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Hydrostatic pressure is a dominant environmental cue for vertically migrating marine organisms but the physiological mechanisms of responding to pressure changes remain unclear. Here, we uncovered the cellular and circuit bases of a barokinetic response in the planktonic larva of the marine annelid Platynereis dumerilii. Increased pressure induced a rapid, graded, and adapting upward swimming response due to the faster beating of cilia in the head multiciliary band. By calcium imaging, we found that brain ciliary photoreceptors showed a graded response to pressure changes. The photoreceptors in animals mutant for ciliary opsin-1 had a smaller sensory compartment and mutant larvae showed diminished pressure responses. The ciliary photoreceptors synaptically connect to the head multiciliary band via serotonergic motoneurons. Genetic inhibition of the serotonergic cells blocked pressure-dependent increases in ciliary beating. We conclude that ciliary photoreceptors function as pressure sensors and activate ciliary beating through serotonergic signalling during barokinesis. [ABSTRACT FROM AUTHOR]

Chaetognatha, the second-most abundant zooplankton in the marine ecosystem, is a connecting link between copepods and organisms of the higher trophic level. The present checklist provides detailed information on the morphology and distribution of chaetognaths in the eastern Arabian Sea (northeastern Arabian Sea, southeastern Arabian Sea, and Laccadive Sea). It includes five families under two orders with 34 species belonging to 15 genera and recorded from both shelf, oceanic and deep sea waters of the eastern Arabian Sea, creating a first line data on chaetognaths of the Arabian Sea. [ABSTRACT FROM AUTHOR]

Marine plankton capable of photosynthesis and predation ("mixoplankton") comprise up to 50% of protist plankton and include many harmful species. However, marine environmental management policies, including the European Union Marine Strategy Framework Directive (MSFD) and the USEPA, assume a strict dichotomy between autotrophic phytoplankton and heterotrophic zooplankton. Mixoplankton often differ significantly from these two categories in their response to environmental pressures and affect the marine environment in ways we are only beginning to understand. While the management policies may conceptually provide scope for incorporating mixoplankton, such action is rarely implemented. We suggest that the effectiveness of monitoring and management programs could benefit from explicit implementations regarding the ecological roles and impact of mixoplankton. Taking the MSFD as an example of marine management guidelines, we propose appropriate methods to explicitly include mixoplankton in monitoring and marine management. Integr Environ Assess Manag 2024;20:1366–1383. © 2024 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC). Key Points: Mixoplankton (capable of photo‐ and heterotrophy) are a broad trophic group that is currently not considered by marine environmental management, while they often display different responses to environmental changes than strict phytoplankton or zooplankton due to their unique physiology.Many harmful algal species that are currently being monitored due to their impact on public health and the economy are mixoplankton, and effective forecasting systems may be challenging to establish by not considering their unique trophic mode.We showcase where the current omission of mixoplankton from marine management can misinform on the environmental status of marine ecosystems and how existing management and monitoring programs can benefit from including mixoplankton.Using the European Marine Strategy Framework Directive as an example, we show how mixoplankton can be integrated into existing management programs and where research gaps still exist. [ABSTRACT FROM AUTHOR]

Introduction. Radiolarians are an important group of marine planktonic protists. The polycystines (Phylum Radiozoa, Class Polycystina) are a group of radiolarians whose skeletons are made of opal (amorphous silica) and form the basis for their taxonomic classification. There are few recent studies of radiolarians in Costa Rica. Objective. This research seeks to create the first taxonomic guide of radiolarians present in Holocene sediments (from 11 000 years ago to the present) of the Costa Rican Pacific seabed. Methods. Between late 2018 and early 2019, two oceanic expeditions: Rock Hits and Costa Rica Deep-Sea Connections, respectively, collected 13 sediment cores from the Costa Rican Pacific seabed. Using a modified methodology created for these investigation, 64 samples were obtained from which radiolarian remains were extracted for taxonomic analysis. Obtained radiolarians were mounted for taxonomic analysis using optical and scanning electron (SEM) microscopy. Results. A total of 119 species of Polycystina were identified, distributed among 15 families belonging to the orders Collodaria (one family and eight species), Spumellaria (seven families and 62 species), and Nassellaria (seven families and 49 species). Conclusion. This study identifies several taxa (119) like those reported in studies conducted near the Pacific coast of Costa Rica, but less than half of those reported from the Eastern Equatorial Pacific (EEP). [ABSTRACT FROM AUTHOR]

Zooplankton are the key intermediary between primary production and the fish community and a cornerstone of marine food webs, but they are often poorly represented in models that tend to focus on fish, charismatic top predators, or ocean biogeochemistry. In this study, we use an intermediate complexity end‐to‐end food web model of the North Sea with explicit two‐way coupling of zooplankton to phytoplankton and higher trophic levels to ask whether this matters. We vary the metabolic rate of omnivorous zooplankton (OZ) as a proxy for uncertainties in our understanding and modeling of zooplankton form and function, and moving beyond previous studies we look at the impacts on the food web in concert with climate warming and fishing. We consider impacts on food web state and time to recover the relevant unfished state after fishing ceases. We also consider potential impacts on pelagic and demersal fishing fleets if we assume that they are constrained by the requirement to allow recovery to an unfished state within a certain period of time as a way of ensuring consistency with Good Environmental Status as required by EU and UK legislation. We find that all three aspects considered are highly sensitive to changes in the treatment of zooplankton, with impacts being larger than for warming of 2 or 4°C across most food web functional groups, particularly for apex predators. We call for a programme of research aimed at improving our understanding of zooplankton ecology and its relationship to the wider food web, and we recommend that improved representations of zooplankton are incorporated in future modeling studies as a priority. [ABSTRACT FROM AUTHOR]

Mycoloop is an important aquatic food web composed of phytoplankton, chytrids (one dominant group of parasites in aquatic ecosystems), and zooplankton. Chytrids infect phytoplankton and fragment them for easy consumption by zooplankton. The free-living chytrid zoospores are also a food resource for zooplankton. A dynamic reaction-diffusion-advection mycoloop model is proposed to describe the Phytoplankton-chytrid-zooplankton interactions in a poorly mixed aquatic environment. We analyze the dynamics of the mycoloop model to obtain dissipativity, steady state solutions, and persistence. We rigorously derive several critical thresholds for phytoplankton or zooplankton invasion and chytrid transmission among phytoplankton. Numerical diagrams show that varying ecological factors affect the formation and breakup of the mycoloop, and zooplankton can inhibit chytrid transmission among phytoplankton. Furthermore, this study suggests that mycoloop may either control or cause phytoplankton blooms. [ABSTRACT FROM AUTHOR]

Rotifers' presence and significance are being underestimated among marine zooplankton because rotifers are lost when using larger mesh size nets. Furthermore, samples' preservation often makes species identification difficult, creating a knowledge gap regarding their diversity and abundance in coastal ecosystems. Our study aimed to address this gap by documenting the biodiversity and distribution patterns of the rotifer species, exploring their relationships with the components of the zooplankton community and determining the environmental variables driving their seasonal dynamics. Samplings were carried out in an urban coastal area in the North Aegean Sea in Greece, within two sampling periods. Four coexisting Synchaeta species were encountered, whose temporal distribution patterns were mainly driven by temperature; S. neapolitana exhibited a preference for colder temperatures, contrary to the thermophilic distribution patterns of S. baltica and S. vorax. Network analysis unveiled several negative links among Synchaeta species and other zooplankton taxa, suggesting potential competitive trophic interactions. The present study is one of the very few dealing with marine rotifers across the Mediterranean Sea and thus provides a significant contribution to our understanding of the dynamics of this group of micrometazoans. [ABSTRACT FROM AUTHOR]

The present study aimed to evaluate the ecology considering distribution, abundance, population structure, and fecundity of the marine diplostraceans Penilia avirostris and Pseudevadne tergestina in the Veracruz Reef System National Park, southwest Gulf of Mexico. Surface samples were collected with a 300 µm mesh plankton net at 26 sampling sites in June, August, October (2011), May (2012) and June (2013). Temperature, salinity, and dissolved oxygen were measured in situ. The temperature range was 26.53 ± 0.41 and 29.29 ± 0.27°C, salinity between 33.43 ± 0.49 and 35.91 ± 0.09, and dissolved oxygen between 2.92 ± 0.08 and 6.56 ± 0.08 mg L-1 . P. avirostris and P. tergestina presented the highest density, with 2200 ind 100 m-3 in June and 5980 ind 100 m-3 in October, respectively. Four stages were determined in P. avirostris. In P. tergestina, there were five instars, with males in August and October. The size of parthenogenic females of P. avirostris was 773.4 ± 20.08 µm. In P. tergestina, it was 637.6 ± 49.28 µm. The number of embryos in P. avirostris was 2 to 7, and in P. tergestina, 2 to 8 embryos. The correlations between body length and the number of embryos in both species were statistically significant under the potential model (r > 0.68 for both species, P < 0.001). The transects with the highest abundance were the northern and the southern zones because they are far from the influence of the Jamapa River. The density of these crustaceans is related to optimal temperature, salinity, and dissolved oxygen values. The low proportions obtained from gamogenic individuals of P. avirostris and P. tergestina suggest that in tropical and subtropical regions, gamogenesis is not crucial for the life cycle of these organisms. [ABSTRACT FROM AUTHOR]

Tragic incidents involving mine tailings spills have impacted many aquatic ecosystems around the world. The massive mine tailings dam collapse of Fundão, which occurred in Brazil in 2015, affected several aquatic ecosystems, including shallow and deep lakes in the lower Doce River basin. Until now, the effects of mine tailings on the functional diversity of zooplankton remain poorly understood.We investigated the functional diversity of zooplankton (functional groups, functional richness [FRic] and functional evenness [FEve]) in shallow and deep lakes, exploring the influence of environmental variables and metals. In addition, trends in functional redundancy and functional vulnerability were also assessed to understand patterns of resilience in mining‐impacted ecosystems.Surveys were performed monthly on three deep and three shallow lakes affected by the dam failure, from October 2018 to September 2019.In the deep lakes, the zooplankton community was dominated by smaller filter‐feeders and omnivorous species, associated with cyanobacteria density and chlorophyll‐a. Medium‐sized filters were associated to iron, suspended particulate organic matter and total organic carbon in shallow lakes. The smaller filter‐feeders and omnivorous trophic groups had a higher contribution to increasing the functional diversity of zooplankton than medium‐sized filter‐feeders in both deep and shallow lakes. FRic and FEve were higher in deep lakes than in shallow lakes. Shallow lakes were highly vulnerable to species loss and functional diversity was modulated by environmental changes and metal pollution.Tropical shallow lakes impacted by mining tailings should receive particular attention in conservation plans, as a consequence of their high level of pollutant retention in comparison with deep lakes. In addition, we highlight the importance of using a functional approach to better understand the ecosystem changes resulting from the impacts of mine tailings on aquatic environments. [ABSTRACT FROM AUTHOR]

Recent research highlighted significant marine biological activity during the Arctic winter, with poorly known implications for the biological carbon pump. We used moored instruments to (1) track the development of the pelagic food web of a high‐Arctic marine ecosystem from winter to spring, and (2) assess the role of zooplankton‐mediated processes in the sinking export of particulate organic carbon (POC). Zooplankton collected by a sediment trap at 40 m depth in Kongsfjorden showed a shift in species composition in February coinciding with an inflow of Atlantic water and the return of sunlight. The Atlantic copepod Calanus finmarchicus and the Arctic Calanus glacialis became dominant in the post‐inflow assemblage of large mesozooplankton. However, large copepods were never abundant (0.3–4.6 ind m−3) in January–April in the upper 40 m. Despite the low chlorophyll fluorescence, POC export increased substantially, from 2–13 mg C m−2 d−1 in January–February to 13–35 mg C m−2 d−1 in March–April 2014. By late March, zooplankton fecal pellets contributed largely (23–100%) to this significant POC export before the phytoplankton bloom. The lack of change in copepod and euphausiid population sizes suggests that enhanced feeding activity in the surface layer supported the increasing fecal pellet export. Our results revealed the swift response of active zooplankton in winter, evidenced by increased carbon export, to improved food availability. [ABSTRACT FROM AUTHOR]

All aquatic organisms depend directly or indirectly on plankton as they from an important component of the ecological pyramid. Zooplankton are crucial components of aquatic food webs as primary producers. Zooplankton can have large impacts on trophic transfer efficiencies from phytoplankton to zooplankton and from zooplankton to fish. In addition, they are a valuable source of protein, aminoacids, lipids, fatty acids, vitamins and enzymes. Hence, the present study was attempted to identify the zooplankton composition in three different seasons of the year in a fresh water pond at Kumbakonam, Tamilnadu, India. While the presummer season recorded 23 species, the post summer season registered 17 species and the rainy season recorded 18 species Protozoa was represented by a single species, which preferred the post summer season to record its highest count. Rotifers were represented by 15 species during the presummer season, 12 species during the postsummer season and 11 species during rainy season. There were 7 perennial species. Cladocera was represented by 3 species of which the only perennial species was M. micrura Ostracoda were represented by 2 species of which only C. subglobosa was perennial. Copepods were also represented by 2 species of which only H. viduvs was perennial. Anostraca was represented only by a single species. Shanon-Weiner's diversity index of species, family and species richness index revealed lowest levels in rainy season and highest levels during the presummer season. [ABSTRACT FROM AUTHOR]

Plankton parasites such as viruses, bacteria, fungi, and unicellular eukaryotes are associated symbionts colonizing algal groups in aquatic ecosystems. They occur within a network of microbe–microbe interactions in which they parasitize phytoplankton and seaweeds, i.e., primary producers generating organic carbon and forming the basis of marine food webs. These parasites use algae as a source of nutrients and reproduce at the expense of their host, causing infectious symptoms leading to disease and death. Plankton parasites can reduce the algal populations, and the infection of one specific species may, in turn, favor the development of another, influencing the seasonal succession of algal blooms in oceans, seas, and lakes. Many parasites have free-living stages that zooplankton graze upon, representing a significant trophic link in food webs. The biology and life cycle of plankton parasites are well investigated in marine and freshwater algal hosts. Still, the chemical signaling mediating these microbial interactions and the effect of co-occurring symbionts remain underexplored. This review focuses on the diversity of plankton parasites infecting algae, with a particular emphasis on unicellular eukaryotes. The ecological role of plankton parasites, the mechanisms regulating cellular infection and host resistance, and the interplay of alga-parasite interactions with coexisting microorganisms are discussed. [ABSTRACT FROM AUTHOR]

Environmental change, particularly warming and eutrophication, can alter phenology in aquatic systems. Understanding controls on zooplankton phenology is important due to their central role in food webs. While patterns in zooplankton phenology have been well documented, we lack an understanding of how abiotic and biotic drivers influence lake zooplankton phenology during the summer. We examined the phenology of four common zooplankton taxa (Daphnia retrocurva, Skistodiaptomus oregonensis, Mesocyclops spp., Dreissenid veligers) in western Lake Erie during 1995–2022, a period with increasing eutrophication and Bythotrephes longimanus biomass. Many phenology metrics varied by 3 weeks or more from 1995 to 2022. The dominant controls of phenology were temperature and biotic factors, especially grazer‐defended phytoplankton (cyanobacteria and other colonial or filamentous taxa) and the invasive predator B. longimanus, which frequently interacted. Our results show that aspects of environmental change interact to shape zooplankton phenology, which can influence phytoplankton biomass and energy flow to higher trophic levels. [ABSTRACT FROM AUTHOR]

The timing of spring phytoplankton blooms is crucial to many species that have adapted their development to benefit from the enhanced feeding opportunity they offer. Any change to their timing may affect the productivity of an entire ecosystem. This study explores the relationship between the ocean climate, the timing of the spring bloom and the secondary production on the Newfoundland and Labrador shelf. It is found that over interannual cycles, the ocean climate is significantly correlated with the timing of the bloom and the abundance of Calanus finmarchicus, a key zooplankton species for the ecosystem. It also appears that the spring bloom is initiated by the onset of ocean re‐stratification following winter mixing. Understanding how annual variation in climate relates to the timing of the spring bloom and zooplankton abundance, that is, the base of the marine food web, can inform the development of ecosystem‐informed models for higher trophic levels. [ABSTRACT FROM AUTHOR]

Copepods dominate marine zooplankton in abundance and play key roles in pelagic food webs. These small crustaceans show high taxonomic and functional diversity. Although there has been considerable research on their taxonomy, only a few studies have focused on their functional traits. In this study, we analyzed the functional traits of 95 copepod species, considering their body size, trophic regime, feeding behavior, and spawning strategy. Based on samples collected during two surveys (autumn 2020 and summer 2021) located in the coastal waters of three gulfs (Gaeta, Naples, and Salerno) in the highly populated Campania region (the central Tyrrhenian Sea, NW Mediterranean), we identified nine functional groups of copepods with different characteristics. The group that comprised herbivorous copepods with feeding currents and a broadcast strategy was the most abundant in both seasons and all gulfs. This group was dominated by Acartia clausi, Centropages typicus, Temora stylifera, and the Paracalanus parvus complex. The other functional groups showed differences in their temporal and spatial distribution. Our study reports the functional diversity of copepods along the Campania coast, thus contributing to advancing our knowledge of the planktonic trophic structure in a region of considerable importance due to its marine resources and services. [ABSTRACT FROM AUTHOR]

Urbanisation affects not only large ecosystems but also small ones, such as ponds, through changes in environmental parameters. It consequently impacts the biodiversity of all organisms, including zooplankton. However, disturbances due to urbanisation may have different levels of impact on ecosystems. We therefore aimed to determine how different degrees of disturbance and environmental parameters affect zooplankton species diversity and which zooplankton species could indicate the disturbance degree and water quality of tropical urban ponds. We recorded 63 species, namely, 46 species of rotifers and 17 species of cladocerans. The overall species diversity tended to decrease from the low to the high disturbance areas. The level of disturbance, temperature, salinity, phycocyanin and vegetation affected the zooplankton species composition. More common species were found in the low disturbance areas, and among the few species in the highly disturbed areas, the distribution was more specific. We therefore propose that rotifer and cladoceran species be used as bioindicators to indicate water quality and the degree of disturbance. Our study provides significant insights into the relationship between zooplankton and environmental factors in oriental tropical regions and presents a framework for identifying crucial species associated with levels of disturbance, particularly in the habitats of Oriental Asia. [ABSTRACT FROM AUTHOR]

Here a nonlinear mathematical model for an aquatic ecosystem containing both non-toxic and toxin-producing algal blooms is formulated and analyzed. The presence of harmful algae impacts the aquatic population, subsequently affecting the human population that relies on zooplankton (fish, crabs, etc.). It also deteriorates the water quality, and it is advisable not to use water from lakes containing harmful algae. Here, our focus is to understand the dynamics of aquatic ecosystems when we have both types of algae, one that is non-toxic and acts as food to zooplankton, and another that is toxin-producing algae that causes death to zooplankton. The predation of zooplankton on algae influences the growth of the algae population. First, we consider a deterministic model, and later, this model is extended to stochastic model to check whether it has any impact on the dynamics of the populations under consideration. Various equilibria of the proposed model are derived, and the local stability of these equilibria is thoroughly examined. The existence of Hopf-bifurcation is also demonstrated for a suitable set of parameters. The results of deterministic and stochastic models are compared using numerical simulation. Upon examining our results and simulation data, it is evident that modifying specific key parameters, such as the growth rate of non-toxic algae due to nutrient intake and the parameter associated with the predation of non-toxic algae by zooplankton, has a substantial impact on algal bloom dynamics. Minor adjustments to these parameters can result in an augmented presence of non-toxic algae and a simultaneous decrease in toxin-producing algae, aligning with the primary objectives set by policymakers. [ABSTRACT FROM AUTHOR]

Climate change significantly impacts marine ecosystems, affecting zooplankton and phytoplankton dynamics, crucial components of the pelagic food web. This study utilizes the Regional Ocean Modeling System (ROMS) coupled with a nitrogen-based nutrient, phytoplankton, zooplankton, and detritus (NPZD) model to investigate plankton seasonal patterns in the North of the Gulf of Oman, a region undergoing ecological alterations due to environmental and anthropogenic factors. The model, validated against satellite-derived GMIS chlorophyll-a data from 2008-2009, reveals peak chlorophyll-a concentrations in late winter and early spring, with a reduction in summer due to the presence of a seasonal thermocline layer. The findings underscore the pivotal role of zooplankton grazing in modulating phytoplankton biomass and highlight the intertwined influence of physical and biological processes on plankton seasonality, offering insights into the ecological dynamics of the Oman Sea in the context of climate change. [ABSTRACT FROM AUTHOR]

Ongoing ocean deoxygenation is threatening marine organisms globally. In eastern boundary upwelling systems, planktonic copepods dominate the epipelagic zooplankton, being crucial in the marine food web. Yet, they must cope with severe hypoxia caused by shoaling of the oxygen minimum zone. Based on laboratory experiments during 2021, we found differential responses in the metabolic rate (MR) and critical oxygen partial pressure of three abundant copepods. Calanoides patagoniensis doubled its MR during the upwelling season, so better exploiting the spring phytoplankton bloom for feeding and reproduction while maintaining their critical oxygen partial pressure unchanged between seasons. Contrastingly, Paracalanus cf. indicus and Acartia tonsa, maintained their MRs throughout seasons, but significantly increased their critical oxygen partial pressure during the upwelling period, becoming less tolerant to hypoxia. Field observations showed that oxygen levels equal to or lower than the critical oxygen partial pressure is a common condition (70% of occurrence) that copepods encounter during the year in the upper 50 m layer. These findings suggest a species‐dependent trade‐off between the MR and the critical oxygen partial pressure, where some species can maintain the latter despite fluctuations in their MR (improved hypoxia tolerance) or maintain their MR at the expenses of a larger critical oxygen partial pressure (improved energy expenditures). These adaptive responses, under oxygen levels equal to or lower than the critical oxygen partial pressure, suggest that exacerbated hypoxia, driven by ocean deoxygenation and increased upwelling, will alter copepod distribution and cause higher copepod mortality, with potentially drastic consequences for marine food webs. [ABSTRACT FROM AUTHOR]

Particle mixing by benthic fauna beneath the sediment‐water interface (or bioturbation) fundamentally challenges the proxy based retrieval of past climatic conditions from deep‐sea sediment cores. Previous efforts targeted the impacts of bioturbation on the nature of paleoceanographic changes gleaned from the proxy record, whereas impacts on seasonal and/or interannual variability reconstructions have received less attention. We present TurbIFA (Tracking uncertainty of reworking & bioturbation on IFA), a software that adapts and combines existing algorithms to quantitatively estimate the impact of sediment reworking and other uncertainties and assess significance of ocean and climate variability reconstructions based on individual foraminiferal analyses (IFA). Building upon previous idealized investigations of bioturbation using hydroclimate‐sediment simulations, TurbIFA advances the IFA proxy system modeling such that users may directly assess the sensitivity of their data to various local parameters related to shell reworking across the global ocean. Using the output of state‐of‐the‐art coupled atmosphere‐ocean general circulation models, TurbIFA simulates planktic foraminiferal δ18O or Mg/Ca‐temperature signal carriers and evaluates uncertainties in the sample size, analytical protocols along with as those arising from bioturbation. Application of TurbIFA to synthetic and existing data sets indicates that the significance of IFA‐based reconstructions can be assessed once the impacts of sediment accumulation rates, sediment mixed layer depths, length of time integrated by the chosen IFA sampling interval, and changes in the amplitude of climate variability (i.e., the targeted environmental signal) are comprehensively evaluated. We contend that TurbIFA can aid quantitative assessments of past seasonal and interannual variability gleaned from the paleoceanographic record. Plain Language Summary: Planktic foraminifera are marine zooplankton with a life cycle of approximately a month. They dwell in the upper ocean, where they precipitate calcium carbonate shells that, postmortem, settle through the water column and become a main constituent of deep‐ocean sediments. The geochemical composition of individual planktic foraminiferal shells provides snapshots of past surface ocean temperatures during their lifespan. Statistical distributions of these data inform on the past seasonal and/or interannual climate variability, but post‐depositional processes may bias these reconstructions. Here we quantify the effects of the vertical displacement of foraminiferal shells in sediments by benthic microfauna, which contaminates sediment core samples with older shells deposited under colder or warmer climates. The code routines are available in an open‐source repository. The final user can define their study‐specific variables as inputs, thereby allowing the application of this method to a broad spectrum of climate and sedimentary settings. Key Points: A new software (TurbIFA) quantifies the uncertainties in IFA data sets tied to sampling, analytical errors, and bioturbationTurbIFA assesses the sensitivity of IFA reconstructions to bioturbation parameters and propagates analytical and sampling uncertaintiesApplication to existing data sets showcases its ability to assess statistical significance of IFA‐based climate variability reconstructions [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are a growing concern in marine ecosystems, with their presence reported in various aquatic environments. This editorial highlights the need for a better understanding of the ecological consequences of MPs, particularly their effects on eukaryotic microbes (EM). EM play a crucial role in carbon transfer and are affected by MPs through ingestion and interactions with other components of the microbial loop. The articles featured in this research topic explore the effects of MPs on copepod microbiota, the gut microbiome of ventiferous crabs, prey-predator interactions, and the overall functioning of marine ecosystems. These studies emphasize the far-reaching impacts of MPs on energy flow and the need for further research in this area. [Extracted from the article]

This paper concerns a discrete-time phytoplankton–zooplankton model in which the effects of toxin produced by phytoplankton and refuges provided for phytoplankton on the interactions between phytoplankton and zooplankton are considered. We first discuss the existence and stability of fixed points. When two parameters change, it is shown that there exist some codimension-two bifurcations, including fold-flip bifurcation and strong resonance bifurcations. Moreover, we give the corresponding bifurcation diagrams, phase diagrams and maximum Lyapunov exponent diagrams. The results show that phytoplankton toxin and refuges play important roles in the occurrence and termination of algal blooms in freshwater lakes. [ABSTRACT FROM AUTHOR]

Photosynthesis in the surface ocean and subsequent export of a fraction of this fixed carbon leads to carbon dioxide sequestration in the deep ocean. Ecological relationships among plankton functional groups and theoretical relationships between particle size and sinking rate suggest that carbon export from the euphotic zone is more efficient when communities are dominated by large organisms. However, this hypothesis has never been tested against measured size spectra spanning the >5 orders of magnitude found in plankton communities. Using data from five ocean regions (California Current Ecosystem, North Pacific subtropical gyre, Costa Rica Dome, Gulf of Mexico, and Southern Ocean subtropical front), we quantified carbon-based plankton size spectra from heterotrophic bacteria to metazoan zooplankton (size class cutoffs varied slightly between regions) and their relationship to net primary production and sinking particle flux. Slopes of the normalized biomass size spectra (NBSS) varied from -1.6 to -1.2 (median slope of -1.4 equates to large 1-10 mm organisms having a biomass equal to only 7.6% of the biomass in small 1-10 µm organisms). Net primary production was positively correlated with the NBSS slope, with a particularly strong relationship in the microbial portion of the size spectra. While organic carbon export co-varied with NBSS slope, we found only weak evidence that export efficiency is related to plankton community size spectra. Multi-variate statistical analysis suggested that properties of the NBSS added no explanatory power over chlorophyll, primary production, and temperature. Rather, the results suggest that both plankton size spectra and carbon export increase with increasing system productivity. [ABSTRACT FROM AUTHOR]

As predators of bacteria and viruses and as food sources for microzooplankton, heterotrophic flagellates (HFs) play an important role in the marine micro-food web. Based on the global climate change's impact on marine ecosystems, particularly sea ice melting, we analyzed the community composition and diversity of heterotrophic flagellates, focusing on the Antarctic Cosmonaut Sea. During the 36th China Antarctic research expedition (2019-2020), we collected seawater samples, subsequently analyzing HFs through IlluminaMiSeq2000 sequencing to assess community composition and diversity. Notable variations in HFs abundance were observed between the western and eastern sectors of the Cosmonaut Sea, with a distinct concentration at a 100-meter water depth. Different zones exhibited diverse indicators and dominants taxa influenced by local ocean currents. Both the northern Antarctic Peninsula and the western Cosmonaut Sea, where the Weddell Eddy and Antarctic Land Slope Current intersect, showcased marine stramenopiles as dominant HFs species. Our findings offer insights into dominant taxa, spatial distribution patterns among heterotrophic flagellates, correlations between taxa distribution and environmental factors, and the exploration of potential indicator taxa. [ABSTRACT FROM AUTHOR]

Zooplankton community composition of northern lakes is changing due to the interactive effects of climate change and recovery from acidification, yet limited data are available to assess these changes combined. Here, we built a database using archives of temperature, water chemistry and zooplankton data from 60 Scandinavian lakes that represent broad spatial and temporal gradients in key parameters: temperature, calcium (Ca), total phosphorus (TP), total organic carbon (TOC), and pH. Using machine learning techniques, we found that Ca was the most important determinant of the relative abundance of all zooplankton groups studied, while pH was second, and TOC third in importance. Further, we found that Ca is declining in almost all lakes, and we detected a critical Ca threshold in lake water of 1.3 mg L−1, below which the relative abundance of zooplankton shifts toward dominance of Holopedium gibberum and small cladocerans at the expense of Daphnia and copepods. Our findings suggest that low Ca concentrations may shape zooplankton communities, and that current trajectories of Ca decline could promote widespread changes in pelagic food webs as zooplankton are important trophic links from phytoplankton to fish and different zooplankton species play different roles in this context. [ABSTRACT FROM AUTHOR]

As an important component of lake ecosystems, plankton are often used as indicators to evaluate the health of aquatic ecosystems, such as lakes and reservoirs. The plankton integrity index (P-IBI) is a highly utilized method for evaluating the ecological health of the lakes. This study took Dianchi Lake, located in the Yangtze River Basin, as the research object and analyzed the phytoplankton, zooplankton communities, and environmental factors at 11 sampling points in this lake during the wet season (July) in 2022 and the dry season (February) in 2023. The P-IBI was established to evaluate the health status of this lake ecosystem. The results showed that a total of 83 species of phytoplankton and 31 species of zooplankton were identified in Dianchi Lake, and the number of plankton species in the dry season was significantly higher than that in the wet season. The P-IBI evaluation results for the two hydrological periods were generally "good". Linear regression analysis showed that there was a certain negative correlation between the P-IBI value and the comprehensive trophic level index (TLI), and the evaluation results were generally in line with the actual situation of the water body. Redundancy analysis (RDA) showed that there was a significant correlation between the P-IBI and its constituent parameters and individual water quality environmental factors, such as total nitrogen (TN) and electrical conductivity (EC). In summary, by reducing errors caused by spatial and temporal changes across various hydrological periods, P-IBI represents a more scientifically rigorous technique for lake water ecological health assessments within a certain time range. [ABSTRACT FROM AUTHOR]

Because of its temperate location, high dynamic range of environmental conditions, and extensive human activity, the long-term ecological research site in the coastal Northeastern US Shelf (NES) of the northwestern Atlantic Ocean offers an ideal opportunity to understand how productivity shifts in response to changes in planktonic community composition. Ocean production and trophic transfer rates, including net community production (NCP), net primary production (NPP), gross oxygen production (GOP), and microzooplankton grazing rates, are key metrics for understanding marine ecosystem dynamics and associated impacts on biogeochemical cycles. Although small phytoplankton usually dominate phytoplankton community composition and Chl a concentration in the NES waters during the summer, in August 2019, a bloom of the large diatom genus Hemiaulus, with N 2 -fixing symbionts, was observed in the mid-shelf region. NCP was 2.5 to 9 times higher when Hemiaulus dominated phytoplankton carbon compared to NCP throughout the same geographic area during the summers of 2020–2022. The Hemiaulus bloom in summer 2019 also coincided with higher trophic transfer efficiency from phytoplankton to microzooplankton and higher GOP and NPP than in the summers 2020–2022. This study suggests that the dominance of an atypical phytoplankton community that alters the typical size distribution of primary producers can significantly influence productivity and trophic transfer, highlighting the dynamic nature of the coastal ocean. Notably, summer 2018 NCP levels were also high, although the size distribution of Chl a was typical and an atypical phytoplankton community was not observed. A better understanding of the dynamics of the NES in terms of biological productivity is of primary importance, especially in the context of changing environmental conditions due to climate processes. [ABSTRACT FROM AUTHOR]

In aquatic ecosystems, zooplankton-associated bacteria potentially have a great impact on the structure of ecosystems and trophic networks by providing various metabolic pathways and altering the ecological niche of host species. To understand the composition and drivers of zooplankton gut microbiota, we investigated the associated microbial communities of four zooplankton genera from different seasons in the Baltic Sea using the 16S rRNA gene. Among the 143 ASVs (amplified sequence variants) observed belonging to heterotrophic bacteria, 28 ASVs were shared across all zooplankton hosts over the season, and these shared core ASVs represented more than 25% and up to 60% of relative abundance in zooplankton hosts but were present at low relative abundance in the filtered water. Zooplankton host identity had stronger effects on bacterial composition than seasonal variation, with the composition of gut bacterial communities showing host-specific clustering patterns. Although bacterial compositions and dominating core bacteria were different between zooplankton hosts, higher gut bacteria diversity and more bacteria contributing to the temporal variation were found in Temora and Pseudocalanus, compared to Acartia and Synchaeta. Diet diatom and filamentous cyanobacteria negatively correlated with gut bacteria diversity, but the difference in diet composition did not explain the dissimilarity of gut bacteria composition, suggesting a general effect of diet on the inner conditions in the zooplankton gut. Synchaeta maintained high stability of gut bacterial communities with unexpectedly low bacteria-bacteria interactions as compared to the copepods, indicating host-specific regulation traits. Our results suggest that the patterns of gut bacteria dynamics are host-specific and the variability of gut bacteria is not only related to host taxonomy but also related to host behavior and life history traits. [ABSTRACT FROM AUTHOR]

The ubiquitous occurrence of microplastics and nanoplastics in aquatic environments is of major concern as these priority pollutants are readily ingested by a wide variety of aquatic organisms. Although quantitative data on the interaction of microplastics and even more so on nanoplastics in freshwater environments and their interaction with the aquatic food web are still limited, studies have nevertheless demonstrated that even micro- or nanosized plastic particles can be ingested by various members of the zooplankton functioning as primary consumers. Bacterivorous ciliates are crucial members of the microzooplankton. These fascinating microorganisms are critical components of microbial loops in freshwater environments and are essential links between different trophic levels within the aquatic food web. Ingestion of microscopic plastic particles affects the ciliate cell on a cellular and even on the molecular level. Physical and chemical characteristics such as size, density, and surface properties influence the stability, distribution, retention, transportation, and bioavailability of the microplastic particles for ingestion by ciliates. In turn, the environmental fate of microplastics and nanoplastics can affect their ecotoxicity via surface modifications, such as forming the so-called eco-corona. The consequences of the interaction of ciliates with microplastics and nanoplastics are the potential bioaccumulation of plastic particles through the food web and the possible interference of these emerging pollutants with controlling bacterial and possibly even viral abundance in freshwater environments. Due to the limited data available, studies elucidating the environmental bacterivorous ciliate-micro-/nanoplastics interaction are a priority research topic if we want to holistically assess the environmental fate and ecotoxicity of these pollutants. [ABSTRACT FROM AUTHOR]

Eutrophication, climate-induced warming, and salinity fluctuations are altering the fatty acid profiles and the availability of essential polyunsaturated fatty acids (PUFAs) in marine zooplankton communities. Limnocalanus macrurus Sars G.O., 1863 is a large calanoid copepod inhabiting the low-salinity areas in the Baltic Sea, where it is a major source of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) to commercially important fish. L. macrurus is sensitive to warming, eutrophication and hypoxia. As an opportunistic feeder, it is capable of dietary shifts, which affects its fatty acid profiles. Although much studied in boreal lakes, there are only a few studies on the fatty acid profiles of the Baltic Sea populations. This study aimed to compare the fatty acid profiles of L. macrurus in three basins of the Baltic Sea, in relation to the community fatty acids and environmental variables. We collected samples of L. macrurus and filtered plankton community for gas chromatographic fatty acid analyses in August 2021 on R/V Aranda. The nutritional quality of L. macrurus to consumers was lower in the Gulf of Finland (GoF) compared to the Gulf of Bothnia, indicated by the low levels of DHA and EPA, as well as the low n-3/n-6 ratio of PUFAs. The lower ratio of 18:1n-7 to 18:1n-9 implied higher degree of omnivory in GoF. In contrast, a diatom marker 16:1n-7 had high proportion in the Bothnian Bay. High temperatures in GoF may have restricted feeding in the upper water column, possibly forcing a shift towards cyanobacteria or seston-based diet, as interpreted from a high proportion of 18:2n-6 and 18:3n-3. We conclude that the ability of L. macrurus to utilize multiple food sources increases its resilience to environmental change, while the consequences on the nutritional quality may have further cascading effects on the food webs. [ABSTRACT FROM AUTHOR]

Being chemically inert and morphologically similar (<5 mm in size) to the natural prey of copepods, microplastics (MPs) affect them through entanglement, ingestion, and interference with their natural prey selection. The effects of external factors, such as MP, can be observed in the form of alterations in the functional and numerical responses of copepods. Functional response is explained as the relationship between the intake rate of a consumer and the amount of food available in a particular ecotope. Considered three types of functional response: (i) with increasing food density, when intake rate increases linearly until asymptote, called Type-I functional response; (ii) when the proportion of prey ingested by the consumer decreases monotonically with prey density, considered as a Type-II functional response; and (iii) when ingestion rate and food density show a sigmoid relationship, is considered as Type-III functional response. In the present study, we attempted to elucidate the effects of MP on the functional responses of brackish water, demersal, calanoid copepod, Pseudodiaptomus annandalei, feeding on the rotifer Brachionus rotundiformis, and the ciliate Frontonia microstoma. The ability of P. annandalei to survive environmental fluctuations and its nutritional value make it an ecologically important organism in estuarine ecosystems. The experiment for estimation of functional response included four setups with adult and copepodite stages of P. annandalei, each with six replicates at six different prey densities, in the presence and absence of MP particles. Without MPs, P. annandalei showed a typical Type-II functional response, where the proportion of prey consumed significantly declined with increasing prey density. In the MP- applied medium, the proportion of prey consumed did not exhibit a significant relationship with the initial prey density. The number of ciliates and rotifers ingested by copepodites and adults was significantly lower in MP-contaminated medium than in prey either monospecific or in combination with microalgae. Because of the comparable size of MP to the prey species and unspecialized feeding of P. annandalei in natural waters, we hypothesized reduced predation rates as a result of pseudo-satiation resulting from MP ingestion leading to malnutrition and MP storage in copepod biomass. [ABSTRACT FROM AUTHOR]

Bioluminescence is ubiquitous in marine ecosystems and found in uni- and multicellular organisms. Bioluminescent displays can be used to deter predators, attract mates, and lure and hunt prey. Mechanically stimulated flash kinetics of zooplankton and dinoflagellates are life stage-dependent and species-specific, and could prove effective at identification and monitoring biodiversity in bioluminescent species. Here, we provide a comprehensive review of mechanically stimulated bioluminescence for the main dinoflagellate and zooplankton clades in marine environments and assemble known flash kinetics and spectral emission data. Instruments and methods used in measuring bioluminescence are also discussed. Applications, research gaps, perspectives, and biases in approaches to studying bioluminescence are identified. Moreover, emission kinetics of most zooplankton are very poorly known and constitute a critical gap. Lastly, available knowledge is interpreted in terms of potential future changes in global bioluminescence driven by climate change. [ABSTRACT FROM AUTHOR]

Eutrophication, increased temperatures and stratification can lead to massive, filamentous, N2‐fixing cyanobacterial (FNC) blooms in coastal ecosystems with largely unresolved consequences for the mass and energy supply in food webs. Mesozooplankton adapt to not top‐down controlled FNC blooms by switching diets from phytoplankton to microzooplankton, resulting in a directly quantifiable increase in its trophic position (TP) from 2.0 to as high as 3.0. If this process in mesozooplankton, we call trophic lengthening, was transferred to higher trophic levels of a food web, a loss of energy could result in massive declines of fish biomass. We used compound‐specific nitrogen stable isotope data of amino acids (CSIA) to estimate and compare the nitrogen (N) sources and TPs of cod and flounder from FNC bloom influence areas (central Baltic Sea) and areas without it (western Baltic Sea). We tested if FNC‐triggered trophic lengthening in mesozooplankton is carried over to fish. The TP of cod from the western Baltic (4.1 ± 0.5), feeding mainly on decapods, was equal to reference values. Only cod from the central Baltic, mainly feeding on zooplanktivorous pelagics, had a significantly higher TP (4.6 ± 0.4), indicating a strong carry‐over effect trophic lengthening from mesozooplankton. In contrast, the TP of molluscivorous flounder, associated with the benthic food web, was unaffected by trophic lengthening and quite similar reference values of 3.2 ± 0.2 in both areas. This suggests that FNC blooms lead to a large loss of energy in zooplanktivorous but not in molluscivorous mesopredators. If FNC blooms continue to trigger the detour of energy at the base of the pelagic food web due to a massive heterotrophic microbial system, the TP of cod will not return to lower TP values and the fish stock not recover. Monitoring the TP of key species can identify fundamental changes in ecosystems and provide information for resource management. [ABSTRACT FROM AUTHOR]

The trophic niche of invasive species can vary overtime because of different processes related to ecological opportunity and invader activity that condition biological interactions with the native biodiversity. We conducted an annual-based survey of the trophic niche of the mysid Hemimysisanomala in the largest European peri-alpine lake by combining molecular and isotope analyses. We hypothesized that the population trophic niche width would vary seasonally, expanding in warm periods due to greater ecological opportunities and higher mysid metabolic activity. Molecular analyses identified a diversified set of prey throughout the year ranging from autotrophic protists to zooplankton and converged with isotope analyses to support the diet seasonality hypothesis of H.anomala with wider trophic niches and, in a lower extent, richer diets in spring and summer when compared to autumn and winter. Isotope analyses also highlighted a seasonal pattern in resources used with a dominance of pelagic reliance in summer and autumn. These results underlined the significant seasonal variability in the trophic niche of this invasive mysid suggesting that future assessments of its ecological impacts should account for the temporal variations of its trophic interactions with the native biodiversity. [ABSTRACT FROM AUTHOR]

Knowledge of the trophic structure and variability of planktonic communities is a key factor in understanding food-web dynamics and energy transfer from zooplankton to higher trophic levels. In this study, we investigated how stable isotopes of mesozooplankton species varied seasonally (winter, spring, autumn) in relation to environmental factors and plankton size classes in a temperate coastal ecosystem. Our results showed that spring is characterized by the strongest vertical and size-structured plankton food-web, mainly fueled by the phytoplankton bloom. As a result, spring displayed the largest isotopic niche space and trophic divergence among species. On the contrary, both pelagic and benthic-derived carbon influenced low productive seasons (winter and autumn), resulting in more generalist strategies (trophic redundancy). Stable isotope mixing models were used to explore how different seasonal structures influenced the overall food web up to predatory plankton (i.e., mysids, chaetognaths, and fish larvae). Different feeding strategies were found in spring, with predators having either a clear preference for larger prey items (> 1 mm, for herring and dab larvae) or a more generalist diet (sprat and dragonets larvae). During low productive seasons, predators seemed to be more opportunistic, feeding on a wide range of size classes but focusing on smaller prey. Overall, the food-web architecture of plankton displayed different seasonal patterns linked to components at the base of the food web that shaped the main energy fluxes, either from phytoplankton or recycled material. Additionally, these patterns extended to carnivorous plankton, such as fish larvae, emphasizing the importance of bottom-up processes. [ABSTRACT FROM AUTHOR]

This document is a preface to a special issue series in the journal Aquatic Ecosystem Health & Management, focusing on the ecology and dynamics of Lake Erie. The authors, Mohiuddin Munawar and Stuart A. Ludsin, have a long history of studying Lake Erie and its ecosystem. They discuss the history of monitoring and research efforts on Lake Erie, including the development of the Great Lakes Water Quality Agreement and the establishment of monitoring programs. The preface also mentions the recent Cooperative Science and Monitoring Initiative (CSMI) focused on Lake Erie, which aimed to understand the impacts of eutrophication and harmful algal blooms on the lake's food web. The authors express their gratitude to the contributors and editors involved in the special issue series and hope that it will contribute to a better understanding of Lake Erie's ecology. [Extracted from the article]

This document is a synthesis of several papers that explore the ecology of Lake Erie and the challenges it faces. The papers cover topics such as water chemistry, primary productivity, cyanotoxins, and water quality. The research highlights the impact of anthropogenic changes, such as climate change and invasive species, on the lake's ecosystem. The findings emphasize the need for further monitoring and research to better understand and manage Lake Erie. The studies also emphasize the importance of episodic events in driving spatial and temporal heterogeneity in water quality and the distribution of organisms. [Extracted from the article]

Marine food webs are strongly size-structured and size-based analysis of communities is a useful approach to evaluate food webs in a way that can be compared across systems. Fatty acid analysis is commonly used to identify diet sources of species, offering a powerful complement to stable isotopes, but is rarely applied to size-structured communities. In this study, we used fatty acids and stable isotopes to characterize size-based variation in prey resources and trophic pathways over a nine-month temperate coastal ocean time series of seven plankton size classes, from > 0.7-μm particulate organic matter through > 2000-μm zooplankton. Zooplankton size classes were generally distinguishable by their dietary fatty acids, while stable isotopes revealed more seasonal variability. Fatty acids of zooplankton were correlated with those of their prey (particulate organic matter and smaller zooplankton) and identified trophic pathways, including widespread ties to the microbial food web. Diatom fatty acids also contributed to zooplankton but fall blooms were more important than spring. Concurrent isotope-based trophic position estimates and fatty acid markers of carnivory showed that some indicators (18:1ω9/18:1ω7) are not consistent across size classes, while others (DHA:EPA) are relatively reliable. Both analysis methods provided distinct information to build a more robust understanding of resource use. For example, fatty acid markers showed that trophic position was likely underestimated in 250-μm zooplankton, probably due to their consumption of protists with low isotopic fractionation factors. Applying fatty acid analysis to a size-structured framework provides more insight into trophic pathways than isotopes alone. [ABSTRACT FROM AUTHOR]

The understanding of factors affecting resource uptake is important to elucidate community dynamics in aquatic ecosystems. Here, we analyzed nutrient–phytoplankton and phytoplankton–zooplankton interactions in open water areas without macrophytes and in areas with floating and submerged macrophytes in the tropical Cajueiro reservoir, semiarid Brazil. Phytoplankton species were classified into functional groups according to life form and cell size, and zooplankton species were grouped based on functional feeding groups and trophic guilds. Macrophytes favored the effect of nutrients on phytoplankton and the availability of prey for the zooplankton. In open water, unicellular and flagellated phytoplankton were positively influenced by nitrate and inorganic phosphate, while colonial, filamentous, small, medium and large phytoplankton were positively influenced by total phosphorus and nitrite. Colonial phytoplankton, mainly filamentous cyanobacteria, was positively associated with zooplankton in areas with macrophytes, while flagellated phytoplankton was negatively related to zooplankton in open water areas. Our results showed that the presence of floating and submerged macrophytes has different influences on the effect of nutrients on phytoplankton and on the effects of phytoplankton on zooplankton in Cajueiro reservoir, and this should be considered when analyzing these communities' dynamics in similar environments, i.e. tropical reservoirs. [ABSTRACT FROM AUTHOR]

In the light of the current biodiversity crisis that affects in particular freshwater ecosystems, it is crucial to understand the effects of functional diversity loss on phytoplankton-zooplankton interactions in freshwater food webs. Here, we simulated the loss of phytoplankton trait diversity by applying different intensities of mechanical disturbance to a natural phytoplankton community in a laboratory experiment. Different disturbance regimes clearly affected the trait distribution and functional diversity of these phytoplankton communities. In the experiment's second phase, these altered communities were provided as a food source to the zooplankton grazers Daphnia longispina and Eudiaptomus graciloides and their life-history traits and lipid compositions were investigated. Both zooplankton fitness and reproductive success were affected differently, depending on the grazers' feeding modes. Phytoplankton fatty acid composition was generally reflected in the consumers' tissue. Nevertheless, some selective PUFAs accumulation occurred and mismatches in some fatty acids suggested a possible enzymatic modification of dietary fatty acids adopted to face biochemical deficiencies of the diets. Overall, this study highlights how a loss of specific traits in resource communities could impact consumer communities, and shows how these altered community traits may affect food web dynamics. [ABSTRACT FROM AUTHOR]

The northern Patagonian lakes are located in the South American Andes between 38-41° of Argentina and Chile. In their original stage, these lakes were described as ultraoligotrophic due the presence of perennial native forest that avoided the nutrients inputs from surrounding basin. The first studies described low phytoplankton abundances, but in recent studies, the presence of mixotrophic ciliates has been reported that may be a basis on trophic webs under the ultraoligotrophic status. They can graze on heterotrophic bacteria and nannoflagellates and can also do photosynthesis. Under the ultraoligotrophic status, the bacteria would have the basis on pelagial food webs because these would be grazed by zooplankton and mixotrophic ciliates. Nevertheless, when the lakes have a transition from oligotrophy to mesotrophy, although the bacterial biomass increases, they would not have an exclusive role because of a complex interaction between phytoplankton and grazer zooplankton. [ABSTRACT FROM AUTHOR]

The current investigation was conducted on hydrobiological parameters and plankton diversity in the Yamuna River at Okhla Barrage. The various water quality parameters were investigated, and found that the pH ranged from 7.35±0.02 to 8.10±0.09, temperature varied from 20.79±0.02 to 32.29±0.05!, dissolved oxygen (DO) levels range from 1.72±0.08 to 3.6±0.12 mg/l, total dissolved solids (TDS) ranged from 179.625±36.605 to 382.75±0.875 mg/L, electrical conductivity (EC) went from 759.25±9.37 to 1527.25±3.47 μs/cm and free CO2 levels varied from 8.4±0.93 to 10.5±0.27 mg/L. There are 51 genera of plankton, including 31 genera of phytoplankton and 20 genera of zooplankton. Phytoplanktons are categorized into four major groups: Bacillariophyceae, Chlorophyceae, Cyanophyceae, and Euglenophyceae, and zooplankton belonging to Protozoa, Rotifera, Copepoda and Cladocera. The phytoplankton population exhibited fluctuations, reaching its peak in October (13,000 per litre) and its lowest point in July (10,400 per litre). On the other hand, the highest zooplankton population was recorded in October, reaching 11,600 per litre, while the lowest count was observed in August, with only 5,200 zooplankton per litre. Regarding diversity indices, the highest and lowest values for phytoplankton occurred in July (1.054) and August (0.849), respectively. The diversity index of zooplankton ranged from 1.381 in November to 1.249 in August, with November having the highest diversity index value. [ABSTRACT FROM AUTHOR]

A two-year (July 2021 - June 2023) study was done the physico-chemical parameters and zooplankton diversity of the Dholi Dhaja Dam in Surendranagar, Gujarat, India. To assess waterbody efficiency, various parameters were monitored, including pH, solids (total dissolved, total, and suspended), and oxygen levels (dissolved and biological oxygen demand). Water samples were collected from specific points, 21 distinct zooplankton species belonging to five taxonomic groups: Protozoa, Rotifera, Copepoda, Cladocera, and Ostracoda were identified from the selected study site. Significant positive correlations were observed between zooplankton diversity and both pH (r = .710**, p < .01) and BOD (r = .598**, p < .01). This suggests that increased alkalinity and nutrient richness in the water promote greater zooplankton diversity. These findings contribute to our understanding of Dholi Dhaja Dam's ecological status and the relationship between zooplankton and physicochemical parameters of this study site. [ABSTRACT FROM AUTHOR]

This article discusses the field of aquatic viral ecology and the role of viruses in planktonic food webs. It highlights the significant impact of viruses on mortality and disease in aquatic ecosystems, particularly in plankton populations. The article also explores the interactions between viruses and zooplankton, as well as the role of viruses in biogeochemical cycles and ecosystem recovery. Additionally, it discusses the influence of global climate change on virus-host interactions and the need for further research in this area. Overall, the article emphasizes the importance of understanding virus-plankton interactions for ecosystem stability and carbon flow. [Extracted from the article]

Microplastics (MPs) are plastic particles <5 mm in size, that end up ultimately in marine and freshwater ecosystems, adversely affecting various ecological functions. With the multifaceted roles of fungi and their diverse modes of interaction such as saprobic, epibiotic, endobiotic, parasitic, and symbiotic or being a nutritionally enriched food source in aquatic ecosystems, the effect of MPs on fungi-plankton interactions is still less explored. Properties of MPs such as ⑴ size range similar to those of microeukaryotes, (ii) substrate for unique microbiota, (iii) ability to be transported from the source to faraway waterbodies, and (iv) sorption of pollutants, have adverse effects on various guilds of ecological organization. MPs also tend to alter nutrient cycling and inhibit efficient energy transfer through microbial and mycoloop in an ecosystem. This paper comprehensively reviews the effect of MPs at the population and community level on the complex ecological (fungi-phytoplankton-zooplankton) interactions with an emphasis on the role of fungi in the aquatic ecosystem. Examination of existing literature revealed that MPs can interfere in ecosystem functioning by acting in synergy with fungi, while antagonistically affecting the community and vice-versa. Herein, we explore current understanding of the effect of MPs on major components of microbial and mycoloop in the marine food web, elaborating MPs-mediated changes in the ecosystem functioning, identifying research gaps, and highlighting the need for future research. [ABSTRACT FROM AUTHOR]

Interspecific hybridization events are on the rise in natural systems due to climate change disrupting species barriers. Across taxa, microsatellites have long been the molecular markers of choice to identify admixed individuals. However, with the advent of high‐throughput sequencing easing the generation of genome‐wide datasets, incorrect reports of hybridization resulting from microsatellite technical artefacts have been uncovered in a growing number of taxa. In the marine zooplankton genus Calanus (Copepoda), whose species are used as climate change indicators, microsatellite markers have suggested hybridization between C. finmarchicus and C. glacialis, while other nuclear markers (InDels) never detected any admixed individuals, leaving the scientific community divided. Here, for the first time, we investigated the potential for hybridization among C. finmarchicus, C. glacialis, C. helgolandicus and C. hyperboreus using two large and independent SNP datasets. These were derived firstly from a protocol of target‐capture applied to 179 individuals collected from 17 sites across the North Atlantic and Arctic Oceans, including sympatric areas, and second from published RNA sequences. All SNP‐based analyses were congruent in showing that Calanus species are distinct and do not appear to hybridize. We then thoroughly re‐assessed the microsatellites showing hybrids, with the support of published transcriptomes, and identified technical issues plaguing eight out of 10 microsatellites, including size homoplasy, paralogy, potential for null alleles and even two primer pairs targeting the same locus. Our study illustrates how deceptive microsatellites can be when applied to the investigation of hybridization. [ABSTRACT FROM AUTHOR]

Copepods are the most abundant organisms in marine zooplankton and the primary components of the food chain. They are hotspots for highly adaptable microorganisms, which are pivotal in biogeochemical cycles. The microbiome, encompassing microorganisms within and surrounding marine planktonic organisms, holds considerable potential for biotechnological advancements. Despite marine microbiome research interests expanding, our understanding of the ecological interactions between microbiome and copepods remains limited. This review intends to give an overview of the recent studies regarding the microbiome associated with marine copepods, with particular focus on the diversity of bacteria and fungi. The significance of copepod-associated microbiomes in different contexts, such as aquaculture and biodegradation processes, was evaluated. The ability of the microbiome to mitigate harmful bacterial growth in cultured organisms was also explored. The microbiome associated with copepods has demonstrated efficacy in reducing the proliferation of detrimental bacteria in aquaculture, paving the way for the commercial utilization of natural zooplankton in fish rearing. Additionally, copepod-associated microbiomes may play a role in addressing marine environmental challenges, such as the bioremediation of polluted marine matrices. Overall, this review represents a basis for investigating intricate copepod-associated microbiomes and their diverse applications, enhancing our comprehension of the ecological and evolutionary significance of marine microbiomes. [ABSTRACT FROM AUTHOR]

Shipping is a large industry responsible for atmospheric emissions of hazardous substances including SOX, NOX, and particulate matter. Many ships have installed exhaust gas cleaning systems (scrubbers) to remove primarily SOX from the exhaust, but the hazardous substances are instead transferred to the water used in the scrubbing process. Ships with closed-loop scrubbers recirculate the water but can still discharge around 126-150 m³ directly to the surrounding marine environment every day. The discharged water contains metals and organic substances, such as polycyclic aromatic hydrocarbons, that are known to be toxic to marine zooplankton. Here we show that closed-loop scrubber washwater is toxic to communities of marine mesozooplankton at our lowest tested dilution, 1.5% (v/v), and affects survival, reproduction, diversity, and ability to predate on microzooplankton. The cumulative toxic unit of the undiluted closed-loop scrubber washwater was estimated to 17, which indicates that the water could be toxic at levels below what was tested in this study. Among all detected substances, vanadium, copper, benzo[ghi]perylene, nickel, and zinc were identified as toxicity-driving substances in the order listed. Closed-loop scrubber washwater has been shown to affect development and survival in single species of copepods, but here we find evidence of toxicity at the community level, irrespective of seasonal community structure, and that the exposure has potential to disrupt the interactions between trophic levels in the pelagic food web. We show that the closed-loop scrubber washwater cause both lethal and sublethal effects in marine zooplankton, due to contaminants, some of which are persistent in the marine environment. [ABSTRACT FROM AUTHOR]

Zooplankton plays an essential role in marine ecosystems as the link between primary producers (phytoplankton) and higher trophic levels in food webs, and as a dynamic pool of recruits for invertebrates and fish. Zooplankton communities are diverse with a patchy distribution at different spatial scales, influenced by oceanographic processes. The continental shelf of eastern South Africa is narrow and exposed to the western‐boundary Agulhas Current, with some shelter against strong directional flow provided by the broader KwaZulu‐Natal Bight, a coastal offset adjacent to an estuary. We compared zooplankton species richness, diversity and relative abundance of key taxa among sheltered and exposed shelf areas using metabarcoding and community analysis, to explore the ecological role of the bight in a highly dynamic ocean region. Metabarcoding recovered higher richness and diversity at a finer resolution than could previously be achieved with traditional microscopy. Of 271 operational taxonomic units (OTUs) recovered through metabarcoding, 63% could be matched with >95% sequence similarity to reference barcodes. OTUs were dominated by malacostracan crustaceans (161 spp.), ray‐finned fishes (45 spp.) and copepods (28 spp.). Species richness, diversity and the relative abundance of key taxa differed between sheltered and exposed shelf areas. Lower species richness in the bight was partly attributed to structurally homogeneous benthic habitats, and an associated reduction of meroplanktonic species originating from local benthic–pelagic exchange. High relative abundance of a ray‐finned fish in the bight, as observed based on fish eggs and read counts, confirmed that the bight is an important fish spawning area. Overall, zooplankton metabarcoding outputs were congruent with findings of previous ecological research using more traditional methods of observation. [ABSTRACT FROM AUTHOR]

This study was carried out to predict the zooplankton density in the Cip reservoir (Elazığ) with an artificial neural network, using some water quality parameters. The plankton samples were collected monthly from Cip Reservoir in 2021- 2022, using a standard plankton net from three stations. Water temperature, dissolved oxygen, pH, electrical conductivity, secchi disk, alkalinity, total nitrogen and total phosphorus were measured. The actual values of zooplankton density and results obtained from the artificial neural networks were compared. Mean absolute percent error (MAPE) values were calculated with actual values and ANNs values. ANNs values were determined to be close to the real data. MAPE percentage value at the first station was determined as 1.143 for Rotifer, 0.118 for Cladocera, and 0.141 for Copepoda. The MAPE percentage value at the second station was determined as 0.941 for Rotifer, 0.377 for Cladocera, and 0.185 for Copepoda. The MAPE percentage value at the third station was determined as 0.342 for Rotifer, 0.557 for Cladocera, and 0.301 for Copepoda. In the present study, it has been seen that artificial neural networks with a learning feature are successful in predicting zooplankton densities in an aquatic environment. It can be concluded from the study that ANNs are a powerful tool for understanding their relationships with the environment [ABSTRACT FROM AUTHOR]