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A tenet of conservation palaeobiology is that knowledge of past extinction patterns can help us to better predict future extinctions. Although the future is unobservable, we can test the strength of this proposition by asking how well models conditioned on past observations would have predicted subsequent extinction events at different points in the geological past. To answer this question, we analyse the well-sampled fossil record of Cenozoic planktonic microfossil taxa (Foramanifera, Radiolaria, diatoms and calcareous nanoplankton). We examine how extinction probability varies over time as a function of species age, time of observation, current geographical range, change in geographical range, climate state and change in climate state. Our models have a 70-80% probability of correctly forecasting the rank order of extinction risk for a random out-of-sample species pair, implying that determinants of extinction risk have varied only modestly through time. We find that models which include either historical covariates or account for variation in covariate effects over time yield equivalent forecasts, but a model including both is overfit and yields biased forecasts. An important caveat is that human impacts may substantially disrupt range-risk dynamics so that the future will be less predictable than it has been in the past. This article is part of a discussion meeting issue 'The past is a foreign country: how much can the fossil record actually inform conservation?'

Marine bacteria and archaea play key roles in global biogeochemistry. To improve our understanding of this complex microbiome, we employed single-cell genomics and a randomized, hypothesis-agnostic cell selection strategy to recover 12,715 partial genomes from the tropical and subtropical euphotic ocean. A substantial fraction of known prokaryoplankton coding potential was recovered from a single, 0.4 mL ocean sample, which indicates that genomic information disperses effectively across the globe. Yet, we found each genome to be unique, implying limited clonality within prokaryoplankton populations. Light harvesting and secondary metabolite biosynthetic pathways were numerous across lineages, highlighting the value of single-cell genomics to advance the identification of ecological roles and biotechnology potential of uncultured microbial groups. This genome collection enabled functional annotation and genus-level taxonomic assignments for >80% of individual metagenome reads from the tropical and subtropical surface ocean, thus offering a model to improve reference genome databases for complex microbiomes.

Single-cell genomics has transformed many fields of biology, marine microbiology included. Here, we consider the impact of single-cell genomics on a specific group of marine microbes-the planktonic marine archaea. Despite single-cell enabled discoveries of novel metabolic function in the marine thaumarchaea, population-level investigations are hindered by an overall lower than expected recovery of thaumarchaea in single-cell studies. Metagenome-assembled genomes have so far been a more useful method for accessing genome-resolved insights into the Marine Group II euryarchaea. Future progress in the application of single-cell genomics to archaeal biology in the ocean would benefit from more targeted sorting approaches, and a more systematic investigation of potential biases against archaea in single-cell workflows including cell lysis, genome amplification and genome screening. This article is part of a discussion meeting issue Single cell ecology.

Single-cell genomics has transformed many fields of biology, marine microbiology included. Here, we consider the impact of single-cell genomics on a specific group of marine microbes-the planktonic marine archaea. Despite single-cell enabled discoveries of novel metabolic function in the marine thaumarchaea, population-level investigations are hindered by an overall lower than expected recovery of thaumarchaea in single-cell studies. Metagenome-assembled genomes have so far been a more useful method for accessing genome-resolved insights into the Marine Group II euryarchaea. Future progress in the application of single-cell genomics to archaeal biology in the ocean would benefit from more targeted sorting approaches, and a more systematic investigation of potential biases against archaea in single-cell workflows including cell lysis, genome amplification and genome screening. This article is part of a discussion meeting issue 'Single cell ecology'.

Phytoplankton and associated microbial communities provide organic carbon to oceanic food webs and drive ecosystem dynamics. However, capturing those dynamics is challenging. Here, an in situ, semi-Lagrangian, robotic sampler profiled pelagic microbes at 4 h intervals over ~2.6 days in North Pacific high-nutrient, low-chlorophyll waters. We report on the community structure and transcriptional dynamics of microbes in an operationally large size class (>5 μm) predominantly populated by dinoflagellates, ciliates, haptophytes, pelagophytes, diatoms, cyanobacteria (chiefly Synechococcus), prasinophytes (chiefly Ostreococcus), fungi, archaea, and proteobacteria. Apart from fungi and archaea, all groups exhibited 24-h periodicity in some transcripts, but larger portions of the transcriptome oscillated in phototrophs. Periodic photosynthesis-related transcripts exhibited a temporal cascade across the morning hours, conserved across diverse phototrophic lineages. Pronounced silica:nitrate drawdown, a high flavodoxin to ferredoxin transcript ratio, and elevated expression of other Fe-stress markers indicated Fe-limitation. Fe-stress markers peaked during a photoperiodically adaptive time window that could modulate phytoplankton response to seasonal Fe-limitation. Remarkably, we observed viruses that infect the majority of abundant taxa, often with total transcriptional activity synchronized with putative hosts. Taken together, these data reveal a microbial plankton community that is shaped by recycled production and tightly controlled by Fe-limitation and viral activity.

Variability in community composition is often attributed to underlying differences in physical environments. However, predator–prey interactions can play an equally important role in structuring communities. Although environmental differences select for different species assemblages, less is known about their impacts on trait compositions. We develop a trait-based analysis of plankton communities of the southern California Current System across multiple trophic levels, from bacteria to mesozooplankton, and over a gradient of environmental conditions, from the oligotrophic open ocean to coastal upwelling. Across a factor of four differences in total community biomass, we observe similarities in the size structure along the environmental gradient, with the most pronounced departures from proportional variations in the biomasses found in the largest protists (> 40 µm). Differences in the trait distributions emerge within a small range of size groups: greater biomass contribution of larger autotrophs (> 10 µm) is observed only for the upwelling region.

Plankton live under the countervailing selective pressures of predation and ultraviolet radiation (UVR). In lakes, zooplankton are transparent reducing visibility to predatory fishes but are pigmented in the absence of fishes, hypothetically reducing UVR damage. In the sea, planktivorous fishes are widespread, so plankton typically are transparent and ascend to productive surface waters at night to forage and descend during the day to reduce visibility to predators. However, larvae of some species face the unique constraint of traveling in surface currents in the daytime during migrations between adult and larval habitats. We would expect these larvae to be transparent since companion studies demonstrated increased predation risk of pigmented larvae under strong sunlight. Paradoxically, larvae range from being darkly to lightly pigmented. We hypothesize that some larvae are more heavily pigmented to reduce UVR damage, while other species travelling in subsurface currents with low UVR might be more transparent. Linking larval morphology to depth-dependent selective pressures would add a key element to help improve predictions of larval vertical distributions, which are important for simulating larval transport trajectories. We quantitatively tested the hypothesis that selection may have favored photoprotective pigmentation for larvae in the predominantly transparent plankton community while testing the differential effects of UVA and UVB radiation. We measured larval pigmentation of 12 species of crabs and exposed them to visible light only, visible + UVA, or visible + UVA + UVB in the tropics. Controlling for phylogeny, more pigmented species survived UVR better than less pigmented species, especially on sunnier days, though intraspecific comparisons for four species were equivocal. Most species died even from UVA exposure, which has long been regarded as relatively harmless despite penetrating deeper underwater than UVB. Thus, we demonstrate with a phylogenetically controlled analysis that crab larvae are pigmented in the predominantly transparent planktonic community to protect from UVR, improving our understanding of the selective forces acting on animal coloration and the factors determining planktonic distributions, survival, and dispersal. This linkage of morphology with susceptibility will be important for developing mechanistic models of environmental stress responses to better predict larval dispersal in current and future climates.

Plankton is used as a bioindicator of water conditions because plankton has tolerance limits to certain substances, because the presence of plankton in water can provide information about water conditions. Phytoplankton as a biological indicator can determine water quality either through the approach of species diversity and indicator species. Phytoplankton as a biological indicator not only determines the level of water fertility, but also the phase of pollution that occurs in the waters. The study was conducted for 6 (six) months in the waters of the Negara River, which is located in the South Hulu Sungai Regency, South Kalimantan. Sungai Negara is an ecosystem that is important for the life of living things and the surrounding environment. The presence of plankton in waters can provide information about the Negara of the waters. So the purpose of this research is to obtain data on the composition, and diversity of phytoplankton in the waters of the Sungai Negara. The results of the research on the composition, yield and diversity of phytoplankton in the waters of the Negara River were mostly by the type of Navicula sp. which was found at all stations for each sampling.

In Central Europe, a significant proportion of shallow lake ecosystems are represented by artificial fishponds, where phytoplankton and zooplankton are an essential part of the food web. Owing to their high fish stocks and intensive fishery management, most fishponds are now eutrophic or hypertrophic, which has had clear impacts on plankton assemblages. To obtain a better understanding of phytoplankton-zooplankton coupling in fishponds, this study examines their ecological relationships in a cascade of three small fishponds over two subsequent years. In all, 133 phytoplankton taxa were recorded, mostly chlorophytes, diatoms and euglenophytes, and 60 zooplankton taxa. Multivariate analysis revealed dissolved oxygen content, dissolved inorganic nitrogen and biochemical oxygen demand as the main factors influencing phytoplankton biomass, while the most significant environment variables affecting zooplankton composition were dissolved oxygen, phosphate concentrations and conductivity. Co-correspondence analysis revealed a significant relationship between phytoplankton and zooplankton density, with cross-correlations from 76% to 87% within the first four axes. Such a high cross-correlation denotes a strong relationship between phytoplankton and zooplankton, even within the hypertrophic conditions determining fishpond ecosystems.

Marine aggregates are one of the main contributors to carbon sequestration in the deep sea through the gravitational settling of biogenic particles formed from the photosynthetic products of phytoplankton. The formation of large particles due to aggregation processes has been the focus of studies in the past, but recent findings on the spatio-temporal distribution of particles suggests that the fragmentation of aggregates plays an important role in aggregate dynamics. Here, we assessed the yield strength of aggregates derived from natural planktonic communities in order to analyze the cohesive bond strength and further understand fragmentation. The experimental approach was designed around the use of a Couette device, which produces a constant laminar shear flow of water. Aggregates were found to have a higher yield strength (~289 ± 64 nN) during phases of nutrient depletion than those of mineral particles such as montmorillonite. Based on an estimated cohesive bond strength of 96 nN a numerical model to predict the temporal variation of aggregate size was created. The output of this model indicates that cohesive bond strength is a major determinant of the size of aggregates in motion. Our findings suggest that the dynamics of marine aggregates are greatly influenced by cohesive bond strength and the role in fragmentation.

Abstract Community assembly is often treated as deterministic, converging on one or at most a few possible stable endpoints. However, in nature, we typically observe continuous change in community composition, which is often ascribed to environmental change. But continuous changes in community composition can also arise in deterministic, time‐invariant community models, especially food web models. Our goal was to determine why some models produce continuous assembly and others do not. We investigated a simple two‐trophic‐level community model to show that continuous assembly is driven by the relative niche width of the trophic levels. If predators have a larger niche width than prey, community assembly converges to a stable equilibrium. Conversely, if predators have a smaller niche width than prey, then community composition never stabilizes. Evidence that food webs need not reach a stable equilibrium has important implications, as many ecological theories of community ecology based on equilibria may be difficult to apply to such food webs.

Plankton microorganisms play a huge role in the aquatic food web. Recently, it has been proposed to use plankton as a biosensor, since they can react to even minimal perturbations of the aquatic environment with specific physiological changes, which may lead to alterations in morphology and behavior. Nowadays, the development of high-resolution in-situ automatic acquisition systems allows the research community to obtain a large amount of plankton image data. Fundamental examples are the ZooScan and Woods Hole Oceanographic Institution (WHOI) datasets, comprising up to millions of plankton images. However, obtaining unbiased annotations is expensive both in terms of time and resources, and in-situ acquired datasets generally suffer from severe imbalance, with only a few images available for several species. Transfer learning is a popular solution to these challenges, with ImageNet1K being the most-used source dataset for pre-training. On the other hand, datasets like the ZooScan and the WHOI may represent a valuable opportunity to compare out-of-domain and large-scale plankton in-domain source datasets, in terms of performance for the task at hand.In this paper, we design three transfer learning pipelines for plankton image classification, with the aim of comparing in-domain and out-of-domain transfer learning on three popular benchmark plankton datasets. The general framework consists in fine-tuning a pre-trained model on a plankton target dataset. In the first pipeline, the model is pre-trained from scratch on a large-scale plankton dataset, in the second, it is pre-trained on large-scale natural image datasets (ImageNet1K or ImageNet22K), while in the third, a two-stage fine-tuning is implemented (ImageNet → large-scale plankton dataset → target plankton dataset). Our results show that an out-of-domain ImageNet22K pre-training outperforms the plankton in-domain ones, with an average boost in test accuracy of around 6%. In the next part of this work, we adopt three ImageNet22k pre-trained Vision Transformers and one ConvNeXt, obtaining results on par (or slightly superior) with the state-of-the-art, corresponding to the usage of CNN models ensembles, with a single model. Finally, we design and test an ensemble of our Vision Transformers and the ConvNeXt, outperforming the state-of-the-art existing works on plankton image classification on the three target datasets. To support scientific community contribution and further research, our implemented code is open-source and available at https://github.com/Malga-Vision/plankton_transfer. [ABSTRACT FROM AUTHOR]

Marine microbial communities in coastal environments are subject to both seasonal fluctuations and anthropogenic alterations of environmental conditions. The separate influences of temperature and resource‐dependency on phytoplankton growth, community, and ecosystem metabolism are relatively well understood. However, winners and losers in the ocean are determined based on the interplay among often rapidly changing biological, chemical and physical drivers. The direct, indirect, and interactive effects of these conditions on planktonic food web structure and function are poorly constrained. Here, we investigated how simultaneous manipulation of temperature and nutrient availability affects trophic transfer from phytoplankton to herbivorous protists, and their resulting implications at the ecosystem level. Temperature directly affected herbivorous protist composition; ciliates dominated (66%) in colder treatment and dinoflagellates (60%) at warmer temperatures. Throughout the experiments, grazing rates were < 0.1 d−1, with higher rates at subzero temperatures. Overall, the nutrient–temperature interplay affected trophic transfer rates antagonistically when nutrients were amended, and synergistically, when nutrients were not added. This interaction resulted in higher percentages of primary production consumed under nutrient unamended compared to nutrient amended conditions. At the ecosystem level, these changes may determine the fate of primary production, with most of the production likely exported out of the pelagic zone in high‐temperature and nutrient conditions, while high‐temperature and low‐nutrient availability strengthened food web coupling and enhanced trophic transfer. These results imply that in warming oceans, management of coastal nutrient loading will be a critical determinant of the degree of primary production removal by microzooplankton and dependent ecosystem production. [ABSTRACT FROM AUTHOR]

The advent of metabarcoding (metaB) in aquatic ecology has provided a huge amount of information on plankton biodiversity worldwide. However, the large datasets obtained with that approach are still partially explored, especially for what concerns the study of trophic interactions and food webs. In this study, we analysed a metaB time series from the Long‐Term Ecological Research station MareChiara (LTER‐MC) in the Gulf of Naples, Mediterranean Sea, Italy, to describe the link between plankton diversity and food‐web structure. We derived co‐occurrence networks from metaB time series, identified putative trophic interactions among co‐occurrences based on biological information (body size and trophic habit) available for planktonic organisms detected by metaB, and converted co‐occurrence networks into conceptual models of food webs. The latter showed structural properties resembling ecological processes, because network modularity (the presence of semi‐independent sub‐networks) paralleled trophic hierarchy (the dimensional difference between predator and prey). We also analysed the role of planktonic organisms in maintaining network modularity. The largest predators occupied distinct modules, suggesting niche partitioning, whereas the smallest preys worked as fundamental connectors between larger predators (and different modules). Overall, the presence of trophic hierarchy and modularity shown herein supports the view of the high ecological resilience of plankton, pursued via food‐web rewiring, to environmental shifts. [ABSTRACT FROM AUTHOR]

Artisanal and small-scale gold mining (ASGM) activity in Way Ratai River produces heavy metal wastes; therefore, further information regarding heavy metal concentrations in the water was needed, especially in plankton samples. Furthermore, the determination of plankton diversity was also carried out in the waters of Way Ratai to determine the bioconcentration factor (BCF). Eight sampling sites were chosen along the river reaching the coast of Way Ratai. The research was conducted in November 2020 and March 2021. Ten heavy metals, Ag, Cd, Co, Cr, Cu, Fe, Mn, Pb, and Zn that are commonly found in mining areas, were determined in the water and plankton samples by using ICP-OES. The results indicated that the highest concentration found was Fe in plankton samples (0.725 mg/L in the river and 1.294 mg/L on the coast). Meanwhile, contents of Cd, Cu, Fe, Mn, and Zn in the river exceeded the predetermined water quality standards, while Ag and Pb metals were not detected. The Cd, Cr, Cu, Pb, and Zn content in seawater also exceeded quality standards. The highest BCF value (12.96) was found for Fe at station G, whereas the lowest BCF value (0.13) was found for Ag at stations G and H. [ABSTRACT FROM AUTHOR]

Previous studies provided evidence of the mixing of boreal–tropical cladocerans (Crustacea) in the Far East of Eurasia, as well as the presence of numerous pre-Pleistocene relict endemics. In this study, we hypothesize that the colonization history is reflected in the proportions of endemic/boreal/tropical taxa among different habitat types within this region. We analyzed 442 qualitative samples collected from seven sub-regions of the Far East of Russia and South Korea along a latitudinal transect of approximately 2200 km, where we identified 101 Cladocera species. Our results showed a significantly higher proportion of endemic taxa in the plankton compared to the littoral and benthic zones. The proportions of endemic/boreal/tropical taxa in the permanent and temporary waters were similar. We observed a distinct shift in dominance in benthos and littoral zone across our transect: boreal taxa were prevalent in the northern sub-regions (1–4), while tropical taxa were prevalent in the southern sub-regions (5–7), with a pronounced boreal–tropical transition zone (sub-regions 4–5). Our findings suggest that this pattern arose due to the unhindered dispersion of the two faunas in a latitudinal direction until they met at the boundary during their arrival in the Late Pleistocene. In contrast, the proportions of the boreal and tropical taxa in plankton did not exceed 16% in any of the studied sub-regions, and the proportion of boreal taxa decreased from 16% to 10%, while that of the tropical taxa increased from 0% to 10% from north to south. We propose that the lower proportions and the absence of mixing of fauna in the plankton can be explained by the strong presence (sometimes dominance) of relics that occupy these water bodies before the arrival of colonizers from the north and south. Our findings highlight the significant role of biotic interactions in the formation of biogeographic boundaries, which was previously underestimated. [ABSTRACT FROM AUTHOR]

Aim: The so‐called regime shifts in North Sea plankton communities provide an important historical case study to understand marine regime shifts. Previous studies characterized regime shifts using a variety of community metrics (e.g., indicator species abundances, taxonomic composition and chlorophyll biomass) but left the functional traits of plankton unassessed. Here, we explicitly re‐assess the historically recognized North Sea regime shifts through the lens of plankton functional traits to gain a better understanding of these events. Location: The North Sea (NW European shelf). Time period: 1958–2018, focusing on the 1980s and 1996–2003 regime shifts. Major taxa studied: Marine phyto‐ and zooplankton. Methods: We compute trait spaces for both phyto‐ and zooplankton of the North Sea using traits from the literature and a Gower's distance‐based method. Using abundance data from the Continuous Plankton Recorder Survey, we then compute monthly time series of the centroids of the communities, an indicator of functional composition. We then use principal component analysis on the centroids to assess the main temporal changes in plankton functional composition associated with the 1980s and 1996–2003 regime shifts. Results: Little change in plankton functional composition was associated with the 1980s regime shift. In contrast, the functional composition of plankton communities changed markedly after the 1996–2003 regime shift, with an increase in the summer relative abundance of non‐motile autotrophs (i.e., diatoms) and the spring relative abundance of meroplankton. Main conclusions: The North Sea regime shifts were not associated systematically with changes in functional composition, calling into question the definition of regime shifts and illustrating the importance of taking different metrics into account to interpret ecological events accurately. Taking into account functional composition, we interpret the 1980s so‐called regime shift as a latitudinal shift in communities that was insufficient to impact functional composition and the 1996–2003 so‐called regime shift as a period of change in bentho‐pelagic coupling. [ABSTRACT FROM AUTHOR]

In Laudato Si', Pope Francis highlights the oceans as integral to our threatened common home and stresses the need for more effective ocean governance. Theologians can help to meet that need. By turning their attention to the UN Convention on the Law of the Sea (UNCLOS) and its further development, and by practicing "ocean empathy," they can join ocean scientists, NGOs, international lawyers, and others in caring for the oceans by shoring up the law of the sea. [ABSTRACT FROM AUTHOR]

Estuarine environments are influenced by both river flows and oceanic tidal movement of water, sediment, and nutrients, often forming ecosystems that are rich in resources and biodiversity. The Yellow River once carried the world's largest sediment load, but artificial structures have transformed its hydrodynamic processes. An annual Water–Sediment Regulation Scheme (WSRS) was introduced to flush accumulated sediment from the Xiaolangdi Reservoir, which provides flood control and water storage. However, the effect of the WSRS process on the runoff and sediment conditions, nutrients, and ecological environment of the Yellow River Estuary and adjacent ocean are not well understood. In the current study, a coupled hydrodynamic–nutrient–plankton ecosystem dynamics model (FVCOM–FABM–NPZD) was constructed to simulate changes in the ecological parameters and in the vertical response in the Yellow River Estuary before, during, and after the WSRS, This model also was used to quantify the effects of changes in the incoming material flux on the hydrodynamic and ecological environment of the estuary, using the Yellow River Xiaolangdi Reservoir water transfer and sand transfer as an example. The study found that the WSRS changed the spatial and temporal distribution of temperature, salinity, sediment, inorganic nitrogen, and phytoplankton in the Yellow River Estuary and adjacent waters. It also had a significant effect on the temperature, salinity, and ecology of the adjacent near-shore marine environment. The spatial and temporal responses of zooplankton and phytoplankton to the WSRS differed. Zooplankton showed a lag in response to the WSRS and were mainly influenced by temperature and phytoplankton. The phytoplankton concentration was positively influenced by inorganic nitrogen and negatively influenced by salinity and sediment. In the current study, the effects of changes in the flow and sediment flux from the WSRS on environmental factors and zooplankton in the Yellow River Estuary were simulated, providing a theoretical basis for scheduling the release of water and sediment in the Yellow River basin and providing a reference for water and sediment regulation in other reservoirs upstream of the estuary. [ABSTRACT FROM AUTHOR]

Copyright of Nuclear Safety is the property of Nuclear & Radiation Safety Center and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Among the various exometabolitic effects of marine microorganisms, massive mucilage events in the coastal zones of temperate and tropical seas are the most spectacular and environmentally important. Abundant mucilage material in the form of aggregates appears in late spring/early summer in the water column of the Adriatic Sea. These macroaggregate biopolymers originate mainly from plankton exometabolites, with both autochthonous and allochthonous components, and strongly impact the tourism, fisheries, and economy of coastal countries. In contrast to extensive studies on the structural and chemical nature of macroaggregates performed over past decades, the full elemental composition of these substances remains poorly known, which does not allow for a complete understanding of their origin, evolution, and necessary remediation measures. Here, we report the results of comprehensive analyses of 55 major and trace elements in the composition of macro aggregates collected at the surface and in the water column during massive mucilage events. Through normalization of the elemental chemical composition of the upper earth crust (UCC), river suspended material (RSM), mean oceanic plankton, and mean oceanic particulate suspended material, we demonstrate that the water column macroaggregates reflect a superposition of the signal from plankton and marine particulate matter. The surface macroaggregates were preferentially enriched in lithogenic component, and carried the signature of planktonic material. The rare earth element (REE) signal was strongly dominated by plankton and, to a lesser degree, by oceanic particulate matter, while at the same time being strongly (>80 times) impoverished compared with UCC and RSM. Taken together, the elemental composition of macroaggregates allows for distinguishing the lithogenic and biogenic impacts on the occurrence of these unique large-scale mucilage events, linked to the exometabolism of marine plankton combined with the input of allochthonous inorganic material. [ABSTRACT FROM AUTHOR]

The northern coast of the Iberian Peninsula is an important spawning and nursery area for several marine fish species, some of which are economically exploited by fisheries and under management plans. Larval stages of fish are highly sensitive to environmental change and anthropogenic pressures, and Marine Protected Areas (MPA) can help mitigate the impacts on fish populations. This study investigated the environmental drivers of the temporal and spatial patterns of the larval fish assemblages inhabiting a small coastal MPA along the NW Portuguese Iberian Coast. Seasonal surveys were conducted over two years at nine sampling stations distributed throughout the MPA to collect larval fish samples and water parameters. Results showed that a total of 39 different fish taxa were identified. In terms of abundance, reef-associated species, such as Parablennius gattorugine (54.6%), and marine species that use estuaries as nursery areas, such as Ammodytes tobianus (15.7%) and Clupeidae n.i. (8.8%) dominated the larval fish assemblages. The larval fish assemblages were characterized by a strong temporal pattern that, according to CCA analyses, was related to the temporal variability of water temperature, pH, chlorophyll α, TPM, and also the river flow of an adjacent river. This study showed that 47% of the fish larvae belonged to commercially exploited species, highlighting the importance of this MPA as a nursery area for the early life stages of the fish population. Overall, these new findings emphasize the role of MPAs in ensuring the connectivity of fish species between marine-estuarine habitats and enhancing the conservation of fish populations. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Dalian Ocean University is the property of Journal of Dalian Ocean University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background. Zooplankton plays an important role in the marine ecosystem. A high level of taxonomic expertise is necessary for accurate species identification based on morphological characteristics. As an alternative method to morphological classification, we focused on a molecular approach using 18S and 28S ribosomal RNA (rRNA) gene sequences. This study investigates how the accuracy of species identification by metabarcoding improves when taxonomically verified sequences of dominant zooplankton species are added to the public database. The improvement was tested by using natural zooplankton samples. Methods. rRNA gene sequences were obtained from dominant zooplankton species from six sea areas around Japan and registered in the public database for improving the accuracy of taxonomic classifications. Two reference databases with and without newly registered sequences were created. Comparison of detected OTUs associated with single species between the two references was done using field-collected zooplankton samples from the Sea of Okhotsk for metabarcoding analysis to verify whether or not the newly registered sequences improved the accuracy of taxonomic classifications. Results. A total of 166 sequences in 96 species based on the 18S marker and 165 sequences in 95 species based on the 28S marker belonging to Arthropoda (mostly Copepoda) and Chaetognatha were registered in the public database. The newly registered sequences were mainly composed of small non-calanoid copepods, such as species belonging to Oithona and Oncaea. Based on the metabarcoding analysis of field samples, a total of 18 out of 92 OTUs were identified at the species level based on newly registered sequences in the data obtained by the 18S marker. Based on the 28S marker, 42 out of 89 OTUs were classified at the species level based on taxonomically verified sequences. Thanks to the newly registered sequences, the number of OTUs associated with a single species based on the 18S marker increased by 16% in total and by 10% per sample. Based on the 28S marker, the number of OTUs associated with a single species increased by 39% in total and by 15% per sample. The improved accuracy of species identification was confirmed by comparing different sequences obtained from the same species. The newly registered sequences had higher similarity values (mean >0.003) than the pre-existing sequences based on both rRNA genes. These OTUs were identified at the species level based on sequences not only present in the Sea of Okhotsk but also in other areas. Discussion. The results of the registration of new taxonomically verified sequences and the subsequent comparison of databases based on metabarcoding data of natural zooplankton samples clearly showed an increase in accuracy in species identification. Continuous registration of sequence data covering various environmental conditions is necessary for further improvement of metabarcoding analysis of zooplankton for monitoring marine ecosystems. [ABSTRACT FROM AUTHOR]

In recent decades, Arctic Ocean (AO) sea ice has experienced intense climate‐related modifications, which coincide with earlier melting in spring and delayed formation in the fall. In this study, we use the ECCO2‐Darwin ocean biogeochemistry model to gain a mechanistic understanding of how changes in sea‐ice seasonality impact the phenology of AO phytoplankton blooms. We use a 2006–2013 simulation to show that early sea‐ice melt in 2007 and 2012 triggers earlier phytoplankton blooms (∼1 month earlier compared to other years) and that the blooms dissipate earlier due to more rapid nutrient depletion in the surface AO. Our simulation also confirms that delayed formation of sea ice during fall triggers second fall blooms, in agreement with observations. These results suggest that in a warmer and changing climate, further changes to sea‐ice extent could drastically impact AO phytoplankton, with important consequences for Arctic marine ecosystems. Plain Language Summary: Climate change caused observed modifications of sea‐ice extent and its seasonal cycle in the Arctic Ocean (AO). Data obtained from satellites showed that the earlier break‐up of AO sea ice triggered earlier spring phytoplankton blooms and that a delayed formation of sea ice during fall cause the occurrence of an unprecedented second phytoplankton bloom. In this study we used a numerical ocean model (physical and biological) of the AO run under present climate conditions. Our model can capture the seasonal changes of phytoplankton blooms of the surface AO although some differences remain between model and data. Two main reasons explain why our model can capture the observed seasonal changes: (a) our sea‐ice model can correctly simulate the climate‐induced sea‐ice extent changes and (b) the plankton ecosystem model can realistically simulate the response to changes in light and nutrients availability at seasonal time scales caused by sea‐ice alterations. Some of these observed and simulated changes might be a window into the future for AO phytoplankton dynamics responding to climate changes if sea ice continues to decrease. Key Points: We use an ocean biogeochemistry model (ECCO2‐Darwin) to investigate phytoplankton bloom dynamics in the surface Arctic OceanSimulations show that seasonal changes in sea‐ice formation directly impact bloom phenologyModel results provide insight into the processes impacting the Arctic phytoplankton blooms phenology [ABSTRACT FROM AUTHOR]

The wind speed, the sea surface temperature, the chlorophyll a concentration (MODIS-Aqua/Terra satellite data), the bioluminescence intensity and biomass of zooplankton (data collected onboard a research vessel), the primary productivity, and the indices of lower-than-normal atmospheric pressure and water mass transfer (model calculations) were used to assess the current state and functional characteristics of a pelagic ecosystem of the northern open areas of the Black Sea. The ecosystem was found to have reached a state of relative stability in its structure and function in the past two decades (2000–2020), after natural cataclysms associated with eutrophication and trophic pressure from invasive plankton species in the 1990s. The state is characterized by the absence of trends in the interannual variability of its identifying parameters. The problem of regional differences in long-term trends of physical factors and biological interactions is discussed on a broader (global) scale. [ABSTRACT FROM AUTHOR]

A major premise of ecological neutral theory is that population size is inversely related to extinction risk. This idea is central to modern biodiversity conservation efforts, which often rely on abundance metrics to partially determine species extinction risk. However, limited empirical studies have tested whether extinction is indeed more probable for species with low abundances. Here we use the fossil record of Neogene radiolaria to test the relationship between relative abundance and longevity (time from first to last occurrence). Our dataset includes abundance histories for 189 polycystine radiolarian species from the Southern Ocean, and 101 species from the tropical Pacific. Using linear regression analyses, we show that neither maximum nor average relative abundance are significant predictors of longevity in either oceanographic region. This suggests that neutral theory fails to explain the plankton ecological-evolutionary dynamics we observe. Extrinsic factors are likely more important than neutral dynamics in controlling radiolarian extinction. Abundance or rarity of species in the fossil record, contrary to expectation of neutral theory, does not predict their longevity in ocean ecosystems. [ABSTRACT FROM AUTHOR]

Background: Planktonic microbial communities have critical impacts on the pelagic food web and water quality status in freshwater ecosystems, yet no general model of bacterial community assembly linked to higher trophic levels and hydrodynamics has been assessed. In this study, we utilized a 2-year survey of planktonic communities from bacteria to zooplankton in three freshwater reservoirs to investigate their spatiotemporal dynamics. Results: We observed site-specific occurrence and microdiversification of bacteria in lacustrine and riverine environments, as well as in deep hypolimnia. Moreover, we determined recurrent bacterial seasonal patterns driven by both biotic and abiotic conditions, which could be integrated into the well-known Plankton Ecology Group (PEG) model describing primarily the seasonalities of larger plankton groups. Importantly, bacteria with different ecological potentials showed finely coordinated successions affiliated with four seasonal phases, including the spring bloom dominated by fast-growing opportunists, the clear-water phase associated with oligotrophic ultramicrobacteria, the summer phase characterized by phytoplankton bloom-associated bacteria, and the fall/winter phase driven by decay-specialists. Conclusions: Our findings elucidate the major principles driving the spatiotemporal microbial community distribution in freshwater ecosystems. We suggest an extension to the original PEG model by integrating new findings on recurrent bacterial seasonal trends. 6DDRKdq8UhqLvueZRvryQw Video Abstract [ABSTRACT FROM AUTHOR]

The frequency of marine heatwaves (HWs) is projected to increase in the Mediterranean Sea over the next decades. An in situ mesocosm experiment was performed in a Mediterranean lagoon for 33 days. Three mesocosms were used as controls following the natural temperature of the lagoon. In three others, two HWs of + 5 °C compared to the controls were applied from experimental day (d) 1 to d5 (HW1) and from d11 to d15 (HW2). High-frequency data of oxygen, chlorophyll-a (chl-a), temperature, salinity and light from sensors immersed in all mesocosms were used to calculate gross primary production (GPP), respiration (R) and phytoplankton growth (µ) and loss (L) rates. Nutrients and phytoplankton community structure from pigments were also analyzed. HW1 significantly increased GPP, R, chl-a, µ and L by 7 to 38%. HW2 shifted the system toward heterotrophy by only enhancing R. Thus, the effects of the first HW resulted in the attenuation of those of a second HW on phytoplankton processes, but not on community respiration, which was strongly regulated by temperature. In addition, natural phytoplankton succession from diatoms to haptophytes was altered by both HWs as cyanobacteria and chlorophytes were favored at the expense of haptophytes. These results indicate that HWs have pronounced effects on Mediterranean plankton communities. [ABSTRACT FROM AUTHOR]

Background: Enterococcus faecalis (E. faecalis) is frequently isolated from root canals with failed root canal treatments. Due to the strong ability of E. faecalis to resist many often-used antimicrobials, coping with E. faecalis infections remains a challenge. The aim of this study was to investigate the synergistic antibacterial effect of low-dose cetylpyridinium chloride (CPC) and silver ions (Ag+) against E. faecalis in vitro. Methods: The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and the fractional inhibitory concentration index (FICI) were used to confirm the existence of the synergic antibacterial activity between low-dose CPC and Ag+. Colony-forming unit (CFU) counting, time-killing curve and dynamic growth curve were used to evaluate the antimicrobial effects of CPC and Ag+ combinations against planktonic E. faecalis. Four weeks biofilms were treated with drug-contained gels to determine the antimicrobial effect on biofilm-resident E.faecalis, and the integrity of E.faecalis and its biofilms were observed by FE-SEM. CCK-8 assays was used to test the cytotoxicity of CPC and Ag+ combinations on MC3T3-E1 cells. Results: The results confirmed the synergistic antibacterial effect of low-dose CPC and Ag+ against both planktonic and 4-week biofilm E. faecalis. After the addition of CPC, the sensitivity of both planktonic and biofilm-resident E. faecalis to Ag+ improved, and the combination showed good biocompatibility on MC3T3-E1 cells. Conclusions: Low-dose CPC enhanced the antibacterial ability of Ag+ against both planktonic and biofilm E.faecalis with good biocompatibility. It may be developed into a novel and potent antibacterial agent against E.faecalis, with low toxicity for root canal disinfection or other related medical applications. [ABSTRACT FROM AUTHOR]

In order to understand the relative strength of top-down and bottom-up control in lakes of grazing alien fish, Protosalanx chinensis, investigations were designed in Lake Longhu (Lake L, P. chinensis introduced in 2013) and Lake Qijia (Lake Q, P. chinensis free). Plankton samples were collected bimonthly through the whole life cycle of P. chinensis (from February to December in 2018). A total of 133 phytoplankton and 68 zooplankton species were recorded in the two lakes. The total density and biomass of phytoplankton and zooplankton were 991.89 × 104 ind/L and 9.2418 mg/L as well as 5212 ind/L and 20.2646 mg/L, respectively. This study revealed that P. chinensis grazing did not deplete the zooplankton resources in the lake where it was stocked. Biodiversity in Lake L was not significantly different from that in Lake Q based on both phytoplankton and zooplankton. Overall, the over grazing of P. chinensis was not found in Lake L. Nevertheless, compared to Lake Q, the correlation between phytoplankton and zooplankton was weakened in Lake L, which meant there were still some effects of stocking P. chinensis on the ecological equilibrium of the plankton community, although no dramatic influences were found in Lake L yet. We also found that P. chinensis and Cladocera were significantly correlated, which should account for the top-down influences. Long-term successive investigations are suggested for sustainable resource utilization and maintaining biological balance. [ABSTRACT FROM AUTHOR]

Google Scholar Google Preview OpenURL Placeholder Text WorldCat COPAC 26 Lo Bianco, S. (1888) Notizie biologiche riguardanti specialmente il periodo di maturità sessuale degli animali del golfo di Napoli. Google Scholar Google Preview OpenURL Placeholder Text WorldCat COPAC 21 Groeben, C. (2005) LO BIANCO, Salvatore. Google Scholar Google Preview OpenURL Placeholder Text WorldCat COPAC 34 Lo Bianco, S. (1906a) Azione della pioggia di cenere caduta durante l'eruzione del Vesuvio dell'Aprile 1906 sugli animali marini. Google Scholar OpenURL Placeholder Text WorldCat 22 Groeben, C. (2007) Alfred Krupp, Anton Dohrn und Salvatore Lo Bianco: Pelagische Tiefseekampagnen um Capri 1900-1902. [Extracted from the article]

The interaction between biological and short-term physical processes affects plankton distribution and composition variability, with consequences for the entire ecosystem. Aspects of the plankton distribution at smaller scales have been understudied, mainly in coastal regions where highly variable conditions promote variations in the biophysical environment. This work aimed to investigate the short-term variations in the distribution of plankton along the inner shelf off Ubatuba, Brazil. We quantified the abundance and diversity of the main planktonic taxa (>100 μm) and their spatiotemporal distribution in winter 2018 and summer 2019 using high-resolution sensors and a shadowgraphic imaging system at cross-shore and fixed stations (12 and 24 h). Summer–winter environmental contrast was evident in the water column stability and plankton abundance. In the summer, higher values of plankton abundance and diversity were obtained. Our results suggested that spatiotemporal variations related to wind-induced mixing and water mass intrusions lead to variabilities in plankton populations on a time scale of a few hours, vertically between depth layers and at spatial scales ˂2 km. This study contributes to the knowledge of the mechanisms of biophysical interactions and their spatiotemporal variation, which is crucial for assessing the effects of climate variability on plankton-mediated ecosystem services. [ABSTRACT FROM AUTHOR]

The aim of this study was to test the effect of different ionic adjustments in low salinity water on the composition and temporal variation of plankton from intensive shrimp nurseries with a synbiotic system. For this, a Penaeus vannamei nursery (35 days) was carried out with three treatments: T1 – diluted seawater (control; salinity ∼2.5 g L−1), T2 – salinity ∼2.5 g L−1 with K+ adjustment to approximate the seawater equivalent concentration, and T3 – salinity ∼2.5 g L−1 with Ca:Mg:K ratio adjusted to 1:3:1. Rice bran processed by probiotic microorganisms was used as an organic carbon source. Phytoplankton and zooplankton were sampled weekly and analysed using standard methods. The temporal variation of phytoplankton and zooplankton composition were more pronounced than differences among treatments indicating that the ionic adjustment had little effect on these communities. During the experimental time, the dominant phyla in phytoplankton were Ochrophyta, Cyanophyta and Chlorophyta, whereas zooplankton's dominant phyla were Ciliophora, Amoebozoa, and Cercozoa. Cyanophyta's relative abundance was lower than traditional biofloc systems, suggesting a higher control of these microorganisms in synbiotic systems. Ionic adjustments have then a low potential to affect plankton, likely because limitation by these ions was not achieved under the ionic manipulations tested. [ABSTRACT FROM AUTHOR]

Climate warming alters the seasonal timing of biological events. This raises concerns that species‐specific responses to warming may de‐synchronize co‐evolved consumer‐resource phenologies, resulting in trophic mismatch and altered ecosystem dynamics. We explored the effects of warming on the synchrony of two events: the onset of the phytoplankton spring bloom and the spring/summer maximum of the grazer Daphnia. Simulation of 16 lake types over 31 years at 1907 North African and European locations under 5 climate scenarios revealed that the current median phenological delay between the two events varies greatly (20–190 days) across lake types and geographic locations. Warming moves both events forward in time and can lengthen or shorten the delay between them by up to ±60 days. Our simulations suggest large geographic and lake‐specific variations in phenological synchrony, provide quantitative predictions of its dependence on physical lake properties and geographic location and highlight research needs concerning its ecological consequences. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the aggregation of a floating tracer into clusters. Motivated by observations of dense patches of buoyant material in the real ocean (e.g., microplastic pollutants, plankton, and sargassum), we develop an idealized model that can reproduce the clustering process. A stochastic, kinematic 2D velocity field is chosen to represent turbulent oceanic surface currents, with a weakly divergent component. Lagrangian particles are introduced and we track their concentrations. We differ from delta‐correlated fields used in previous studies by including finite time correlations. Clustering in these fields can be compared to the traditional setting, through global measures and cluster detection algorithms. The enhanced velocity fields can be deformed using various interpolation methods. We can then investigate the sensitivity of clustering to the representation of temporal/spatial velocity structure to inform future studies of this phenomenon. We find coherency of time‐correlated velocities leads to significantly faster rates of clustering, causing a larger number of longer lived/more populated clusters to form. Clustering is likely relevant to a host of biogeochemical processes of urgent interest, such as phytoplankton blooms and the ecological risk of microplastic pollutants. This work aims to establish an accurate basis for clustering simulations, to enable further exploration. Plain Language Summary: Floating material, such as microplastic waste and certain marine species, have a tendency to form dense patches on the ocean surface. Interest in this phenomenon is increasing, largely due to recent observations of the "garbage islands" of plastic pollution. We are attempting to develop greater understanding of the way these structures form by using simple models. These models give us the opportunity to assess the methodologies generally used in Lagrangian particle studies and how they impact numerical simulations of clustering floating material. They also allow us to try new methods of inter‐comparison between models, which we have done to investigate the impact of common numerical approximations on the results of clustering simulations. Key Points: Expanding on other kinematic studies of clustering buoyant tracers, we include simple temporal structure in the carrying velocity fieldsWe utilize global measures of clustering, as well as a cluster tracking algorithm, to compare the process quantitatively between modelsOur results show the sensitivity of clustering to distortions of time structure, which can inform future studies in dynamical contexts [ABSTRACT FROM AUTHOR]

Drivers of phytoplankton and zooplankton dynamics vary spatially and temporally in estuaries due to variation in hydrodynamic exchange and residence time, complicating efforts to understand controls on food web productivity. We conducted approximately monthly (2012–2019; n = 74) longitudinal sampling at 10 fixed stations along a freshwater tidal terminal channel in the San Francisco Estuary, California, characterized by seaward to landward gradients in water residence time, turbidity, nutrient concentrations, and plankton community composition. We used multivariate autoregressive state space (MARSS) models to quantify environmental (abiotic) and biotic controls on phytoplankton and mesozooplankton biomass. The importance of specific abiotic drivers (e.g., water temperature, turbidity, nutrients) and trophic interactions differed significantly among hydrodynamic exchange zones with different mean residence times. Abiotic drivers explained more variation in phytoplankton and zooplankton dynamics than a model including only trophic interactions, but individual phytoplankton–zooplankton interactions explained more variation than individual abiotic drivers. Interactions between zooplankton and phytoplankton were strongest in landward reaches with the longest residence times and the highest zooplankton biomass. Interactions between cryptophytes and both copepods and cladocerans were stronger than interactions between bacillariophytes (diatoms) and zooplankton taxa, despite contributing less biovolume in all but the most landward reaches. Our results demonstrate that trophic interactions and their relative strengths vary in a hydrodynamic context, contributing to food web heterogeneity within estuaries at spatial scales smaller than the freshwater to marine transition. [ABSTRACT FROM AUTHOR]

Obtaining in situ measurements of biological microparticles is crucial for both scientific research and numerous industrial applications (e.g., early detection of harmful algal blooms, monitoring yeast during fermentation). However, existing methods are limited to offer timely diagnostics of these particles with sufficient accuracy and information. Here, we introduce a novel method for real‐time, in situ analysis using machine learning (ML)‐assisted digital inline holography (DIH). Our ML model uses a customized YOLOv5 architecture specialized for the detection and classification of small biological particles. We demonstrate the effectiveness of our method in the analysis of 10 plankton species with equivalent high accuracy and significantly reduced processing time compared to previous methods. We also applied our method to differentiate yeast cells under four metabolic states and from two strains. Our results show that the proposed method can accurately detect and differentiate cellular and subcellular features related to metabolic states and strains. This study demonstrates the potential of ML‐driven DIH approach as a sensitive and versatile diagnostic tool for real‐time, in situ analysis of both biotic and abiotic particles. This method can be readily deployed in a distributive manner for scientific research and manufacturing on an industrial scale. [ABSTRACT FROM AUTHOR]

Because of the way that water is a restricted asset, it is a subject of stress due to the natural issues that are related with its weakening. Water is the pith of life on the planet. Significant regular sea-going environments that give an assortment of biological system administrations are known as lentic water assets. There is a significant misfortune in the sporting, stylish, and oceanic biological system administrations of lakes because of the convoluted landwater associations and human contributions of composts. Lakes are promptly harmed by these variables. Checking the physicochemical characteristics of the water as well as the development of tiny fishes and sea-going plants is one method for assessing the nature of the water. The biological examinations that were completed on Dal lake are being featured in this distribution. [ABSTRACT FROM AUTHOR]

Tectonic, paleoenvironmental, and paleoclimatic unstable conditions preceding the onset of the Messinian Salinity Crisis (MSC) highly affected marine life. Changes in calcareous plankton association are overall registered in the Mediterranean. They consist of a general transition from abundant and well-diversified planktonic associations to strictly oligotypic assemblages that precede their total disappearance at the onset of evaporitic precipitation. In this work, an accurate quantitative analysis of calcareous plankton, both foraminifers and nannofossils, has been carried out in the Torrente Vaccarizzo Section of Sicily (southern Italy). The aim is to independently define a chronostratigraphic pattern of bioevents preceding the MSC in the absence of magnetostratigraphic or radiometric constraints. The fluctuating abundance of the genus Orbulina fits well with the 100 ky Eccentricity maxima, and it is successfully applied to build an astronomically calibrated age-model for the section. On this basis, all the biohorizons have been recalibrated and discussed with regard to the previous literature. Abundant influxes of selected species demonstrated to be of local significance since they are highly affected by paleoenvironmental and paleoclimatic conditions. A chronological sequence of foraminifer and nannofossil events marks the onset of the MSC with a derived age of 5.957 My, which agrees well with previous findings from other Mediterranean sections. This methodology and the new biostratigraphic events may be useful for future studies on pre-evaporitic successions of the Mediterranean. [ABSTRACT FROM AUTHOR]

With climate change, oceans are becoming increasingly nutrient limited, favouring growth of prokaryotic picoplankton at the expense of the larger protist plankton whose growth support higher trophic levels. Constitutive mixoplankton (CM), microalgal plankton with innate phototrophic capability coupled with phagotrophy, graze on these picoplankton, indirectly exploiting the excellent resource acquisition abilities of the prokaryotes. However, feeding rates can be very low (e.g., a few bacteria d−1). For the first time, the significance of such low consumption rates has been quantified. We find that while prokaryote-carbon (C) supply to CM grown at non-limiting light was so low that it may appear insignificant (< 10%), contributions of nitrogen (N) and phosphorus (P) from ingestions of 1–12 prokaryotes d−1 were significant. Under limiting light, contributions of ingested C increased, also raising the contributions of N and P. The order of nutritional importance for CM growth from predation was P > N > C. Further, provision of N through internal recycling of ingested prey-N stimulates C-fixation through photosynthesis. Importantly, coupled photo-phago-mixoplanktonic activity improved CM resource affinities for both inorganic and prey-bound nutrients, enhancing the nutritional status and competitiveness of mixoplankton. With warming oceans, with increased prokaryote abundance, we expect CM to exhibit more phagotrophy. [ABSTRACT FROM AUTHOR]