Monitoring underwater environments is crucial for industrial applications, providing data that can be used for reporting against corporate sustainability and environmental goals. This study presents a novel approach to integrating high-resolution underwater imaging and high-tech water quality sensing with deep learning models to detect fish, estimate turbidity in Nephelometric Turbidity Units (NTU), and analyze their interactions. An IP-based underwater camera and two advanced water quality sensors were deployed at the Port of Mackay (northern Queensland, Australia) to collect synchronized visual and water quality data. A significant portion of collected images lacked valid turbidity values due to camera and sensor synchronization issues. To address this, we developed a custom Convolutional Neural Network (CNN) model for image-based turbidity estimation. Additionally, YOLOWorld-based prompt-able object detectors were used and evaluated for fish detection, with YOLOWorld-v1 Large emerging as the best choice, achieving 89.7 % accuracy without any training. Our proposed CNN water turbidity estimation model gained root mean square error of 1.6 NTU. Using these deep learning models, we found a non-linear correlation between fish count and water turbidity with an R of 0.93. This finding is aligned with previous research and highlights the complex interplay of environmental factors in marine ecosystems, while showcasing how technological advances can streamline ecological studies. Downstream applications of this technology could include permanently installed underwater cameras in port waters that record real-time data. Management responses could then be automatically triggered when water quality parameters exceed threshold levels, providing early warnings and enabling timely actions to protect marine ecosystems.

Estuarine ecosystems act as major sinks for land-derived pollutants entering the marine environment, and the co-occurrence of microplastics and antibiotics, along with their potential ecological effects on estuarine microalgae, has become an increasingly prominent marine environmental issue. However, little is known about the role of extracellular polymeric substances (EPS) from estuarine microalgae on the joint toxicity of microplastics and antibiotics. This study investigated the protective role of EPS in the typical estuarine diatom Skeletonema costatum by comparing physiological responses with and without EPS under combined stress from polypropylene (PP) and polyethylene (PE) microplastics and the antibiotic sulfamethazine (SM). To further elucidate the regulatory mechanisms through which microalgal EPS responds to co-stress, changes in EPS composition under combined stress were investigated. The results showed that microalgal with EPS exhibited varying degrees of oxidative stress under combined exposure, whereas high-concentration treatments may inhibit SOD production due to cell death. EPS removal compromised the algal resistance, leading to severe chlorophyll a damage, a significant reduction in the DNA synthesis preliminary phase (G0/G1), and a notable increase in the apoptotic cells (Sub-G1). The protein and polysaccharide contents in tightly bound EPS were considerably reduced by combined stress. This study reveals that EPS plays a crucial protective role in microalgae under combined pollution stress by regulating its composition and physicochemical properties. These findings provide a theoretical basis for accurately assessing the ecological risks of emerging contaminants in estuarine environments and offer important guidance for developing pollution control strategies based on biological processes in estuarine environments.

Mediterranean marine caves are biodiversity hotspots and protected habitats under EU legislation. However, there is still limited knowledge from an ecological and environmental perspective, and anthropogenic pollution remains an unexplored topic. This research aimed to investigate the presence of microplastics (MPs) in sediments and benthic foraminifera from two caves: Ficarella Cave (NW Sicily) and Favignana Cave (Egadi Islands). Different pollution degrees were observed between the two caves (39 ± 41 items/kg and 8 ± 7 items/kg sediment, respectively), with the highest variability of polymer materials in the Ficarella cave. Foraminiferal assemblages of both caves were characterized, identifying typical cave assemblages, and species with different types of tests (Textularia bocki and Sigmoilopsis schlumbergeri from the Ficarella cave, and Lobatula lobatula from Favignana cave) were analyzed through μFTIR. Spectra of all the specimens showed peaks attributable to different exogenous organic materials, among which was polyethylene. Then, benthic foraminifera were confirmed as an early indicator of MP pollution. These results confirmed that the integrated study of MPs in different environmental matrices is a promising approach to recognizing the transfer of these pollutants between different environmental compartments. However, for the development of these new studies and the comparison of results, there is a need to define specific sampling methods and, at the same time, standardized analytical methods. To begin a process of harmonization of the methods to be adopted in these environments, this study, considering also the few earlier studies, also focused on defining specific sampling and analytical methods to detect MPs in different environmental matrices and their incorporation into benthic foraminifera.

Anthropogenic debris poses an increasing threat in the marine environment due to its persistence and adverse effects on marine biota and ecosystem services. Previous anthropogenic debris research has centred on shorelines, surface waters, the water column, coastal seafloor and deep-sea domain, leaving sea-caves largely overlooked. This study introduces a novel quantitative approach tailored for sea cave systems, broadening the scope of marine litter research beyond previously targeted environments. All surveyed sea caves contained debris, with densities ranging from 0.044 to 96.839 items m. Most debris was primarily transported via sea-based pathways, and consisted mainly of fragmented plastics (66 %). Occasionally debris was found embedded within tar layers, producing "plastitar" deposits on cave walls. Analyses revealed that wave exposure and available beach area influenced debris retention, while differences in cave architecture resulted in distinct interior spatial deposition patterns across two cave types, leading to the formation of accumulation hotspots. Findings demonstrate that semi-submerged sea caves serve as important reservoirs for anthropogenic marine debris alongside toxic chemical components and potentially associated harmful microbiomes. Such contamination poses risks to sea cave biota and likely compromises the conservation efforts for the Mediterranean monk seal (Monachus monachus).

This study provides the first directly comparable estimates of seawater contamination with microplastics (MPs, 0.3-5 mm) and mesoplastics (MePs, 5-25 mm) during the five sampling expeditions in November and December 2024 in the south-eastern part of the Baltic Sea. Bulk seawater sampling was carried out in two nearby locations simultaneously during different stages of storm activity on sandy and pebbly sea shores. The polymeric composition of the microparticles was identified using μ-Raman and FTIR spectroscopy. The maximum abundance of MPs in seawater near pebbly and sandy shores was 1360 and 1300 items/m, respectively. The maximum content of MPs was 12,160 items/m in water samples with sand suspension near pebbly shores. The average abundance of MePs was 35.6 times higher during the storm compared to the post-storm period at both stations combined. Two key trends were observed during the post-storm period: (i) a decrease in average fiber length, and (ii) an increase in the ratio of MPs to MePs. This confirms that storms in swash zone lead to the fragmentation of large plastic particles into microplastics.

One of the biggest issues harming aquatic organisms in marine environments, including fish, is heavy metal (HML) pollution, which can impact the health of people who consume these species. This study aimed to evaluate nine HML (Nickel (Ni), Vanadium (V), Copper (Cu), Chromium (Cr), Cobalt (Co), Iron (Fe), Selenium (Se), Zinc (Zn), and Manganese (Mn) accumulation in three grouper fish (Epinephelus areolatus, Epinephelus bleekeri, and Epinephelus latifasciatus) with the aim of understanding interspecies differences and estimating the associated environmental and health risks. Results reported that the maximum iron concentration (Fe: 67.44 μg/g wet wt basis) was determined in E. areolatus and the minimum V (0.01 μg/g wet wt basis) in E. latifasciatus, while vanadium in E. bleekeri was below the detection limit. However, the order of elements within species was Fe > Zn > Mn > Se > Cu > Cr > Ni > Co > V for E. areolatus and Fe > Zn > Cu > Cr > Ni > Se > Mn > Co > V for E. bleekeri and E. latifasciatus. From a health risk perspective, the estimated dietary intake (EDI-HML) and weekly intake (EWI-HML) values for all HML were below the safety thresholds, suggesting no immediate non-carcinogenic risk. Similarly, contamination indices suggested low overall contamination. However, the carcinogenic risk (CR-HML) values for Ni and Cr exceeded the acceptable limit, suggesting a potential long-term health concern, particularly among children. Continuous monitoring of HML accumulation in edible marine fish and the implementation of pollution control measures are therefore strongly recommended.

Microbial communities normally consist of generalists and specialists. Ship ballast tank is a special ecological system containing abundant bacteria, yet the mechanisms that shape the diversity patterns of generalists and specialists therein remain poorly understood. Here, the taxonomic and phylogenetic diversity, environmental adaptation and assembly processes of generalists and specialists were systematically examined in ballast sediments. Our results showed generalists were more widely distributed but their richness and variations were significantly lower than those of specialists. Firmicutes and Proteobacteria dominated the bacterial composition of generalists and specialists, respectively. Moreover, complex co-occurrence network was contributed by specialists and it played a more important role in the biodiversity maintenance of ballast sediments. Generalists had broader adaptation to the majority of environmental properties than the specialists, particularly for heavy metals. Stochastic processes, especially "undominated" and dispersal limitation dominated the community assembly of generalists and specialists, respectively. Furthermore, the influence of deterministic processes was higher on the assembly of specialists as compared to generalists. Besides, SO could mediate the balance between stochastic and deterministic processes in the assembly of both generalists and specialists. Importantly, stochastic dispersal or sulfate-mediated deterministic selection occurring in these communities can pose invasion risks through ship transport. Overall, our study provides fresh views into the bacterial community and its ecological processes in ballast sediments, and offers targeted insights into its management.

This study investigates the short-distance variability in microplastics (MPs) and tire wear particles (TWPs) concentrations in coastal sediment environments, aiming to refine sampling strategies for accurate environmental assessments. Grid sampling was conducted at two Danish sites, Strandby (∼0.57 km, 16 sampling points with distance ranging from 215 to 1070 m) and Odense (∼0.95 km, 13 sampling points, with distances ranging from 215 to 1577 m), followed by MP and TWP extraction and quantification. The results revealed significant variation in MP and TWP concentrations within and between sites, with Odense showing much higher contamination levels than Strandby likely due to the proximity to pollution sources and differences in depositional environments. No TWPs were detected at Strandby, likely due to its distance to road surfaces, as TWPs are made from the friction between tires and road surfaces. Monte Carlo simulations indicated that with 10 sampling points, the mean of the samples has a 50 % probability of being within 94-119 % of the true mean, defined here as the overall mean obtained from this study. The findings underscore the importance of collecting multiple samples to accurately represent MP pollution in the sediment compartment and provide recommendations for future monitoring efforts and sampling strategies.

We conducted the largest microplastic (MP) survey ever conducted in the Global South, covering ≈7500 km of the Brazilian coastline and collecting 4134 surface water samples from 1024 beaches across 213 municipalities in 17 states (April 2023-April 2024). Samples were grouped into five coastal macroregions-Amazonian Equatorial, Northeastern, Eastern, Southeastern, and Southern-to align responses and predictors. MPs were quantified by epifluorescence microscopy after Nile Red staining and Calcofluor White/Evans Blue counterstaining, under rigorous quality control procedures. Concentrations showed pronounced spatial heterogeneity, with the Eastern Coastline reaching 16.87 MPs/L, followed by the Northeastern (6.95), Southeastern (5.25), Southern (3.36), and Amazonian Equatorial (1.29 MPs/L). Regional contrasts reflected hydrodynamic and anthropogenic influences: the Eastern sector, characterized by high salinity, elevated pH, and proximity to sewage outlets and highways, exhibited maximum accumulation; the Amazonian Equatorial region, with low salinity, high chlorophyll a, and enhanced surface velocity, showed dissipative conditions and vertical export; and the Southern coast displayed low loads associated with wide shelves and greater distance from point sources. Morphometric analysis revealed a gradient from larger, degraded particles in high-abundance regions to smaller, intact particles in low-abundance regions. Network analysis indicated sparse connectivity in the Eastern Coastline and denser, multi-factorial interactions in the Northeastern and Southeastern regions. These findings establish the first macroregional quantitative baseline of MP pollution in Brazilian marine surface waters, providing a standardized reference for future large-scale monitoring and interregional comparisons.

Nutrient enrichment in coastal ecosystems not only degrades water quality but also imposes substantial economic burdens on regional fisheries, tourism, and coastal infrastructure. This study investigates the riverine nutrient inputs and seasonal eutrophication dynamics in the Bohai Rim coastal zone, one of China's most industrially active and economically vital regions. Field observations and secondary datasets from 2022 to 2023 were analyzed for dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), chlorophyll-a, and dissolved oxygen across river mouths and adjacent coastal waters during wet (July) and dry (January) seasons. Results reveal that DIN concentrations consistently exceeded China's Class III seawater standard, with nitrogen loads dominated by agricultural runoff and industrial effluents. Seasonal eutrophication patterns were strongly linked to economic activity: peak nitrogen fluxes in the dry season coincided with higher energy consumption and fertilizer demand. Dissolved oxygen levels frequently dropped below 4 mg L near the Haihe and Liaohe river estuaries, indicating localized hypoxia risk. Econometric estimation suggests that a 10 % reduction in DIN load could yield annual welfare benefits of approximately 1.8 billion CNY, mainly through restored fishery productivity and reduced water treatment costs. Findings emphasize that nutrient management is not merely an ecological issue but an economic imperative-particularly under China's "Beautiful Bay" and "Dual Carbon" policy frameworks. Strengthened river basin governance, nitrogen-use efficiency improvements, and green agricultural transitions are recommended to align coastal water quality protection with sustainable economic development.

The Deepwater Horizon (DWH) spill was one of history's largest oil spills. The marine-oil snow sedimentation and flocculation accumulation event, known as the MOSSFA event, occurred after the oil rig's blowout. Patterns in Gulf of Mexico benthic foraminiferal assemblages during the DWH spill were identified and their potential use as indicators of past oil spills was investigated. Wall composition, assemblage composition and species diversity were analyzed and compared to levels of dark particulate matter (DPM) concentrations in core DSH 10. An increase in agglutinated taxa from below to within the DPM interval, and a correspondence between tubular agglutinated species and DPM, were revealed. Variations in the ecology of tubular agglutinated taxa imply that this response may have been due to the MOSSFA event as well as a direct response to the DWH spill. Species of the agglutinated genus Trochammina are major contributors to assemblages prior to and after DPM deposition. Elemental analysis of DPM and published geochemistry on the DSH 10 cores suggest that DPM deposition was the result of the MOSSFA event, and certain agglutinated species are potentially oil spill event indicators.

Green tide events caused by Ulva prolifera have emerged as a significant ecological issue in the western coast of Yellow Sea. This study investigated the morphological and physiological changes of U. prolifera as it drifted from the initiation region (Subei Shoal) to the southern coastline of Shandong Peninsula. The goal was to elucidate the underlying mechanism of its adaptation and responses to the environmental variability along its drifting path. The results indicated that U. prolifera experienced a morphological shift from compact thalli with few branches to fragmented, densely branched forms during its northward migration, that enhance its surface area for nutrient uptake and light capture. Photosynthetic activity of lateral branches was significantly higher than that of the main blades, especially in the southern regions. Correlation analyses identified salinity and latitude as the most influential environmental variables, with lower salinity in the southern Yellow Sea facilitating the dense formation of branches. The strong correlations with nutrient availability also highlighted the role of resource availability in shaping the morphology of U. prolifera. Additionally, nitrogen content decreased along the drift path, contributing to an increase in the C/N ratio, which likely influenced the algal morphology and growth rate. These findings revealed that the morphological plasticity of U. prolifera plays a critical role in its ability to adapt to environmental gradients and supports its rapid bloom development. Our results highlight the importance of managing nutrient inputs, especially nitrogen, and suggest that controlling early fragmentation and improving aquaculture practices could mitigate green tide events.

Microplastics (MPs) have been recognized as a new type of environmental pollutant by the scientific and the public, and long-term exposure to them can have harmful effects on organisms. However, the effects of different types of MPs on the release of low molecular weight organic acids (LMWOAs) from a typical marine microalgae Dunaliella salina is extremely limited. This study investigated the effects of different types of MPs, including polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS), polyethylene terephthalate (PET) and polytetrafluoroethylene (PTFE), on the cell growth, nutrient utilization and LMWOA release of Dunaliella salina by series cultivation experiments. Results indicated that the mean inhibition rate (IR) values of MPs on Dunaliella salina were in the order of: PTFE (-2.44 %) > PET (-7.39 %) > PVC (-12.10 %) > PS (-13.94 %) > PE (-14.91 %). The removal rates of NO-N in the culture media of the PE, PVC, PS, PET, PTFE and control groups were 94.96 %, 79.47 %, 84.20 %, 85.37 %, 81.61 % and 69.45 %, respectively. Dunaliella salina could release lactic acid, acetic acid and formic acid to the culture media. The mean concentration order of the three LMWOAs in the media during the cultivation period was lactic acid > acetic acid > formic acid. The release of lactic and acetic acid was significantly affected with the additions of PS, PE and PVC in the media. The additions of various MPs also caused accumulations of the three LMWOAs in the media. The results of this study enriched the understanding of the toxicity of different MPs to Dunaliella salina.

Anthropogenic marine litter poses ecological and economic risks to coastal environments, and its accumulation dynamics remain poorly understood at precise spatial and temporal scales. Most studies lack high-frequency data and rarely consider variations between beach use zones. Therefore, we investigate how social and environmental factors influence the daily accumulation rates of anthropogenic marine debris in different use zones of a tourist beach in Jericoacoara National Park, a conservation unit in Brazil's northeast. Sampling was conducted for one full week each month, from July 2022 to June 2023, across three distinct user zones. Two hierarchical generalized additive models (HGAMs) were applied to test the influence of monthly rainfall and number of monthly tourists on zonal daily litter accumulation rates. A total of 22,375 litter items were recovered, with average daily accumulation rates (1.77 items.m.day) peaking during the tourist season. The accumulation varied notably between zones, with the most impacted site reaching nearly triple the rates of the other sites. Cigarette butts emerged as the most abundant item (average = 0.95 items.m.day), followed by metals (0.24 items.m.day), paper (0.20 items.m.day), hard plastics (0.16 items.m.day) and flexible plastics (0.13 items.m.day). Modeling revealed that litter accumulation patterns were significantly shaped by temporal dynamics, followed by zonation, the number of visitors, and rainfall regimes. These findings highlight the interplay between human activity and environmental factors in driving litter accumulation on urban beaches, offering key insights for targeted coastal management strategies.

Lost large pieces of fishing gear (FG) have well-documented impacts on marine ecosystems, yet the environmental risks of their degradation products remain poorly understood. Assessing these risks requires quantifying the microplastics, nanoplastics, and associated chemicals generated by different FG types. However, regional-scale data on FG used, lost, and beached are scarce. Using the Southeastern Bay of Biscay as a case study, we applied models to estimate the quantities of used and lost plastic FG. Additionally, eight beaches were sampled in four seasons during 2023. Fishing-related items were identified by FG origin using a novel identification key specifically developed for this purpose. Once fishing related items were identified by FG origins, their polymers were determined by ATR-FTIR. In total, we estimated that 211 tons of plastic FG were used and 6 tons were lost in 2023. Gillnets (2.7 tons), and longlines (2.5 tons), were the most frequently lost FG. Altogether, 7.6 % of items collected in the beaches were identified as coming from the fishing sector. Of these, 89.8 % of the items were mending pieces, 2.6 % were lines, and 2.5 % were longlines. In total, we estimated that 3 tons of FG were beached in the coastline during the studied period. Regarding polymer composition, polyethylene and polypropylene accounted for 95.1 % of the FG and polyamide for 3.3 %. This study presents a useful methodology and provides new data for the identification and quantification of used, lost, and beached plastic FG, contributing to future assessments of the environmental risk associated with their degradation products.

Coral reef ecosystems constitute a vital component of global marine biodiversity. In recent years, climate change has induced severe degradation and bleaching in these ecosystems. Accurately predicting coral reef habitat distribution holds significant scientific and practical value. This study integrates multi-source marine biochemical and geographic data to develop a habitat distribution prediction model for South China Sea coral reefs using the Maximum Entropy algorithm (MaxEnt) under two CMIP6 global climate scenarios (SSP1-1.9 and SSP5-8.5). Key environmental drivers and their response curves were analyzed, with projections of habitat evolution trends and optimal biochemical and geographic conditions. The results demonstrate: (1) Projected habitat evolution suggests coral reefs in the South China Sea face near-extinction by 2050 under high-emission scenarios (SSP5-8.5). Waters surrounding the Nansha Islands and affiliated atolls exhibit greater climate adaptability, thus warranting prioritized conservation. (2) The main biochemical and geographic factors and their optimal ranges for suitable coral reef areas in the South China Sea are: bathymetry (0-22 m), slope (1.2-14.5°), minimum monthly mean silicate (2.9-4.7 mmol/m), salinity (32.8-33.5 PSU), minimum monthly mean dissolved molecular oxygen (197.9-199.6 mmol/m), and chlorophyll (0.08-0.094 mmol/m). The model's reliability and generalizability were validated, providing a scientific foundation for coral reef ecosystem management and conservation.

The benthic dinoflagellate Amphidinium carterae is notable for its hemolytic toxins and blooms in many coastal regions, threatening local aquaculture and marine ecosystems. Light is the trigger for the photosynthetic and hemolytic activity of A. carterae; however, the response of photosystem II activity and hemolytic activity to light irradiance and quality is still unclear. Therefore, a series of experiments were conducted on A. carterae to investigate how light irradiance (10, 25, 50, 100, and 200 μmol·m·s of LED white light) and wavelength (white, blue, green, and red LED light at 50 μmol·m·s) interact with the photosynthetic and hemolytic activities of A. carterae. The results revealed that half saturation irradiance (50 μmol·m·s) maintained high photosynthetic efficiency (F/F) and light-regulated nonphotochemical energy dissipation (Y) but reduced the effective photochemical quantum yield (Y) and cell growth. High light, >50 μmol·m·s, increased the Y, relative electron transport rate (rETR) and cell growth but reduced F/F and Y, similar to blue light. However, red light increased F/F and Y but reduced cell growth. Interestingly, the hemolytic activity of A. carterae was strongly affected by light irradiance but not by light quality. Low light, < 50 μmol·m·s, limited the growth and toxin quota of A. carterae, as well as Y. High levels of hemolytic activity were produced by A. carterae, but relatively fast cell growth redirected cellular resources toward growth rather than toward toxin synthesis, resulting in a negative correlation between the hemolytic toxin production rate and the growth rate when light irradiance exceeded 50 μmol·m·s and across all light spectra. Whereas higher photoprotection (Y) of A. carterae induced hemolytic activity under high light, which indicates that hemolytic components associated with photoprotection may be induced during light stress. Taken together, the ability of A. carterae to produce high levels of hemolytic toxins at irradiances greater than 50 μmol·m·s makes it possible for A. carterae to become a toxic vector in the corresponding environment, whereas the migration of cells from high light (surface) to low light (bottom) may reduce the toxic effect of A. carterae during blooms.

Marine heterotrophic protists (MHP) are significant components of marine microbial food webs and play key roles in organic matter remineralization and carbon cycling. However, their diversity and vertical distribution in the Bay of Bengal (BoB) and the Eastern Indian Ocean (EIO) remain poorly characterized. In the present study, we showed the first molecular assessment of depth-resolved MHP communities across the epipelagic (5 m, DCM, 100 m), mesopelagic (200 m, OMZ, 1000 m), and bathypelagic (1500-2000 m) zones in the BoB and EIO using high-throughput sequencing. We observed distinct depth-related MHP patterns. The epipelagic zone was dominated by autotrophic and mixotrophic genera, including Ostreococcus, Bathycoccus, Gyrodinium, Scrippsiella, Collosphaera, and Hexacontium. The mesopelagic zone harboured more parasitic genera, with major genera including Hexacontium, Syndiniales, Thalassiosira, and Neobodo. The bathypelagic zone was characterized by parasitic radiolarians such as Cladococcus and Hexacontium, as well as bacterivorous taxa including Monosiga. The detection of bacterivorous Monosiga and parasitic Syndiniales associated with radiolarians highlights the prevalence of bacterivory and parasitism in deep-water communities. Redundancy analysis (RDA) indicated a limited influence of environmental variables on the MHP community at mesopelagic and bathypelagic depths. Correlation network analysis revealed a decrease in connectivity and an increase in modularity with depth, indicating more compartmentalized interactions in deeper layers. This study provides the first comprehensive characterization of MHP communities in the BoB and EIO across vertical depth gradients, revealing distinct taxonomic assemblages and interaction patterns with depth. These findings provide critical baseline information on MHP diversity and community assemblies in these oligotrophic and stratified oceanic regions.

With the progress of industrialization and urbanization, human activities are exerting increasing pressure on estuarine ecosystems. Accurately assessing the of benthic ecological quality status (EcoQs) has become increasingly critical for the management and restoration of estuarine systems. This study investigates the community structure and spatiotemporal patterns of macrobenthos in two small estuaries (Oujiang estuary and Aojiang estuary). We use five macrobenthos-based biotic indices (Shannon-Wiener diversity index (H'), the AZTI marine biotic index (AMBI), multivariate AZTI marine biotic index (M-AMBI), benthic index (BENTIX), Benthic Opportunistic Polychaete Amphipoda index (BOPA)) to assess the EcoQs. and examine the consistency among indices. A total of 148 macrobenthic species were recorded in the two estuaries. Mollusks and polychaetes dominated in the intertidal and subtidal zones, respectively, with pollution-tolerant and opportunistic species prevailing across both estuaries. The five benthic indices exhibited low consistency in their ecological assessments. EcoQs were inconsistent at over 50 % of the stations. Among the stations with relatively consistent ratings, the majority reflected acceptable EcoQs. Both AMBI and BENTIX tended to overestimate EcoQs, whereas the H' significantly underestimated it. The discriminative capacity of BENTIX was notably limited in areas subjected to mild pollution or low disturbance. M-AMBI showed correlations with multiple environmental factors and effectively reflected gradients of environmental change within the estuaries. Compared to the other biotic indices, M-AMBI appears to be more suitable for evaluating benthic EcoQs in the study area.

Heavy metal pollution in marine environments is a persistent global challenge. Marine organisms absorb, transfer, and accumulate these metals from their surroundings. While numerous studies have documented heavy metal concentrations in various marine ecosystems and organisms worldwide, the interspecific variations across taxonomic groups and their underlying mechanisms remain poorly understood. The key drivers of differential metal accumulation among marine species are yet to be fully elucidated. This study investigated Bohai Bay, a representative coastal bay, analyzing the spatial distribution of six heavy metals (Cu, Pb, Cd, Zn, As, Hg) in water and sediments across nine stations at varying distances from shore. Concurrently, we measured metal concentrations in 23 commercially important marine species. Our results revealed significant inter-taxonomic differences in metal accumulation: fish < mollusks < crustaceans for Cu, Zn, As, and fish < crustaceans < mollusks for Pb, Cd, Hg. Within the fish, species inhabiting lower water layers and occupying higher trophic levels exhibit elevated concentrations of heavy metals. Our results from ten fish species showed that habitat types, migration patterns and feeding habits could influence the heavy metals concentrations, while no significant correlation between size/weight with heavy metals concentration was obtained in fish. Comparative analysis of bioaccumulation factor (BAF) revealed that Cd, Zn and As were highly enriched in mollusks (BAF > 5000), while Zn and As showed significant accumulation in crustaceans (BAF > 5000). This study provides a comprehensive analysis of taxon-specific metal accumulation patterns, offering new insights into marine ecotoxicology in Bohai Bay and underscoring the need for taxon-specific risk assessments to safeguard seafood safety and marine ecosystem health.

For the first time, a set of microcosm experiments were conducted at six locations for seven days along the west coast of India. The hypothesis of this study is that atmospheric dust has a significant impact on coastal primary production, resulting in changes to the composition of the phytoplankton community. Specifically examining how it alters nutrient availability, phytoplankton composition, and primary productivity, highlighting the crucial role of aerosol-driven nutrients in shaping marine biogeochemistry. Airmass back trajectory (AMBT) analysis indicated mixed marine-terrestrial origins of aerosols, with high levels of total suspended particulates (TSP), nitrate, phosphate, and sulphate varying between locations. Microcosm trials showed that adding aerosols significantly increased nitrate and phosphate levels by up to 99 % and 94 %, respectively, alongside a decrease in pH of 0.088-0.205 units. These nutrient enhancements prompted shifts in phytoplankton community structure, characterized by reduced species diversity but increased cell abundance, resulting in phytoplankton blooms. Initially, diatoms such as Thalassiosira sp. and Chaetoceros sp. were dominant, confirmed through microscopy and HPLC analysis. Later, there was a shift toward dominance by picophytoplankton, indicating a two-phase bloom succession driven by changing nutrient levels. Ecological indicators revealed shifts in diversity and dominance patterns, with region-specific responses to blooms and declines. Primary production increased by up to 160 % following aerosol enrichment, a correlation that was strongly observed with nutrient uptake. Despite a decrease in pH, an increase in phytoplankton biomass, pigment content, and primary productivity suggests that the atmospheric aerosols contributed to enhanced coastal productivity.