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Initiated in 2018, solinst levellogger data is available until 2023. Data is collected each year and is uploaded soon after the water year is over. Some loggers were moved to different sites or had technical difficulties, therefore dates that have gaps in data represent a time period where data is not available.

In April and May of 2020, a large phytoplankton bloom composed primarily of the dinoflagellate Lingulodinium polyedra reached historic levels in geographic expanse, duration, and density along the coast of southern California, United States, and Baja California Norte, Mexico. Here, we report the water quality parameters of dissolved oxygen and pH over the course of the red tide, as measured by multiple sensors deployed in various locations along San Diego County, and document the extent of mass organism mortality using field surveys and community science observations. We found that dissolved oxygen and pH corresponded with bloom dynamics, with extreme hypoxic and hyperoxic conditions occurring at multiple locations along the coast, most notably within select estuaries where dissolved oxygen reached 0 mg L−1 and hypoxia occurred for up to 254 consecutive hours, as well as along the inner shelf of the open coast where dissolved oxygen dropped as low as 0.05 mg L−1. Similarly, pH ranged widely (6.90–8.79) across the bloom over both space and time, largely corresponding with dissolved oxygen level. Extreme changes in dissolved oxygen and pH, in addition to changes to other water parameters that affect organismal health, ultimately led to documented mortalities of thousands of demersal and benthic fishes and invertebrates (primarily within estuarine and inner-shelf environments), and long-term surveys within one lagoon showed protracted changes to benthic infaunal density and species composition. In addition to field observations, we also quantified water quality parameters and organism mortalities from four local aquarium facilities, with varying levels of filtration and artificial oxygenation, and documented the morphological changes in the gills of captive-held Pacific sardine in response to the red tide. We show that multiple factors contributed to organismal stress, with hypoxia likely being the most widespread, but not the only, cause of mortality.

Cyanobacterial phytoplankton blooms are more prevalent in the freshwater Sacramento-San Joaquin Delta (Delta) since the late 1990s, including blooms driven by overgrowths of potentially toxigenic organisms of the genus Microcystis. Data from 2014 to 2021 were used to show how flow dynamics, water temperature, and water clarity drive occurrence of Microcystis. We used a Microcystis bloom in the central Delta from 2021 as a case study for how novel monitoring tools can track blooms in real-time and be used post hoc to evaluate the effects of management actions.Microcystis was detected throughout the Delta in all but the highest-flow years, and bloom incidence and severity increased during drier years. In the South Delta, Franks Tract, lower San Joaquin River, and Old River regions, where blooms are most prevalent, higher water temperatures and clarities combined with lower exports from state and federal water projects were the best explanatory factors for the occurrence of Microcystis blooms. Nutrient concentrations were lower in summer than in winter, but only became limiting at high phytoplankton concentrations.We used satellite data and in situ continuous monitoring of flow, phytoplankton communities, and water quality to track hydro-biogeochemical conditions during the 2021 case study Microcystis bloom in the Central Delta. We did not find evidence that changes to Delta outflow regulatory standards contributed to this bloom, but changes in flow caused by a salinity barrier placed in west False River may have exacerbated the bloom. The frequency and severity of droughts are expected to increase in the future as a result of climate change, and our study demonstrates how continued monitoring of cyanotoxins, water quality, and phytoplankton communities could help improve management of cyanobacterial blooms in the Delta and other estuaries.

Multi-year droughts are ever-present and transformational features of California’s Mediterranean climate and can fundamentally affect the water quality and the ecosystem responses of the San Francisco Estuary and the Sacramento–San Joaquin Delta. This study assessed data collected by long-term monitoring programs over the past 46 water years (1975–2021) to evaluate how water quality in the estuary changes during multi-year droughts. Data were aggregated by region (South-Central Delta, North Delta, confluence, Suisun Bay, and Suisun Marsh) and season, then differences between multi-year drought periods, multi-year wet periods, and neutral periods were compared using generalized linear models. We found that multi-year drought periods altered multiple physical and chemical parameters in the estuary, increasing water temperature, salinity, water clarity, and nutrient levels. This trend was consistent across regions and seasons, with few exceptions. Increases in these parameters during drought periods were likely caused by reduced Delta inflows that intensified in each successive dry year because of reduced precipitation and managed estuarine inflows and outflows. Drought periods did not substantially affect tidal velocities within the estuary, which remained mostly consistent across wet and drought periods. Trends in chlorophyll concentrations during drought periods were more nuanced with higher concentrations occurring in the South-Central Delta region and during the winter and spring. Together, these results characterized drought in the estuary as warm, clear, high in nutrients, with patchy phytoplankton blooms (as indexed by chlorophyll), all of which have implications for higher trophic levels. Considering that droughts are expected to increase in frequency and intensity in California with climate change, understanding the effects of multi-year droughts on the water quality conditions of the estuary can help inform water management decisions.

Detection sensitivity of aquatic species using environmental DNA (eDNA) generally decreases in turbid water but is poorly characterized. In this study, eDNA detection targeted delta smelt (Hypomesus transpacificus), a critically endangered estuarine fish associated with turbid water. eDNA sampling in the field was first paired with a trawl survey. Species-specific detection using a Taqman qPCR assay showed concordance between the methods, but a weak eDNA signal. Informed by the results of field sampling, an experiment was designed to assess how turbidity and filtration methods influence detection of a rare target. Water from non-turbid (5 NTU) and turbid (50 NTU) estuarine sites was spiked with small volumes (0.5 and 1 mL) of water from a delta smelt tank to generate low eDNA concentrations. Samples were filtered using four filter types: cartridge filters (pore size 0.45 μm) and 47 mm filters (glass fiber, pore size 1.6 μm and polycarbonate, pore sizes 5 and 10 μm). Prefiltration was also tested as an addition to the filtration protocol for turbid water samples. eDNA copy numbers were analyzed using a censored data method for qPCR data. The assay limits and lack of PCR inhibition indicated an optimized assay. Glass fiber filters yielded the highest detection rates and eDNA copies in non-turbid and turbid water. Prefiltration improved detection in turbid water only when used with cartridge and polycarbonate filters. Statistical analysis identified turbidity as a significant effect on detection probability and eDNA copies detected; filter type and an interaction between filter type and prefilter were significant effects on eDNA copies detected, suggesting that particulate-filter interactions can affect detection sensitivity. Pilot experiments and transparent criteria for positive detection could improve eDNA surveys of rare species in turbid environments.

Aim: Estuarine vegetation routinely experiences natural tidal fluctuations and is highly vulnerable to extreme events such as heavy rainfall, leading to changes in plant population structure and adaptability. Genetic and epigenetic modifications are widely considered to be mechanisms of phenotypic variation, triggered in plants responding to extreme changing environments. However, understanding on correlations among genetic, epigenetic, and phenotypic variation of wild plant populations is still limited. Location: China. Methods: In this study, populations of the typical wetland clonal species Phragmites australis were selected from four estuaries along various latitudes in China. Genetic and epigenetic diversity and phenotypic variation of these populations were analysed. Results: Phenotypic variation of P. australis populations was the highest at Yellow River Estuary and the lowest at Min River Estuary. Across all estuaries, Genetic and epigenetic diversity was strongly linear‐correlated. Genetic diversity had significant correlations with variation in reproductive traits, whereas epigenetic diversity had significant correlations with variation in growth traits. Climatic factors of mean annual temperature and precipitation, as well as soil nitrogen and phosphorus, were negatively correlated with variation in genetic diversity, epigenetic diversity, and variation in reproductive traits of P. australis populations along latitudes. Variation in growth traits was negatively correlated with soil salinity, reflecting the limiting effect of salinity on plant growth. Main Conclusion: Our findings found that genetic and epigenetic variations may play different roles in phenotypic variation of P. australis populations along latitudes, the variation becomes greater when the climatic and edaphic conditions deteriorate. The findings shed new light on the adaptation and evolution of wetland plant populations along a large latitudinal scale, and may contribute to the revegetation of estuary wetlands. [ABSTRACT FROM AUTHOR]

Hypoxia is one of the predominant water quality issues affecting estuaries and coastal ecosystems, and its impact is often monitored using benthic macroinvertebrates. The M-AMBI (Multivariate AZTI Marine Biotic Index) is an index that meets the needs of small and large-scale monitoring as it is scalable. However, gaps remain as to the sensitivity of M-AMBI to hypoxia as few studies are available. Using Pensacola Bay in the northern Gulf of Mexico (USA) as a case study, we sought to evaluate the time scales over which benthic macrofauna respond to dissolved oxygen conditions from May through September 2017. Combined continuous DO monitoring and benthic sampling identified important differences in DO exposure on benthic habitat condition based on both the duration and frequency of low oxygen. We identified periods of 7 to 31 days as critical windows of exposure prior to a measurable benthic response, and that both duration and exposure to varying low oxygen conditions as well as the recovery period of oxygen to > 5 mg L−1 are important to benthic habitat health. While the duration of exposure to DO from < 2 mg L−1 to near anoxia remains an important factor in benthic health, benthic organisms can better tolerate periods of low oxygen when reoxygenation occurs after a short time interval. More research is needed to better quantify the relationship between oxygen stress and recovery on benthic habitats, particularly in systems where low DO exposure and recovery can vary over timescales of hours to days. [ABSTRACT FROM AUTHOR]

Erosion poses a significant threat to coastal and estuarine environments worldwide and is further exacerbated by anthropogenic activities and increasing coastal hazards. While conventional engineered structures, such as seawalls and revetments, are commonly employed to protect shorelines from wave impact and erosion, they can also cause detrimental environmental effects. By creating/restoring coastal habitats with engineered structures, hybrid living shorelines offer coastal protection and other co-benefits. Using aerial imagery, we studied the rates of shoreline change before and after living shoreline installation, and between living shorelines and adjacent bare shorelines in three estuaries in New South Wales, Australia. Mangroves had established behind most rock fillets and displayed a trend of increasing canopy cover with fillet age. In the first 3 years since installation, the rates of lateral shoreline change reduced from − 0.20, − 0.16, and − 0.10 m/year to − 0.03, − 0.01, and 0.06 m/year in living shorelines in Hunter, Manning, and Richmond Rivers, respectively. However, when compared to control shorelines, the effectiveness in reducing erosion varied among living shorelines with mean effect sizes of 0.04, − 0.28, and 1.74 across the three estuaries. A more positive rate of shoreline change was associated with an increasing percentage of mangrove canopy area and an increasing length of protected shoreline at wide channels. While hybrid mangrove living shorelines are a promising solution for mitigating erosion and creating habitats at an estuary-wide scale, they may also contribute to downdrift erosion, emphasising the importance of considering site-specific hydrogeomorphology and sediment movement when installing living shorelines. [ABSTRACT FROM AUTHOR]

This review presents an analysis of recent sedimentation rates (SRs) in the Atlantic estuaries of northern Spain. Sedimentation rates were derived from sediment core dating using radiometric methods, including 210-Pb, 137-Cs, and 14-C, and were compiled from the existing literature. The observed SRs are consistent with global estimates, ranging from 0.04 to 55.1 mm/year. No correlation was found between SRs and estuarine morphology, basin size, or estuary size, and no apparent geographical pattern emerged. However, certain SRs were directly linked to human activities in the catchment area or the estuarine environment. Temporally, a general increase in SRs has occurred since the early 20th century, particularly notable from the mid-20th century, with indications of stabilization or reduction in the 21st century. Further research is essential to investigate these relationships more comprehensively to ensure the sustainability of these fluvial–marine environments. [ABSTRACT FROM AUTHOR]

Microplastic ingestion by marine organisms presents a challenge to both ecosystem functioning and human health. We characterized microplastic abundance, shape, size, and polymer types ingested by the West African mangrove oyster, Crassostrea tulipa (Lamarck, 1819) sampled from estuaries and lagoons from the Gambia, Sierra Leone, Ghana, Benin, and Nigeria using optical microscopy and Fourier transform infrared (FTIR) techniques. A total of 780 microplastics were isolated in the whole tissues of the 250 oysters (n = 50 oysters per country). The abundance and distribution of microplastics in the oysters followed the pattern: the Gambia > Ghana > Sierra Leone > Nigeria > Benin. The Tanbi wetlands in the Gambia recorded the highest average of 10.50 ± 6.69 per oyster while the Ouidah lagoon in Benin recorded the lowest average of 1.80 ± 1.90 per oyster. Overall, microplastic numbers varied significantly (p < 0.05) among the five countries. Microfibers, particularly those within 1001–5000 μm size, dominated the total microplastic count with a few fragments and films. No spherical microplastics were isolated in the oysters. In the Sierra Leone and Benin oysters, fragments and films were absent in the samples. Microplastic between the 1001 and 5000 μm size class dominated the counts, followed by 501–1000 μm, 101–500 μm, and 51–100 μm. Five polymer groups namely polyethylene, polyester, nylon, polypropylene, and polyamide were identified across the five countries, with polyethylene occurring in oysters from all five countries and polyester occurring in all but the oysters from Nigeria. This diversity of polymers suggests varied sources of microplastics ingested by the studied oysters. The absence of microspheres across the five supports findings from other studies that they are the least ingested and highly egested by the oysters. [ABSTRACT FROM AUTHOR]

This study assessed the efficacy of artificial collectors in recruiting Mytella strigata along the Amazon Macrotidal Mangrove Coast. The experiment involved three treatments (PVC plate, PET, and polyethylene screen), each repeated thrice. The study was conducted over 315 days, during which settlement density, bivalve biometry within the collectors, and environmental variables, such as temperature (°C), salinity (g.kg-1), chlorophyll-a (mg.m-3), particulate organic matter (POM), particulate inorganic matter (PIM) (mg.L-1), water transparency (determined using a Secchi disc), and rainfall data (mm), were assessed at 45-day intervals. The recruitment of M. strigata was observed predominantly during the rainy season. Both mussel shell size and average settlement density significantly varied (p < 0.05) based on the type of collector, collection period, and their interaction. Polyethylene mesh collectors demonstrated a higher settlement density compared to PET and PVC substrates (p < 0.05), but mussel shell size was lower in this treatment compared to the shell size of juveniles in PVC and PET collectors. Among the collectors, PVC ones proved more effective for collecting M. strigata, considering the quantity of fixed juveniles and the size of the individuals. Regarding the region's environmental conditions, recommendations are that producers place collectors in the water from January, with juvenile recruitment occurring February‒June. [ABSTRACT FROM AUTHOR]

Shallow coastal and estuarine habitats play an essential role in the life cycles of many fish species, providing spawning, nursery, feeding, and migration areas. However, these ecologically valuable habitats are increasingly threatened by anthropogenic activities, causing substantial changes in both habitat availability and quality. Fish species use these shallow coastal habitats and estuaries during various life stages, leading to their categorization into guilds based on how and when they rely on these areas. This differential functional use of estuaries means that changes to these habitats may affect each guild differently. To understand the impact of estuarine habitat degradation on fish populations, it is therefore necessary to consider the full life cycle of fish and when they rely on these coastal habitats. Here, we use conceptual size‐structured population models to study how estuarine habitat degradation affects two functionally different guilds. We use these models to predict how reduced food productivity in the estuary affects the demographic rates and population dynamics of these groups. Specifically, we model estuarine residents, which complete their entire life cycle in estuaries, and marine estuarine–dependent species, which inhabit estuaries during early life before transitioning offshore. We find that total fish biomass for both guilds decreases with decreasing food productivity. However, the density of juveniles of the marine estuarine–dependent guild can, under certain conditions, increase in the estuary. This occurs due to a shift in the population biomass distribution over different life stages and a simultaneous shift in which life stage is most limited by food. At the individual level, somatic growth of juveniles belonging to the estuarine‐dependent guild decreased with lower food supply in the estuary, due to increased competition for food. The somatic growth rates of fish belonging to the resident guild were largely unaffected by low food supply, as the total fish density decreased at the same time and therefore the per‐capita food availability was similar. These outcomes challenge the assumption that responses to habitat degradation are similar between fish guilds. Our study highlights the need to assess not only fish biomass but also size distributions, survival, and somatic growth rates for a comprehensive understanding of the effects of habitat degradation on fish populations. This understanding is crucial not only for estuary fish communities but also for successful conservation and management of commercially harvested offshore population components. [ABSTRACT FROM AUTHOR]

Laboratory microcosm experiments help to understand the degradation pattern of different sources derived from organic matter (OM) at the sediment–water interface and relate it to field processes. Microcosm experiments were carried out for 65 days to assess the degradation of organic materials such as diatoms, zooplankton, and mangrove leaves using source‐specific fatty acid (FA) biomarkers. The viable bacterial population in the microcosm sediment was low on day 1, but on day 3, it increased substantially by two to threefold in all the treatments. An increase in the bacterial population resulted in a decrease in the FAs specific to organic materials during the initial incubation phase (10 days), suggesting the degradation of organic materials derived from different sources. The FAs specific to diatoms showed faster degradation when compared to zooplankton and mangrove‐specific FAs. The degradation of FAs was influenced by the nature of the source material, unsaturation of FAs, and the sediment type. Sandy sediment facilitated higher degradation of diatom and zooplankton‐specific FAs, whereas mangrove‐specific FAs showed higher degradation in silty‐clay sediment. Thus, bacterial community composition coupled with the habitat characteristics, the OM composition, and the grain size of the sediment, influenced the degradation of FAs. The degradation of mangrove‐specific long‐chain FAs was ~1.11–2.5 times higher when spiked with plankton‐derived labile OM from mixed sources, which otherwise took a longer time for degradation pointing toward co‐metabolism (priming effect), which could play a significant role in the cycling of terrestrial plant‐derived OM in an estuarine ecosystem. [ABSTRACT FROM AUTHOR]

Estuaries are one of the most productive ecosystems in the world, supporting a variety of flora and fauna. Primary productivity by phytoplankton is a rich source of organic carbon, substantial for the aquatic food web. Monitoring phytoplankton (i.e., chlorophyll-a) is essential to assess the health of estuaries and other continental shelves subjected to constant anthropogenic stress (e.g., developmental activities). In this study, a three-endmember combination Spectral Decomposition Algorithm (SDA) was developed to estimate the phytoplankton in the micro-tidal Yura estuary of Japan using Landsat-8 (30 m), and Sentinel − 2A (10 m). The endmember water, phytoplankton, and submerged aquatic vegetation (SAV) yielded the best results with both the satellite sensors (R2 > 0.80) owing to the limited influence of non-phytoplankton suspended solids (NPSS) in the estuary. Chlorophyll-a was used as the proxy for phytoplankton. The estimated root mean square error (RMSE) was relatively higher in Landsat-8 (RMSE = 0.187 µg/L) than the Sentinel-2A (RMSE = 0.162 µg/L). The results were validated using the ground truth data of the Yura Estuary (26 sampling points). Furthermore, the results indicate low chlorophyll-a concentration in the Yura estuary (< 2µg/L) except near the shorelines (~ 6 µg/L). A good fit (R2 = 0.79) between observed chlorophyll-a and turbidity indicated phytoplankton-dominated turbidity in the tide-less estuary of Japan. The estimated maximum turbidity was 1.4 FTU using both sensors, suggesting a low anthropogenic influence on the Yura Estuary. The study demonstrates a successful application of the spectral decomposition algorithm (SDA) in the coastal waters which could further be used to assess the horizontal and temporal variability in phytoplankton in estuarine water. [ABSTRACT FROM AUTHOR]

This study records a new introduction of the estuarine, invasive bivalve Mytilopsis cf. sallei in southeastern Brazil. The new record lies close to the largest port of the country (the Port of Santos, in São Paulo state), raising serious concerns related to the probable expansion of this bivalve in future years. Two out of five sampling stations showed live specimens of M. cf. sallei in the soft sediment, in sites with polluted waters and salinity below 20 ppt, reaching a maximum abundance of 1983 specimens/m2. According to COI evidence, two lineages of M. cf. sallei are present in the region, one of which was previously recorded from northeastern Brazil (where it is probably exotic), and another previously recorded from Florida (native) and Asia (exotic). Potential sources for the introduction are discussed, as well as the role of ballast water vs. biofouling as vectors. Because adults of M. cf. sallei are tolerant to long periods in marine waters, it is possible that biofouling from distant sources contributed to this introduction. In order to enable a robust mitigation plan, a complete spatial evaluation for the presence of this bivalve should be conducted in the Santos Estuary. [ABSTRACT FROM AUTHOR]

Background: Discoveries of new species often depend on one or a few specimens, leading to delays as researchers wait for additional context, sometimes for decades. There is currently little professional incentive for a single expert to publish a stand-alone species description. Additionally, while many journals accept taxonomic descriptions, even specialist journals expect insights beyond the descriptive work itself. The combination of these factors exacerbates the issue that only a small fraction of marine species are known and new discoveries are described at a slow pace, while they face increasing threats from accelerating global change. To tackle this challenge, this first compilation of Ocean Species Discoveries (OSD) presents a new collaborative framework to accelerate the description and naming of marine invertebrate taxa that can be extended across all phyla. Through a mode of publication that can be speedy, taxonomy-focused and generate higher citation rates, OSD aims to create an attractive home for single species descriptions. This Senckenberg Ocean Species Alliance (SOSA) approach emphasises thorough, but compact species descriptions and diagnoses, with supporting illustrations and with molecular data when available. Even basic species descriptions carry key data for distributions and ecological interactions (e.g., host-parasite relationships) besides universally valid species names; these are essential for downstream uses, such as conservation assessments and communicating biodiversity to the broader public. New information: This paper presents thirteen marine invertebrate taxa, comprising one new genus, eleven new species and one re-description and reinstatement, covering wide taxonomic, geographic, bathymetric and ecological ranges. The taxa addressed herein span three phyla (Mollusca, Arthropoda, Echinodermata), five classes, eight orders and twelve families. Apart from the new genus, an updated generic diagnosis is provided for four other genera. The newly-described species of the phylum Mollusca are Placiphorella methanophila Vončina, sp. nov. (Polyplacophora, Mopaliidae), Lepetodrilus marianae Chen, Watanabe & Tsuda, sp. nov. (Gastropoda, Lepetodrilidae), Shinkailepas gigas Chen, Watanabe & Tsuda, sp. nov. (Gastropoda, Phenacolepadidae) and Lyonsiella illaesa Machado & Sigwart, sp. nov. (Bivalvia, Lyonsiellidae). The new taxa of the phylum Arthropoda are all members of the subphylum Crustacea: Lepechinella naces Lörz & Engel, sp. nov. (Amphipoda, Lepechinellidae), Cuniculomaera grata Tandberg & Jażdżewska, gen. et sp. nov. (Amphipoda, Maeridae), Pseudionella pumulaensis Williams & Landschoff, sp. nov. (Isopoda, Bopyridae), Mastigoniscus minimus Wenz, Knauber & Riehl, sp. nov. (Isopoda, Haploniscidae), Macrostylis papandreas Jonannsen, Riehl & Brandt, sp. nov. (Isopoda, Macrostylidae), Austroniscus indobathyasellus Kaiser, Kniesz & Kihara, sp. nov. (Isopoda, Nannoniscidae) and Apseudopsis daria Esquete & Tato, sp. nov. (Tanaidacea, Apseudidae). In the phylum Echinodermata, the reinstated species is Psychropotes buglossa E. Perrier, 1886 (Holothuroidea, Psychropotidae). The study areas span the North and Central Atlantic Ocean, the Indian Ocean and the North, East and West Pacific Ocean and depths from 5.2 m to 7081 m. Specimens of eleven free-living and one parasite species were collected from habitats ranging from an estuary to deep-sea trenches. The species were illustrated with photographs, line drawings, micro-computed tomography, confocal laser scanning microscopy and scanning electron microscopy images. Molecular data are included for nine species and four species include a molecular diagnosis in addition to their morphological diagnosis. The five new geographic and bathymetric distribution records comprise Lepechinella naces Lörz & Engel, sp. nov., Cuniculomaera grata Tandberg & Jażdżewska, sp. nov., Pseudionella pumulaensis Williams & Landschoff, sp. nov., Austroniscus indobathyasellus Kaiser, Kniesz & Kihara, sp. nov. and Psychropotes buglossa E. Perrier, 1886, with the novelty spanning from the species to the family level. The new parasite record is Pseudionella pumulaensis Williams & Landschoff, sp. nov., found in association with the hermit crab Pagurus fraserorum Landschoff & Komai, 2018. [ABSTRACT FROM AUTHOR]

The composition of the fish population of the Mekong River is one of the richest on the planet, however, despite the high diversity (~1200 species) and productivity, the basis of fishing in the Mekong Delta is made up of several dozen species, the most valuable of which are members of the families Pangasiidae, Polynemidae and Sciaenidae. Information on the distribution of these taxa is fragmentary, and the role of various parts of the delta in their reproduction has not been studied. Distribution of families Pangasiidae, Polynemidae and Sciaenidae in the Mekong Delta was assessed in the dry season by midwater trawl catches in 2019 (April, December), 2021 (January, April) and 2022 (March–May). A total of 237 trawls were carried out, in the catch of which 45.9 thousand fish belonging to 36 families were found. Representatives of each of the families Pangasiidae, Polynemidae, and Sciaenidae were noted in 42–57% of all catches within the studied part of the Mekong Delta, however, the frequency of their occurrence in its various parts varies significantly. According to the Mekong Delta zonation scheme, based on the analysis of the taxonomic composition of the fish population, representatives of Pangasiidae are confined to areas of the upper and middle reaches, Polynemidae—to areas of the middle and lower reaches, while significant differences in the horizontal distribution of Sciaenidae in different parts of the delta have not been identified. Significant differences in the vertical distribution of all studied taxa were also not found. The maximum concentrations of juveniles of Pangasiidae and Polynemidae were found in the middle reaches of the delta, and Sciaenidae in the lower reaches, which indicates the important role of the respective areas in the reproduction of representatives of the studied taxa. [ABSTRACT FROM AUTHOR]

Under the best circumstances, achieving or sustaining optimum ecological conditions in estuaries is challenging. Persistent information gaps in estuarine data make it difficult to differentiate natural variability from potential regime shifts. Long-term monitoring is critical for tracking ecological change over time. In the United States (US), many resource management programs are working at maximum capacity to address existing state and federal water quality mandates (e.g., pollutant load limits, climate impact mitigation, and fisheries management) and have little room to expand routine sampling efforts to conduct periodic ecological baseline assessments, especially at state and local scales. Alternative design, monitoring, and assessment approaches are needed to help offset the burden of addressing additional data needs to increase understanding about estuarine system resilience when existing monitoring data are sparse or spatially limited. Research presented here offers a pseudo-probabilistic approach that allows for the use of found or secondary data, such as data on hand and other acquired data, to generate statistically robust characterizations of ecological conditions in estuaries. Our approach uses a generalized pseudo-probabilistic framework to synthesize data from different contributors to inform probabilistic-like baseline assessments. The methodology relies on simple geospatial techniques and existing tools (R package functions) developed for the US Environmental Protection Agency to support ecological monitoring and assessment programs like the National Coastal Condition Assessment. Using secondary estuarine water quality data collected in the Northwest Florida (US) estuaries, demonstrations suggest that the pseudo-probabilistic approach produces estuarine condition assessment results with reasonable statistical confidence, improved spatial representativeness, and value-added information. While the pseudo-probabilistic framework is not a substitute for fully evolved monitoring, it offers a scalable alternative to bridge the gap between limitations in resource management capability and optimal monitoring strategies to track ecological baselines in estuaries over time. [ABSTRACT FROM AUTHOR]

Computed tomography (CT) is a relatively new technique in ichnofossil analysis, which permits superior identification of individual trace fossils, their morphology, infill, tiering relationships, and preservation potential, thus providing better environmental interpretations. It also allows non-professional ichnologists to interpret trace fossils in 3D slices with ease, especially in relatively homogeneous and mud-rich sediments. Herein, CT imagery results have been compared with conventional core logging results based on two push core samples from a muddy tidal flat of the Mira River estuary, Portugal. CT images provide a significantly more accurate description of cores and their environmental interpretation due to enhanced visibility of physical and biogenic sedimentary structures. They also reveal complex tiering relationships between burrows with preferential preservation of deeper tiers. The appearance of stacked Scalichnus-like and other siphonichnidal burrows made by infaunal bivalves indicates discontinuous deposition on a tidal flat likely caused by seasonally related fluctuations in an estuarine environment. [ABSTRACT FROM AUTHOR]

Simple Summary: The Pearl River Estuary (PRE) in China, a highly urbanized coastal area, presents a unique opportunity to study the effects of environmental changes on the phytoplankton com-munity. In September 2018, a field study was conducted to examine how the photosynthetic status and spatial distribution of these organisms varied from freshwater to oceanic waters. Dinophyta and Haptophyta were prevalent in seawater, while Chlorophyta and Cryptophyta dominated from freshwater to estuarine water. Bacillariophyta were found across all regions. Phytoplankton in the mixing zone showed signs of stress due to fluctuating environmental conditions, whereas those in freshwater and oceanic areas appeared more photosynthetically active. Human activities have in-creased nutrient levels in the estuary, leading to higher chlorophyll concentrations and more diverse phytoplankton communities upstream. Understanding these patterns helps us assess the health of coastal ecosystems, which is crucial for managing the impacts of climate change and human development on marine environments. The Pearl River Estuary (PRE) is one of the world's most urbanized subtropical coastal systems. It presents a typical environmental gradient suitable for studying estuarine phytoplankton communities' dynamics and photosynthetic physiology. In September 2018, the maximum photochemical quantum yield (Fv/Fm) of phytoplankton in different salinity habitats of PRE (oceanic, estuarine, and freshwater zones) was studied, revealing a complex correlation with the environment. Fv/Fm of phytoplankton ranged from 0.16 to 0.45, with taxa in the upper Lingdingyang found to be more stressed. Community composition and structure were analyzed using 18S rRNA, accompanied by a pigment analysis utilized as a supplementary method. Nonmetric multidimensional scaling analysis indicated differences in the phytoplankton spatial distribution along the estuarine gradients. Specificity-occupancy plots identified different specialist taxa for each salinity habitat. Dinophyta and Haptophyta were the predominant taxa in oceanic areas, while Chlorophyta and Cryptophyta dominated freshwater. Bacillariophyta prevailed across all salinity gradients. Canonical correlation analysis and Mantel tests revealed that temperature, salinity, and elevated nutrient levels (i.e., NO3−-N, PO43−-P, and SiO32−-Si) associated with anthropogenic activities significantly influenced the heterogeneity of community structure. The spatial distribution of phytoplankton, along with in situ photosynthetic characteristics, serves as a foundational basis to access estuarine primary productivity, as well as community function and ecosystem health. [ABSTRACT FROM AUTHOR]

Understanding the connectivity in estuarine waters is important for sustainable fisheries management and safeguarding of estuarine ecological environments. Knowledge regarding the functional connectivity for some "estuarine opportunist" fish species between the Yangtze River estuary (YRE) and its adjacent coastal waters is still scarce. We investigated the connectivity for an exploited sciaenid, the small yellow croaker (Larimichthys polyactis), using otolith elemental composition. In 2020, 115 juveniles were collected in four putative habitat patches, and elemental fingerprints (strontium, barium, magnesium, manganese) of the otolith margin were used to determine spatial differentiation. The results indicated that multi-elemental fingerprints had limited efficacy in identifying habitat patches at a fine spatial scale. However, an elevated Ba/Ca ratio proved to be effective in identifying the presence of L. polyactis in the YRE, which was found to be 12.5 ± 0.7 µmol/mol. In 2021, 51 adult fish were collected from the Lvsi fishing grounds, and the core-to-edge Ba/Ca profiles of the adult fish were analyzed to evaluate the connectivity in the YRE and its adjacent waters. Among the specimens examined, 41% exhibited a life history associated with estuarine habitats. In addition, among the fish with estuarine life history, 72% of the estuarine life history occurred during the juvenile stage, and almost none at the larval stage. The functional connectivity of L. polyactis in estuarine habitats is conspicuous and closely linked to ontogeny. This study emphasizes the need to incorporate the concept of functional connectivity for a more comprehensive understanding of estuarine ecosystems. Furthermore, it highlights the significance of estuaries for "estuarine opportunist" fish, warranting increased attention and research. [ABSTRACT FROM AUTHOR]

Denitrification and nitrate-ammonification are the responsible processes for nitrate removal in the estuaries. Temperature, nitrate and organic carbon availability are key factors controlling a rate of the nitrate reduction processes. This mixed cultures chemostat study investigates the competition ability and their nitrate reduction end-products of the bacteria isolated from an estuary at different temperatures. This study will help us to understand the seasonal nitrate reduction processes in an estuary. The experiments showed that a nitrate-ammonifier was the predominant process in the steady-state chemostat at high temperature. While a facultative denitrifier-nitrate ammonifier was the predominant process at low temperature. However, the main end products of nitrate reduction at high temperature were up to 61% N2 indicating a denitrifier still had an important role in the end products of nitrate reduction in the estuary. The data also showed that a nitrite respiring bacterium reduced nitrite to N2, that responsible for approximately 6-9% of total N2 produced in the culture. This study confirmed that nitrate ammonifiers out-compete denitrifiers at high temperature, however, denitrifiers still had an important role in end products of nitrate reduction. [ABSTRACT FROM AUTHOR]

The city of Mosul contains a single water source, which represents the main artery of this city, namely the Tigris River. It was necessary to study and evaluate the quality of water, especially in the Rashidieh area since it represents the beginning of the entry of the Tigris River from the northern region, as well as addressing the extent of pollution in it and the extent of water susceptibility to self-purification.Water samples were collected from the Rashidieh area, and five sites were selected along the course of the Tigris River passing within that area. The results of the current study showed that the average temperature ranged between 10.25-14.25°C, and some indicators were measured and the highest value of the pH function was recorded (2.4) at the second site and the lowest value was recorded (0.08) at site 5. Moreover, the average values of TDS, DO, T.H, PO33⁻, NO3- and Clranged from 253.7–338.7, 5.29-8.46,115.6-254.8, 0.248–5.26, 1.73-18.08, and 30.5– 56mg/l, respectively, and most of the values were within the permissible limits and fall within the Iraqi and international standards, except for the acid function, dissolved oxygen and phosphate that recorded values exceeding the permissible limits, especially in the Rashidiya estuary area, the second site, which greatly and significantly affected the Tigris River. Therefore, the sites were classified based on the values of the Canadian index, and the values ranged from good for the Tigris River to poor quality for the Rashidiya estuary and questionable for site 3, while site 4 and 5 were classified as acceptable, and thus the ability of the Tigris River to self-purify was not at the required level. [ABSTRACT FROM AUTHOR]

In salt marsh ecosystems, daggerblade grass shrimp, Palaemon (Palaemonetes) pugio, play a crucial role in food webs and serve as the definitive host for the bopyrid isopod Probopyrus pandalicola. These ectoparasites infest the branchial chambers of grass shrimp, which can lead to decreased energy availability and sterilization of infected hosts. Although bopyrid isopod infestation of daggerblade grass shrimp has been frequently reported in literature from coastal marshes of the southeastern United States, the prevalence of this parasite has not been recently documented in daggerblade grass shrimp from marshes of the northeastern United States. The goal of this project was to quantify the prevalence of Pr. pandalicola infestations in Pa. pugio across Cape Cod, Massachusetts. We evaluated bopyrid isopod prevalence from shrimp collected from 5 different salt marsh habitats along Cape Cod in August 2021. Bopyrid isopod infestations were found in shrimp at 4 of 5 salt marshes, with prevalence ranging from 0.04 to 14.1%. Seasonal resampling of one of the salt marshes revealed the highest average infestation prevalence in spring (<17.1%) and an isolated high of 30.3% prevalence in a single salt panne. A series of linear and multivariate models showed that panne area, shrimp abundance, and distance to shoreline were related to Pr. pandalicola shrimp infestations in salt pannes in summer. This study describes the prevalence of the bopyrid isopod infesting daggerblade grass shrimp in salt marshes in New England, with implications for how parasitized shrimp influence salt marsh food webs in which they are found. [ABSTRACT FROM AUTHOR]

Mapping the sedimentary character of the seafloor in large water‐filled basins is fundamental for understanding landform dynamics to inform research, management, intervention and conservation actions. Seabed mapping methods have undergone considerable development in the last two decades, including the uptake of machine learning approaches for sediment size prediction and classification. However, predictions of surficial sediment characteristics are often hindered by the availability of ground truthing data, their arrangement in space and the modelling approach chosen. Spatially informed sampling designs provide an opportunity to significantly improve the accuracy and uncertainty of predicted sediment distributions. In this study, we apply a machine learning algorithm to predict sediment distributions across Port Phillip Bay, a large (1930 km2) structurally controlled estuary on the southeast coast of Victoria, Australia. Surface sediment samples (n = 252) were collected using a spatially balanced design, ensuring that sampling effort was spread evenly within the embayment with increased sampling intensity placed in more heterogeneous areas. Surficial textural metrics were modelled using the random forest algorithm with bathymetric and hydrodynamic predictor variables. Models highlighted trends in sediment grain size, sorting and composition consistent with predicted wave‐ and current‐induced sediment mobilisation. Model predictions were accurate (normalised‐root mean squared error [NRMSE]: 0.14–0.16); however, standard error was not homogeneous across the study area. Uncertainty maps highlighted areas where additional sampling effort may be needed, including areas where transitional bathymetry impacted surficial sediment character and areas of anthropogenic modifications to the seabed. This study shows the benefits of undertaking spatially informed sample design, block cross‐validation during model fitting and quantifying spatial uncertainty in predictive maps to accurately quantify the fundamental boundary conditions of sediment size. The results of this study are intended to inform local coastal management, including beach renourishment activities. However, approaches outlined are applicable to any study where the seafloor grain size is a fundamental variable in understanding landscape change. [ABSTRACT FROM AUTHOR]

Abstract Background Shellfish reef restoration is relatively new in Australia, particularly to intertidal estuarine environments. In late 2019/early 2020 the first large-scale shellfish reef restoration project of the Sydney rock oyster, Saccostrea glomerata was undertaken in the Myall and Karuah Rivers, Port Stephens, on the mid north coast of New South Wales (NSW), Australia. The present study aimed to determine whether locally sourced clean conspecific oyster shells, and/or locally quarried rocks were better for natural recruitment of natural S. glomerata for large-scale oyster reef restoration, and subsequent recruitment of fishes and invertebrates. Over two years, recruitment of S. glomerata spat, and associated fishes and invertebrates were assessed on reefs made of: (1) rock, and (2) rock and shell. Results The mean (± SE) density of oyster spat on rock reefs (Myall River: 1790 ± 48, Karuah River: 1928 ± 68) was significantly greater (Myall River: ANOVA Si: MS 2, 18 = 31080167, F = 96.05, P

Estuaries feature diverse ecosystems with great biological production and favourable resources and landscapes for ecotourism. Increasing natural disasters have threatened the lives and safety of over 70% of the region's population in recent years. Rapid urbanisation and tourism have changed land use. This changes ecosystem structure and function, impacting service provision. This study developed a Bayesian Belief Network (BBN) model to assess the imbalance between socio-economic development and resource conservation using an ecosystem services (ES) approach. The BBN model helps synthesise and exchange information, provide decision-making data, evaluate trade-off possibilities and anticipate future situations when assessing ES. The BBN network model probabilistically evaluates ecosystem services using expertise, statistical modelling, geographic information systems and interviews. We assessed the comprehensive value of 17 forms of ES for four ecosystem groups over a period of 30 years. As a result, the cultural ecosystem services of some estuarial regions in Vietnam have the highest value and are showing an increasing trend, while the regulating ecosystem services are continuously fluctuating and decreasing. Provisioning ecosystem services are stable with small changes. This study also examined ES values in six landscape categories and created two ES change scenarios. The findings can help managers choose land-use and resource exploitation policies, understand the value of ecosystem services at the regional level and develop estuary sustainability strategies for long-term ecosystem service balance.

Epibenthic invertebrates in three estuaries of the Mekong River, namely Co Chien, Ba Lai, and Cua Dai, were sampled for ecological analysis in November 2022. The objectives of this research were to provide the first baseline survey of epibenthic communities in the Mekong estuaries and to describe more precisely the relationships between epibenthic characteristics and environmental parameters. In total, seven major taxa, including Bivalvia, Decapoda, Gastropoda, Isopoda, Molpadida, Stomatopoda, and Xiphosura were recorded in this estuarine system. The abundances of the epibenthic invertebrates range from 48 to 176 inds/1000 m2. Decapos always occupy the highest numbers with a percentage ranging from 86‒95%. There are 24 decapod species were recorded in this study with the following as dominant families Palaemonidae, Penaeidae, and Paguridae. Our findings highlight that the diversity of epibenthic communities, particularly for decapods, is notably high; however, the epibenthic density is considerably low. Epibenthic density and diversity were significantly correlated with salinity, TDS, depth, and pH but also other factors may play a role. The assessment of epibenthic assemblage diversity and its correlation with environmental factors holds significant importance in the formulation of conservation strategies. [ABSTRACT FROM AUTHOR]

Estuaries as a connecting link between freshwater and marine ecosystems play a special role in salmon rivers. The success of adaptation of juvenile salmonids during the transition to the marine period of life depends on the conditions in estuaries. The work continues the previously started series of publications on the rivers of Sakhalin Island. Using the example of one of the small watercourses in the southeastern part of the island, the hydrological parameters and the structural organization of benthos communities in the atypical estuary have been considered. In the absence of storm surges, penetration of sea water into the water body does not occur; at high tide, water with a salinity of more than 12 psu is observed only at the mouth at the bottom; at low tide, the estuary is completely filled with water with a salinity of 0.1 psu and lower. Studies of the hydrological regime and composition of the bottom fauna were carried out in July 2022. Zoobenthos samples were taken along the longitudinal profile of the estuary at five sections (75 samples in total). Most of the estuarine reach is inhabited by species characteristic of the lower parts of the island watercourses. High environmental variability determines the formation in the estuary of young and unstable benthos communities represented by rapidly reproducing small-sized species.

Variations in primary production in relation to selected physicochemical and biological parameters of the Oum Er Rbia River estuary were measured monthly from November 2018 to January 2020 at two stations using the clear and dark bottle method. Gross primary production (GPP) ranged from 9.28 to 467.07 mg C/m3/h; net primary production (NPP) ranged from 3.09 to 248.13 mg C/m3/h; and respiration (R) ranged from 4.03 to 262.73 mg C/m3/h. GPP, NPP and R are lowest in summer, increasing to peak in spring. In summer and winter, significantly positive correlations were observed between GPP and NPP on the one hand, and phaeopigments on the other. In summer, there is also a significant positive correlation between respiration and dissolved oxygen concentration. In winter, significant negative correlations were found between conductivity and salinity, on the one hand, and GPP, and in summer and winter, on the other, with NPP. Spatial and seasonal variations in productivity depend on the environmental and meteorological conditions at each station, including water temperature, salinity, conductivity, nutrient inputs and light availability.

Microplastics (MPs) are gaining global attention in recent years due to its widespread distribution and potential health impacts. The present study focuses on the distribution and characterisation of microplastics in the sediments and its transfer into the organisms living in Kavvayi and Kumbla backwaters of Northern Malabar region, Kerala, India. MP isolation procedures including density separation, organic matter digestion, and membrane filtration followed by visual and spectral analyses using optical microscope and confocal Raman spectroscopy have been utilised for the microplastic evaluation. Microplastics of size range up to 1 μm was analysed, and the presence of MPs was detected in all samples with an average abundance of 99.5 ± 69.43 particles/kg and 96.57 ± 29.96 particles/kg in Kavvayi and Kumbla backwaters respectively. Raman spectral analysis confirmed that almost 50% of MPs to be synthetic elastomers with the remaining half encompassed by polyamide, polyethylene, polyester, polyurethane, and polypropylene. Higher abundance of MPs in the edible aquatic organisms like clams, prawns, and fishes confirmed the transfer of MP from the environment into living organisms envisages the need of further investigation on toxicological impacts and management strategies. [ABSTRACT FROM AUTHOR]

Globally, stable isotopic methods are rapidly being employed in food web studies to quantify the relative proportions of diverse primary carbon sources in an animal diet. Tropical estuarine ecosystems, one of the vital marine habitats, harbor complex food webs due to the multiplicity of habitats and resources. The complex system of inputs and exchanges of organic matter sometimes complicate identification of the carbon sources that support the higher trophic levels. To assess the primary food sources of four abundant amphipod species in the anthropogenically influenced upper Vashishti estuary, Carbon and Nitrogen stable isotopes were employed. Seasonal variations were significant for δ13C and δ15N of suspended particulate organic matter (SPOM) and also for δ13C of sediment organic matter (SOM), but not for the isotopic values of individual amphipod species. Significant variations in the δ13C and δ15N values between amphipods suggested species-specific diets. Mixing model output indicated discrepancies in seasonal variations of food preferences between species. Trophic level values of all amphipod species indicated seasonality with lower values during post-monsoon. The low δ15N values of SPOM, SOM, and amphipod species were possibly due to the anthropogenic input of nitrogen in the estuary. [ABSTRACT FROM AUTHOR]

When species are introduced to a new environment, they can quickly adapt to the environment and may differ from the indigenous species. The indigenous population of Protosalanx chinensis has a high level of genetic diversity, but it is unclear on the genetic diversity of the introduced populations in northeast China, which supports the major production of P. chinensis in the world. A total of 556 individuals of P. chinensis were collected during 2016–2021, from Lianhuan Lake (LHL), Xingkai Lake (XK), and Shuifeng Reservoir (SF), and one population was collected from the indigenous Taihu Lake (TH). Overall, 36 haplotypes were detected, and the genetic differences in P. chinensis populations within and between river basins were investigated. The nucleotide diversity (π) of the populations ranged from 0.0005 to 0.0032, and the haplotype diversity (Hd) ranged from 0.455 to 0.890, with the highest genetic diversity in the TH population, followed by the SF population, and lower genetic diversity in the XK and LHL populations. The analysis of the genetic differentiation index (Fst) and the genetic distance between populations showed that there was significant genetic differentiation between the TH population and the other populations. More sampling points have been set up in LHL for further analysis; the Dalong Lake (DL) and the Xiaolong Lake (XL) populations were far from the other populations within the LHL population. In this study, we didn't find a correlation between population size, stability, and genetic diversity, and the ecological measures of management should be decisive to the population dynamics. These results provide a basis for the rational utilization and effective management of P. chinensis. [ABSTRACT FROM AUTHOR]

A submarine landslide on the edge of the Norwegian shelf that occurred around 8150 ± 30 cal. years BP triggered a major ocean-wide tsunami, the deposits of which are recorded around the North Atlantic, including Scotland. Ground-penetrating radar (GPR) was used here to investigate tsunami sediments within estuaries on the coast of northeastern Scotland where the tsunami waves were funnelled inland. Around the Dornoch Firth, the tsunami deposits are up to 1.6 m thickness, which is exceptionally thick for tsunami deposits and about twice the thickness of the 2004 IOT or 2011 Tohoku-oki tsunami deposits. The exceptional thickness is attributed to a high sediment supply within the Dornoch Firth. At Ardmore, the tsunami appears to have overtopped a beach ridge with a thick sand layer deposited inland at Dounie and partly infilled a valley. Later, fluvial activity eroded the tsunami sediments locally, removing the sand layer. At Creich, on the north side of the Dornoch Firth, the sand layer varies in thickness; mapping of the sand layer with GPR shows lateral thickness changes of over 1 m attributed to a combination of infilling an underlying topography, differential compaction, and later reworking by tidal inlets. Interpretation of the GPR profiles at Wick suggests that there has been a miscorrelation of Holocene stratigraphy based on boreholes. Changes in the stratigraphy of spits at Ardmore are attributed to the balance between sediment supply and sea-level change with washovers dominating a spit formed during the early Holocene transgression, while spits formed during the subsequent mid-Holocene high-stand are dominated by progradation. [ABSTRACT FROM AUTHOR]

Aim: Spatial assessments of Ecosystem Services (ES) are increasingly used in environmental management, but rarely provide information on the prediction accuracy. Uncertainty estimates are essential to provide confidence in the quality and credibility of ES assessments for informed decision making. In marine environments, the need for uncertainty assessments for ES is unparalleled as they are data scarce, poorly (spatially) defined, with complex interconnectivity of seascapes. This study illustrates the uncertainty associated with a principle‐based method for ES modelling by accounting for model variability, data coverage and uncertainty in thresholds and parameters. Location: Tauranga, New Zealand. Methods: A sensitivity analysis was applied on ES models for marine bivalves (Austrovenus stutchburyi and Paphies australis) and their contribution to Food provision, Water quality regulation, Nitrogen removal and Sediment stabilisation. ES estimates from the sensitivity analysis were compared against baseline ES predictions. Spatial uncertainty patterns were analysed for individual ES through bi‐plots and multiple ES through spatial prioritisation using Zonation. Results: Our study showed spatially explicit differences in uncertainty patterns for ES and between species. Food provision had highest maximum uncertainty (>5 points) but also the largest area of high ES and high certainty conditions. Zonation analysis conducted on baseline and conservative ES values showed overall robust outcomes of top 30% area, but important nuances through shifts in top 5% and 10% areas that allowed for a consistently better representation of ES when accounting for uncertainty. Main Conclusions: The spatial prioritisation in combination with the ES uncertainty biplots provide tools for spatial planning of individual and multiple ES to focus on area of highest value with highest certainty and can thereby help reduce risk and aid decision‐making at acceptable confidence levels. This type of information is urgently needed in marine ES assessments and their management, but likewise extends to other environments to improve transparency. [ABSTRACT FROM AUTHOR]

The Pasur-Sibsa and Baleshwari River Estuary (PSBE) is the longest estuary located in the southwest part of Bangladesh on the Ganges-Brahmaputra delta which flows into the Bay of Bengal. The study was conducted to investigate the diversity and abundance of the zooplankton from three gateways (S1 station: Pasur river gateway; S2 station: Sibsa river gateway and S3 station: Baleshwari river gateway) in the PSBE from July 2022 to December 2022. Water samples were collected from these gateways using plankton net (55 µm mesh size) and preserved for analyzing in the laboratory. A total of 34 species of zooplankton belonging to 9 orders and 17 families were documented. The dominant orders were Calanoida and Dendrobranchiata, covering 59.52% and 18.20%, respectively. Acartia bilobata was the dominant species, while Sagitta sp. was the inferior species throughout the gateways. The Pasur river estuary gateway showed the highest percentage of abundance, accounting for 36.39% of the total individuals. The study calculated the Shannon-Wiener Diversity Index, Simpson's Dominance Index, Simpson's Index of Diversity, Margalef's Richness Index, and Evenness ranged from 1.33 to 1.43, 0.24 to 0.30, 0.70-0.76, 1.11 to 1.21, and 0.74-0.80, respectively. The results showed that the zooplankton composition was rich in the S1 station, which serves as a good indicator of marine productivity like zooplankton. The density of zooplankton in a body of water is indicative of the fish stocking rate. [ABSTRACT FROM AUTHOR]

The invasion process and the persistence of invasive species across environments can be explained by their tolerance to stressors, such as salinization. Urochloa arrecta (Poaceae) exhibits high invasive potential and has already established in various natural and artificial aquatic ecosystems. Here, we experimentally evaluate the effects of water salinity on the traits of three exotic populations of U. arrecta derived from naturally occurring populations across a salinity gradient. Specifically, we measured the difference in the number and perimeter of intercellular spaces for individuals from the different populations across three experimental treatments of salinity. Our results demonstrate that high water salinity levels affected anatomical traits in all populations. However, the traits of freshwater populations were the more significantly impacted by increasing salinity compared with populations sampled from naturally higher occurring salinity. Populations of U. arrecta established in places with certain degree of salinity can be more resistance to salt increases compared with populations established in freshwater habitats that are more distant geographically. However, the resistance of freshwater populations to certain high salinity levels suggests that these populations may exhibit rapid adaptation and to survive under some degree of salinity, demonstrating the species' high resilience across various environments. [ABSTRACT FROM AUTHOR]

Objective: Low survival of emigrating salmonid smolts through the interior regions of California's Sacramento–San Joaquin River Delta (hereafter, "Delta") and large‐scale water extraction from that region have prompted managers to seek to predict and manipulate smolt route use through the tidal Delta. The local flow variables previously used in modeling are not the metrics used in management. Here, I investigate the predictive utility of variables representing both localized flow conditions and remote management metrics to predict routing of juvenile steelhead Oncorhynchus mykiss at two river junctions on the San Joaquin River in the south Delta. Methods: Individual‐based generalized linear models were used with detections of over 4000 acoustic‐tagged juvenile hatchery‐reared steelhead to relate routing to the presence of a rock barrier, simulated localized flow conditions from a hydrodynamic model, and daily management metrics, including upstream river discharge and water pumping rates elsewhere in the Delta. Models were developed for the first two diffluences encountered by smolts entering the Delta (head of Old River and Turner Cut). Result: Exclusive use of the management metrics in routing models underestimated the subdaily, tidally dominated fluctuations in fish routing compared to localized flow covariates. The daily rate of water extraction 20–30 km away contributed to use of non‐main‐stem routes, but the effect was small compared to subhourly flow conditions at the river junctions themselves. Conclusion: Water resource and fish managers are advised to monitor conditions at the locations of interest rather than depending solely on remote metrics. In the Delta, use of a flow barrier and reduction of water pumping operations when smolts are migrating should be combined with habitat improvement in interior Delta regions to optimize migratory survival through this complex and heavily modified system. Impact statementThis research developed a juvenile steelhead routing model that can be used in adaptive management. It highlighted the limitations of common management measures for predicting route use and the importance of monitoring local flow conditions for predictive purposes. [ABSTRACT FROM AUTHOR]

Mytilopsis sallei is a small bivalve that has invaded Asian waters, including southeast Asia. This shellfish has become a pest in coastal and estuary waters in Southeast Asia. This study is the first report on the presence and structure of the M. sallei population in Indonesia, precisely in the coastal lakes of Medan City, North Sumatra Province. This research was conducted in Lake Siombak, Medan City, North Sumatra, which is one of the tropical tidal lakes in Indonesia. Mytilopsis sallei shellfish samples were taken for a year from September 2018--August 2019. Mytilopsis sallei were obtained using a Petersen Grab with a mouth opening of 30 x 30 cm. The measurement of M. sallei consisted of the shell length, shell width, shell thickness, and body weight. The analysis of the population structure parameters with ELEFAN I was accommodated in the FiSAT II software. Spatially, M. sallei highest density in Siombak Lake is at station 5 with 24,100 and 23,948 ind.m-2 and the lowest at station 7 is only 967 ind.m-2. Monthly, M. sallei hase the highest density in the dry season (Feb--Jul) compared to the wet season (Aug--Jan). The density of M. sallei in the dry season reaches 1213--13,187 ind.m-2 and in wet seasons reaches 369-3,029 ind.m-2. The Mytilopsis sallei in Siombak Lake has a maximum length of 42.14 mm and the smallest size is 3.00 mm. The growth model of M. sallei in Lake Siombak is Lt = 42.14 (1-e-1.1(t-0.1598)). Mytilopsis sallei recruitment took place in January (fifth month). The instantaneous mortality rate (Z) of M. sallei mussels was 5.32 with an exploitation rate (E) of 0.66. [ABSTRACT FROM AUTHOR]

Under increasing anthropogenic impacts, the hydrology, weathering, turbidity, and biogeochemistry of the Amazon and Pará river catchments are changing, potentially affecting the concentration and speciation of nitrogen (N) entering the estuary, as well as the subsequent primary productivity. Primary production and several N‐cycling rates have been studied in the northern river plume, and new studies focusing on specific processes in the river mouth emerged. Yet, a general overview is still lacking. For the first time, we provide an overview of primary production along with nitrification, ammonium (NH4+), nitrate (NO3−), and amino acid uptake rates in the Amazon and Pará river mouths which exhibit different degrees of catchment land use. Our results indicate that the Amazon supplies tenfold more NH4+ and NO3−, and its nitrification rates are four times higher than in the Pará River. The stable isotope composition of ambient water and NO3− confirmed that nitrification is a dominant pathway, with fluxes reaching 8.5 × 108 mol N d−1 in the Amazon. Nutrients are transported to regions with reduced turbidity and little nitrification, facilitating NH4+ (0.2–2.4 × 108 mol N d−1) and carbon uptake (4.6 and 14.0 × 108 mol C d−1 in the Pará and the Amazon, respectively) by phytoplankton. The lower N‐cycling rates measured in the Pará relative to the Amazon River mouth likely originate from differences in river discharge and watershed characteristics. Plain Language Summary: Riverine nitrogen can support intense production at the base of the food web in coastal oceans. Such productive ecosystems often show flourishing life and act as a strong atmospheric carbon sink. Since the extent of this nitrogen source is greatly influenced by the status of the river catchment area, it is crucial to have a good understanding of the amount and reactivity of riverine nitrogen at a given study site. Here, we used nitrogen isotope tracers to measure nitrogen assimilation and nitrification rates in the Amazon and Pará river mouths. We found that nitrification was happening at high rates in the Amazon River Mouth. In both estuaries, nitrate production is greater than consumption, allowing nitrate export beyond the turbid waters of the river mouths. Because the Amazon and Pará drainage basins are facing drastic changes, this nitrogen budget gives a baseline for nitrogen cycle pathways and export that will help to monitor the effect of these changes on estuarine nitrogen processes. Key Points: Nitrogen uptake and nitrification measurements reveal intense nitrification of autochthonous ammonium in the Amazon and Pará estuariesIn the turbid parts, nitrate produced via nitrification is not entirely consumed by primary production, leading to its exportRates of nitrogen cycle processes are 10 times higher in the Amazon River mouth, likely due to higher riverine nitrogen discharged [ABSTRACT FROM AUTHOR]

Variations in primary production in relation to selected physicochemical and biological parameters of the Oum Er Rbia River estuary were measured monthly from November 2018 to January 2020 at two stations using the clear and dark bottle method. Gross primary production (GPP) ranged from 9.28 to 467.07 mg C/m3/h; net primary production (NPP) ranged from 3.09 to 248.13 mg C/m3/h; and respiration (R) ranged from 4.03 to 262.73 mg C/m3/h. GPP, NPP and R are lowest in summer, increasing to peak in spring. In summer and winter, significantly positive correlations were observed between GPP and NPP on the one hand, and phaeopigments on the other. In summer, there is also a significant positive correlation between respiration and dissolved oxygen concentration. In winter, significant negative correlations were found between conductivity and salinity, on the one hand, and GPP, and in summer and winter, on the other, with NPP. Spatial and seasonal variations in productivity depend on the environmental and meteorological conditions at each station, including water temperature, salinity, conductivity, nutrient inputs and light availability. [ABSTRACT FROM AUTHOR]

Co-occurring predators often exhibit ecological niche partitioning, resulting from competition over evolutionary time. However, in productive estuarine ecosystems with high resource availability, predators may occupy similar niches without conflict. Determining the degree of niche partitioning and overlap among co-occurring predators can provide insights into a food web's function and its potential resiliency to perturbations. This study used stable isotope analysis to assess the trophic ecology of four predators in Galveston Bay, Texas, USA: spotted seatrout, black drum, bull shark, and alligator gar. Spatially distinct primary producer isotopic ratios emerged for both δ13C and δ15N following salinity regimes, which translated to similar patterns in predator tissue. The volume and overlap among species' trophic niches also varied spatially, with species-specific expansion and contraction of niches across the freshwater-marine continuum. The observed niche patterns were likely related to movements, with implications for trophic coupling across the estuarine landscape. Using regional delineations for baseline values yielded trophic position estimates that were validated by compound-specific stable isotopes and were similar (3.77 to 3.96) for all species but black drum (3.25). Trophic position increased with body length for all species but black drum, and these relationships differed when using estuary-wide versus regionally distinct baselines. Alligator gar gut contents were examined, which primarily aligned with piscivory but also included previously unreported taxa (insect, mammal). Collectively, these results provide evidence for spatial and ontogenetic shifts in trophic ecology within this predator assemblage and highlight the importance of spatial scale when using stable isotopes to examine estuarine food webs. [ABSTRACT FROM AUTHOR]

The integrated assessment of ecological quality in estuarine ecosystems holds significant importance for environmental management. Previous monitoring programs predominantly focused on environmental data, lacking a comprehensive quality assessment approach. To address this gap, this study aimed to integrate environmental factors with macrofaunal community information to evaluate the ecological quality status of the Yellow River Estuary. A total of 13 stations were routinely monitored in August for four consecutive years to collect environmental and biological data. Candidate indicators were screened based on variation coefficients, distribution ranges, and redundancy analysis, identifying 16 indicators belonging to three categories (i.e., seawater, sediment, and biology). The model fit and the interrelationship of the components were determined using structural equation modelling (SEM). The main results were as follows. (1) A total of 144 macrofaunal taxa, belonging to eight animal phyla and 98 families, were identified, with a dominance of Annelida (37.8%) and Mollusca (33.3%). The environmental variables most strongly correlated with the macrofaunal community were TOC, DO, Cd, and Md. (2) NO2 and heavy metals represented the two most direct factors of environmental pollution, while the factor load of biodiversity indices (H', J, and D) was large in the biology category. (3) The evaluation results indicated that 78.85% of the total samples were between the average and upper levels of ecological quality, but only 7.69% of samples were at the "high" level. The framework system for the evaluation of ecological quality constructed in this study provides a theoretical and practical basis for the evaluation of the effectiveness of conservation management of the Yellow River Estuary. [ABSTRACT FROM AUTHOR]

The existence of ultraviolet (UV) biofluorescence in nature has been documented in a wide range of flora and fauna. Biofluorescence is utilised throughout biological and ecological functionality, and although invisible to the human visual perception, this spectral range is known to be integral for communication across flocks, swarms, shoals and between individuals. Under UV illumination, European eel juveniles (glass eel) were found to fluoresce bright yellow. Follow‐up experiments using the UV light source on preceding eel life stages such as pigmented glass eels (elvers), 'bootlace eels' (juvenile yellow eels), older yellow eels and migrating silver eels, all found that these stages had lost the capacity for biofluorescence. The information gathered from this study suggests that the use of UV light for presence/absence glass eel arrival surveying could be a useful and effective tool for researchers in the research field. [ABSTRACT FROM AUTHOR]