Using a combination of quantitative culture, molecular, and infrastructure data to rank potential sources of fecal contamination in Town Creek Estuary, North Carolina.

Estuarine water quality is declining worldwide due to increased tourism, coastal development, and a changing climate. Although well-established methods are in place to monitor water quality, municipalities struggle to use the data to prioritize infrastructure for monitoring and repair and to determine sources of contamination when they occur. The objective of this study was to assess water quality and prioritize sources of contamination within Town Creek Estuary (TCE), Beaufort, North Carolina, by combining culture, molecular, and geographic information systems (GIS) data into a novel contamination source ranking system. Water samples were collected from TCE at ten locations on eight sampling dates in Fall 2021 (n = 80). Microbiological water quality was assessed using US Environmental Protection Agency (U.S. EPA) approved culture-based methods for fecal indicator bacteria (FIB), including analysis of total coliforms (TC), Escherichia coli (EC), and Enterococcus spp. (ENT). The quantitative microbial source tracking (qMST) human-associated fecal marker, HF183, was quantified using droplet digital PCR (ddPCR). This information was combined with environmental data and GIS information detailing proximal sewer, septic, and stormwater infrastructure to determine potential sources of fecal contamination in the estuary. Results indicated FIB concentrations were significantly and positively correlated with precipitation and increased throughout the estuary following rainfall events (p < 0.01). Sampling sites with FIB concentrations above the U.S. EPA threshold also had the highest percentages of aged, less durable piping materials. Using a novel ranking system combining concentrations of FIB, HF183, and sewer infrastructure data at each site, we found that the two sites nearest the most aged sewage infrastructure and stormwater outflows were found to have the highest levels of measurable fecal contamination. This case study supports the inclusion of both traditional water quality measurements and local infrastructure data to support the current need for municipalities to identify, prioritize, and remediate failing infrastructure.

Linking tidal wetland vegetation mosaics to micro-topography and hydroperiod in a tropical estuary.

Although saltmarshes are critical coastal ecosystems they are threatened by human activities and sea-level rise (SLR). Long-term restoration and management strategies are often hampered by an insufficient understanding of the past, present, and future processes that influence tidal wetland functionality and change. As understanding vegetation distribution in relation to elevation and tidal hydroperiod is often the basis of restoration and management decisions, this study investigated the relationships between micro-topography, tidal hydroperiod, and the distribution of saltmarshes, mangroves, and unvegetated flats in a tropical estuary situated within a Great Barrier Reef Catchment in North Queensland, Australia. A combination of high-resolution unattended-aerial-vehicle (UAV)-derived digital elevation model (DEMs) and land cover coupled with 2D hydrodynamic modelling was used to investigate these aspects. Zonation was more complex than generally recognised in restoration and legislation, with overlapping distribution across elevation. Additionally, although each type of tidal wetland cover had distinct mean hydroperiods, and elevation and hydroperiods were strongly correlated, elevation explained only 15% of the variability in tidal wetland cover distribution. This suggests that other factors (e.g., groundwater dynamics) likely contribute to tidal wetland cover zonation patterns. These findings underline that simplistic rules in the causality of tidal wetlands need to be applied with caution. Their applicability in management and restoration are likely to vary depending on contexts, as observed in our study site, with varying environmental and biological factors playing important roles in the distribution patterns of tidal wetland components. We also identified strong monthly variability in tidal hydroperiods and connectivity experienced by each tidal wetland cover (e.g., 10.26% of succulent saltmarshes were inundated during lower-than-average tides compared to 66% in higher than-average tides), highlighting the importance of integrating temporal dynamics in tidal wetland research and management. Additionally, we explored the potential effects of sea-level rise (SLR) on the tidal hydroperiods and connectivity of our study site. The results show that the inundation experienced by each tidal wetland cover may increase importantly if vegetation does not keep up with SLR (e.g., under a 0.8 m sea level scenarios, mean maximum depth of succulent saltmarsh in higher-than-average tides is 184.1 mm higher than the current mean-maximum inundation depth of mangroves). This underlines the importance of acquiring detailed spatio-temporally resolved data to enable the development of robust long-term and adaptive saltmarsh management strategies. Our results are discussed from a management and restoration perspective. We highlight the uncertainties and complexities in understanding the processes influencing tidal wetland functionality, and hence, their management and restoration prospects.

Variations in thyroid hormone levels in endangered St. Lawrence Estuary belugas: Potential linkage with stress and organohalogen contaminant exposure.

The St. Lawrence Estuary (SLE) beluga (Delphinapterus leucas) population is highly exposed to an array of contaminants that were identified as one of the causes to the non-recovery of this endangered and declining population. In the last decade, an increasing number of parturition-associated complications and calf mortality has been reported in this population. It was suggested that elevated exposure to organohalogens (e.g., the halogenated flame retardants polybrominated diphenyl ethers [PBDEs]) and stress could play a role in this phenomenon by perturbing thyroid hormones. The objective of this study was to investigate the impact of concentrations of organohalogen contaminants and stress (cortisol levels) on thyroid hormone variations in adult male and female SLE belugas. Because plasma could not be collected in SLE belugas for ethical reasons, skin biopsy (n = 40) was used as a less-invasive alternative matrix to determine organohalogens (PBDEs and other halogenated flame retardants, polychlorinated biphenyls, and organochlorine pesticides), cortisol, and thyroid hormones (triiodothyronine [T3] and thyroxine [T4]), and their metabolites reverse T3 and 3,5-diiodothyronine [3,5-T2]). Cortisol and thyroid hormones were analyzed by ultra-performance liquid chromatography-multiple reactions monitoring mass spectrometry (UPLC-MRM/MS). This method was compared using skin and plasma samples obtained from Arctic belugas. Comparisons of linear models showed that cortisol was a weak predictor for T4, rT3 and 3,5-T2. Specifically, there was a weak significant negative association between T4 and cortisol levels. Moreover, in male SLE belugas, a weak significant positive association was found between T3 and Σ34PBDE concentrations in skin. Our findings suggest that stress (i.e., elevated skin cortisol levels) along with organohalogen exposure (mainly PBDEs) may be associated with thyroid hormone level perturbations in skin of cetaceans.

Simulated nitrogen load promoted mineralization of N2P1 compounds and accumulation of N4S2 compounds in soil dissolved organic matter in a typical subtropical estuarine marsh.

Soil dissolved organic matter (DOM) is the most reactive pool in estuarine marshes, playing an important role in the biogeochemical processes of biogenetic elements. To investigate the impacts of enhanced nitrogen (N) load on DOM molecular composition and its interactions with microbes in typical Cyperus malaccensis mashes of the Min River estuary, a field N load experiment with four N levels (0, 37.50, 50 and 100 g exogenous N m-2 yr-1, respectively; applied monthly for a total of seven months) was performed. DOM molecular composition was characterized by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), the microbial community compositions (MCC, including fungi and bacteria) were determined by high-throughput sequencing technique, and their relationships were presented by co-occurrence network analysis. The results indicated that enhanced N load had significant impacts on soil DOM molecular composition, with N/C and P/C of DOM decreasing but S/C increasing markedly. Meanwhile, enhanced N load decreased the percentages of N2P1 compounds (primarily lipids) but increased those of N4S2 compounds (mainly lignins and lipids). The relative abundances of lignins significantly increased with increasing N load levels, whereas the proportions of lipids decreased. The abundance of N2P1 and N4S2 compounds was primarily positively correlated with eutrophic and oligotrophic microorganisms, respectively. Therefore, mineralization of N2P1 compounds might act as a source to replenish inorganic P, while enrichment of N4S2 compounds may make great contribution to organic S accumulation. Overall, enhanced N load promoted P depletion and S enrichment via altering plant growth, litter decomposition and MCC.

Bioaccumulation and trophic transfer of per- and polyfluoroalkyl substances in a subtropical mangrove estuary food web.

Mangrove estuaries are an important land-sea transitional ecosystem that is currently under various pollution pressures, while there is a lack of research on per- and polyfluoroalkyl substances (PFAS) in the organisms of mangrove estuaries. In this study, we investigated the distribution and seasonal variation of PFAS in the tissues of organisms from a mangrove estuary. The PFAS concentrations in fish tissues varied from 0.45 ng/g ww to 17.67 ng/g ww and followed the order of viscera > head > carcass > muscle, with the highest tissue burden found in the fish carcass (39.59 ng). The log BAF values of PFDoDA, PFUnDA, and PFDA in the whole fish exceeded 3.70, indicating significant bioaccumulation. The trophic transfer of PFAS in the mangrove estuary food web showed a dilution effect, which was mainly influenced by the spatial heterogeneity of PFAS distribution in the estuarine environment, and demonstrated that the gradient dilution of PFAS in the estuary habitat environment can disguise the PFAS bio-magnification in estuarine organisms, and the larger the swimming ranges of organisms, the more pronounced the bio-dilution effect. The PFOA-equivalent HRs of category A and B fish were 3.48-5.17 and 2.59-4.01, respectively, indicating that mangrove estuarine residents had a high PFAS exposure risk through the intake of estuarine fish.

Influence of microplastics and biogenic particles on the size spectra of tropical estuarine and marine pelagic ecosystems.

Size spectra analysis has been widely used to study pelagic ecosystems worldwide. It has a solid theoretical and empirical basis and can be used to provide useful information on ecosystem structure and trophic efficiency. The objective of this study was to obtain complete Normalized Biovolume Size Spectra (NBSS), including zooplankton, microplastics, and other suspended particles, along an estuary-shelf gradient. Plankton net samples (300 µm mesh) were obtained in the Rio Formoso Estuary, in Tamandaré Bay and on the continental shelf off Tamandaré, Brazil, during two years (from April/2013 to May/2015). Particles were identified by image analysis (ZooScan) and infrared spectroscopy (FTIR). Generally, NBSS slopes were close to -1 (i.e., between -1.09 and -0.85), except for NBSSz (zooplankton only) in the Estuary (-1.59) and in the Bay (-1.44), where the steepest slopes were observed, due to the importance of small-sized zooplankton in these areas. The NBSSz slope was significantly steeper in the Estuary and in the Bay than on the Shelf. The inclusion of particles into the NBSS (NBSSp) turned the slope significantly less steep in the Estuary and in the Bay. Intercepts were significantly higher in the Estuary than in the other areas, after including particles in the analysis (NBSSp), due to the extremely high total volume of biogenic particles in the estuary. The most relevant impacts of microplastics were detected within the larger size classes (> 2.60 mm Feret length, > 0.58 log10 mm3). In the Estuary, large-sized microplastics were similarly important (in terms of volume) as zooplankton. Large-sized polyethylene and polypropylene were more relevant in the Bay, large-sized nylon fibers on the Shelf (in the rainy season). The present study, a pioneering effort towards a synthetic analysis of zooplankton, microplastics, and other particles, highlights the importance of including non-living particles in size-based studies and ecosystem models.

Haplosporidium nelsoni and Perkinsus marinus occurrence in waters of Great Bay Estuary, New Hampshire.

In Great Bay Estuary, New Hampshire, USA, Haplosporidium nelsoni and Perkinsus marinus are 2 active pathogens of the eastern oyster Crassostrea virginica (Gmelin), that cause MSX (multinucleated sphere with unknown affinity 'X') and dermo mortalities, respectively. Whereas studies have quantified infection intensities in oyster populations and determined whether these parasites exist in certain planktonic organisms, no studies thus far have examined both infectious agents simultaneously in water associated with areas that do and do not have oyster populations. As in other estuaries, both organisms are present in estuarine waters throughout the Bay, especially during June through November, when oysters are most active. Waters associated with oyster habitats had higher, more variable DNA concentrations from these pathogenic organisms than waters at a non-oyster site. This finding allows for enhanced understanding of disease-causing organisms in New England estuaries, where oyster restoration is a priority.

Characterization of polychaetes inhabiting estuaries and inner bays by composition analysis of amino acids and lactate enantiomers.

In this study, we investigated the composition of free amino acids and lactate (Lac) in polychaetes in river estuaries and inner bays using chromatographic techniques. Both L-amino acids and D-amino acids (D-asparagine, D-alanine (D-Ala), D-serine, D-aspartic acid, and D-proline (D-Pro)) were detected, indicating that polychaetes contain some D-amino acids. Some polychaete species exhibited notable amino acid levels, such as glycine in Capitellidae sp. and Thelepus sp., D-Pro in Glycera sp., and ß-Ala in Scoletoma nipponica and Scoletoma sp.. High D-Lac levels were detected in Tylorrhynchus osawai and Hediste diadroma, (691 and 797 µmol/100 g-wet, respectively), with the D-form exceeding 98%. T. osawai was dominant in the upper tidal-sensitive zone, wherein other organisms were less abundant because of low salinity (3-8 PSU). Seasonal differences in the concentrations of components in T. osawai were observed, particularly a significant increase in D-Lac in the reproductive period. Notably, the D-Lac concentrations of T. osawai were higher upstream than downstream. Thus, D-Lac might be involved in strategies underlying adaptations to low salinity and reproductive activity. These results suggest that both the D-form of Lac and amino acids may play certain physiological roles in the life of polychaetes.

Variable effects of substrate colour and microtexture on sessile marine taxa in Australian estuaries.

Concrete infrastructure in coastal waters is increasing. While adding complex habitat and manipulating concrete mixtures to enhance biodiversity have been studied, field investigations of sub-millimetre-scale complexity and substrate colour are lacking. Here, the interacting effects of 'colour' (white, grey, black) and 'microtexture' (smooth, 0.5 mm texture) on colonisation were assessed at three sites in Australia. In Townsville, no effects of colour or microtexture were observed. In Sydney, spirorbid polychaetes occupied more space on smooth than textured tiles, but there was no effect of microtexture on serpulid polychaetes, bryozoans and algae. In Melbourne, barnacles were more abundant on black than white tiles, while serpulid polychaetes showed opposite patterns and ascidians did not vary with treatments. These results suggest that microtexture and colour can facilitate colonisation of some taxa. The context-dependency of the results shows that inclusion of these factors into marine infrastructure designs needs to be carefully considered.

Human health risk assessment of metal-contaminated soils in Sydney estuary catchment (Australia).

Sydney estuary catchment supports the largest city in Australia and provides essential eco-social and environmental services; however, the region has been influenced by extensive anthropogenic modification. Soil metal concentrations in the catchment had been studied previously; however, the current investigation was designed to determine the risk posed by these contaminants to human health. Soil metal concentrations were higher than observed in most global capitals and increased substantially in the south and south-east of the catchment and close to the central business district. Road-side soils and road dust contained the highest concentration of metals in the catchment. Lead in catchment soils was closely related to traffic density and sourced from the historic use of Pb in petrol. A human health assessment indicated that soil Cd, Ni and Zn posed no non-carcinogenic risk (NCR), or carcinogenic risk (CR) for children, or adults in Sydney estuary catchment and that Cu and Cr may pose minor NCR for children. Vehicle-related Pb raised the greatest human health risk in catchment soils and may pose NCR at 32% and 4.3% of sites for children and adults, respectively. Inconsistent analytical techniques used in CR and NCR evaluations produce incomparable assessments and a consistent` methodology is suggested to improve interpretation. Human health risk may well be higher than commonly calculated due to pollutants present in urban soil not being included in assessments.

Assessing petrochemical effluent effect on heavy metal pollution in Musa Estuary: A numerical modeling approach.

The objective of this study is to assess the effect of petrochemical effluent on heavy metal pollutant in the Musa Estuary ecosystem in the North-western region of the Persian Gulf, through numerical modeling. The outfall of 30 petrochemical plants poses a potential threat to the estuary's seawater and sediment quality, environment, and public health. A combined hydrodynamic and ecologic modeling framework is applied to predict the spatial distribution of BOD and hazardous heavy metals in this estuary. MIKE 21 Flow Model (FM) CFD software is applied to simulate the tidal waves hydrodynamics, next to applying the MIKE ECO Lab models to predict the distribution of BOD and heavy metals in ambient water. The accuracy of the modeling framework is validated against measured water level, current speed, and water quality data. The results reveal that the level of lead concentration corresponds with the national standard, while the BOD, arsenic, molybdenum and vanadium exceed the limit in some areas, particularly in the tidal zone. The optimal outlet locations that effectively meet the standard concentrations of the heavy metals in the ambient water of the estuary are determined. The results confirm that the new outlet configuration corresponds with the standards: 0.198 µg/L for arsenic concentrations, 0.182 µg/L for molybdenum, 1.530 µg/L for vanadium, and 1.132 mg/L for BOD, at maximum. This study contributes to the perception of estuarine dynamics and provides practical implications for estuarine sustainable management and pollution control.

Seasonality, rather than estuarine gradient or particle suspension/sinking dynamics, determines estuarine carbon distributions.

Estuaries are important components of the global carbon cycle; exchanging carbon between aquatic, atmospheric, and terrestrial environments, representing important loci for blue carbon storage and greenhouse gas emissions. However, how estuarine gradients affect sinking/suspended particles, and dissolved organic matter dynamic interactions remains unexplored. We fractionated suspended/sinking particles to assess and characterise carbon fate differences. We investigated bacterial colonisation (SYBR Green I) and exopolymer concentrations (TEP/CSP) with microscopy staining techniques. C/H/N and dry weight analysis identified particle composition differences. Meanwhile, nutrient and carbon analysis, and excitation and emission matrix evaluations with a subsequent parallel factor (PARAFAC) analysis characterised dissolved organic matter. The lack of clear salinity driven patterns in our study are presumably due to strong mixing forces and high particle heterogeneity along the estuary, with only density differences between suspended and sinking particles. Elbe estuary particles' organic portion is made up of marine-like (sinking) and terrestrial-like (suspended) signatures. Salinity did not have a significant role in microbial degradation and carbon composition, although brackish estuary portions were more biologically active. Indicative of increased degradation rates, leading to decreased greenhouse gas emissions, which are especially relevant for estuaries, with their disproportionate greenhouse gas emissions. Bacterial colonisation decreased seawards, indicative of decreased degradation, and shifts in microbial community composition and functions. Our findings span diverse strands of research, concerning steady carbon contributions from both marine and terrestrial sources, carbon aromaticity, humification index, and bioavailability. Their integration highlights the importance of the Elbe estuary as a model system, providing robust information for future policy decisions affecting dissolved and particulate matter dynamics within the Elbe Estuary.

Anthropogenic-induced ecological risks on marine ecosystems indicated by characterizing emerging pollutants in Pearl River Estuary, China.

Anthropogenic Contaminants of Emerging Concern (CECs) in marine environments have raised significant concerns. Yet, analyses detailing their origins, fate, and environmental effects are limited. This study employs an integrated non-target screening methodology to elucidate CECs existence across 46 sampling sites in the Pearl River Estuary (PRE) of the South China Sea. Assisted by advanced liquid chromatography-high resolution mass spectrometry, we discovered 208 chemicals in six usage categories, with pesticides (33 %) and pharmaceuticals (29 %) predominating. Several CECs drew attention for their consistent detections, profound abundance, and significant ecotoxicities. The wide detection of them at offshore sites further implies that anthropogenic activities may contribute to large-scale contamination. Meanwhile, distinct distribution patterns of CECs across PRE are evident in semi-quantitative results, indicating regional anthropogenic influences. Identified transformation products may establish a novel and non-negligible negative contribution to ecology through elevated environmental toxicities, exemplified by HMMM and atrazine. Based on the ecological risks, we compiled a prioritized list of 21 CECs warranting intensified scrutiny. Our findings indicate the introduction of various CECs into the South China Sea via PRE, emphasizing the urgent necessity for ongoing surveillance of discharged CECs at estuary areas and assessment of their marine ecological consequences.

Spatial and ontogenetic modulation of fatty acid composition in juvenile European sea bass (Dicentrarchus labrax) from two French estuaries.

This study evaluated how estuary of origin and ontogenetic stage influence the fatty acid (FA) composition in the tissues of wild European sea bass juvenile. We evidenced tissue-specific patterns, with the brain exhibiting a distinct FA composition from the liver and muscle. Ontogenetic stage and estuary influenced the general FA profile, and particularly the essential FA (EFA) like docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and arachidonic acid (ARA) in all tissues. The data also revealed the ability of wild sea bass to modulate, at the molecular level, FA biosynthesis pathways and suggest a potential dietary DHA limitation in the natural environment. The distribution of FA within tissues might reflect shifts in diet, metabolic demands, or adaptations to environmental conditions. This study provides insights about FA dynamics in euryhaline fish during juvenile life stage, improving our understanding of the metabolism need and EFA trophic availability in a changing environment.

Climatic, oceanic, freshwater, and local environmental drivers of New Zealand estuarine macroinvertebrates.

Understanding the responses of organisms to different environmental drivers is critical for improving ecosystem management and conservation. Estuarine ecosystems are under pressure from multiple anthropogenic stressors (e.g. increasing sediment and nutrient loads, pollution, climate change) that are affecting the functions and services these ecosystems provide. Here, we used long-term estuarine benthic invertebrate monitoring data (∼30 year time-series) to evaluate the responses of macrobenthic invertebrate communities and indicator species to climatic, oceanic, freshwater, and local environmental drivers in New Zealand estuaries. We aimed to improve our ability to predict ecosystem change and understand the effects of multiple environment drivers on benthic communities. Our analyses showed that the abundance and richness of macrobenthic fauna and four indicator taxa (bivalves known to have differing tolerances to sediment mud content: Austrovenus stutchburyi, Macomona liliana, Theora lubrica, and Arthritica bifurca) responded to unique combinations of multiple environmental drivers across sites and times. Macrobenthic responses were highly mixed (i.e., positive and negative) and site-dependent. We also show that responses of macrobenthic fauna were lagged and most strongly related to climatic and oceanic drivers. The way the macrobenthos responded has implications for predicting and understanding the ecological consequences of a rapidly changing environment and how we conserve and manage coastal ecosystems.

Nutrient characteristics driven by multiple factors in large estuaries during summer: A case study of the Yangtze River Estuary.

Nutrients directly control the level of primary productivity and are crucial for the stability of marine ecosystems. Focusing on the survey results in August 2020 of the Yangtze River Estuary, this study elucidated the distribution characteristics and controlling factors of three nutrients: NO3-N, PO4-P, SiO3-Si. The results showed that the concentrations of NO3-N, PO4-P, SiO3-Si in the study area were generally higher near the shore than far shore, with average concentrations of 11.40, 0.70, and 23.73 µmol/L, respectively. The ocean currents drove the distribution of nutrients, and the transport of CDW and YSCC increased the nutrient levels. The resuspension of sediment caused by factors such as terrain and weather may lead to an abnormal increase in nutrients in the bottom waters. The main controlling factors of the three nutrients were different. NO3-N was significantly affected by human activities, PO4-P and SiO3-Si were mainly affected by natural factors.

Spatial heterogeneity of sedimentary organic matter sources in the Yangtze River estuary: Implications from fatty acid biomarkers.

This study investigated the sources of sedimentary organic matter (OM) in the Yangtze River estuary (YRE), using multiple biomarkers. The results of stable carbon isotope (δ13C) and total organic carbon to nitrogen ratio (TOC/TN) suggests the contribution of marine-derived OM significantly increased seawards, while fatty acid (FA) composition provides more specific information on OM sources. In total, 30 components of FAs were identified at the studied 17 sites, which mainly composed of phytoplankton FA, followed by ubiquitous FA and bacterial FA, while terrestrial FA contributed less to the total FAs. Under the strong impacts of the large physicochemical gradients in the YRE, TOC, TN and FA components showed higher concentrations in the estuary mixing zone (especially within the turbidity maximum zone), attributing to their strong binding with OM-enriched fine particles. The spatial heterogeneity of sedimentary OM sources was highly impacted by salinity and Chl-a, as well as bacteria-mediated OM degradation.

An evaluation of microplastic contamination in the marine waters and species in the coastal region of the South Yellow Sea, China.

Microplastics (MPs) contamination of marine environments poses a significant ecological risk, although impacts on species' realized niche spaces remain unclear. The current study investigates MPs distribution across pelagic habitats, benthic sediments, and key biota in the South Yellow Sea, China. Samples were collected via trawling across estuarine transects, and tissues were digested to extract MPs. Density gradient separations and vacuum-filtrations prepared particle extracts for ATR-FTIR and Micro-Raman spectroscopic characterization. Sampling along industrialized river transects reveals ubiquitous plastic particle presence, with concentrations ranging from 0 to 51.68 item/L seawater. Contamination levels reach their peak at station estuaries before dispersing offshore, indicating significant waste stream inputs. Importantly, MPs detected in demersal and pelagic fish species, as well as in bivalves, confirm exposure across trophic niches. Gastrointestinal tract and gill concentrations reached 0.6 items/g fresh tissue, reflecting significant biological uptake and in vivo retention. The greatest population of organisms occurred adjacent to polluted areas. Overall, distribution of MPs from polluted rivers to coastal food webs was evident, suggesting potential negative impacts on key ecological functions in this system. These findings underscore the need to develop upstream mitigation efforts so as to minimize MPs contamination in areas where nearshore and offshore niches intersect.

Organophosphate ester additives and microplastics in benthic compartments from the Loire estuary (French Atlantic coast).

We report the first empirical confirmation of the co-occurrence of organophosphate esters (OPEs) additives and microplastics (MPs) in benthic compartments from the Loire estuary. Higher median concentrations of MPs (3387 items/kg dw), ∑13tri-OPEs (12.0 ng/g dw) and ∑4di-OPEs (0.7 ng/g dw) were measured in intertidal sediments with predominance of fine particles, and under higher anthropogenic pressures, with a general lack of seasonality. Contrarily, Scrobicularia plana showed up to 4-fold higher ∑tri-OPE concentrations in summer (reaching 37.0 ng/g dw), and similar spatial distribution. Polyethylene predominated in both compartments. Tris(2-ethylhexyl) phosphate (TEHP), its degradation metabolite (BEHP) and tris-(2-chloro, 1-methylethyl) phosphate (TCIPP) were the most abundant OPEs in sediments, while TCIPP predominated in S. plana. The biota-sediment accumulation factors suggest bioaccumulation potential for chlorinated-OPEs, with higher exposure in summer. No significant correlations were generally found between OPEs and MPs in sediments suggesting a limited role of MPs as in-situ source of OPEs.

Spatiotemporal dynamics of bacterioplankton communities in the estuaries of two differently contaminated coastal areas: Composition, driving factors and ecological process.

Seasonal variations of environmental parameters usually lead to considerable changes in microbial communities. Nevertheless, the specific response patterns of these communities in coastal areas subjected to different levels of contamination remain unclear. Our results revealed notable fluctuations in the bacterioplankton community both seasonally and spatially, with seasonal variations being particularly significant. The diversity and composition of bacterioplankton communities in the estuaries varied significantly across seasons and between seas. Some bacterial phyla that were highly abundant in the dry season (e.g., Patescibacteria and Epsilonbacteraeota) were almost absent in the wet season. Furthermore, the network analysis revealed that the bacterioplankton networks were more complex during the wet season than in the dry season. In the wet season, the estuarine bacterioplankton network in the Yellow Sea region was more complex and stable, while the opposite was true in the dry season. According to the neutral community model, stochastic processes played a more significant role in the formation of bacterioplankton communities during the wet season than during the dry season. Estuarine bacterioplankton communities in the Yellow Sea region were more affected by stochastic processes compared to those in the Bohai Sea. In summary, in the estuaries of two differently contaminated coastal areas, the seasonal increase in nutrient levels enhanced the deterministic processes and network complexity of the bacterioplankton communities.