Microalgal range expansions are increasing in frequency and magnitude but generally remain unnoticed until mass development occurs. Gonyostomum semen is a freshwater raphidophyte that causes nuisance blooms in lakes and has recently expanded its distribution across Europe. G. semen was considered to mainly occur in humic lakes in the boreal region but is now found in high density also in other freshwater

Harmful algae bloom (HAB) forecasting has developed rapidly over recent decades, but predicting harmful levels of marine biotoxins in shellfish is still a challenge. New discoveries suggest that predator-prey interactions may be an important driver in the formation of HABs. Key species of harmful algae respond to copepod infochemicals with increased toxin production. In addition, copepods feed selectively

The oceanographic conditions in the Gulf of Maine, Scotian Shelf, Slope Sea, and surroundings are determined by interplay of two major circulation systems—the Gulf Stream and Labrador Current. This study aims to better understand regional long-term climate trends caused by the Gulf Stream decadal variability. The in situ data analysis confirms a continuous slow warming within all three areas over the

Intensification of brown color in surface waters has been observed over several decades in many areas. We examined a 64-yr daily record (1947–2010) of visual water color, a measure of chromophoric dissolved organic matter (CDOM), in the Mississippi River at Minneapolis, Minnesota. Although no monotonic trends in daily or mean annual color were evident, our analyses revealed trends in seasonal metrics

Field data and numerical modeling were used to investigate the effects of the riverine inflows on the seasonality of the lake mean temperature, thermal structure, and basin-scale internal waves in a tropical Andean reservoir. Lake temperature and external forcing were measured during contrasting hydrological periods modulated by severe cold (2011–2012) and warm (2015–2016) phases of El Niño–Southern

Heterotrophic microbes initiate the degradation of high molecular weight organic matter using extracellular enzymes. Our understanding of differences in microbial enzymatic capabilities, especially among particle-associated taxa and in the deep ocean, is limited by a paucity of hydrolytic enzyme activity measurements. Here, we measured the activities of a broad range of hydrolytic enzymes (glucosidases

Reductions in ice cover duration and earlier ice breakup are two of the most prevalent responses to climate warming in lakes in recent decades. In dimictic lakes, the subsequent periods of spring mixing and summer stratification are both likely to change in response to these phenological changes in ice cover. Here, we used a modeling approach to simulate the effect of changes in latitude on long-term

The rapid turnover of dimethylsulfoniopropionate (DMSP), likely the most relevant dissolved organic sulfur compound in the surface ocean, makes it pivotal to understand the cycling of organic sulfur. Dimethylsulfoniopropionate is mainly synthesized by phytoplankton, and it can be utilized as carbon and sulfur sources by marine bacteria or cleaved by bacteria or algae to produce the volatile compound

Mesoscale eddies may enhance nutrient injection into the photic zone and ultimately the magnitude and composition of particle export to depth. Using satellite altimetry, we identified 38 cyclonic eddies that passed in close proximity to the Hawaii Ocean Time-series (HOT) Station ALOHA, located in the North Pacific Subtropical Gyre, from 1993 to 2018. Particulate carbon (C), nitrogen (N), and biogenic

Increased duration and frequency of droughts under global change may affect both temporary and formerly permanent watercourses. Streambed desiccation, cooccurring solar radiation, and high temperature all may affect the composition and metabolism of photoautotrophic organisms in benthic biofilms. To test these effects, we characterized the composition of pigments when biofilms were exposed to dry conditions

For spiny lobsters (Palinuridae), the co-occurrence of final-stage larvae (phyllosomata) and postlarvae (pueruli) in sampling stations over oceanic waters is indicative of metamorphosis zones, some of which have been found in boundary currents. We hypothesized that metamorphosis of Panulirus argus and P. guttatus off the Mexican Caribbean coast, which has a very narrow shelf, occurs in the swift Yucatan

External nutrient supply from the land and ocean is crucial for sustaining high primary productivity in coastal seas. Submarine groundwater discharge (SGD) is recognized as one of the most important sources of terrestrial nutrients. However, the relative importance of SGD-derived nutrients from different sources in coastal ecosystems controlled by offshore exchange has not been well quantified. Here

The ratio of primary production to ecosystem respiration rates (P:R ratio) is an ostensibly simple calculation that is used to characterize lake function, including trophic status, the incorporation of terrestrial organic carbon into lacustrian food webs, and the direction of carbon dioxide (CO2) flux between a lake and the atmosphere. However, many predictive links between P:R ratios and lake ecosystem

Hurricane Harvey delivered over 124 trillion liters of freshwater to the Texas–Louisiana coast and the northwestern Gulf of Mexico (GOM) in late August-early September 2017. Environmental conditions, size-fractionated phytoplankton biomass, and pico- and nanoplankton abundances (picocyanobacteria, picoeukaryotes, autotrophic, and heterotrophic nanoplankton) were characterized along nearshore-offshore

It is generally anticipated that particulate organic carbon (POC) for most part is degraded by attached microorganisms during the descent of “marine snow” aggregates toward the deep sea. There is, however, increasing evidence that fresh aggregates can reach great depth and sustain relatively high biological activity in the deep sea. Using a novel high-pressure setup, we tested the hypothesis that increasing

Understanding the ecological interactions that enhance the resilience of threatened ecosystems is essential in assuring their conservation and restoration. Top-down trophic interactions can increase resilience to bottom-up nutrient enrichment, however, as many seagrass ecosystems are threatened by both eutrophication and trophic modifications, understanding how these processes interact is important

Zooplankton contribute a major component of the vertical flux of particulate organic matter to the ocean interior by packaging consumed food and waste into large, dense fecal pellets that sink quickly. Existing methods for quantifying the contribution of fecal pellets to particulate organic matter use either visual identification or lipid biomarkers, but these methods may exclude fecal material that

The vertical turbulent fluxes of nitrate to the base of the euphotic zone were quantified to assess the role of turbulent mixing in modulating new production inside cyclonic and anticyclonic eddies in an oligotrophic ocean. Although the turbulent nitrate flux (0.35 ± 0.11 mmol N m−2 d−1) at the base of the euphotic zone inside the cyclonic eddy was higher than that (0.07 ± 0.03 mmol N m−2 d−1) inside

Dinitrogen (N2) fixation is a major source of bioavailable nitrogen to oligotrophic ocean communities. Yet, we have limited understanding how ongoing climate change could alter N2 fixation. Most of our understanding is based on short-term laboratory experiments conducted on individual N2-fixing species whereas community-level approaches are rare. In this longer-term in situ mesocosm study, we aimed

Oceanic production and occurrence of dimethyl sulfide (DMS) and its subsequent ventilation to the atmosphere significantly contribute to the global sulfur cycle and impact the climate regulation. Spatial distributions of DMS, dimethylsulfoniopropionate (DMSP, precursor of DMS), and dimethyl sulfoxide (DMSO, oxidation product of DMS), production and removal processes of DMS (including biological production

Sustained periods of anoxia, driven by eutrophication, threaten coastal marine systems and can lead to mass mortalities of even resilient animals such as bivalves. While mortality rates under anoxia are well-studied, the specific mechanism(s) of mortality are less clear. We used a suite of complementary techniques (LT50, histology, 16S rRNA amplicon sequencing, and valvometry) to show that the proliferation

Submesoscale eddies and fronts are important components of oceanic mixing and energy fluxes. These phenomena occur in the surface ocean for a period of several days, on scales between a few hundred meters and few tens of kilometers. Remote sensing and modeling suggest that eddies and fronts may influence marine ecosystem dynamics, but their limited temporal and spatial scales make them challenging

Foraging based on prey elemental content could be more pronounced if consumers leveraged differences in physical traits among stoichiometrically distinct prey to ingest more favorable food, allowing consumers to meet their threshold elemental ratios (TER), the ratio of nutrients in the food where neither carbon nor nitrogen is limiting. We offered the marine copepod, Acartia tonsa, different combinations

The Red Sea depicts a north–south gradient of positively correlated temperature and nutrient concentration. Despite its overall oligotrophic characteristics, primary production rates in the Red Sea vary considerably. In this study, based on five cruises and a 2-year time series (2016–2018) sampling in the Central Red Sea, we determined phytoplankton photosynthetic rates (PP) by using 13C as a tracer

Although tidal marshes are known for their coastal defense function during storm surges, the impact of extreme wave forcing on tidal marsh development is poorly understood. Seedling survival in the first season after germination, which may involve exposure to extreme wave events, is crucial for the natural establishment and human restoration of marshes. We hypothesize that species-specific plant traits

Many aquatic processes (i.e., organism locomotion, macrophyte response to unsteady flow and mass/heat transfer) involve oscillatory or undulatory movements perpendicular to the direction of flow and perpendicular to the plane of oscillation (i.e., spanwise). The reduction of boundary layer (BL) thickness () and increased turbulence have been identified as the mechanisms for faster heat and mass transfer

The biodiversity associated with subtidal Irish kelp forests dominated by Laminaria hyperborea has never been described. To enumerate species assemblages in these ecosystems, subtidal surveys were done throughout the calendar year to investigate species assemblages within kelp forests, composition of benthic communities, species colonizing kelp thalli, recruitment to kelp forests, and habitat recovery

In dimictic lakes, the stable density stratification during summer and winter inhibits vertical mixing of nutrients and oxygen. This favors the development of hypolimnetic hypoxia, which degrades cool-water fish habitat and enhances nutrient mineralization from the sediments. Fall and spring turnover events, therefore, provide a crucial biannual link between surface and bottom waters. However, the

Corrigendum for: Meyer-Kaiser, K. S., M. Bergmann, T. Soltwedel, and M. Klages. 2019. Recruitment of Arctic deep-sea invertebrates: Results from a long-term hard-substrate colonization experiment at the Long-Term Ecological Research observatory HAUSGARTEN. Limnol. Oceanogr. 64: 1924–1938. doi: 10.1002/lno.11160 Since the publication of this article, it has been revealed that the crinoid specimens do

Benthic iron (Fe) fluxes from continental shelf sediments are an important source of Fe to the global ocean, yet the magnitude of these fluxes is not well constrained. Processing of Fe in sediments is of particular importance in the Arctic Ocean, which has a large shelf area and Fe limitation of primary productivity. In the Arctic fjords of Svalbard, glacial weathering delivers high volumes of Fe-rich

The silica frustules of diatom are regarded as an important physical defense against predation. While the biogenic silica content of diatoms is a major factor controlling the ingestion rate of copepods, how it affects the three-dimensional structure and the mechanical properties of the frustules, and consequently copepod grazing, has not been studied. In this study, the diatoms Thalassiosira weissflogii

Effective seed dispersal is critical for enabling rapid state shift from a bare tidal flat to a vegetated marsh. While tidal currents are the main dispersal vector in coastal environments, biological characteristics that keep seeds afloat have been shown to influence primary seed dispersal, i.e., seed departure from the parent plant. In contrast, secondary seed dispersal processes that move (germinated)

Sinking particulate organic matter controls the flux of carbon (C) from the surface ocean to the deep sea. Microorganisms actively colonize particles, but the extent to which microbial metabolism influences particle export remains uncertain. We conducted experiments to quantify rates of bacterial production (derived based on 3H-leucine incorporation) and dark C-fixation (based on 14C-bicarbonate assimilation)

Light is a fundamental resource for phytoplankton. To utilize the available light, most phytoplankton species possess pigments in taxon-specific combinations and quantities, which in turn result in a specific use of certain wavelengths. This optimizes the light use efficiency, allows for a complementary use of light, and may be an additional driver for community structure. While the effects of light

The episodic stranding of millions of pelagic red crabs (Pleuroncodes planipes) along California beaches is a striking and puzzling phenomenon. Pleuroncodes planipes are usually abundant off Baja California, Mexico, and their appearance in central California is thought to coincide with anomalously warm waters and northward advection related to El Niño. This anecdotal association has stimulated many

The picocyanobacteria Prochlorococcus and Synechococcus are found throughout the ocean's euphotic zone, where the daily light:dark cycle drives their physiology. Periodic deep mixing events can, however, move cells below this region, depriving them of light for extended periods of time. Here, we demonstrate that members of these genera can adapt to tolerate repeated periods of light energy deprivation

Heterotrophic prokaryotes have the capacity to uptake inorganic nitrogen (N) substrates. However, it remains unclear what the potential competition is between heterotrophic prokaryotes and autotrophic plankton for N in the ocean, which would shunt the flow of N supporting primary production. To date, it has been difficult to distinguish heterotrophic prokaryotic N uptake from that of autotrophic picoplankton

Estuarine sediments make an important contribution to the global carbon cycle, but we do not know how this will change under a future climate, which is expected to have lower pH oceans and frequent high-temperature days. Six combinations of warming and partial pressures of CO2 (pCO2) were chosen to investigate the combined and individual effects of short-term pressures on the diel metabolic response

Disturbances are one of the most important processes affecting natural systems, but there is a gap between simple conceptual models of disturbance and complex empirical studies. We studied the perturbation caused by headward-eroding creeks in southeastern USA salt marshes. We measured disturbance responses (magnitude and recovery trajectory) of 19 variables. Some variables (shoot density, root biomass

Aquatic habitats are closely linked to surrounding terrestrial systems via reciprocal subsidies. Much of the research on aquatic–terrestrial subsidies has focused on streams and lakes, while subsidies across aquatic–terrestrial boundaries of other systems, like temporary ponds, have received less attention. To address the lack of information regarding cross-habitat subsidies of temporary ponds, we

Mathematical modeling offers an avenue to predict distributions of microplastics in the ocean. With this goal in mind this study presents a simple analytic model describing the deterministic dynamics of long-time vertical motion of buoyant microplastics that have succumbed to biofouling in a quiescent ocean. The model couples equations governing vertical particle position and algal population dynamics

Both abiotic and biotic factors control phytoplankton dynamics. Among the multiple factors regulating the variability of phytoplankton production and biomass, physical transport that distributes both phytoplankton and other substances (e.g., nutrients, salts, and suspended solids) is one of the key factors in coastal aquatic systems. While the effect of transport processes is best understood by the

Lake Michigan is one of the largest lakes in the world and the second largest of the North American Great Lakes by volume. Over the last two decades, the lake has witnessed significant ecological changes due to proliferation of invasive quagga mussels into its deeper offshore regions. The impact of these changes on the labile dissolved organic matter pool available for bacterial consumption and the

Global change, including rising temperatures and acidification, threatens corals globally. Although bleaching events reveal fine-scale patterns of resilience, traits enabling persistence under global change remain elusive. We conducted a 95-d controlled-laboratory experiment investigating how duration of exposure to warming (~28, 31°C), acidification (pCO2 ~ 343 [present day], ~663 [end of century]

Anthropogenic and climatic stressors on freshwater ecosystems are of global concern. However, the interactions and effects of multiple stressors (e.g., nutrient enrichment, climate warming, altered wind and precipitation) acting over different spatial and temporal scales are often complex and remain controversial. Here, we reconstructed one-century dynamics of eutrophication and primary producer communities

Small pelagics, or forage fish, link lower and higher trophic levels in marine food webs. Recently, attention has been given to the management of forage fish, including anadromous river herring (Alewife Alosa pseudoharengus, blueback herring A. aestivalis) and American shad (A. sapidissima) due to their current depleted status and historically important ecological and economic roles. Little is known

Arctic rivers are sensitive to climate and environmental change, but the biogeochemical response remains poorly understood. Monthly size-fractionated dissolved organic matter (DOM) samples from the lower Yukon River were characterized using UV–visible, fluorescence, and Fourier transform-infrared (FT-IR) spectroscopy techniques. The EEM-PARAFAC analysis revealed three major fluorescent DOM components

Temporal Secchi depth trends are used in lake assessment to evaluate lake condition and possible shifts in trophic state. For accurate lake assessments, it is important to differentiate regional trends from lake-specific trends, but this can be confounded by interacting factors. We present a divergent trend analysis which uses temporal patterns of Secchi depth water clarity from 1999 to 2018 for five

Coccolithophores are among the most important calcifying pelagic organisms. To assess how coccolithophore species with different coccolith-carbonate mass and distinct ecological resilience to ocean warming will influence the “rain ratio” and the “biological carbon pump”, 1 yr of species-specific coccolith-carbonate export fluxes were quantified using sediment traps moored at four sites between NW Africa

Extreme wind storms can strongly influence short-term variation in lake ecosystem functioning. Climate change is affecting storms by altering their frequency, duration, and intensity, which may have consequences for lake ecosystem resistance and resilience. However, catchment and lake processes are simultaneously affecting antecedent lake conditions which may shape the resistance and resilience landscape

Use of mangrove ecosystems for coastal flood protection requires reliable predictions of mangrove wave attenuation, especially if this capacity lessens due to storm-induced forest damage. Quantifying and understanding the variation in drag forces and mechanical properties of mangrove vegetation can improve assessment of mangrove protective capacity. We studied five mangrove species common in the subtropical

Recent observations in marine ecosystems show that the presence of thiamine regulates primary production, but little is known about the ecological effect of thiamine in streams. We conducted nutrient enrichment experiments in four streams in the New York's Adirondack Mountains using nutrient diffusing substrates to evaluate the influence of thiamine (vitamin B1) on the growth of stream periphyton.

Declining calcium in freshwater lakes has become a serious threat to aquatic organisms, which may affect the anti-fish defense of cladocerans with high calcium demand. To evaluate the effects of low calcium on life history strategies of cladocerans for defending against fish predation, we exposed Ceriodaphnia cornuta to eight concentrations of calcium ranging from 0.5 to 50.0 mg L−1 in the absence

Seagrasses and bare sediment represent alternative stable states, with sediment resuspension being a key driver of system stability via the Seagrass–Sediment–Light (SSL) feedback. We explore the SSL feedback by quantifying the sediment stabilization by seagrass, and using these measurements to calculate under which conditions seagrass ends up in a turbid environment. We quantified in-situ sediment

Lakes and streams in mountain regions are important contributors to carbon (C) fluxes. However, detailed carbon balances of the stream-lake continuum are rare. Combining eddy covariance (EC) measurements of lake-atmosphere net ecosystem CO2 exchange with measurements of fluvial C fluxes (dissolved organic C, DOC; particulate organic C, POC; dissolved inorganic C, DIC), and in-lake sedimentation, we

We report a 12-yr data set (August 2006–October 2018) of nearly continuous estimates (n = 3275) of gross primary production (GPP), community respiration (CR), and net community production (NCP) in a Posidonia oceanica seagrass meadow, computed from O2 measurements on a mooring at 10 m bottom depth in the Bay of Revellata (Corsica). Both NCP and CR were correlated to GPP and followed the leaf biomass

Submarine groundwater discharge is recognized as a major source of chemicals to the global ocean, exerting large control over coastal water composition. Radon and 226Ra are used to evaluate, for the first time, the occurrence and magnitude of submarine groundwater discharge in the Ría de Vigo, a large, highly productive embayment affected by seasonal, wind-driven upwelling. The system is naturally

Often considered detrimental to the environment and human activities, jellyfish blooms are increasing in several coastal regions worldwide. Yet, the overall effect of these outbreaks on ecosystem productivity and structure are not fully understood. Here we provide evidence for a so far unanticipated role of jellyfish in marine nitrogen cycling. Pelagic jellyfish release nitrogen as a metabolic waste

Lake respiration is supported by a mixture of autochthonous and allochthonous resources, but the relative significance and interaction of these sources are uncertain across gradients of primary production and organic matter inputs. We manipulated autochthonous resources by adding inorganic nitrogen and phosphorus to two lakes during three summers and monitored a third reference lake. Allochthonous

We examined biogenic silica production and elementary composition (biogenic Si, particulate organic carbon and particulate organic nitrogen) of Rhizaria and diatoms in the upper 200 m along a transect in the Southwest Pacific sector of the Southern Ocean during austral summer (January–February 2019). From incubations using the 32Si radioisotope, silicic acid uptake rates were measured at 15 stations