia Giulietti, Carmela Dell’Aversano, Cecilia Totti

    The benthic dinoflagellate Prorocentrum hoffmannianum M.A. Faust is typical of tropical warm waters and produces biotoxins responsible for diarrhetic shellfish poisoning (DSP). In this study, the effect of temperature and nutrient limitation on growth and toxin production of P. hoffmannianum isolated from field samples collected in the Florida Keys was investigated. Batch culture experiments were ran at two temperatures (i.e. 21 ± 0.1 and 27 ± 0.1 °C) and under nitrogen-limited (14.7 μmol L−1 N-NO3- and 18.1 μmol L−1 P-PO43-) and phosphorus-limited (441 μmol L−1 N-NO3- and 0.6 μmol L−1 P-PO43-) levels with respect to control nutrient conditions (441 μmol L−1 N-NO3-and 18.1 μmol L−1 P-PO43-). Both temperature and nutrient conditions significantly affected growth rates and maximum yield of P. hoffmannianum with the maximum values being recorded at the higher temperature and in the replete medium. Production of okadaic acid was induced under all conditions (from 13.5 to 859.8 pg cell−1), with values up to one order of magnitude higher than those observed in other DSP toxin producing species. Toxin production was enhanced under P limitation at 27 °C, corroborating the theory that toxin production is modulated by cell physiological conditions, which are in turn affected by a wide spectrum of factors, including environmental stressors such as nutrient availability. Toxin fraction released in the growth medium was negligible. No okadaic acid esters were detected in this strain of P. hoffmannianum.

    更新日期:2018-11-21
  • Low-dose stimulation of growth of the harmful alga, Prymnesium parvum, by glyphosate and glyphosate-based herbicides
    Harmful Algae (IF 4.138) Pub Date : 2018-11-17
    Brittanie L. Dabney, Reynaldo Patiño

    Glyphosate-based herbicides (GBH) are widely used around the globe. While generally toxic to phototrophs, organic phosphorus in glyphosate can become available to glyphosate-resistant phytoplankton and contribute to algal bloom development. Few studies have examined the effects of GBH on growth of eukaryotic microalgae and information for the toxic bloom-forming haptophyte, Prymnesium parvum, is limited. Using a batch-culture system, this study examined the effects on P. parvum growth of a single application of Roundup Weed and Grass Killer Super Concentrate Plus® (Roundup SC), Roundup Weed and Grass Killer Ready-to-Use III® (Roundup RtU), and technical-grade glyphosate at low concentrations [0–1000 μg glyphosate acid equivalent (ae) l−1]. Roundup formulations differ in the percent of glyphosate as active ingredient (Roundup SC, ∼50%; Roundup RtU, 2%), allowing indirect evaluation of the influence of inactive ingredients. Roundup SC enhanced exponential growth rate at 10–1000 μg glyphosate ae l−1, and a positive monotonic association was noted between Roundup SC concentration and early (pre-exponential growth) but not maximum cell density. Glyphosate and both Roundup formulations enhanced growth rate at 100 μg glyphosate l−1, but only Roundup SC and glyphosate significantly stimulated early and maximum density. This observation suggests the higher concentration of inactive ingredients and other compounds in Roundup RtU partially counteracts glyphosate-dependent growth stimulation. When phosphate concentration was varied while maintaining other conditions constant, addition of Roundup SC and glyphosate at 100 μg l−1 influenced growth more strongly than equivalent changes in phosphate-associated phosphorus. It appears, therefore, that low doses of glyphosate stimulate growth by mechanisms unrelated to the associated small increases in total phosphorus. In conclusion, glyphosate and GBH stimulate P. parvum growth at low, environmentally relevant concentrations. This finding raises concerns about the potential contribution to P. parvum blooms by glyphosate-contaminated runoff or by direct application of GBH to aquatic environments.

    更新日期:2018-11-17
  • Analysis of free and metabolized microcystins in samples following a bird mortality event
    Harmful Algae (IF 4.138) Pub Date : 2018-11-03
    Amanda J. Foss, Christopher O. Miles, Ingunn A. Samdal, Kjersti E. Løvberg, Alistair L. Wilkins, Frode Rise, J. Atle H. Jaabæk, Peter C. McGowan, Mark T. Aubel

    In the summer of 2012, over 750 dead and dying birds were observed at the Paul S. Sarbanes Ecosystem Restoration Project at Poplar Island, Maryland, USA (Chesapeake Bay). Clinical signs suggested avian botulism, but an ongoing dense Microcystis bloom was present in an impoundment on the island. Enzyme-linked immunosorbent assay (ELISA) analysis of a water sample indicated 6000 ng mL−1 of microcystins (MCs). LC-UV/MS analysis confirmed the presence of MC-LR and a high concentration of an unknown MC congener (m/z 1037.5). The unknown MC was purified and confirmed to be [D-Leu1]MC-LR using NMR spectroscopy, LC-HRMS and LC–MS2, which slowly converted to [D-Leu1,Glu(OMe)6]MC-LR during storage in MeOH. Lyophilized algal material from the bloom was further characterized using LC-HRMS and LC–MS2 in combination with chemical derivatizations, and an additional 24 variants were detected, including MCs conjugated to Cys, GSH and γ-GluCys and their corresponding sulfoxides. Mallard (Anas platyrhynchos) livers were tested to confirm MC exposure. Two broad-specificity MC ELISAs and LC–MS2 were used to measure free MCs, while ‘total’ MCs were estimated by both MMPB (3-methoxy-2-methyl-4-phenylbutyric acid) and thiol de-conjugation techniques. Free microcystins in the livers (63–112 ng g−1) accounted for 33–41% of total microcystins detected by de-conjugation and MMPB techniques. Free [D-Leu1]MC-LR was quantitated in tissues at 25–67 ng g−1 (LC–MS2). The levels of microcystin varied based on analytical method used, highlighting the need to develop a comprehensive analysis strategy to elucidate the etiology of bird mortality events when microcystin-producing HABs are present.

    更新日期:2018-11-05
  • Pseudo-nitzschia, Nitzschia, and domoic acid: New research since 2011
    Harmful Algae (IF 4.138) Pub Date : 2018-10-27
    Stephen S. Bates, Katherine A. Hubbard, Nina Lundholm, Marina Montresor, Chui Pin Leaw

    Some diatoms of the genera Pseudo-nitzschia and Nitzschia produce the neurotoxin domoic acid (DA), a compound that caused amnesic shellfish poisoning (ASP) in humans just over 30 years ago (December 1987) in eastern Canada. This review covers new information since two previous reviews in 2012. Nitzschia bizertensis was subsequently discovered to be toxigenic in Tunisian waters. The known distribution of N. navis-varingica has expanded from Vietnam to Malaysia, Indonesia, the Philippines and Australia. Furthermore, 15 new species (and one new variety) of Pseudo-nitzschia have been discovered, bringing the total to 52. Seven new species were found to produce DA, bringing the total of toxigenic species to 26. We list all Pseudo-nitzschia species, their ability to produce DA, and show their global distribution. A consequence of the extended distribution and increased number of toxigenic species worldwide is that DA is now found more pervasively in the food web, contaminating new marine organisms (especially marine mammals), affecting their physiology and disrupting ecosystems. Recent findings highlight how zooplankton grazers can induce DA production in Pseudo-nitzschia and how bacteria interact with Pseudo-nitzschia. Since 2012, new discoveries have been reported on physiological controls of Pseudo-nitzschia growth and DA production, its sexual reproduction, and infection by an oomycete parasitoid. Many advances are the result of applying molecular approaches to discovering new species, and to understanding the population genetic structure of Pseudo-nitzschia and mechanisms used to cope with iron limitation. The availability of genomes from three Pseudo-nitzschia species, coupled with a comparative transcriptomic approach, has allowed advances in our understanding of the sexual reproduction of Pseudo-nitzschia, its signaling pathways, its interactions with bacteria, and genes involved in iron and vitamin B12 and B7 metabolism. Although there have been no new confirmed cases of ASP since 1987 because of monitoring efforts, new blooms have occurred. A massive toxic Pseudo-nitzschia bloom affected the entire west coast of North America during 2015–2016, and was linked to a ‘warm blob’ of ocean water. Other smaller toxic blooms occurred in the Gulf of Mexico and east coast of North America. Knowledge gaps remain, including how and why DA and its isomers are produced, the world distribution of potentially toxigenic Nitzschia species, the prevalence of DA isomers, and molecular markers to discriminate between toxigenic and non-toxigenic species and to discover sexually reproducing populations in the field.

    更新日期:2018-10-27
  • MHBMDAA: Membrane-based DNA array with high resolution and sensitivity for toxic microalgae monitoring
    Harmful Algae (IF 4.138) Pub Date : 2018-10-19
    Chunyun Zhang, Guofu Chen, Yuanyuan Wang, Rui Sun, Xiaoli Nie, Jin Zhou

    Harmful algal blooms (HAB) involving toxic microalgae have posed a serious threat to the marine industry and environment in the past several decades. Efficient techniques are required to monitor the marine environment to provide an effective warning of imminent HAB. Sequenced the partial large subunit rDNA (D1-D2) sequences of eight toxic harmful algae that are commonly distributed along the Chinese coast were cloned. Specific padlock probes (PLP) that contain linker regions composed of universal primer binding sites and Zip sequences were designed from the obtained target DNA. Taxonomic probes complementary to the Zip sequences were tailed and spotted onto a nylon membrane to prepare a DNA array. An optimized multiplex hyperbranched rolling circle amplification (MHRCA) was used to produce biotin-labeled amplified products. Heat-denatured MHRCA products were used to hybridize with DNA array, followed by dot coloration. An MHRCA-based membrane DNA array assay (MHBMDAA) for detecting toxic microalgae was developed. The specificity of the MHBMDAA was confirmed by double cross-reactivity tests of PLP and taxonomic probes. The MHBMDAA was competent for detecting the simulated samples with 103 to 10−1 cells mL−1, which is 10-fold more sensitive than a multiplex PCR-based membrane DNA array. The effectiveness of the MHBMDAA was also validated by testing with natural samples from the East China Sea. Results indicated that the MHBMDAA provides a valuable tool for the sensitive and reliable detection of toxic microalgae for early warning and research purposes.

    更新日期:2018-10-22
  • The successional formation and release of domoic acid in a Pseudo-nitzschia bloom in the Juan de Fuca Eddy: A drifter study
    Harmful Algae (IF 4.138) Pub Date : 2018-10-21
    Charles G. Trick, Vera L. Trainer, William P. Cochlan, Mark L. Wells, B.F. Beall

    Blooms of Pseudo-nitzschia species are frequent, but presently unpredictable, in the Juan de Fuca Eddy region off the coasts of Washington (US) and British Columbia (Canada). This upwelling eddy region is proposed to be the bloom commencement site, before cells are entrained into the coastal surface currents. During a shipboard study, we characterized the different stages of the Pseudo-nitzschia bloom development from its initiation and intensification, to its eventual sinking and dissipation. Specifically, we followed a water mass using lagrangian ARGOS-tracked drifters released at the eddy water mass and quantified production of dissolved and particulate domoic acid, and the physiological status of the Pseudo-nitzschia cells with regards to photosynthesis, nutrient needs and sinking rates, along with its relationship with competing species – in this case, the marine euglenoid, Eutreptiella spp. The drifter study allows for an interpretation of the presence or absence of Pseudo-nitzschia and domoic acid against active environmental factors – particularly copper and iron.

    更新日期:2018-10-22
  • A Greek Cylindrospermopsis raciborskii strain: Missing link in tropic invader’s phylogeography tale
    Harmful Algae (IF 4.138) Pub Date : 2018-10-15
    Manthos Panou, Sevasti-Kiriaki Zervou, Triantafyllos Kaloudis, Anastasia Hiskia, Spyros Gkelis
    更新日期:2018-10-15
  • Anatoxins are consistently released into the water of streams with Microcoleus autumnalis-dominated (cyanobacteria) proliferations
    Harmful Algae (IF 4.138) Pub Date : 2018-10-10
    Susanna A. Wood, Laura Biessy, Jonathan Puddick

    Proliferations of potentially toxic, mat-forming Microcoleus are increasing in streams globally. A range of cyanotoxins are produced by Microcoleus, with the neurotoxic anatoxins (anatoxin-a, dihydro-anatoxin-a, homoanatoxin-a and dihydro-homoanatoxin-a) the most commonly reported. The anatoxins produced by Microcoleus are thought to be largely contained within the cells. More knowledge on whether anatoxins are been released into the overlying stream water is required to better assess health risks to human, animals, and aquatic organisms. Field studies were conducted in three streams experiencing toxic Microcoleus autumnalis (basionym Phormidium autumnale)-dominated proliferations. Samples were collected every 1.5–3 h over a 24- or 26-h sampling period. Water samples were analyzed for total (intracellular and dissolved) and dissolved anatoxins, and time-integrated anatoxin samples were collected using solid phase adsorption tracking technology (SPATT). Anatoxins were detected in all stream water and SPATT samples (max. 0.91 ng mL−1 and 95 ng g-1 of strata-x hr−1). At two sites, anatoxins were largely dissolved, whereas at the third site only total anatoxins could be detected. Temporal variability in anatoxin concentrations was observed, but there were no evident patterns between sampling sites. Linear regression showed a very weakstatistically significant relationship (R2 = 0.24, p = 0.002) between total anatoxin concentrations in water and SPATT, however, when tested per site, only one of the three showed a significant relationship. These results highlight the potential for chronic exposure to anatoxins for humans (i.e., through drinking water) and aquatic organisms in streams with M. autumnalis proliferations. The health implications of this are unknown.

    更新日期:2018-10-11
  • Development of an LC–MS/MS method to simultaneously monitor maitotoxins and selected ciguatoxins in algal cultures and P-CTX-1B in fish
    Harmful Algae (IF 4.138) Pub Date : 2018-10-09
    J. Sam Murray, Michael J. Boundy, Andrew I. Selwood, D. Tim Harwood
    更新日期:2018-10-09
  • Isolation of an algicidal bacterium and its effects against the harmful-algal- bloom dinoflagellate Prorocentrum donghaiense (Dinophyceae)
    Harmful Algae (IF 4.138) Pub Date : 2018-10-06
    Xinguo Shi, Lemian Liu, Yue Li, Yuchun Xiao, Guangmao Ding, Senjie Lin, Jianfeng Chen

    The relationship between algicidal bacteria and harmful-algal-bloom-forming dinoflagellates is understudied and their action modes are largely uncharacterized. In this study, an algicidal bacterium (FDHY-03) was isolated from a bloom of Prorocentrum donghaiense and the characteristics of its action against P. donghaiense was investigated at physiological, molecular, biochemical and cytological levels. 16S rDNA sequence analysis placed this strain in the genus of Alteromonas in the subclass of γ-proteobacteria. Algicidal activity was detected in the bacterial filtrate, suggesting a secreted algicidal principle from this bacterium. Strain FDHY-03 showed algicidal activity on a broad range of HAB-forming species, but the greatest effect was found on P. donghaiense, which showed 91.7% mortality in 24 h of challenge. Scanning electron microscopic analysis indicated that the megacytic growth zone of P. donghaiense cells was the major target of the algicidal action of FDHY-03. When treated with FDHY-03 culture filtrate, P. donghaiense cell wall polysaccharides decreased steadily, suggesting that the algicidal activity occurred through the digestion of cell wall polysaccharides. To verify this proposition, the expression profile of beta-glucosidase gene in FDHY-03 cultures with or without P. donghaiense cell addition was investigated using reverse-transcription quantitative PCR. The gene expression level increased in the presence of P. donghaiense cells, indicative of beta-glucosidase induction by P. donghaiense and the enzyme’s role in this dinoflagellate’s demise. This study has isolated a new bacterial strain with a strong algicidal capability, documented its action mode and biochemical mechanism, providing a potential source of bacterial agent to control P. donghaiense blooms.

    更新日期:2018-10-08
  • Habitat effects on Ostreopsis cf. ovata bloom dynamics
    Harmful Algae (IF 4.138) Pub Date : 2018-10-05
    L. Meroni, M. Chiantore, M. Petrillo, V. Asnaghi

    In the last few decades, Ostreopsis spp., toxic benthic dinolagellates of tropical origin, generated large interest in the Mediterranean Sea, where several bloom events have been observed. Ecology and proliferation dynamics of O. cf. ovata are driven by complex interactions among biotic and abiotic drivers, and understanding mechanisms triggering bloom events is still far from being complete. The aim of the present study is to highlight the role of different habitat conditions, elucidating the effects of i) exposure to hydrodynamic conditions, ii) macroalgal community and iii) urbanisation level, in driving O. cf. ovata bloom dynamics. A significant effect of hydrodynamics was observed only for cells in seawater, with higher abundances in sheltered zones, irrespective of the urbanisation level. Similarly, a significant effect of the dominant macroalgal community, with higher abundances in Corallinales and turf dominated communities, and lower ones in Cystoseira amentacea canopies, has been recorded, consistently in the differently urbanised sites. Additionally, stretches of the coast suffering from a more intense anthropic exploitation are in general more prone to the proliferation of potentially toxic benthic microalgae. All these results imply a larger risk exposure to toxic effects for humans in urban beaches and sheltered areas, usually more attended by swimmers and bathers. These findings underline the need to preserve, and eventually restore, canopy dominated assemblages, which presently are under regression because of human threats, providing a straightforward example that restoration of relevant habitats implies a cascading improvement of human welfare.

    更新日期:2018-10-06
  • Production of domoic acid from large-scale cultures of Pseudo-nitzschia multiseries: A feasibility study
    Harmful Algae (IF 4.138) Pub Date : 2018-10-06
    Nancy I. Lewis, Stephen S. Bates, Michael A. Quilliam

    The commercial demand for domoic acid (DA), the phycotoxin responsible for Amnesic Shellfish Poisoning, is currently met by extraction from a diminishing supply of stockpiled contaminated mussels (Mytilus edulis). As this supply becomes scarce, a more reliable source is needed. Purification of the toxin from an algal source would be easier and more economical than from shellfish tissue if algal growth and yield of toxin were maximized. This project was initiated to determine if DA could be produced using large-scale semi-continuous algal cultures, which should reduce labour and shorten the time required for biomass production. Pseudo-nitzschia multiseries was grown in 300-L fibreglass photobioreactors called a Brite-Box™. The effect of temperature and nutrient depletion on the yield of DA by P. multiseries was examined. A decline in maximum cell number without a substantial increase in cellular DA was associated with increased temperature. Maximum total cellular DA (8.8 pg cell−1) was achieved at 20 °C. Semi-continuous culture of P. multiseries is accompanied by increasing amounts of DA lost to the medium. The process was deemed to be feasible for growing P. multiseries but methods to recover this extracellular DA are necessary for this process to be economical.

    更新日期:2018-10-06
  • Fish gill damage by harmful microalgae newly explored by microelectrode ion flux estimation techniques
    Harmful Algae (IF 4.138) Pub Date : 2018-09-28
    Jorge I. Mardones, Lana Shabala, Sergey Shabala, Juan José Dorantes-Aranda, Andreas Seger, Gustaaf M. Hallegraeff

    Harmful algal blooms (HAB) are responsible for massive mortalities of wild and aquacultured fish due to noticeable gill damage, but the precise fish-killing mechanisms remain poorly understood. A non-invasive microelectrode ion flux estimation (MIFE) technique was successfully applied to assess changes in membrane-transport processes in a model fish gill cell line exposed to harmful microplankton. Net Ca2+, H+, K+ ion fluxes in the rainbow trout cell line RTgill-W1 were monitored before and after addition of lysed cells of this Paralytic Shellfish Toxins (PST) producer along with purified endocellular dinoflagellate PST. It was demonstrated that PST alone do not play a role in fish gill damage during A. catenella outbreaks as previously thought, but that other ichthyotoxic metabolites from lysed algal cells (i.e. lipid peroxidation products or other unknown metabolites) result in net K+ efflux from fish gill cells and thereby gill cell death.

    更新日期:2018-09-28
  • Effects of light intensity, temperature, and salinity on the growth and ingestion rates of the red-tide mixotrophic dinoflagellate Paragymnodinium shiwhaense
    Harmful Algae (IF 4.138) Pub Date : 2018-09-27
    Hae Jin Jeong, Kyung Ha Lee, Yeong Du Yoo, Nam Seon Kang, Jae Yoon Song, Tae Hoon Kim, Kyeong Ah Seong, Jae Seong Kim, Eric Potvin

    Among mixotrophic dinoflagellates, the maximum mixotrophic growth rate of the red-tide dinoflagellate Paragymnodinium shiwhaense is relatively high, whereas mortality due to predation is low. To investigate the effects of major environmental parameters on P. shiwhaense, growth and ingestion rates of one strain of P. shiwhaense on the algal prey species Amphidinium carterae (also a dinoflagellate) were determined under various light intensities (0–500 μE m−2s-1), water temperatures (5–30 °C), and salinities (5–40). Cells of P. shiwhaense did not grow well in darkness but grew well at light intensities ≥ 10 μE m−2s-1. There were no significant differences in either growth or ingestion rates of P. shiwhaense fed A. carterae at light intensities between 10 and 500 μE m−2s-1. Furthermore, P. shiwhaense did not grow at 5 °C or ≥ 28 °C. Its growth rates between 7 and 26 °C were significantly affected by temperature, and the optimal temperature for maximal growth was 25 °C. With increasing salinity from 5 to 20, the growth rate of P. shiwhaense fed A. carterae increased and became saturated at salinities between 20 and 40, while the ingestion rate at salinities between 10 and 40 did not significantly change. Thus, overall, the growth and ingestion rates of P. shiwhaense fed A. carterae were affected by temperature and salinity, but not by light intensity other than darkness. These findings provide a beginning basis for understanding the ecology of this potentially harmful algal species in marine coastal ecosystems.

    更新日期:2018-09-27
  • Economic and sociocultural impacts of fisheries closures in two fishing-dependent communities following the massive 2015 U.S. West Coast harmful algal bloom
    Harmful Algae (IF 4.138) Pub Date : 2018-09-27
    Jerilyn Ritzman, Amy Brodbeck, Sara Brostrom, Scott McGrew, Stacia Dreyer, Terrie Klinger, Stephanie K. Moore

    In the spring of 2015, a massive harmful algal bloom (HAB) of the toxin-producing diatom Pseudo-nitzschia occurred on the U.S. West Coast, resulting in the largest recorded outbreak of the toxin domoic acid and causing fisheries closures. Closures extended into 2016 and generated an economic shock for coastal fishing communities. This study examines the economic and sociocultural impacts of the Dungeness crab and razor clam fisheries closures on two fishing-dependent communities. Semi-structured interviews were conducted with 36 community members from two communities impacted by the event – Crescent City, California and Long Beach, Washington. Interviewees included those involved in the fishing, hospitality, and retail industries, local government officials, recreational harvesters, and others. Interviews probed aspects of resilience in economic, social, institutional, and physical domains, based on the contention that community resilience will influence the communities’ ability to withstand HAB events. Dimensions of vulnerability were also explored, encompassing sensitivity of the communities to HAB events and their adaptive capacity. Common themes that emerged from the interview responses indicate that economic hardships extended beyond fishing-related operations and permeated through other sectors, particularly the hospitality industry. Significant barriers to accessing financial and employment assistance during extended fisheries closures were identified, particularly for fishers. Long-held traditions surrounding crab and shellfish harvest and consumption were disrupted, threatening the cultural identities of the affected communities. Community members expressed a desire for clearer, more thorough, and more rapid dissemination of information regarding the management of fisheries closures and the health risks associated with HAB toxins. The likelihood of intensifying HABs under climate change heightens the need for actions to increase the resilience of fishing communities to the economic and sociocultural impacts caused by HAB-related fisheries closures.

    更新日期:2018-09-27
  • Can domoic acid affect escape response in copepods?
    Harmful Algae (IF 4.138) Pub Date : 2018-09-21
    Sara Harðardóttir, Bernd Krock, Sylke Wohlrab, Uwe John, Torkel Gissel Nielsen, Nina Lundholm

    Copepods are important grazers on toxic phytoplankton and serve as vectors for algal toxins up the marine food web. Success of phytoplankton depends among other factors on protection against grazers like copepods, and same way copepod survival and population resilience relies on their ability to escape predators. Little is, however, known about the effect of toxins on the escape response of copepods. In this study we experimentally tested the hypothesis that the neurotoxin domoic acid (DA) produced by the diatom Pseudo-nitzschia affects escape responses of planktonic copepods. We found that the arctic copepods Calanus hyperboreus and C. glacialis reduced their escape response after feeding on a DA-producing diatom. The two species were not affected the same way; C. hyperboreus was affected after shorter exposure and less intake of DA. The negative effect on escape response was not related to the amount of DA accumulated in the copepods. Our results suggest that further research on the effects of DA on copepod behavior and DA toxicity mechanisms is required to evaluate the anti-grazing function of DA.

    更新日期:2018-09-25
  • Diversity, distribution, and azaspiracids of Amphidomataceae (Dinophyceae) along the Norwegian coast
    Harmful Algae (IF 4.138) Pub Date : 2018-09-20
    Urban Tillmann, Bente Edvardsen, Bernd Krock, Kirsty F. Smith, Ruth F. Paterson, Daniela Voß

    Azaspiracids (AZA) are a group of lipophilic polyether compounds which have been implicated in shellfish poisoning incidents around Europe. They are produced by a few species of the dinophycean genera Azadinium and Amphidoma (Amphidomataceae). The presence of AZA toxins in Norway is well documented, but knowledge of the distribution and diversity of Azadinium and other Amphidomataceae along the Norwegian coast is rather limited and poorly documented. On a research survey along the Norwegian coast in 2015 from the Skagerrak in the South to Trondheimsfjorden in the North, plankton samples from 67 stations were analysed for the presence of Azadinium and Amphidoma and their respective AZA by on-board live microscopy, real-time PCR assays specific for Amphidomataceae, and liquid chromatography-tandem mass spectrometry (LC–MS/MS). Microscopy using live samples and positive real-time PCR assays using a general family probe and two species specific probes revealed the presence of Amphidomataceae distributed throughout the sampling area. Overall abundance was low, however, and was in agreement with a lack of detectable AZA in plankton samples. Single cell isolation and morphological and molecular characterisation of established strains revealed the presence of 7 amphidomatacean species (Azadiniun spinosum, Az. poporum, Az. obesum, Az. dalianense, Az. trinitatum, Az. polongum, Amphidoma languida) in the area. Azaspiracids were produced by the known AZA producing species Az. spinosum, Az. poporum and Am. languida only. LC–MS/MS analysis further revealed that Norwegian strains produce previously unreported AZA for Norway (AZA-11 by Az. spinosum, AZA-37 by Az. poporum, AZA-38 and AZA-39 by Am. languida), and also four novel compounds (AZA-50, -51 by Az. spinosum, AZA-52, -53 by Am. languida), whose structural properties are described and which now can be included in existing analytical protocols. A maximum likelihood analysis of concatenated rDNA regions (SSU, ITS1-ITS2, partial LSU) showed that the strains of Az. spinosum fell in two well supported clades, where most but not all new Norwegian strains formed the new Ribotype B. Ribotype differentiation was supported by a minor morphological difference with respect to the presence/absence of a rim around the pore plate, and was consistently reflected by different AZA profiles. Strains of Az. spinosum from ribotype A produce AZA-1, -2 and -33, whereas the new strains of ribotype B produce mainly AZA-11 and AZA-51. Significant sequence differences between both Az. spinosum ribotypes underline the need to redesign the currently used qPCR probes in order to detect all AZA producing Az. spinosum. The results generally underline the conclusion that for the Norwegian coast area it is important that amphidomatacean species are taken into account in future studies and monitoring programs.

    更新日期:2018-09-21
  • Insights into the dynamics of harmful algal blooms in a tropical estuary through an integrated hydrodynamic-Pyrodinium-shellfish model
    Harmful Algae (IF 4.138) Pub Date : 2018-09-07
    Aletta T. Yñiguez, Jennifer Maister, Cesar L. Villanoy, Josephine Dianne Deauna, Eileen Peñaflor, Aldwin Almo, Laura T. David, Garry A. Benico, Ellen Hibay, Irmi Mora, Sandra Arcamo, Jun Relox, Rhodora V. Azanza

    In contrast to temperate Harmful Algal Blooms (HABs), knowledge on the mechanisms driving tropical HABs are less well studied. The interaction of a seasonal temperature window, cysts (for certain species) and large-scale transport are some of the key processes in temperate HABs. In the Philippines, HABs occur not along long open coastlines, but in embayments that are highly influenced by run-off and stratification. These embayments are typically also the sites of cultured or wild harvest shellfish and other aquaculture activities. Sorsogon Bay in the northeastern Philippines has experienced prolonged shellfish-harvesting bans due to blooms by Pyrodinium bahamense var. compressum severely affecting the fisheries industry in this area, as well as leading to Paralytic Shellfish Poisoning illnesses and fatalities. A novel integrated model was developed that mechanistically captures the interactions between hydrodynamic conditions, nutrients, the life history (cells and cysts) of Pyrodinium, as well as the cultured shellfish within the bay and their ensuing toxicities due to ingestion of toxic Pyrodinium cells and cysts. This is the second model developed for HABs in the Philippines, and the first to integrate different components of Pyrodinium bloom dynamics. The model is modularly composed of a watershed nutrient and diffusion model, a 3D hydrodynamic model, a Pyrodinium population model and a shellfish toxin model. It was able to capture the observed temporal variations of Pyrodinium and shellfish toxicity. It was also able to represent some aspects of the spatial distribution in Sorsogon Bay though there were discrepancies. To explore the dynamics of blooms, the linkages between the bloom and decline of the Pyrodinium population with shellfish toxicity as affected by temperature, salinity and nutrients were investigated. Comparisons with field results showed the seasonality of blooms in Sorsogon Bay is driven by increased rainfall. The timing of these conditions is important in facilitating Pyrodinium excystment and reproduction. Model results showed as well the potential significance of shellfish grazing and dinoflagellate cell mortality in influencing the decline of the bloom, and toxicity levels. This approach is promising in helping to understand mechanisms for HABs more holistically, and the model can be further improved to provide more precise quantitative information.

    更新日期:2018-09-09
  • Repeated low level domoic acid exposure increases CA1 VGluT1 levels, but not bouton density, VGluT2 or VGAT levels in the hippocampus of adult mice
    Harmful Algae (IF 4.138) Pub Date : 2018-09-05
    Caitlin E. Moyer, Emma M. Hiolski, David J. Marcinek, Kathi A. Lefebvre, Donald R. Smith, Yi Zuo

    Domoic acid (DA) is a neurotoxin produced during harmful algal blooms that accumulates in marine organisms that serve as food resources for humans. While acute DA neurotoxicity can cause seizures and hippocampal lesions, less is known regarding how chronic, subacute DA exposure in adulthood impacts the hippocampus. With more frequent occurrences of harmful algal blooms, it is important to understand the potential impact of repeated, low-level DA exposure on human health. To model repeated, low-dose DA exposure, adult mice received a single low-dose (0.75 ± 0.05 μg/g) of DA or vehicle weekly for 22 consecutive weeks. Quantitative immunohistochemistry was performed to assess the effects of repeated, low-level DA exposure on hippocampal cells and synapses. Vesicular glutamate transporter 1 (VGluT1) immunoreactivity within excitatory boutons in CA1 of DA-exposed mice was increased. Levels of other vesicular transporter proteins (i.e., VGluT2 and the vesicular GABA transporter (VGAT)) within boutons, and corresponding bouton densities, were not significantly altered in CA1, CA3, or dentate gyrus. There were no significant changes in neuron density or glial fibrillary acidic protein (GFAP) immunoreactivity following chronic, low-dose exposure. This suggests that repeated low doses of DA, unlike high doses of DA, do not cause neuronal loss or astrocyte activation in hippocampus in adult mice. Instead, these findings demonstrate that repeated exposure to low levels of DA leads to subtle changes in VGluT1 expression within CA1 excitatory boutons, which may alter glutamatergic transmission in CA1 and disrupt behaviors dependent on spatial memory.

    更新日期:2018-09-05
  • Diversity and toxicity of Pseudo-nitzschia species in Monterey Bay: Perspectives from targeted and adaptive sampling
    Harmful Algae (IF 4.138) Pub Date : 2018-08-31
    Holly A. Bowers, John P. Ryan, Kendra Hayashi, April L. Woods, Roman Marin, G. Jason Smith, Katherine A. Hubbard, Gregory J. Doucette, Christina M. Mikulski, Alyssa G. Gellene, Yanwu Zhang, Raphael M. Kudela, David A. Caron, James M. Birch, Christopher A. Scholin

    Monterey Bay, California experiences near-annual blooms of Pseudo-nitzschia that can affect marine animal health and the economy, including impacts to tourism and commercial/recreational fisheries. One species in particular, P. australis, has been implicated in the most toxic of events, however other species within the genus can contribute to widespread variability in community structure and associated toxicity across years. Current monitoring methods are limited in their spatial coverage as well as their ability to capture the full suite of species present, thereby hindering understanding of HAB events and limiting predictive accuracy. An integrated deployment of multiple in situ platforms, some with autonomous adaptive sampling capabilities, occurred during two divergent bloom years in the bay, and uncovered detailed aspects of population and toxicity dynamics. A bloom in 2013 was characterized by spatial differences in Pseudo-nitzschia populations, with the low-toxin producer P. fraudulenta dominating the inshore community and toxic P. australis dominating the offshore community. An exceptionally toxic bloom in 2015 developed as a diverse Pseudo-nitzschia community abruptly transitioned into a bloom of highly toxic P. australis within the time frame of a week. Increases in cell density and proliferation coincided with strong upwelling of nutrients. High toxicity was driven by silicate limitation of the dense bloom. This temporal shift in species composition mirrored the shift observed further north in the California Current System off Oregon and Washington. The broad scope of sampling and unique platform capabilities employed during these studies revealed important patterns in bloom formation and persistence for Pseudo-nitzschia. Results underscore the benefit of expanded biological observing capabilities and targeted sampling methods to capture more comprehensive spatial and temporal scales for studying and predicting future events.

    更新日期:2018-09-03
  • Environmental factors influencing the quantitative distribution of microcystin and common potentially toxigenic cyanobacteria in U.S. lakes and reservoirs
    Harmful Algae (IF 4.138) Pub Date : 2018-08-25
    John R. Beaver, Claudia E. Tausz, Kyle C. Scotese, Amina I. Pollard, Richard M. Mitchell

    Many species of cyanobacteria are capable of producing toxins and causing nuisance blooms, however response to environmental conditions is likely taxon-specific. Environmental factors influencing cyanobacterial composition and toxin production in lakes have been examined in many studies; yet are often confined to individual water bodies, or to a small number of systems within the same region. Here, data from the 2012 USEPA National Lakes Assessment are used to examine relationships between biovolume of common potentially-toxigenic cyanobacteria (Aphanizomenon spp., Cylindrospermopsis spp., Dolichospermum spp., Microcystis spp. and Planktothrix spp.) and environmental variables across the entire conterminous United States, and results are compared across nine distinct ecoregions. Total phosphorus and water clarity were identified as the most influential environmental factors correlated with phytoplankton community composition. The Northern, Southern and Temperate Plains ecoregions displayed the highest biovolumes of potentially toxigenic taxa on average, as well as highest mean concentrations of microcystin. In those three ecoregions, samples with microcystin concentrations greater than 1 ppb were primarily dominated by Planktothrix spp. while in all other ecoregions Dolichospermum spp. was the dominant genus. Canonical Correlation Analysis revealed a strong association between high microcystin concentrations and high nutrient concentrations (total nitrogen and total phosphorus), and between high microcystin concentrations and low percentage of watershed forest cover. Results from this study indicate that the likely occurrence of potentially toxigenic taxa in lakes and reservoirs is predictable on a biogeographical basis, depending on morphological and water quality characteristics. Data from this study may be useful to regional managers attempting to prevent or mitigate nuisance cyanobacterial blooms.

    更新日期:2018-08-26
  • Differential feeding by common heterotrophic protists on 12 different Alexandrium species
    Harmful Algae (IF 4.138) Pub Date : 2018-08-23
    Hee Chang Kang, Hae Jin Jeong, Kim So Jin, Ji Hyun You, Jin Hee Ok

    The genus Alexandrium often forms harmful algal blooms causing human illness and large-scale mortality of fish and shellfish. Thus, Alexandrium bloom dynamics are primary concerns for scientists, government officials, aquaculture farmers, and the public. To understand bloom dynamics, mortality due to predation needs to be assessed; however, interactions between many Alexandrium species and their potential predators have not previously been reported. Thus, feeding by five common heterotrophic dinoflagellates (Oxyrrhis marina, Gyrodinium dominans, Polykrikos kofoidii, Pfiesteria piscicida, and Oblea rotunda) and a naked ciliate (Strombidinopsis sp.) on 12 Alexandrium species was examined. Furthermore, the growth and ingestion rates of P. kofoidii on A. minutum CCMP 1888 (previously A. lusitanicum), A. minutum CCMP 113, and A. tamarense were measured as a function of prey concentration. The growth rates of P. kofoidii on the other Alexandrium species at single high prey concentrations were measured, at which the growth rates on A. minutum CCMP 1888 and A. tamarense were saturated. Feeding occurrence by these predators on 12 Alexandrium species could be categorized into 6 different prey groups. Each Alexandrium species was consumed by at least one predator; however, there was no Alexandrium species that was eaten by all six predators. Cells of A. minutum CCMP 1888, A. minutum CCMP 113, and A. tamarense were fed upon by four predators, but A. affine and A. pacificum by only one predator species, P. kofoidii or Strombidinopsis sp. Furthermore, A. minutum CCMP 1888 and A. tamarense supported high growth rates of P. kofoidii, but the other Alexandrium species did not support, but rather inhibited P. kofoidii growth. With increasing prey concentrations, the growth and ingestion rates of P. kofoidii on A. minutum CCMP 1888 and A. tamarense increased and became saturated, whereas those on A. minutum CCMP 113 continuously decreased. The maximum growth rates of P. kofoidii on A. tamarense and A. minutum CCMP 1888 were 1.010 and 0.765 d−1, respectively, and P. kofoidii maximum ingestion rates were 26.2 and 11.1 ng C predator−1d−1, respectively. In contrast, the growth rates of P. kofoidii on the other Alexandrium species at single high prey concentrations were almost zero (A. pacificum) or negative. Based on the feeding occurrence and growth and ingestion rates of predators on 12 Alexandrium species, it is suggested that common heterotrophic protistan predators respond differently to different Alexandrium species, and thus ecological niches of the Alexandrium species may be different from each other. These results may provide an insight into the roles of protistan predators in bloom dynamics of Alexandrium species.

    更新日期:2018-08-23
  • Effect of ciliate strain, size, and nutritional content on the growth and toxicity of mixotrophic Dinophysis acuminata
    Harmful Algae (IF 4.138) Pub Date : 2018-08-18
    Juliette L. Smith, Mengmeng Tong, David Kulis, Donald M. Anderson

    Previous studies indicate differences in bloom magnitude and toxicity between regional populations, and more recently, between geographical isolates of Dinophysis acuminata; however, the factors driving differences in toxicity/toxigenicity between regions/strains have not yet been fully elucidated. Here, the roles of prey strains (i.e., geographical isolates) and their associated attributes (i.e., biovolume and nutritional content) were investigated in the context of growth and production of toxins as a possible explanation for regional variation in toxicity of D. acuminata. The mixotrophic dinoflagellate, D. acuminata, isolated from NE North America (MA, U.S.) was offered a matrix of prey lines in a full factorial design, 1 × 2 × 3; one dinoflagellate strain was fed one of two ciliates, Mesodinium rubrum, isolated from coastal regions of Japan or Spain, which were grown on one of three cryptophytes (Teleaulax/Geminigera clade) isolated from Japan, Spain, or the northeastern USA. Additionally, predator: prey ratios were manipulated to explore effects of the prey’s total biovolume on Dinophysis growth or toxin production. These studies revealed that the biovolume and nutritional status of the two ciliates, and less so the cryptophytes, impacted the growth, ingestion rate, and maximum biomass of D. acuminata. The predator’s consumption of the larger, more nutritious prey resulted in an elevated growth rate, greater biomass, and increased toxin quotas and total toxin per mL of culture. Grazing on the smaller, less nutritious prey, led to fewer cells in the culture but relatively more toxin exuded from the cells on per cell basis. Once the predator: prey ratios were altered so that an equal biovolume of each ciliate was delivered, the effect of ciliate size was lost, suggesting the predator can compensate for reduced nutrition in the smaller prey item by increasing grazing. While significant ciliate-induced effects were observed on growth and toxin metrics, no major shifts in toxin profile or intracellular toxin quotas were observed that could explain the large regional variations observed between geographical populations of this species.

    更新日期:2018-08-18
  • Genetic evidence in tracking the origin of Ulva prolifera blooms in the Yellow Sea, China
    Harmful Algae (IF 4.138) Pub Date : 2018-08-15
    Qing-Chun Zhang, Ren-Cheng Yu, Zhen-Fan Chen, Li-Mei Qiu, Yun-Feng Wang, Fan-Zhou Kong, Hui-Xia Geng, Yue Zhao, Peng Jiang, Tian Yan, Ming-Jiang Zhou

    Recurrent green tides have been recorded in the Yellow Sea for 11 consecutive years. The origin of floating green algae in the Yellow Sea, however, remains a subject of debate. Previous studies suggest that the major bloom-forming green alga Ulva prolifera represent a unique ecotype different from other attached populations of U. prolifera in China. In this study, 97 green algal samples collected during the 2012 green-tide event and from other locations along the coastline of China were analyzed. Based on the sequences of nuclear ribosomal RNA gene (rDNA) internal transcribed spacer (ITS) region and 5S rDNA spacer region, the green alga U. prolifera in the samples were identified. The intraspecific genetic diversity within U. prolifera was then examined using sequences of 5S rDNA spacer and a marker of sequence characterized amplified region (SCAR) highly specific for bloom-forming U. prolifera in the Yellow Sea. The screening results for SCAR marker demonstrated that U. prolifera attached to aquaculture rafts in Subei Shoal belong to the same ecotype of the bloom-forming U. prolifera in the Yellow Sea. These findings offer genetic evidence that aquaculture rafts in Subei Shoal are a major source of floating green algae in the Yellow Sea.

    更新日期:2018-08-15
  • Sympatric occurrence of two Azadinium poporum ribotypes in the Eastern Mediterranean Sea
    Harmful Algae (IF 4.138) Pub Date : 2018-08-14
    Zhaohe Luo, Bernd Krock, Antonia Giannakourou, Amalia Venetsanopoulou, Kalliopi Pagou, Urban Tillmann, Haifeng Gu

    The marine dinoflagellate Azadinium poporum produce azaspiracids (AZA) and has been recorded widely in the world. However, information on its biogeography is still limited, especially in view of the fact that A. poporum comprises several genetically differentiated groups. A total of 18 strains of A. poporum were obtained from the Eastern Mediterranean area by incubating surface sediment collected from Ionian Sea of Greece. The morphology of these strains was examined with light microscopy and scanning electron microscopy. Small subunit ribosomal DNA (SSU rDNA), large subunit ribosomal DNA (LSU rDNA) and internal transcribed spacer (ITS) sequences were obtained from all cultured strains. Molecular phylogeny based on concatenated SSU, LSU and ITS sequences confirmed three ribotypes within A. poporum and revealed two subclades within ribotypes A and C. Greek strains of A. poporum ribotype A were nested within ribotype A2 together with strains from Western Mediterranean Sea and French Atlantic, and Greek strains of A. poporum ribotype C were nested within ribotype C2 together with a strain from the Gulf of Mexico. Growth experiments on four selected strains revealed that ribotypes A and C from Greece differed in their growth at higher temperatures, indicating that they are physiologically differentiated. Azaspiracid profiles were analyzed for 15 cultured A. poporum strains using LCMS/MS and demonstrate that the A. poporum ribotype A from Greece produce low level or no AZA and A. poporum ribotype C from Greece produces predominantly AZA-40 (9.6–30.2 fg cell−1) followed by AZA-2 (2.1–2.6 fg cell−1). The first record of AZA-40 producing A. poporum from the Mediterranean suggests that this species is a potential source for azaspiracid contaminations in shellfish from the Eastern Mediterranean Sea.

    更新日期:2018-08-15
  • Insights into cyanophage-mediated dynamics of nodularin and other non-ribosomal peptides in Nodularia spumigena
    Harmful Algae (IF 4.138) Pub Date : 2018-08-14
    Sigitas Šulčius, Hanna Mazur-Marzec, Irma Vitonytė, Kotryna Kvederavičiūtė, Jolita Kuznecova, Eugenijus Šimoliūnas, Karin Holmfeldt

    The effect of cyanophage infection and lysis on the dynamics of the hepatotoxin nodularin (NOD) and other non-ribosomal peptides (NRPs) produced by cyanobacteria is poorly understood. In this study, changes in concentration of NOD and other NRPs during cyanophage infection of the filamentous cyanobacteria Nodularia spumigena were assessed using incubation experiments. Viral infection and lysis were associated with a significant reduction (93% at the 96 h post infection) of N. spumigena cell density. While no correlation between N. spumigena abundance and total concentration of NOD (ng mL−1) within the infected cells was observed, cellular NOD quota (ng cell−1) gradually increased in the remaining cyanophage resistant N. spumigena subpopulation. Lysis of N. spumigena cells resulted in a substantial increase (>57 times) of dissolved NOD concentration in the culture medium. The relative concentration of other cyclic (anabaenopeptins) and linear (aeruginosins, spumigins) NRPs produced by N. spumigena also increased in response to cyanophage addition. This study highlights the importance of cyanophage infection on the population toxicity of filamentous cyanobacteria and demonstrates a significant contribution of virus-mediated cell lysis on the conversion of NOD from the particulate to dissolved phase.

    更新日期:2018-08-14
  • Habitat complexity affects benthic harmful dinoflagellate assemblages in the fringing reef of Rawa Island, Malaysia
    Harmful Algae (IF 4.138) Pub Date : 2018-08-10
    Hwa Lin Yong, Nurin Izzati Mustapa, Li Keat Lee, Zhen Fei Lim, Toh Hii Tan, Gires Usup, Haifeng Gu, R. Wayne Litaker, Patricia A. Tester, Po Teen Lim, Chui Pin Leaw

    Few studies have investigated the effect of fine-scale habitat differences on the dynamics of benthic harmful dinoflagellate assemblages. To determine how these microhabitat differences affect the distribution and abundance of the major benthic harmful dinoflagellate genera in a tropical coral reef ecosystem, a field study was undertaken between April–September 2015 and January 2016 on the shallow reef flat of the fringing reef of Rawa Island, Terengganu, Malaysia. Sampling of benthic dinoflagellates was carried out using an artificial substrate sampling method (fiberglass screens). Benthic microhabitats surrounding the sampling screens were characterized simultaneously from photographs of a 0.25-m2 quadrat based on categories of bottom substrate types. Five taxonomic groups of benthic dinoflagellates, Ostreopsis, Gambierdiscus, Prorocentrum, Amphidinium, and Coolia were identified, and cells were enumerated using a light microscope. The results showed Gambierdiscus was less abundant than other genera throughout the study period, with maximum abundance of 1.2 × 103 cells 100 cm−2. While most taxa were present on reefs with high coral cover, higher cell abundances were observed in reefs with high turf algal cover and coral rubble, with the exception of Ostreopsis, where the abundance reached a maximum of 3.4 × 104 cells 100 cm−2 in habitats with high coral cover. Microhabitat heterogeneity was identified as a key factor governing the benthic harmful dinoflagellate assemblages and may account for much of the observed variability in dominant taxa. This finding has significant implications for the role of variability in the benthic harmful algal bloom (BHAB) outbreaks and the potential in identifying BHAB-related toxin transfer pathways and the key vectors in the food webs.

    更新日期:2018-08-10
  • Microcystin interferes with defense against high oxidative stress in harmful cyanobacteria
    Harmful Algae (IF 4.138) Pub Date : 2018-08-10
    J. Merijn Schuurmans, Bregje W. Brinkmann, A. Katharina Makower, Elke Dittmann, Jef Huisman, Hans C.P. Matthijs

    Harmful cyanobacteria producing toxic microcystins are a major concern in water quality management. In recent years, hydrogen peroxide (H2O2) has been successfully applied to suppress cyanobacterial blooms in lakes. Physiological studies, however, indicate that microcystin protects cyanobacteria against oxidative stress, suggesting that H2O2 addition might provide a selective advantage for microcystin-producing (toxic) strains. This study compares the response of a toxic Microcystis strain, its non-toxic mutant, and a naturally non-toxic Microcystis strain to H2O2 addition representative of lake treatments. All three strains initially ceased growth upon H2O2 addition. Contrary to expectation, the non-toxic strain and non-toxic mutant rapidly degraded the added H2O2 and subsequently recovered, whereas the toxic strain did not degrade H2O2 and did not recover. Experimental catalase addition enabled recovery of the toxic strain, demonstrating that rapid H2O2 degradation is indeed essential for cyanobacterial survival. Interestingly, prior to H2O2 addition, gene expression of a thioredoxin and peroxiredoxin was much lower in the toxic strain than in its non-toxic mutant. Thioredoxin and peroxiredoxin are both involved in H2O2 degradation, and microcystin may potentially suppress their activity. These results show that microcystin-producing strains are less prepared for high levels of oxidative stress, and are therefore hit harder by H2O2 addition than non-toxic strains.

    更新日期:2018-08-10
  • A decade and a half of Pseudo-nitzschia spp. and domoic acid along the coast of southern California
    Harmful Algae (IF 4.138) Pub Date : 2018-08-10
    Jayme Smith, Paige Connell, Richard H. Evans, Alyssa G. Gellene, Meredith D.A. Howard, Burton H. Jones, Susan Kaveggia, Lauren Palmer, Astrid Schnetzer, Bridget N. Seegers, Erica L. Seubert, Avery O. Tatters, David A. Caron

    Blooms of the marine diatom genus Pseudo-nitzschia that produce the neurotoxin domoic acid have been documented with regularity along the coast of southern California since 2003, with the occurrence of the toxin in shellfish tissue predating information on domoic acid in the particulate fraction in this region. Domoic acid concentrations in the phytoplankton inhabiting waters off southern California during 2003, 2006, 2007, 2011 and 2017 were comparable to some of the highest values that have been recorded in the literature. Blooms of Pseudo-nitzschia have exhibited strong seasonality, with toxin appearing predominantly in the spring. Year-to-year variability of particulate toxin has been considerable, and observations during 2003, 2006, 2007, 2011 and again in 2017 linked domoic acid in the diets of marine mammals and seabirds to mass mortality events among these animals. This work reviews information collected during the past 15 years documenting the phenology and magnitude of Pseudo-nitzschia abundances and domoic acid within the Southern California Bight. The general oceanographic factors leading to blooms of Pseudo-nitzschia and outbreaks of domoic acid in this region are clear, but subtle factors controlling spatial and interannual variability in bloom magnitude and toxin production remain elusive.

    更新日期:2018-08-10
  • The impact of short-term depositions of macroalgal blooms on widgeon-grass meadows in a river-dominated estuary
    Harmful Algae (IF 4.138) Pub Date : 2018-07-27
    Marianna Lanari, Margareth S. Copertino, Leonir A. Colling, Fábio C. Bom

    Macroalgal blooms can trigger adverse biogeochemical conditions at the sediment-water interface of shallow coastal areas, hence threatening critical habitats such as seagrasses meadows. The direction and magnitude of macroalgal blooms impacts on the aquatic ecosystem can be context-dependent, varying according to the local hydrodynamic conditions. Thus, studies investigating the impacts of stagnant algal depositions on the benthos may fail to address realistic situations and interactions which are common in well-flushed systems. This is especially true for the South America coast, where no study has investigated the effects of macroalgal blooms on seagrasses meadows. To fully understand the impacts of macroalgal blooms on sediment biogeochemistry and seagrass habitats across distinct environmental conditions and biogeographical regions, two independent, complementary field experiments replicated the natural temporal patterns of drift macroalgal mats depositions on unvegetated and vegetated (Ruppia maritima meadows) shoals of the Patos Lagoon estuary (PLE), a subtropical, high hydrodynamic system in southern Brazil. Transitory depositions of algal mats alleviated deleterious biogeochemical conditions in the sediment-water interface of unvegetated bottoms. Nevertheless, these unstable algal depositions promoted significant reductions in R. maritima biomass, by reducing their shoot height and density, and rhizome length. That plant biomass reductions were followed by a decrease in the abundance of the dominant infaunal tanaidacean Monokalliapseudes schubarti, indicating that algal impacts on seagrasses were transferred to higher trophic levels. Our results suggest that, although unstable deposition of drift algal mats can attenuate potential adverse impacts at the sediment-water interface, the physical stress during mats advection can still trigger small seagrass losses. This process may diminish the resilience of R. maritima meadows in the PLE, with impacts on estuarine nutrient cycling and secondary production. We conclude that, although harmful drift macroalgal blooms area global phenomenon, the mechanisms through which macroalgae impair seagrass habitats may vary according to the environmental context. Therefore, further studies are necessary to identify the underlying mechanisms of drift macroalgae-seagrass-macrofauna interactions in high hydrodynamic systems and their generality across distinct biogeographical areas.

    更新日期:2018-07-28
  • Seawater nitrogen concentration and light independently alter performance, growth, and resource allocation in the bloom-forming seaweeds Ulva lactuca and Ulvaria obscura (Chlorophyta)
    Harmful Algae (IF 4.138) Pub Date : 2018-07-24
    Kathryn L. Van Alstyne

    Ulva lactuca and Ulvaria obscura are seaweeds that form green tides on Salish Sea shores. They have similar macroscopic morphologies but differ in their biochemistries and physiological responses. To understand how they are affected by changes in environmental conditions, a factorial experiment was conducted in which algae were grown in artificial seawater with either low (10 μM) or high (160 μM) nitrate (NO3−) concentrations at high (29 mol photons·m−2.day−1) and low (4 mol photons·m−2.day−1) light levels. Light and NO3− affected algal responses, but always independently. After two weeks, U. lactuca grown in high light were larger, had lower maximum quantum yields (MQYs), and lower nitrogen (N), carbon (C), pigment, and dimethylsulfoniopropionate (DMSP) concentrations, respectively, relative to algae in low light. In contrast, U. obscura growth was unaffected by light. Like U. lactuca, U. obscura grown in high light had lower MQYs, and N, pigment, and DMSP concentrations. In high light, U. obscura also had 89% higher dopamine concentrations and a tendency to fragment. Both U. lactuca and U. obscura grown in 160 μM NO3− were larger, had higher MQYs, and higher N, pigment, and DMSP concentrations, respectively, than algae in 10 μM NO3−. Also, when U. obscura was grown in the 160 μM NO3− medium, it significantly increased its surface area/mass ratio. Although both species grew faster in high NO3−, high light only promoted the growth of Ulva, which may explain the dominance of Ulva in summer months. High light was physiologically stressful to both species and caused increases in photoprotective mechanisms, such as the production of dopamine, a melanin precursor, in Ulvaria, and DMSP lysis in Ulva to generate antioxidants. Growing in 10 μM NO3- produced responses that were consistent with nitrogen limitation and had greater impacts on Ulvaria than Ulva, suggesting that Ulvaria responds more strongly to eutrophication.

    更新日期:2018-07-24
  • Overvalued allelopathy and overlooked effects of humic acid-like substances on Microcystis aeruginosa and Scenedesmus obliquus competition
    Harmful Algae (IF 4.138) Pub Date : 2018-07-21
    Miaomiao Zhao, Xinyi Chen, Ning Ma, Qiuyue Zhang, Dong Qu, Ming Li

    To form Microcystis blooms, Microcystis must be competitively dominant to other phytoplankton species to produce enough biomass. The aim of this study was to determine the competition mechanisms between Microcystis aeruginosa and Scenedesmus obliquus. M. aeruginosa and S. obliquus were separately cultured in the filtrate of mono and mixed cultures of M. aeruginosa and S. obliquus with varying treatments concerning N, P and iron availability. The inhibition rate for M. aeruginosa was 20–31% when cultured in mono and mixed culture filtrates enriched with N and P, but this rate was reduced to −15 to 19% when cultured in filtrates enriched with N, P and iron. The inhibition rate for M. aeruginosa decreased from 80 to 100% to 11–39% in dialytic filtrates. However, there were no differences in inhibition rate for S. obliquus, regardless of filtrate or dialytic filtrate treatments. The potential allelochemical, 2-butyl-octanol (0.144 mg L−1), was found to have little inhibitory effect to M. aeruginosa or S. obliquus. Thus, previously reported allelopathy to Microcystis would be overestimated. We also report a new mechanism in phytoplankton competition in this study. The phytoplankton secreted humic acid-like substances that can reduce the bioavailability of iron, resulting in the inhibition of other phytoplankton.

    更新日期:2018-07-23
  • Effects of salinity variation on growth and yessotoxin composition in the marine dinoflagellate Lingulodinium polyedra from a Skagerrak fjord system (western Sweden)
    Harmful Algae (IF 4.138) Pub Date : 2018-07-17
    Carolin Peter, Bernd Krock, Allan Cembella

    The marine dinoflagellate Lingulodinium polyedra is a toxigenic species capable of forming high magnitude and occasionally harmful algal blooms (HABs), particularly in temperate coastal waters throughout the world. Three cultured isolates of L. polyedra from a fjord system on the Skagerrak coast of Sweden were analyzed for their growth characteristics and to determine the effects of a strong salinity gradient on toxin cell quotas and composition. The cell quota of yessotoxin (YTX) analogs, as determined by liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS), ranged widely among strains. For two strains, the total toxin content remained constant over time in culture, but for the third strain, the YTX cell quota significantly decreased (by 32%) during stationary growth phase. The toxin profiles of the three strains differed markedly and none produced YTX. The analog 41a-homo-YTX (m/z 1155), its putative methylated derivative 9-Me-41a-homo-YTX (m/z 1169) and an unspecified keto-YTX (m/z 1047) were detected in strain LP29-10H, whereas strain LP30-7B contained nor-YTX (m/z 1101), and two unspecified YTX analogs at m/z 1159 and m/z 1061. The toxin profile of strain LP30-8D comprised two unspecified YTX analogs at m/z 1061 and m/z 991 and carboxy-YTX (m/z 1173). Strain LP30-7B cultured at multiple salinities (10, 16, 22, 28 and 34) did not tolerate the lowest salinity (10), but there was a statistically significant decrease (by 21%) in toxin cell quota between growth at the highest versus lower permissible salinities. The toxin profile for strain LP30-7B remained constant over time for a given salinity. At lower salinities, however, the proportion of the unspecified YTX analog (m/z 1061) was significantly higher, especially with respect to nor-YTX (m/z 1101). This study shows high intra-specific variability in yessotoxin composition among strains from the same geographical region and inconsistency in toxin cell quota under different environmental regimes and growth stages in culture. This variation has important implications for the kinetics of YTX production and food web transfer in natural bloom populations from diverse geographical regions.

    更新日期:2018-07-18
  • The toxic benthic dinoflagellate Prorocentrum maculosum Faust is a synonym of Prorocentrum hoffmannianum Faust
    Harmful Algae (IF 4.138) Pub Date : 2018-07-11
    Francisco Rodríguez, Pilar Riobó, Guillermo D. Crespín, Antonio H. Daranas, Caterina R. de Vera, Manuel Norte, José Javier Fernández, Santiago Fraga

    Three strains of the toxic benthic dinoflagellate Prorocentrum hoffmannianum were isolated in the Canary Islands (north-east Atlantic Ocean, Spain). The identity of the strains was determined by phylogenetic analyses of partial LSU rDNA (D1-D2 regions) but their morphology based on SEM images corresponded to P. maculosum. Their toxin profiles were analyzed by liquid chromatography and high resolution mass spectrometry analysis (LC–HRMS) on cell extracts and culture media. Okadaic acid and three analogs were detected in all strains. Rather, in culture media the detected compounds were variable among strains, two of them being okadaic acid analogs not found on cell extracts. As a result, the taxonomy of the species was revised and P. maculosum is proposed as a junior synonym of P. hoffmannianum whose description is emended.

    更新日期:2018-07-12
  • Domoic acid in California sea lion fetal fluids indicates continuous exposure to a neuroteratogen poses risks to mammals
    Harmful Algae (IF 4.138) Pub Date : 2018-07-07
    Kathi A. Lefebvre, Alicia Hendrix, Barbie Halaska, Padraig Duignan, Sara Shum, Nina Isoherranen, David J. Marcinek, Frances M.D. Gulland

    Domoic acid (DA) is a neuroexcitotoxic amino acid that is naturally produced by some species of marine diatoms during harmful algal blooms (HABs). The toxin is transferred through the food web from plantivorous fish and shellfish to marine mammals resulting in significant morbidity and mortality. Due to the timing and location of DA producing HABs, it is well documented that pregnant female California sea lions (CSL) are regularly exposed to DA through their diet thereby posing exposure risks to a neuroteratogen in developing fetuses. In the present study, fluids from 36 fetuses sampled from naturally exposed pregnant CSLs were examined for DA. Domoic acid was detected in 79% of amniotic fluid (n = 24), 67% of allantoic fluid (n = 9), 75% of urine (n = 4), 41% of meconium (n = 17) and 29% of stomach content (n = 21) samples opportunistically collected from CSL fetuses. The distribution of DA in fetal samples indicates an increased prenatal exposure risk due to recirculation of DA in fetal fluids and continuous exposure to the developing brain.

    更新日期:2018-07-12
  • The polychaete, Paraprionospio pinnata, is a likely vector of domoic acid to the benthic food web in the northern Gulf of Mexico
    Harmful Algae (IF 4.138) Pub Date : 2018-07-04
    Melissa M. Baustian, Sibel Bargu, Wendy Morrison, Chelsea Sexton, Nancy N. Rabalais

    A somewhat disparate, yet temporally cohesive, set of phytoplankton abundance, microphytobenthos, including the diatom Pseudo-nitzschia, benthic infauna, and sediment toxin data were used to develop a theory for the transfer of domoic acid (DA) from the toxic diatom to the benthos in the highly productive waters of the northern Gulf of Mexico near the Mississippi River plume. Archived samples and new data were used to test the theory that DA is likely to be incorporated into benthic consumers. High spring abundances of potentially toxic Pseudo-nitzschia diatoms were simultaneously present in the surface waters, bottom waters and on the seafloor. Examination of the gut contents of a typical deposit-feeding and suspension-feeding polychaete, Paraprionospio pinnata, during similar periods of high Pseudo-nitzschia abundance in surface water indicated consumption of the diatoms. Demersal fishes, particularly Atlantic croaker, are known to consume these polychaetes, with a potential for transfer of DA to even higher trophic levels. These findings warrant a theory to be tested with further studies about the trophic linkage of a phytoplankton toxin into the benthic food web.

    更新日期:2018-07-12
  • Induction of domoic acid production in diatoms—Types of grazers and diatoms are important
    Harmful Algae (IF 4.138) Pub Date : 2018-07-02
    Nina Lundholm, Bernd Krock, Uwe John, Jette Skov, Jinfeng Cheng, Marina Pančić, Sylke Wohlrab, Kristie Rigby, Torkel Gissel Nielsen, Erik Selander, Sara Harðardóttir

    Grazers can induce toxin (domoic acid, DA) production in diatoms. The toxic response has been observed in two species of Pseudo-nitzschia and was induced by Calanus copepods. In this study, interactions between diatoms and copepods were further explored using different species of diatoms and copepods. All herbivorous copepods induced toxin production, whereas exposure to carnivorous copepods did not. In line with this, increasing the number of herbivorous copepods resulted in even higher toxin production. The induced response is thus only elicited by copepods that pose a real threat to the responding cells, which supports that the induced toxin production in diatoms evolved as an inducible defense. The cellular toxin content in Pseudo-nitzschia was positively correlated to the concentration of a group of specific polar lipids called copepodamides that are excreted by the copepods. This suggests that copepodamides are the chemical cues responsible for triggering the toxin production. Carnivorous copepods were found to produce less or no copepodamides. Among the diatoms exposed to grazing herbivorous copepods, only two of six species of Pseudo-nitzschia and none of the Nitzschia or Fragilariopsis strains responded by producing DA, indicating that not all Pseudo-nitzschia species/strains are able to produce DA, and that different diatom species might have different strategies for coping with grazing pressure. Growth rate was negatively correlated to cellular domoic acid content indicating an allocation cost associated with toxin production. Long-term grazing experiments showed higher mortality rates of grazers fed toxic diatoms, supporting the hypothesis that DA production is an induced defense mechanism.

    更新日期:2018-07-12
  • The Yellow Sea green tide: A risk of macroalgae invasion
    Harmful Algae (IF 4.138) Pub Date : 2018-06-02
    Jin Zhao, Peng Jiang, Ri Qiu, Yingying Ma, Chunhui Wu, Huihui Fu, Huaxin Chen, Fuchao Li

    Large scale green tides have bloomed successively in the Yellow Sea since 2007. The floating ecotype of Ulva prolifera, which is responsible for the environmental disaster, drifted a long distance during the blooming time and was exotic to the coastal area. The Yellow Sea green tide can be a potential source to incur bio-invasion. In this study, the distribution pattern and propagule pressure of the floating ecotype was investigated along the Qingdao coastline, which was seriously impacted by the green tide. Two out of 661 attached Ulva specimens collected in different seasons were identified as the floating ecotype by molecular markers, indicating that a few individuals of the floating ecotype had settled down, and their attached population could have spontaneously established. In seawater and sediments, the proportion of the floating ecotype in Ulva propagules reached up to 32% and 69% respectively when the floating algae was accumulating on seashore, which was a great propagule pressure to the local ecosystem. Results of the field test indicated that the available resources and the competition between the floating ecotype and the local Ulva species might be the main restrictions for settlement. Though the current scale of the established population is still small, the risk of biological invasion by the floating ecotype exists and it deserves more attention.

    更新日期:2018-07-12
  • Variability and profiles of lipophilic toxins in bivalves from Great Britain during five and a half years of monitoring: Okadaic acid, dinophysis toxins and pectenotoxins
    Harmful Algae (IF 4.138) Pub Date : 2018-06-19
    Monika Dhanji-Rapkova, Alison O’Neill, Benjamin H. Maskrey, Lewis Coates, Mickael Teixeira Alves, Rebecca J. Kelly, Robert G. Hatfield, Stephanie J. Rowland-Pilgrim, Adam M. Lewis, Myriam Algoet, Andrew D. Turner

    Official control biotoxin testing of bivalve molluscs from Great Britain has been conducted by Cefas for over a decade. Reflecting the changes in legislation, bioassays were gradually replaced by analytical methods, firstly for analysis of Paralytic shellfish toxins, followed by introduction of liquid chromatography tandem mass spectrometric (LCMS/MS) method for lipophilic toxins (LTs) in 2011. Twelve compounds, representing three main groups of regulated lipophilic toxins, as well as two non-regulated cyclic imines were examined in over 20,500 samples collected between July 2011 and December 2016. The toxins belonging to Okadaic acid (OA) group toxins were the most prevalent and were quantified in 23% of samples, predominantly from Scotland. The temporal pattern of OA group occurrences remained similar each year, peaking in summer months and tailing off during autumn and winter, however their abundance and magnitude varied between years significantly, with concentrations reaching up to 4993 μg OA eq./kg. Three toxin profiles were identified, reflecting the relative contribution of the two main toxins, OA and dinophysis toxin-2 (DTX2). Dinophysis toxin-1 (DTX1) was less common and was never detected in samples with high proportions of DTX2. Inter-annual changes in profiles were observed within certain regions, with the most notable being an increase of DTX2 occurrences in north-west Scotland and England in the last three years of monitoring. In addition, seasonal changes of profiles were identified when OA, the dominant toxin in early summer, was replaced by higher proportions of DTX2 in late summer and autumn. The profile distribution possibly reflected the availability of individual Dinophysis species as a food source for shellfish, however persistence of DTX2 during autumn and winter in mussels might have also been attributed to their physiology. Mussels were the only species with higher average proportions of non-esterified toxins, while Pacific oysters, cockles, surf clams, razors and queen scallops contained almost exclusively ester forms. In addition, a temporal change in proportion of OA and DTX2 free form was observed in mussels. Pectenotoxin-2 (PTX2) was quantified only on rare occasions.

    更新日期:2018-07-12
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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