The RNA/DNA ratio is used as indicator of growth in various marine organisms and to assess physiological status at species or community level. To evaluate the utility of the RNA/DNA ratio as a proxy of phytoplankton primary production, the relationships between phytoplankton RNA/DNA, taxon-specific diatom and dinoflagellate 18S rRNA/rDNA ratios and autotrophic phytoplankton biomass were investigated

AbstractDespite the importance of jellyfish in marine ecosystems, many basic biological and ecological aspects remain understudied, especially in tropical regions. Here, we report on scyphozoan jellyfish distribution and ecology to the Amazon coast for the first time, adding the records of Chrysaora lactea, Lychnorhiza lucerna and Stomolophus fritillarius. We also review the records for the three species

AbstractDespite the importance of jellyfish in marine ecosystems, many basic biological and ecological aspects remain understudied, especially in tropical regions. Here, we report on scyphozoan jellyfish distribution and ecology to the Amazon coast for the first time, adding the records of Chrysaora lactea, Lychnorhiza lucerna and Stomolophus fritillarius. We also review the records for the three species

In this paper we analyzed how well the akinete bank in the sediments from a shallow lake reflected past blooms of planktonic Nostocales (cyanobacteria), the akinete bank’s potential for reflecting future blooms and whether different nutrient scenarios affect germination and recruitment using a laboratory experiment. Most species found in the plankton were also found in the akinete bank and in the germination

Environmental factors that interact with increasing temperature under the ongoing global warming are an urgent issue determining marine phytoplankton’s performance. Previous studies showed that nutrient limitation alters phytoplankton responses to temperature and may lower their temperature optima (Topt), making them more susceptible to high temperatures. The generality of this relationship is unknown

Body size is an important functional trait that can be indicative of ecosystem structure and constraints on growth. Both increasing temperatures and eutrophication of lakes have been associated with a shift toward smaller zooplankton taxa. This is important in the context of climate change, as most aquatic habitats are expected to warm over the coming decades. Our study uses data from over 1000 lakes

Hypoxia is a major stressor on biological communities in many oceanic and coastal ecosystems. Various size-dependent processes (e.g. growth and reproduction rates, predator–prey interactions) are adversely affected by hypoxia. We hypothesized that the impacts of hypoxia on planktonic communities would also be reflected in their Normalized Biomass Size Spectra (NBSS) as steeper slopes and lower intercepts

Predators can induce changes in the diel activity patterns of marine copepods. Besides vertical migration, diel feeding rhythms have been suggested as an antipredator phenotypic response. We conducted experiments to assess the non-lethal direct effects of the predator Meganyctiphanes norvegica (northern krill) on the diel feeding patterns of the calanoid copepod Centropages typicus. We also analysed

The prolonged ice cover inherent to alpine lakes incurs unique challenges for aquatic life, which are compounded by recent shifts in the timing and duration of ice cover. To understand the responses of alpine zooplankton, we analyzed a decade (2009–2019) of open-water samples of Daphnia pulicaria and Hesperodiaptomus shoshone for growth, reproduction and ultraviolet radiation tolerance. Due to reproductive

Quantification and attribution of the food web changes associated with the invasion of non-indigenous species in the marine realm often remain a challenge. One of the pelagic non-indigenous species of concern in the recent history of aquatic bioinvasions is the predatory cladoceran Cercopagis pengoi, which invaded the Baltic Sea in the early 1990s. While several studies have reported immediate declines

Marine phytoplankton are believed to account for more than 45% of photosynthetic net primary production on Earth, and hence are at the base of marine food webs and have an enormous impact on the entire Earth system. Their members are found across many of the major clades of the tree of life, including bacteria (cyanobacteria) and multiple eukaryotic lineages that acquired photosynthesis through the

The invasive freshwater hydromedusa Craspedacusta sowerbii Lankester, 1880 (phylum Cnidaria, class Hydrozoa, family Olindiidae) is native from East Asia but for more than 20 years, reports of this species have been increasing in Europe, North America, and Australia. Due to the sporadic presence of the medusa stage and difficulties in the sample polyp stage, there is a lack of data on the physiological

Summer upwelling off Hainan Island (northern South China Sea) is influenced by fresher coastal water masses. To assess the ecological effects of this complicated oceanography, a cruise was conducted in August 2016. We investigated the spatial patterns of phytoplankton size structure, diversity and quantity of small eukaryotes (0.2–20 μm) across the upwelling system. In the inner-shelf waters, nanophytoplankton

Egg size has numerous ecological implications for zooplankton, and can influence hatching duration and female fecundity. In this study, temperature functions of embryonic development time (EDT) were determined in the copepod Eodiaptomus japonicus from Lake Biwa, in the cold and warm seasons, to clarify synergistic effects of egg size and temperature on EDT. EDT was longer for cold season eggs than

Predators not only have direct impact on biomass but also indirect, non-consumptive effects on the behavior their prey organisms. A characteristic response of zooplankton in aquatic ecosystems is predator avoidance by diel vertical migration (DVM), a behavior which is well studied on the population level. A wide range of behavioral diversity and plasticity has been observed both between- as well as

This 6-month study characterized the contribution of deep chlorophyll maximum (DCM) to lake phytoplankton diversity and primary production, in relation to stratification during the ice-free season. Phytoplankton and zooplankton dynamics were examined with environmental drivers in a small stratified lake that presents vertical gradients of light and nutrients. The phytoplankton, first composed of diatoms

Cyanea nozakii is a common bloom-forming Scyphomedusa in coastal waters of China. To understand the diet of this jellyfish and its trophic relationship with other zooplankton groups, stable isotope δ13C and δ15N values of C. nozakii in the bloom area within the northern East China Sea (ECS) in August 2017 were analyzed. We examined: first, the size-based variation in C. nozakii stable isotope values

Ciliates represent an important trophic link between nanoplankton and mesoplankton. Many species acquire functional chloroplasts from photosynthetic prey, being thus mixotrophs. Little is known about which algae they exploit, and of the relevance of inorganic carbon assimilation to their metabolism. To get insights into these aspects, laboratory cultures of three mixotrophic Strombidium spp. were established

Spatiotemporal overlap between fish larvae and their planktonic prey is an important source of recruitment variability. Over the past decade, one species of redfish, Sebastes mentella, from the Gulf of St. Lawrence (GSL) produced multiple strong cohorts following decades of low recruitment, which has generated strong interest in identifying potential drivers of larval survival. The present study provides

Reproductive rates of copepods are temperature-dependent, but poorly known for small copepods at low temperatures, hindering the predictions of population dynamics and secondary production in high-latitude ecosystems. We investigated egg hatching rates, hatching success and egg production of the small copepods Oithona similis and Microsetella norvegica (sac spawners) and Microcalanus pusillus (broadcast

Evolution has direct and indirect consequences on species–species interactions and the environment. However, Earth systems models describing planktonic activity invariably fail to explicitly consider organism evolution. Here we simulate the evolution of the single most important physiological characteristic of any organism as described in models—its maximum growth rate (μm). Using a low-computational-cost

Although consumers may use selective feeding to cope with suboptimal resource quality, little work has examined the mechanisms that underlie selective feeding, the efficiency of this behavior or its influence on consumer growth rate. Furthermore, a consumer’s exposure to suboptimal resources may also influence the consumer’s behavior and life history, including growth rate. Here, we studied how the

Oxygen minimum zones (OMZs) support ocean biogeochemical cycles of global importance. The OMZ off central Chile is characterized by seasonally variable oxygen concentrations due to upwelling events. Bacterial and archaeal communities from this area have been previously described; however, picoeukaryote communities remain largely unexplored. In order to improve our knowledge on picoeukaryote ecology

The influence of a warming climate on patterns of abundance and seasonality of the lobate ctenophore Mnemiopsis leidyi is of interest worldwide, especially in regions where the species occurs at or near the limits of its thermal niche or is shifting its spatial distribution poleward. A 47-year (1972–2019) time series of weekly observations of M. leidyi abundance in Narragansett Bay, the northern limit

Zooplankton community assembly after flooding in temporary ponds depends mostly on abundance and diversity of the dormant propagule bank. However, our understanding of the hatching patterns of zooplankton is imperfect. We performed an ex situ experiment to study the species composition and temporal sequence of zooplankton emergence from sediments in three ponds that were restored at different times:

MacdougallDoug. Endless Novelties of Extraordinary Interest. The Voyage of H.M.S. Challenger and the Birth of Modern Oceanography. Yale University Press, 2019, pp. 257, £20 hardback. ISBN 978-0-300-23 205-9.

Many coastal oceans experience not only increased loads of nutrients but also changes in the stoichiometry of nutrient supply. Excess supply of nitrogen and stable or decreased supply of silicon lower silicon to nitrogen (Si:N) ratios, which may decrease diatom proportion in phytoplankton. To examine how Si:N ratios affect plankton community composition and food web structure, we performed a mesocosm

Deep-water larval fish and zooplankton utilize structurally complex, cold-water coral and sponge (CWCS) habitats as refuges, nurseries and feeding grounds. Fine-scale sampling of these habitats for larval fish and zooplankton has proven difficult. This study implemented a newly designed, autonomous, noninvasive plankton pump sampler that collected large mesozooplankton within 1 m of the seafloor. It

The physiology of invertebrates inhabiting many coastal ecosystems is challenged by strong temporal fluctuations in salinity. We investigated how food availability influences vital rates in the tropical cyclopoid copepod Apocyclops royi subjected to different salinities (5–32 PSU). We hypothesized that (i) mortality decreases and egg production rate increases with food availability; (ii) under suboptimal

Gamete release has been frequently observed in laboratory cultures of various species of planktonic foraminifera. Those observations have been taken as evidence that these organisms produce new generations exclusively by sexual reproduction. We report here the first observation of asexual reproduction in Globigerinita uvula, a small, microperforate foraminifera. The asexual phase was associated with

Trait-based ecology allows much of the complexity of ecosystems to be projected onto a low-dimensional trait space. We conjecture that three key traits capture the main aspects of diversity of unicellular planktonic organisms: cell size, trophic strategies (relative investment in photosynthesis and phagotrophy) and vacuolation. The three selected traits are representative of two groups: mixotrophic

Jellyfish population play an important role in aquatic food chains, and many animals predate on this ‘mostly water containing’ organisms. However, what gelativores predators could gain from their prey is still poorly understood. This study provides insight into the nutritional value of the moon jelly (Aurelia aurita) by means of its fatty acid (FA) composition, while investigating seasonal variability

Corresponding editor: John Dolan

Shifts in the composition of terrestrial plant communities could have significant effects on freshwater zooplankton due to changes in the quality of inputs of terrestrially derived dissolved organic matter (DOM). Leachate from native red maple (RM) and invasive Amur honeysuckle (AH) were used to explore the effects of DOM source on survival and growth of juvenile Daphnia ambigua. Prior research with

Scaphocalanus magnus is a large copepod species with a worldwide distribution. Information on the ecology of this species is scarce. In this study, S. magnus was collected using vertically stratified net sampling from an ice station in the western Arctic Ocean over a year. The vertical distribution differed between periods of polar night and midnight sun, with core depth distributions of 264–381 m

A multivariate approach was used to analyze spring zooplankton abundance in Shelikof Strait, western Gulf of Alaska. abundance of individual zooplankton taxa was related to environmental variables using generalized additive models. The most important variables that correlated with zooplankton abundance were water temperature, salinity and ordinal day (day of year when sample was collected). A long-term

The present study quantified prey preferences by adult males and females of the mysid Mesopodopsis wooldridgei fed the calanoid copepods Pseudodiaptomus hessei and Paracartia longipatella at varying proportions. Both sexes of M. wooldridgei showed a lack of prey switching and a strong preference for the smaller, less active P. longipatella irrespective of density. Given a lack of low-density prey refuge

Freshwater pollution is a major global concern. Common methods for determining the effects of contaminants on freshwater organisms involve short-term laboratory experiments with otherwise healthy organisms. However, in natural systems, organisms are commonly exposed to parasites, which could alter their ability to survive exposure to aquatic contamination. We used a freshwater crustacean (Daphnia dentifera)

Assigning species to functional response groups in phytoplankton ecology reduces the number of functional units, which helps understand the processes that shape diversity and functioning of planktonic assemblages. Although the concept has become widespread in recent years, numerical characterization of the groups’ positions in the niche space remained a challenging task. Using a large river phytoplankton

The dynamics of diatoms and dinoflagellates have been monitored for many decades at the Helgoland Roads Long-Term Ecological Research site and are relatively well understood. In contrast, small-sized eukaryotic microbes and their community changes are still much more elusive, mainly due to their small size and uniform morphology, which makes them difficult to identify microscopically. By using next-generation

The South China Sea (SCS) is a semi-enclosed marginal sea. And in the northern SCS (NSCS), the Pearl River plume, mesoscale eddies and Kuroshio intrusion may influence the structure of pelagic ecosystems. Here, based on mesozooplankton samples collected in the NSCS from December 2014 to January 2015, spatial variations of mesozooplankton biomass, abundance, normalized biomass size spectra (NBSS), size

The Laurentian Great Lakes are among the planet’s fastest-warming lakes. Recent paleolimnological studies have shown changes in the diatom community of the system, including shifts towards taxa characteristic of strongly stratified systems and ongoing cell-size diminution. Relationships between species’ cell size and establishment in—or extirpation from—the system have not been addressed. Examining

Thiamin (vitamin B1) is primarily produced by bacteria and phytoplankton in aquatic food webs and transferred by ingestion to higher trophic levels. However, much remains unknown regarding production, content and transfer of this water-soluble, essential micronutrient. Hence, the thiamin content of six phytoplankton species from different taxa was investigated, along with the effect of thiamin amendment

We describe the ontogenetic variation in elemental and stoichiometric composition of two copepod species with very contrasted life history patterns, the calanoid Paracartia grani and the cyclopoid Oithona davisae. The first species is a broadcasting, highly productive copepod, whereas the latter is an egg-carrying copepod, much less productive. We reared cultures of both species under conditions of

Diadema africanum is a recently described sea urchin from the Eastern Atlantic archipelagos, and adults play a major ecological role mediating the transition between two alternative ecosystem states: macroalgal beds and urchin barrens. The aim of this study was to describe for the first time the egg characteristics, fertilization and larval development. To determine basic life-history characteristics

Chaetognaths are ubiquitous in the marine environment and are among the most abundant carnivorous plankton. Nevertheless, characterization of physiological parameters remains limited largely due to the difficulty in obtaining the data from pelagic chaetognaths in laboratory studies. This study therefore aimed to determine the feeding and growth rates of Zonosagitta nagae under laboratory rearing condition

AbstractComparisons over 6 years of three Norwegian fjord populations of the deep-water scyphomedusa Periphylla periphylla are presented. A minor part of the population in Lurefjord is migrating to the surface during night, which benefits mating encounters by increasing abundance per unit volume and decreasing the distance between individuals. Simulations using a typical water-column density profile

To produce viable offspring, organisms may assess mates via criteria that include traits, such as sex, species, age, reproductive status, population identity and individual quality. Copepods are small, ubiquitous crustaceans that live in freshwater and marine systems around the world whose patterns of mate choice have been long studied in numerous species. Herein, we synthesized decades of experiments

Apherusa glacialis is a common, sea ice-associated amphipod found throughout the Arctic Ocean and has long been considered permanently associated with the sea ice habitat. However, pelagic occurrences of A. glacialis have also been reported. It was recently suggested that A. glacialis overwinters at depth within the Atlantic-water inflow near Svalbard, to avoid being exported out of the Arctic Ocean

Climate change is altering light regimes in lakes, which should impact disease outbreaks, since sunlight can harm aquatic pathogens. However, some bacterial endospores are resistant to damage from light, even surviving exposure to UV-C. We examined the sensitivity of Pasteuria ramosa endospores, an aquatic parasite infecting Daphnia zooplankton, to biologically relevant wavelengths of light. Laboratory

Copepod swimming behavior is governed by chemical and hydro-mechanical cues. The environment of copepods, however, is frequently impacted by anthropogenic activities, in particular increased levels of suspended sediment due to coastal development. To better understand the effects of sediments on copepod behavior, we used video recordings to document free-swimming in Acartia tonsa under five sediment

The Cushing Prize is an annual award in the honor of the memory of David Cushing, Founding Editor of Journal of Plankton Research. The Cushing distinguishes the best paper by an early career stage scientist (aged 30 or younger) published in the Journal of Plankton Research in the past year. The prize distinguishes, and we hope helps to foster, interesting and high-quality papers by young scientists

Life-history theory predicts that animals adjust their resource allocation to somatic growth or to reproduction to maximize fitness. Resource allocation in Daphnia is known to respond to quantitative food limitation as well as to kairomones released from predators. Here we investigated in a full-factorial design how kairomone from larvae of Chaoborus flavicans, a gape-limited predator, and food quantity

We compared two metabolome profiles of a small centric diatom species, Stephanodiscus hantzschii Grun., grown under conditions with enriched nutrients but different temperatures. This species proliferates in eutrophic rivers during winter. We investigated the population dynamics and internal metabolite changes of Stephanodiscus by performing a simple culture experiment at different temperatures (5

Studies on freshwater Perkinsea are scarce compared to their marine counterparts; they are therefore not well ecologically characterized. In this study, we investigated the diversity, distribution and ecological role of Perkinsea in freshwater ecosystems. Our approach included (1) the phylogenetic analyses of near full-length SSU and LSU sequences of freshwater Perkinsea, (2) a meta-analysis of public

Journal of Plankton Research, (2019) 41(5), 723–739.

Large river estuaries experience multiple anthropogenic stressors. Understanding plankton community dynamics in these estuaries provides insights into the patterns of natural variability and effects of human activity. We undertook a 2-year study in the Columbia River Estuary to assess the potential impacts of abiotic and biotic factors on planktonic community structure over multiple time scales. We

Alexandrium catenella, the main species associated with harmful algal blooms, has progressively increased its distribution through one of the most extensive and highly variable fjord systems in the world. In order to understand this successful expansion, we evaluated the effects of different salinities, light intensity, temperatures, nitrogen (N) forms and nitrogen/phosphate (N:P) ratio levels on the

Krill species play a pivotal role in energetic transfer from lower to upper trophic levels. However, functional feeding responses, which determine how food availability influences ingestion rates, are still not well defined for northern krill species. Here, we estimated and compared the functional feeding responses on natural communities of phytoplankton and mesozooplankton of two coexisting species

We evaluated the effects of two morphs of the rotifer Keratella tropica (long-posterior spines, LS; short-posterior spines, SS) on life-table parameters and population dynamics of the rotiferan predator Asplanchna brightwelli. At the prey densities of 10 and 30 ind./mL, A. brightwelli showed significantly higher intrinsic rate of population increase, net reproductive rate and population growth rate