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The Atlantic bluefin tuna (ABFT) population ranges throughout the Atlantic Ocean and Mediterranean Sea, and consists of multiple contingents that use diverse habitats and show different movement patterns over the life cycle. Based on body size, elemental and isotopic data of C and N in muscle and liver, we analysed eastern-stock ABFT by comparing mid-sized individuals caught by hook-and-line gears with larger individuals harvested from traps in the Strait of Gibraltar (SoG). Our results show that trophic-related chemical markers have potential for separating temporarily sympatric contingents throughout the ABFT population range, reflecting size-dependent spatial distribution and differential patterns of residency and migration. We present evidence of long-term residency of ABFT in the SoG that persists until the estimated age of ∼5 years (size of ∼140 cm in straight fork length). This age apparently marks a turning point in the life history, where there occurs an ontogenetic switch in the migratory behaviour and distributional pattern. This study contributes new insight into our knowledge about size structure and residency-movement patterns in eastern ABFT. It shows distinct size-dependent migratory and spatial dynamics. The present results encourage further investigation on poorly studied ABFT contingents for a better understanding of the population dynamics towards more comprehensive management plans., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The Arctic warming leads to a decline in sea-ice extent and thickness, rapid warming and freshening of the sea surface which impact the distribution of phytoplankton size composition. Picophytoplankton is an ecologically important component of Arctic pelagic marine ecosystems, and its role may be altered by global warming. In this study, the abundance and biomass, the chlorophyll a (Chl-a) and primary production (PP) of picophytoplankton, and its spatial and temporal distribution were investigated in the Kara Sea during the ice-melt season in July 2019. Picophytoplankton played a major role in the surface PP in the southern and western areas of the Kara Sea. In the surface layer, the contribution of picophytoplankton to total Chl-a increased insignificantly, and the contribution of picophytoplankton to total PP decreased significantly with the time of sea ice retreat. In the euphotic zone, the Chl-a concentration of picophytoplankton and its contribution to total Chl-a decreased with the time of sea ice retreat. The average picophytoplankton biomass determined in the present study (2.72 ± 5.10 mg C m -3 ) corresponded to the biomass estimates in the Arctic. The picophytoplankton community was strongly dominated by eukaryotes, cyanobacteria were only detected at 3 out of 11 stations, with maximum abundances (0.07 × 10 9  cells m -3 ) observed at depths below 15 m. The obtained results contribute significantly to the study of the picophytoplankton dynamics during the ice-melting season in the hard-to-reach Kara Sea., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Clams, razor clams and cockle are intertidal bivalve species collected on foot in the shellfish grounds of the Rías Altas (NW Spain). Spatio-temporal distribution of these bivalves are typically at the expenses of the environmental conditions of the region; however, the responses to the abiotic conditions are poorly understood. Using data from 6 species (Ruditapes decussatus, Venerupis corrugata, Ruditapes philippinarum, Cerastoderam edule, Donax trunculus and Solen marginatus) sampled in 51 intertidal shellfish grounds during 2007 and 2008, we characterized the influence of the environment (temperature, salinity, nutrient salts, suspended organic matter, or sediment granulometry and composition) on the distribution and size of these species through a comparative statistical analysis. Shellfish grounds were grouped according to their sediment and water characteristics revealing a land-ocean gradient and the influence of the geological imprint that separates bivalve grounds from West to East. Statistical models showed that R. decussatus, V. corrugata and R. philippinarum together with C. edule were more abundant in sites combining a strong marine influence with organic-rich finer sediments. However, each of those species also had different environmental niches mostly related to their particular sediment affinities, the proximity to the river mouth, and their physiological tolerances to temperature and salinity. D. trunculus was only found in outer exposed shellfish grounds, while S. marginatus abundance increased in muddy sediments. River distance was a sound descriptor of individual shell length and length variability with contrasting effects on the different species. Furthermore, slopes of length-weight relationships were steeper in autumn than in spring, and this allometry tended to be more positive in sites located closer to the rivers' mouth, which had a higher organic matter C/N ratio. Overall, harvested intertidal bivalves had identifiable environmental preferences that influence their spatial distribution in abundance, body size, and allometric growth., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Seagrass beds, as an important coastal blue carbon ecosystem, are excellent at storing organic carbon and mitigating the impacts of global climate change. However, seagrass beds are under threat due to increased human activities and ubiquitous presence of microplastics (MPs) in marine environments. Bibliometric analysis shows that the distribution and accumulation of microplastics in seagrass beds has been widely documented worldwide, but their impacts on seagrass beds, particularly on carbon sequestration capacity, have not been given sufficient attention. This review aims to outline the potential impacts of MPs on the carbon sequestration capacity of seagrass ecosystems across five key aspects: (1) MPs act as sources of organic carbon, contributing to direct pollution in seagrass ecosystems; (2) Impacts of MPs on seagrasses and their epiphytic algae, affecting plant growth and net primary productivity; (3) Impacts of MPs on microorganisms, influencing production of recalcitrant dissolved organic carbon and greenhouse gas; (4) Impacts of MPs on seagrass sediments, altering the quality, structure, properties and decomposition processes of plant litters; (5) Other complex impacts on the seagrass ecosystems, depending on different behaviors of MPs. Latest progress in these fields are summarized and recommendations for future work are discussed. This review can provide valuable insights to facilitate future multidisciplinary investigations and encourage society-wide implementation of effective conservation measures to enhance the carbon sequestration capacity of seagrass beds., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

This study investigated the distribution, abundance, and mass budget of microplastics (MPs) in the Beibu Gulf, Northern South China Sea, focusing on their ecological significance and anthropogenic influence. Microplastics were found in all water and sediment samples, with concentrations in surface water ranging from 0.10 to 0.89 items/m³, and in bottom water from 0 to 0.85 items/m³. Sediment samples exhibited higher levels, ranging from 13.12 to 155.59 items/kg. The spatial distribution revealed higher concentrations along the northern Gulf and Guangxi Province, suggesting significant human influence from coastal activities, such as mariculture and industrial discharges. The study utilized both field data and a mass balance box model to estimate the MPs mass budget, revealing that oceanic flow and riverine discharge are major contributors, accounting for 49% and 52% of MPs, while Atmospheric deposition and sedimentation represents 8% and 1%, respectively. The inventory estimation calculated that 0.24 tons of MPs exist in the water column, and 137 tons in the sediment, emphasizing the substantial environmental burden posed by these pollutants. The significance of this research lies in its comprehensive assessment of MPs in a semi-enclosed gulf, providing critical insight into the role of coastal and hydrodynamic processes in MP distribution. This study highlights the urgent need for better waste management practices in coastal regions to mitigate microplastic pollution and its detrimental effects on marine ecosystems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Seasonal and interannual dynamics of mesozooplankton abundance, biodiversity, ecological status of the marine environment and concurrent variability of abiotic forcings in the north-eastern part of the Black Sea in 2016-2023 were discussed. Mesozooplankton biomass, total biomass (mesozooplankton plus Noctiluca scintillans), biomass of Copepoda and Parasagitta setosa and harmful heterotrophic dinoflagellate Noctiluca scintillans have been considered along with the water temperature, wind, precipitation and salinity. Natural seasonal dynamic of mesozooplankton, disrupted by the invasion of M. leidyi in 1980s was found to be restored to some extent. General tendencies of interannual variability of mesozooplankton parameters and abiotic factors were documented: biomass exhibited maximums in 2017 and 2022, coincided with negative anomalies of SST and along-coast wind (upwelling conditions) and increased/decreased precipitation/salinity. Steady increase of Shannon index during considered period from 1.5-2 to 2.2-2.6 indicates growing biodiversity in the area. Marine environment had BAD ecological status in 2016-2018 and in 2022-2023 and GOOD one in 2019-2021. Ecological hazard of N. scintillans extensive development have been noticed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Changes in oceanographic conditions can affect species distribution in marine habitats. Global climate change may negatively influence the oceanographic factor-species distribution relationship. Here, we assessed the influence of oceanographic conditions on chub mackerel (Scomber japonicus) distribution in northeastern Taiwan by constructing and using a habitat ensemble model incorporating chub mackerel fishery, climatic oscillation, and oceanography data. Our results indicated that the chub mackerel catch was mainly influenced by the Western Pacific Oscillation. Moreover, sea-surface height and mixed-layer depth exerted the most and least significant effects on chub mackerel distribution, respectively. The chub mackerel catch rate peaked in the study area with a sea-surface temperature of 29 °C, sea-surface chlorophyll of 0.25 mg/m 3 , sea-surface salinity of 33.7 psμ, and SSH of 0.575 m. Chub mackerel was the most widely distributed in the area between 25°N, 120.5°E and 26.2°N, 121.5°E. Our findings can be used to develop critical adaptation plans for managing chub mackerel fisheries in the northeastern waters of Taiwan. Considering changing climate conditions globally, the incorporation of this knowledge into managerial strategies may aid decision-makers in protecting not only other ocean fisheries but also individuals dependent on them., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Temperature rising and seawater intrusion are expected to influence the hydrologic regime and redox conditions in coastal soil, and the fate and mechanisms of biogeochemical cycling of Arsenic (As) in the specific environment are poorly understood. This work was carried out in an anaerobic operating chamber by adding sulfate to simulate seawater intrusion under various temperature. Results demonstrated the microbial community diversity was influenced by temperature and the highest Shannon and lowest Simpson index were found at 28 °C. Firmicutes was the dominant bacteria, accounting for 81.16%-93.99%. Desulfosporosinus, with the proportion increasing with temperature, showed a significantly positive correlation with S 2- for sulfate addition treatments. Actually, transformation of As was meditated by the concentration and valence of sulfur and iron in soil. The dissimilatory reduction of arsenic-bearing Fe oxides occurring in the initial stage, is suspected to be the primary driver of As release. Then, concentration of As declined in aqueous phase due to the reduction of sulfate, and the proportion of residual speciation of As in solid phase increased with temperature, ranging from 6.78% to 27.70%. The results displayed the reducing condition due to seawater intrusion and temperature change could regulate the release and sequestration of As in the coastal soil., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Industrial activities increase Apostichopus japonicus exposure to toxic heavy metals. This study evaluates the efficacy of three dietary silicate minerals (montmorillonite, zeolite, and kaolin) in relieving cadmium and lead toxicity in A. japonicus. Over four weeks, juvenile A. japonicus (7 - 9 g) were fed diets incorporating montmorillonite, zeolite, or kaolin, replacing sea mud at a 1:1 ratio. Experimental groups were: SM (control with sea mud), M (montmorillonite), Z (zeolite), and K (kaolin). Each group was exposed to cadmium (50 mg kg -1 ) or lead (100 mg kg -1 ) at the minimal toxic dose (MTD). Groups M and K demonstrated excellent growth performance, marked by improvements in weight gain rate (WGR), specific growth rate (SGR), feed conversion ratio (FCR), and survival rate (SR). Their coelomic fluid revealed higher enzymatic activities, such as acid phosphatase (ACP), alkaline phosphatase (AKP), catalase (CAT), and superoxide dismutase (SOD). Additionally, groups M and K showed a reduced accumulation of cadmium and lead in their tissues; group K notably excelled in mitigating intestinal tissue damage. In contrast, Group Z exhibited significantly poorer performance. In other aspects, the trends among the three experimental groups were generally similar: the activity of intestinal digestive enzymes declined, intestinal microbiota diversity decreased, and the stability of community composition increased. In summary, the supplementation of montmorillonite and kaolin effectively reduces cadmium and lead toxicity, diminishes oxidative damage, and promotes intestinal health in A. japonicus. These findings provide valuable insights for enhancing safety in A. japonicus aquaculture., Competing Interests: Declaration of competing interest The authors involved in this experiment have all disclosed their relevant contributions, and there are no remaining conflicts of interest present in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Understanding the migratory cycle of the European eel is crucial for implementing effective conservation measures. The reasons why some glass eels settle in lower estuaries rather than migrating upriver remain unclear. This study aims to identify metabolomic signatures that distinguish active (migrant) from inactive (non-migrant) glass eels. Using a combination of target and non-target screening (NTS) approaches, the metabolite profile of glass eels was studied, and a PLS-DA classification model was applied to find differences between behavioural phenotypes. This model highlighted methionine, glutaryl-L-carnitine, and palmitoylcarnitine as key metabolites, with methionine being significantly different between groups. Glutaryl-L-carnitine strongly correlated with activity, suggesting it might be a more sensitive indicator of glass eel activity than previously studied parameters such as weight loss and oxygen consumption. The findings suggest that differences between active and inactive eels result from both swimming activity and intrinsic metabolic differences, with methionine linked to both factors. We also explored potential differences in how diazepam affects active and inactive glass eels. However, our metabolomic approach lacked the sensitivity to detect significant variations. Overall, this study provides valuable insights into the metabolomic distinctions between active and inactive glass eels, establishing a foundation for future research in this field., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

While the direct impact of oyster calcification and respiration on the seawater inorganic carbon system is well-acknowledged, their indirect effect through filter feeding activities remains unclear. Here we studied the impact of large-scale oyster farming on the removal of dissolved inorganic carbon (DIC) from seawater. Field investigations showed that the DIC level in the oyster farming area in Sanggou Bay, China were significantly lower than that in the non-farming area. In-lab incubation showed that regardless of whether incubated in high or low-transparent environments, the DIC removal rate of seawater from the oyster farming area was significantly higher than that of the non-farming area. These results indicate that cultivated oysters facilitate the removal of seawater DIC in the farming area. To reveal the indirect effect of filter feeding activities on DIC removal, we used 6-m 3 ponds to simulate the oyster-farming environment. Results showed that the average DIC level of the oyster-cultivating groups was 105.83 μmol/kg lower than that of the control groups (without of oyster) after a six-day cultivation. Surprisingly, the average concentration of Chl-a in oyster-cultivating groups was significantly higher than that of the control group at the end of the experiment. Similarly, DIC level declined faster while Chl-a concentration increased faster in seawater that previously experienced 12～20 h of oyster cultivation than that in the control seawater. It was noticed that the transparency of seawater within 6-m 3 ponds increased significantly just after hours of oyster cultivation. This enhanced transparency created a favorable light environment that supported phytoplankton photosynthesis and simultaneously accelerated the DIC removal rate. Overall, oysters not only remove the inorganic carbon in the seawater through calcification but also create a suitable environment for phytoplankton photosynthesis through their filtering activity, and subsequently accelerating the removal of inorganic carbon in the seawater of the oyster farming area., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The haptophytes, are essential components of the marine pico- and nano-plankton but little is known about their diversity and abundance due to the small size. In this study, the taxonomic composition, geographical distribution, and seasonal variation of the haptophytes in the Bohai Sea, the Yellow Sea, and the East China Sea were investigated using DNA metabarcoding in April and October of 2021. A total of 623 and 3756 haptophyte amplicon sequence variants (ASVs) were obtained in spring and autumn, respectively. All currently described or detected haptophyte orders were retrieved, including several deep-branching novel environmental lineages with relative high abundance. The predominant groups were Chrysochromulina, Clade HAP 2-3-4-5, Phaeocystis, and Prymnesium in spring, and Chrysochromulina, Phaeocystis, and Emiliania/Gephyrocapsa compelx in autumn. The richness and diversity showed seasonal variation, with higher alpha diversity occurred in autumn than that of spring. Different haptophyte taxa exhibited unique spatial distribution patterns and water temperature was significantly correlated with the observed community dissimilarities and was the most influential driving factor in both seasons. Our results highlight the high hidden diversity and seasonal variations of haptophytes in the Chinese seas., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Bisphenol A (BPA) analogues are emerging contaminants, whose ecotoxicological profile for aquatic species, particularly marine ones, is little known. In this study, the effects of an environmentally realistic concentration (300 ng/L) of three BPA analogues (BPAF, BPF, and BPS) - alone or as a mixture (MIX) - were evaluated for the first time on the crab Carcinus aestuarii. A multibiomarker approach was adopted to assess the effects of 7 and 14 days of exposure on haemolymph parameters, gill and hepatopancreas biochemical parameters, and physiological responses of crabs. Bioaccumulation of the three bisphenols was also investigated in crabs by UHPLC-HRMS. A significant reduction in total haemocyte counts was recorded in crabs exposed for 7 days to BPAF and MIX and for 14 days to the MIX, whereas an increase was found in crabs treated for 14 days with BPAF. Cell proliferation increased significantly in crabs exposed for 14 days to BPS and MIX. An imbalance of the antioxidant system, as well as oxidative damage, was recorded in gills and hepatopancreas. No neurotoxic effects were observed in crabs. At the physiological level, exposure to MIX increased the respiration rate of crabs. As for bioaccumulation, only bisphenol AF was detected in crabs. Overall, the present study demonstrated that BPA analogues can affect some important cellular parameters, induce oxidative stress and alter physiological responses in crabs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

To elucidate the impacts of scallop farming on the biogeochemical characteristics of low molecular weight (LMW, <1 kDa) dissolved organic matter (DOM), samples collected from a bay scallop mariculture area (MA) and its surrounding areas were determined for absorption and fluorescence spectroscopy after microfiltration and centrifugal ultrafiltration. The values of absorption coefficient a 350 showed a spatial variation trend of inshore area (IA) > MA > non-mariculture area (NMA) for both bulk (<0.7 μm) and LMW fractions. Four fluorescent components, namely two protein-like components (tryptophan-like C1 and tyrosine-like C2) and two humic-like components (microbial humic-like C3 and terrestrial humic-like C4), were identified. Scallop farming influenced DOM transformation by altering phytoplankton abundance and promoting microbial degradation. In July, the net contributions of phytoplankton to the spectroscopy parameters of LMW-DOM in the surface seawater were 11.0% for a 350 , 4.3% for C1, 0.8% for C2, 0.6% for C3 and 3.0% for C4, respectively; the corresponding values of bulk DOM in the surface seawater were 24.3% for a 350 , 20.1% for C1, 5.9% for C2, 2.0% for C3, 2.9% for C4, respectively. Compared with NMA, the contributions of microbial degradation to a 350 in MA's surface seawater increased by 9.0% for LMW-DOM and 6.9% for bulk DOM in July; however, the effects on different fluorescent components varied. In August, compared with NMA, the contributions of microbial degradation to spectroscopy parameters in the bottom water of MA decreased by 35.7% for a 350 , 6.3% for C2, 1.3% for C3, and 4.4% for C4 for LMW-DOM fraction; for bulk DOM, the corresponding contribution decreased by 10.8% for C1. These variations indicate that protein-like substances from scallop aquaculture are easily degraded into LMW substances, while humic-like substances degradation diminishes over time., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Coastal hypoxia, exacerbated by the combined influence of eutrophication and global warming, presents a significant environmental challenge. However, the lag correlation between organic matter (OM) export from the upper layers and bottom dissolved oxygen (DO BOT ) reduction still lack clear elucidation. This study investigated the coupling between net ecosystem production (NEP, representing the maximum OM export) and DO BOT in the Changjiang River plume (CRP), using a wave-driven profiler system. The high-resolution profiles revealed rhythmic fluctuations in water column NEP, with sediment-water exchange (-74.6%) and NEP (-4.0%) dominating DO BOT reduction. Notably, surface NEP impacts DO BOT with a lag time of 25.65 h, indicating an OM sinking speed of 1.32 mm s -1 . NEP at a depth of 3.4 m exerted the most significant influence on DO BOT , explaining a 12% reduction. These findings elucidate the response mechanism of DO BOT reduction to upper OM export and provide insights for hypoxia prediction in coastal and estuarine areas., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Human activities have intensified the global challenge of coastal eutrophication. Recently, water resource managers have encountered difficulties in formulating precise pollutant reduction strategies to mitigate coastal eutrophication. Despite the recognized importance of coastal wetlands and pollution sources in influencing coastal nutrient levels, accurately quantifying their impact remains difficult. To address this challenge, this study introduces a novel approach for optimizing water environmental capacity. A coupled model integrating hydrodynamics, water quality, and wetland nutrient mechanisms was developed to simulate the spatio-seasonal distribution of water, sediment, and vegetation nutrients in a semi-enclosed bay (Liaodong Bay, China) and a large-scale coastal wetland (Liaohe estuary wetland, China). Model parameters and simulation results were calibrated and validated using extensive long-term field investigations and laboratory experiments. The average root mean square errors between simulated and observed values for all validation points were as follows: 0.80 mg L -1 , 0.53 mg L -1 , 0.08 mg L -1 , 6.70 μg L -1 , and 0.50 μg L -1 for dissolved oxygen, chemical oxygen demand, dissolved inorganic nitrogen, dissolved inorganic phosphorus, and chlorophyll-a, respectively. The total nitrogen (TN) and total phosphorus (TP) in the sediment were 0.10 g kg -1 and 0.05 g kg -1 , respectively. For Suaeda salsa, the TN and TP were 2.91 g kg -1 and 0.08 g kg -1 , respectively. For Phragmites australis, the TN and TP were 114.22 g kg -1 and 6.21 g kg -1 , respectively. The results suggest that excessive river discharge and a stable residual circulation structure contribute to the persistent eutrophication in Liaodong Bay. The Liaohe estuary wetland enhances the environmental capacity of dissolved inorganic nitrogen and dissolved inorganic phosphorus in Liaodong Bay to 271 ± 31 t yr -1 and 8 ± 1 t yr -1 , respectively, accounting for 1.8 ± 0.2% and 1.3 ± 0.2% of their respective environmental capacities. The reduction in dissolved inorganic nitrogen concentration is significant, with a maximum decrease of 0.17 mg L -1 . The maximum contributions of atmospheric deposition and aquaculture wastewater to dissolved inorganic nitrogen concentration are 0.08 mg L -1 and 0.03 mg L -1 , respectively, with higher contributions in spring and summer than in fall and winter. These findings highlight the critical role of coastal wetlands in mitigating eutrophication and underscore the need for spatio-seasonal water management programs. This work serves as a model for effectively reducing global coastal pollution emissions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Ocean warming and acidification negatively affect organisms and biogeochemical cycles. To date, emphasis has been placed on the study of the impact on the structures of calcifying species; however, there is limited knowledge about the influence of the increase of these two variables on the solid structures of non-calcifying species as jellyfish. Here, we study the effects that the increase of temperature and acidity would cause on the statoliths of newly released ephyrae of the Mediterranean jellyfish Rhizostoma pulmo. Six combinations of temperature and P CO2 (18, 24 and 30 °C with a P CO2 of 500 and 1000 ppm each), according to the projections of the SSP5-8.5 (IPCC, 2021) scenario for the year 2100, were applied during 32 days to different groups of polyps randomly selected. Statoliths of the released ephyrae were counted and their size was measured. Our results show that, even though neither temperature nor P CO2 increase exerted a representative effect on the amount of statoliths synthesized in newly released ephyra from R. pulmo, it did exert an impact on the size of these structures: warming led to the formation of larger statoliths, while the rise in P CO2 induced the production of smaller structures. Under the simultaneous increase of both variables, acidification attenuated the effects of temperature, but still slightly larger statoliths were synthesized. The size differences observed in these structures could negatively impact the equilibrium system of this jellyfish species, potentially affecting its ability to survive., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

As one of the commonly used and cost-effective nanomaterials, nanosized aluminum oxide (nAl 2 O 3 ) posses unique properties and chemical stability. However, its extensive use and resultant dissemination into aquatic ecosystems prompt concerns over the proliferation and repercussions of harmful algal blooms, particularly those caused by dinoflagellates producing toxins. This study investigated the sub-chronic effects of nAl 2 O 3 on growth, physiological activities, and paralytic shellfish toxins (PSTs) production in Alexandrium tamarense. Results showed dose-dependent inhibition in growth (EC 50  = 20.6 mg L -1 ), esterase activity, and photosynthetic efficiency (F v /F m ) during the sub-chronic exposure (13-day). The internalization of nAl 2 O 3 in microalgal cells and the significant decrease in the total cellular PSTs content were observed under high nAl 2 O 3 concentrations (>40 mg L -1 ). The study also demonstrated a clear decrease in the content of some derivatives of PSTs (GTX5, C1/2, and GTX2/3) with the increase in nAl 2 O 3 concentrations, accompanied by the induction of an unknown derivative. Excessive ROS production, dissolved Al, and physical inhibition were suggested as potential mechanisms for n Al 2 O 3 toxicity and changes in PSTs toxin profile. Overall, this research enhances our understanding of the potentiated risks and threats on the possible concurrent events of toxic dinoflagellate, such as Alexandrium species and nanoparticles in aquatic environments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

In recent years the microplastics research community has called for methods harmonization and standardized metrics of reporting microplastic attributes. While alignment of research practices is essential in obtaining robust microplastic data, resource managers need to balance how the cost and effort of methodologies compare to data output. The intention of this study is to compare two recommended methods for isolating anthropogenic microparticles in fish gastrointestinal tracts. Using Icelandic capelin (Mallotus villosus) as a study species, with potassium hydroxide (KOH) digestion, we compared a 1.2 μm filtration and 45 μm sieving protocols for isolating ingested anthropogenic microparticles. We compared methods based on the amount of time they took to conduct, the cost of the materials and equipment required, levels of procedural contamination, and data output. We found no significant differences in the materials costs or procedural contamination between the two methods. However, the two protocols resulted in anthropogenic microparticles with significantly different characteristics (i.e. colour, length, morphology), and the 45 μm sieving protocol took longer to conduct per sample. Our results contribute towards a more holistic understanding of microplastic research methods, their relative costs, and how they contribute to data outputs and development of large-scale monitoring programs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Crown Copyright © 2024. Published by Elsevier Ltd. All rights reserved.)

In recent years, there has been a notable increase in cooling water intake blockage caused by marine organism blooms at coastal nuclear power plants worldwide, resulting in shutdowns of nuclear power plants and large economic losses. A sizable portion of these incidents were caused by blooms from jellyfish, a planktonic invertebrate with a unique growth pattern. Suitable external conditions are conducive to the rapid growth of jellyfish, and blooms can occur within a few days. In order to better predict jellyfish bloom and enable nuclear power plants to prepare for it in advance, this study explores the numerical relationship between jellyfish biomass and environmental parameters. A series of time windows (evaluation intervals) were defined and constructed by a time-series recursive approach, which solved the problem of poor correlation between jellyfish biomass and environmental parameters at non-bloom points. The optimal time window length D = 10 was obtained, and the key environmental parameters affecting jellyfish biomass were screened as sea surface temperature, salinity, voltage value, dissolved oxygen, and chlorophyll. According to the ADF and KPSS tests, the key parameters have no significant time dependence, which ensures the stability and reliability of the subsequent predictions. The jellyfish bloom prediction model was derived by calculating the score F through the recursive Principal Component Analysis of the key environmental parameter in the time interval preceding the prediction point. The sudden change moments of score F correspond well to the jellyfish bloom moments, and the sudden change moments are all advanced for a period of time compared to the bloom time, which can provide valuable time for the nuclear power plant to organize manpower to deal with the blockage. Finally, a maximum score F threshold model was proposed to be coupled with the jellyfish bloom prediction model to provide a more robust basis for early warning of jellyfish at nuclear power plants., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The macrophyte Gelidium corneum (Hudson) J. V. Lamouroux, 1813 plays an important role as an ecosystem engineer on temperate rocky shores on the northeastern Atlantic coast. However, its cover and population biomass have declined in recent decades within the southern Bay of Biscay. This study aimed to identify the environmental thresholds, with respect to seawater temperature and irradiance, that influence the development capacity of newly formed individuals of G. corneum through vegetative reproduction. Therefore, an in situ experiment was conducted at two depths within the range of distribution of this species (5 and 12 m) and at two coastal sites on the north coast of Spain (east and west coasts of the Cantabria region, Spain). Our results revealed that G. corneum apical fragments undergoing vegetative propagation developed many new shoots over a period of sixteen weeks. The temperature and irradiance seemed to contribute to the length reached by the new fronds, whereas the number of recruits remained constant throughout the duration of the experiment. Given the slow growth rate characteristic of this species, the total shoot length in this study reached 2.97 cm, which confirms the gradual and restrained developmental pattern during the early stages of its life. We also quantified bite marks at the tips of the new plants, and more than three-quarters of them presented these signs by the final month of the study. Our study provides valuable insights into the growth process of the endangered species G. corneum through vegetative propagation and elucidates the impact that abiotic and biotic factors can have on its growth., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Typhoons greatly affect ocean hydrodynamics, thereby altering ocean productivity and biogeochemistry. This study used stable isotopes and geochemical indicators of particulate organic matter (POM) to investigate the impact of Typhoon Talim (2023) on marine productivity and POM dynamics in Zhanjiang Bay. During the typhoon, an ocean front formed in the upper bay, resulting in a nearly twofold increased POM and enhanced decomposition of resuspended POM, due to the strengthened vertical mixing. Despite of strong decomposition, the supplementation of terrestrial nutrient inputs maintained minimal changes in chlorophyll in the upper bay. By contrast, in the lower bay, chlorophyll and POM decreased significantly, primarily attributed to decomposition of fresh POM and nitrogen limitation resulting from high-salinity seawater intrusion induced by the typhoon. This study suggests that after typhoons, in the area where the ocean front forms, the decomposition degrades a large amount of resuspended POM, which is not conducive to the burial of organic carbon., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The strong western Pacific boundary current of the Kuroshio significantly affects the oceanographic and ecological processes of the East China Sea through its branches. To understand the seasonal variation of Kuroshio intrusion and its ecological effects, 10 cruises were conducted from February 2015 to January 2016 in the waters adjacent to the Changjiang River estuary to collect hydrological data and abundances of phytoplankton assemblages of Prochlorococcus (Pro), Synechococcus (Syn) and picoeukaryotes. High salinity bottom water representing the Nearshore Kuroshio Branch Current (NKBC) appeared in the spring, peaked in the summer, and then almost disappeared at the end of the autumn. During this period, the seasonal variations of Pro and Syn subgroup with lower orange fluorescence (dim type Syn) abundances correlated and synchronized with the intensity of the NKBC intrusion. Water masses analysis further illustrated that the spring was the critical season for NKBC to influence and transport phytoplankton along the pathway to coastal waters. NKBC will further impact the phytoplankton dynamics and ecological processes in this sea area., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Oyster reefs are critically endangered coastal habitats which provide valuable ecosystems services. Despite their importance, there remains a significant knowledge gap in our understanding of how oyster and sediment characteristics influence the ecological functioning and biodiversity of remnant Australian flat oyster (Ostrea angasi) reefs. To inform restoration efforts, we assessed relationships between community respiration rates (CR), inorganic nitrogen fluxes, filtration rates, biodiversity, and oyster morphometrics as well as sediment conditions for three remanent flat oyster reefs (Oyster Cove, Ralphs Bay, and Quarantine Bay) in southeast Tasmania. Additionally, we explored relationships between net denitrification, and flat oyster morphometrics and sediment conditions at one of the sites (Ralphs Bay) in southeast Tasmania. We observed positive relationships between CR, inorganic nitrogen fluxes, filtration rates, and live flat oyster biomass, as well as between the richness and biomass of associated taxa and total flat oyster biomass (both tissue and shell including dead shell), across all three locations. We also found an increase in net denitrification associated with live oyster biomass at one of the oyster reefs (Ralphs Bay). The CR, inorganic nitrogen fluxes, filtration rates, diversity of taxa and biomass of bivalves and flat oyster biomass was higher at Ralphs Bay, which has the most intact reef, compared to the other two locations. In contrast to other studies, the organic and silt content of the sediment showed limited influence on CR, inorganic nitrogen fluxes, filtration rates and net denitrification. CR, and inorganic nitrogen fluxes in these flat oyster reefs were like other restored and natural oyster reefs globally, but net denitrification, filtration rate and taxonomic richness exceeded those previously observed globally. These results highlight the important role of oyster biomass in enhancing water quality and biodiversity. Burgeoning flat oyster reef restoration initiatives should prioritise the enhancement of both live oyster populations and dead shells to recover their associated ecological functions and biological diversity., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Elisabeth Strain reports financial support was provided by The Nature Conservancy. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The present work aims at providing a multi-disciplinary approach for environmental monitoring in marine-coastal areas. A monitoring campaign of 13 months (October 2022-October 2023) was carried out on sandy foreshore sediments (SFSs). The SFSs were analysed for potentially toxic elements (PTEs) and rare earth elements (REEs) content determination. In the investigated area, variable contamination trends were assessed through Friedman and Nemenyi tests. Further results also indicated the usefulness of statistical data elaboration in the identification of potential contamination sources. In fact, from Spearman test, significant positive correlations (between 0.650 and 0.981) were observed among PTEs of possible anthropogenic origin (such as Co, Cr, Cu, Pb, V, and Zn). For REEs, La and Nd showed strong correlations with Ce (0.909 and 0.920, respectively). The study also integrated luminescence inhibition (Aliivibrio fischeri), algal growth inhibition (Phaeodactylum tricornutum), and embryotoxicity assessment (Paracentrotus lividus) on sediment elutriates showing varying degrees of toxicity. Also these data were analysed through statistics in order to highlight possible correlations between contaminants and observed ecotoxicological effects on the involved bioindicators. The results outline an approach useful for more comprehensive monitoring of marine areas quality and identification of suitable environmental restoration strategies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Recently, coral-associated microorganisms have attracted widespread attention, and most of these studies have focused on stony and soft corals. However, our knowledge of the diversity and bioactivity of microorganisms in gorgonian corals is still limited. In this study, the biodiversity of microbes in two gorgonian corals (Leptogorgia rigida and Menella kanisa) from the South China Sea was investigated by combining traditional culture method with molecular biology technique (bacterial 16S or fungal internal transcribed spacer (ITS) rRNA gene sequences). A total of 216 bacterial and 98 fungal isolates were obtained using 4 different isolation media. These isolates were identified and belonged to 31 bacterial and 12 fungal species, suggesting an unexpectedly diverse microbial community harbored in the South China Sea gorgonian corals L. rigida and M. kanisa. Furthermore, 56% of the tested microbial isolates displayed various antifouling activities against four biofouling organisms (including two microfouling bacteria Micrococcus luteus and Shewanella onedensis, and two macrofouling organisms Bugula neritina and Balanus amphitrite). Among the microbial isolates with antifouling activity, Bacillus firmus SCAU-038 and Streptomyces parvulus SCAU-062 displayed moderate or strong antifouling activity against all tested biofouling organisms. This is the first study on the biodiversity and antifouling activity of microorganisms associated with gorgonians L. rigida and M. kanisa from the South China Sea. These results contribute to the further understanding of microorganisms associated with gorgonian corals and provide potential resources for new natural antifouling agents., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Tropical cyclones (TCs) in the Bay of Bengal (BoB) caused significant changes in the sea surface as they passed through the sea. To quantitatively study the differences in oceanic responses caused by TCs during pre-monsoon and post-monsoon seasons in the BoB from 2003 to 2020 and the varying importance of TC intensity and translation speed in modulating oceanic responses, the oceanic environmental parameters affected by TCs were composited and analyzed. The spatial distributions show that the responses of sea surface temperature (SST) rather than chlorophyll-a (Chl-a) concentrations and sea surface salinity (SSS) coincided with the maximum response centers of the wind power index (WPi). All the temporal changes in SST, Chl-a, and SSS indicated that the changes induced by TCs began approximately 2-3 days before TC passage, continued to increase during cyclone passage, and then slowly returned to the initial state after at least 8 days. Compared with TC intensity, TC translation speed generally played a less important role in influencing the ocean responses of SST, Chl-a and SSS. This result is somewhat different from previous results in which the response of Chl-a was correlated with TC translation speed rather than TC intensity in the northern Indian Ocean. In addition, the SSS response was positively proportional (R = 0.886) to the TC translation speed in the BoB, which was different from that in the Northwest Pacific. The differences in the responses during pre-monsoon and post-monsoon seasons were mainly in terms of quantity, as all the composited results were similar. In addition, they were more pronounced in their responses but less significant in their correlations during pre-monsoon., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Defining and delineating species distribution and habitat is critical to informed management and conservation. This process is complicated in marine environments, where detection of marine taxa and characterization of marine habitat is more difficult. Small pelagic fishes and forage fishes are particularly challenging, though insights may be more accessible in species highly dependent on particular habitat. Pacific sand lance (Ammodytes personatus) is a common and ecologically-important pelagic fish that relies on specific benthic sediments for rest and refuge from predation. We applied multibeam echosounder (MBES) bathymetric data to develop high-definition benthic habitat maps and implemented multiyear sampling to assess potential habitat for sand lance via in situ sampling of sediments. We also applied acoustic Doppler current profilers (ADCP) data and tidally-driven volume-based ocean models to measure current strength and to visualize currents. We leveraged this data to further define and describe habitat for this important forage species. Sediment transport processes were mapped and areas of dispersal, embedment, and accumulation were evaluated. Dynamic bedform habitats, banner banks and glacial banks were identified as potential habitat and sampled for fish presence, density and sediment composition. In the central Salish Sea, approximately 25% of benthic substrates represent potential sand lance habitat. Sand lance prevalence and density correlated with substrate type and sediment coarseness. Densities were highest in areas of coarse grain sediments and presence was limited by fine particulates, such as silt and mud. Tidal currents appear important. Presence and densities of sand lance were correlated with current velocity and distance from current flow path. Nearly all viable sites were located on the immediate margins of high flow (<0.16 km from tidal currents with max speed of 1.72-2.58 m/s). While both flood and ebb were important, processes related to flood were dominant. Viable habitat was not constrained by depth. These results inform a developing atlas for sand lance in the central Salish Sea, provide new insights to subtidal sand lance habitat, characterize conditions that create and maintain subtidal benthic habitat, and provide a template for mapping habitat for this species in the coastal Pacific Ocean., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

As emerging pollutants, microplastics can aggregate microorganisms on their surfaces and form biofilms, enriching antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs). Consequently, microplastic biofilms have become a focal point of research. Horizontal gene transfer is one of the primary mechanisms by which bacteria acquire antibiotic resistance, with much of the research focusing on suspended bacteria. However, microplastic biofilms, as hotspots for horizontal gene transfer, also merit significant investigation. This study primarily explored and compared the frequency of ARG conjugative transfer between suspended bacteria and microplastic biofilms. The results demonstrated that, compared to suspended bacteria, microplastic biofilms enhanced the frequency of ARG conjugative transfer by 7.2-19.6 times. Among them, biofilms on polyethylene microplastics showed the strongest promotion of conjugation. After the formation of microplastic biofilms, there was a significant increase in bacterial density within the biofilms, which raised the collision frequency of donor and recipient bacteria. Then microplastic biofilms facilitated the gene expression levels of outer membrane proteins, enhanced bacterial gene transfer capabilities, promoted the synthesis of conjugative pili, accelerated the formation of conjugative pairing systems, and elevated the expression levels of genes related to DNA replication and transfer systems, thereby enhancing the conjugative transfer of ARGs within microplastic biofilms. Among different types of microplastic biofilms, polyethylene biofilms exhibited the highest bacterial density, thus showing the highest frequency of ARG conjugation. This study highlights the risks associated with ARG conjugative transfer following the formation of microplastic biofilms and provides insights into the risks of microplastic and antibiotic resistance propagation in estuarine environments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

China is the largest mariculture country, and shellfish and algae output ranks first, showing high carbon sink capacity. In recent years, the single cultivation of macroalgae (Pyropia yezoensis) has been changed to macroalgae-shellfish mariculture in Haizhou Bay to increase the yield of P. yezoensis and improve the water environment quality. In this study, four surveys were carried out in July 2022 during the monoculture period of oyster (Magallana gigas), as well as at different stages of P. yezoensis culture (head-crop period, November 2022, peak growing season, January 2023, and end of harvesting, March 2023) in the mariculture and the surrounding waters of Haizhou Bay. The effects of different stages of culture on the seawater environment and seasonal and spatial variations in the carbonate system were analyzed, and the carbon sink capacity was preliminarily estimated. The results showed that in summer, the calcification of M. gigas and the primary production process of phytoplankton effectively reduced the dissolved inorganic carbon (DIC) level in the culture area. The culture area acts as a CO 2 sink, with an average air-sea CO 2 flux of -4.5 mmol m -2 d -1 . During the polyculture period, the P. yezoensis culture activities maintained the stability of the seawater carbonate system, and the culture area shows strong CO 2 sinks, with the average air-sea CO 2 flux of -24.10 mmol m -2 d -1 , -37.68 mmol m -2 d -1 , and -38.99 mmol m -2 d -1 , respectively. The absorption of CO 2 by large-scale cultured P. yezoensis through the "biological pump" effect is the main factor affecting the CO 2 exchange process at the air-sea interface, and the absorption rate of CO 2 by P. yezoensis at the mature stage is higher than that at the growth stage before harvesting. The study revealed that macroalgae-shellfish mariculture could promote mutual growth, alleviate environmental pressure, and enhance the carbon sink of the culture area. The relationship between mariculture and the carbon cycle of a mariculture ecosystem is very complicated, and its biochemical process should be given great attention for further study., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

In this study, we examined the effect of near future ocean acidification (OA) on the transcriptome of a sensory organ in contact with surrounding water, the tongue in adult European sea bass (Dicentrarchus labrax) by mean of RNAseq experiment. We acquired a total of 14.1 Mb quality-trimmed reads covering 18,703 expressed genes from the tongue of fish reared from two generations at actual (pH 8.0 condition) and predicted near-future seawater pH (pH 7.6 condition). Gene ontologies analyses of expressed genes support the evidence that the tongue exhibits biological processes related to the sensory system, tooth mineralization and immune defences among others. Our data revealed only 295 OA-induced regulated genes with 114 up- and 181 down-regulated by OA. Functions over-represented encompass processes involved in organic substance metabolic process, RNA metabolism and especially RNA methylation which, combined with the regulation of some hsp genes expression, suggest a molecular response to stress which might contribute to lingual cell homeostasis under OA. The immune system process is also found enriched within OA-induced regulated genes. With the exception of one fatty acid receptor, known taste perception effectors were not impacted by OA in the tongue. However, a complementary droplet digital PCR approach dedicated to genes involved in gustatory signal transduction revealed the down regulation by OA of pyrimidinergic receptor (p2ry4) transcript expression in the gills of the fish. Combined with scanning electron microscopy analysis, our RNAseq data revealed that OA has no impact on processes related to teeth development and mineralization. Altogether, our data reveal that multigenerational exposure to OA has not a substantially effect on the tongue transcriptome but emphasis should be placed on investigating the potential physiological consequences related to the regulation of genes related to cell stress, immune system and fatty acid sensitivity to conclude on species resilience in face of OA., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Mazurais reports financial support was provided by interdisciplinary graduate school for the blue planet ISBlue. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Kuroshio Extension (KE) is the most active region of oceanic change in the North Pacific Ocean, which provides an essential place for the survival of marine microorganisms. However, Vertical changes in microbial communities in the Kuroshio Extension and the mechanisms by which environmental factors drive vertical changes in community structure remain unclear. In this work, microbial diversity, abundance, and community structure of 12 water layers (from surface to bottom) at five stations were uncovered by 16S rRNA gene high-throughput sequencing. Microbial diversity and richness decreased with increasing seawater depth. Microorganisms in the euphotic zone can be well separated from other zones based on NMDS analysis. Proteobacteria (65.20%), Bacteroidota (8.48%), Actinobacteriota (5.76%), and Crenarchaeota (4.49%) accounted for a relatively large proportion and their distribution is similar in four zones. Most of microorganisms were significantly (Spearman test, p < 0.05) correlated with salinity, density, pressure, and temperature. This work enhances our understanding of vertical microbial diversity and provides insights into the pelagic microbial community structure., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Evaluating the functional structure of benthic macrofaunal communities provides insights into how environmental drivers shape the ecosystem and establishes a baseline knowledge of the communities' dynamics and functioning. This understanding allows the prediction of responses to environmental changes and the implementation of efficient conservation and management strategies. Here we examine the structures and functions of benthic macrofaunal communities on the Northwest Iberian coast concerning environmental factors such as depth, hydrodynamic energy, and bottom type. The results suggest that the community assemblages and their function are structured by factors which influence food availability and habitat heterogeneity. The different sites exhibited different trait compositions and functional structures, indicating that distinct functions are performed according to environmental conditions. The communities found in sandy bottom areas with low hydrodynamic conditions presented frail functionality and demonstrated high vulnerability to alterations in their environment. Conversely, the communities found in rocky bottoms with high hydrodynamic conditions exhibited a fulfilled functional niche space, rendering them more resilient to such changes and less prone to loss of function. Although the analyses did not reveal significant differences in the factor depth, its influence on several factors seems relevant in shaping the functional structure of the communities. These findings highlight the importance of understanding the impact of local environmental conditions on ecosystem functioning, to effectively implement monitoring, management, and conservation strategies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Ocean alkalinity enhancement is considered as an effective atmospheric CO 2 removal approach, but currently, little is known about the carbon sequestration potential of implementing olivine addition in offshore waters. We investigated the effect of olivine addition on the seawater carbonate system by carrying out a deck incubation experiment in the Northern Yellow Sea; the dissolution rate of olivine was calculated based on the increase in seawater alkalinity (TA), and the CO 2 sequestration potential was evaluated. The results showed that the dissolution of olivine increased seawater TA and decreased partial pressure of CO 2 , resulting in oceanic CO 2 uptake from the atmosphere through sea-air exchange; it also increased seawater pH and mitigated ocean acidification to a certain extent. The addition of 1 ‰ olivine had a more significant effect on the seawater carbonate system than 0.5 ‰ olivine addition. The average dissolution rate constant of olivine was 1.44 ± 0.15 μmol m -2  d -1 . Assuming that olivine settles completely on the seabed due to gravity, the theoretically maximum amount of CO 2 removed by applying 1 tonne of olivine per square meter area in the Northern Yellow Sea is only 2.0 × 10 -4  t/m 2 . Therefore, when olivine addition is implemented in the offshore waters, it is necessary to consider reducing the olivine size, prolonging the settling time of olivine in the water column; and spreading olivine in well-mixed waters to prolong the residence time through repeated resuspension, thus increasing its potential in carbon sequestration., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Knowledge of predator-prey interactions is key in ecological studies and understanding ecosystem function, yet this is still poorly explored in the deep-sea environment. Carbon (δ 13 C: 13 C/ 12 C) and nitrogen (δ 15 N: 15 N/ 14 N) stable isotope ratios of a deep-diving species, the short-finned pilot whale (Globicephala macrorhynchus), were used to explore knowledge gaps on its ecological niche and foraging habitats in the Webbnesia marine ecoregion (Tenerife Island, n = 27 animals vs. Madeira, n = 31; 500 km apart) where animals display distinct levels of site fidelity. Specifically, we tested whether intraspecific isotopic variation results from differences between geographic areas (due to possible foraging plasticity between regions), sexes, and/or years (2015-2020) using Generalized Linear Models. In general, significant differences (p < 0.05) were found in the stable isotope profiles of pilot whales between the two archipelagos, which were also reflected in their isotopic niche. The higher mean and wider range of δ 15 N values in Tenerife suggest that pilot whales consume prey of higher trophic levels and more diverse than Madeira. The higher mean and wider range of δ 13 C values in Madeira suggest that in that island, pilot whales rely on prey from more diverse habitats. There was significant variation between some years, but not between sexes. Finally, we discuss pilot whales' foraging strategies worldwide and infer the reliance on benthic or benthopelagic food sources in the Webbnesia., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Ocean acidification (OA) interacts with multiple environmental drivers, such as temperature, nutrients, and ultraviolet radiation (UVR), posing a threat to marine primary producers. In this study, we conducted a quantitative meta-analysis of 1001 experimental assessments from 68 studies to examine the combined effects of OA and multiple environmental drivers (e.g., light, nutrient) on the biochemical compositions of marine primary producers. The results revealed significant positive effects of each environmental driver and their interactions with OA according to Hedge's d analysis. The results revealed significant positive effects of multiple environmental drivers and their interactions with OA. Additive effects dominated (71%), with smaller proportions of antagonistic (20%) and synergistic interactions (9%). The antagonistic interactions, although fewer, had a substantial impact, causing OA and other environmental drivers to interact antagonistically. Significant differences were observed among taxonomic groups: haptophytes and rhodophytes were negatively affected, while bacillariophytes were positively affected by OA. Our findings also indicated that the interactions between OA and multiple environmental drivers varied depending on specific type of the environmental driver, suggesting a modulating role of OA on the biochemical compositions of marine primary producers in response to global change. In summary, our study elucidates the complex interactions between OA and multiple environmental drivers on marine primary producers, highlighting the varied impacts on biochemical compositions and elemental stoichiometry., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Bioturbation in coastal sediments plays a crucial role in biogeochemical cycling. However, a key knowledge gap is the extent to which bioturbation influences bacterial community diversity and ecosystem processes, such as nitrogen cycling. This study paired bacterial diversity, bioturbation activity and in situ flux measurements of oxygen and nitrogen from bioturbated sediments at six estuaries along the East coast of Australia. Bacterial community diversity, composition and predicted functional profiles were similar across burrow and surface sediments but were significantly influenced by bioturbator activity (measured as number of burrows) at sites with higher fine grain content. Sediment oxygen demand increased with bioturbator activity but changes in nitrogen cycling (as measured by fluxes and predicted bacterial functional gene analysis) were more spatially variable and were unrelated to bioturbator activity and bacterial community shifts. This study highlights how bioturbator activity influences bacterial community structure and functioning and what implications this has for biogeochemical cycles in estuarine sediments., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Ana Bugnot, Paul Gribben, Katherine Dafforn reports financial support was provided by Australian Research Council. Julia Palmer reports financial support was provided by Macquarie University. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Mitogen-activated protein kinase kinase (MKK), the key element of the Mitogen-activated protein kinase (MAPK) signaling pathway, is crucial for the immune response to adverse environments in aquatic animals. Nevertheless, there is limited information regarding the role of the MKK gene family in mollusks. In our study, genome data and transcriptome were used to identify four MKK genes (CnMKK4, CnMKK5, CnMKK6, and CnMKK7) in the noble scallop. The result of the gene structure, motif analysis, and phylogenetic tree revealed that MKK genes are relatively conserved in bivalves. Moreover, four CnMKK genes were significantly highly expressed in immune-related tissues, suggesting that CnMKKs may related to bivalve immunity. Furthermore, CnMKK6 and CgMKK4 were significantly differentially expressed (P < 0.05) under 24 h of temperature stress, and all CnMKKs were significantly differentially expressed (P < 0.05) under 24 h of Vibrio parahaemolyticus infection. These results showed that the CnMKKs may have a significant impact under biotic and abiotic stresses. In conclusion, the result of the CnMKKs provides valuable insights into comprehending the function of MKK genes in mollusks., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Intertidal wetlands undergo dynamic water and salinity variations, creating both promising and challenging habitats for diverse organisms. Crabs respond strongly to these variations by means such as altering their movements, thereby restructuring their spatial distribution and influencing coastal ecosystem resilience. However, the movements of crabs under varying environmental conditions require further elucidation. We conducted a systematic mesocosm experiment using the ubiquitous intertidal crab species Helice tientsinensis with four amount levels and six salinity levels of sprayed water applied through a custom apparatus, with a primary focus on crab movement. Crab movement from the experimental side of the apparatus (with altered conditions) to the control side (resembling field conditions of the intertidal wetlands of China's Yellow River Delta) and vice versa was recorded. The results revealed significant differences in moving out of the experimental side and moving in among the different water and salinity conditions, both separately for the two factors and simultaneously. Decreases in water content had a more pronounced effect on crab movement, leading to an increased number of crabs moving out of the experimental side of the apparatus. Conversely, as the experimental side became wetter, crabs tended to move towards it, and this movement was intensified by increases or decreases in water salinity. A structural equation model revealed that the moving-out and moving-in played fundamental roles in determining the number of resident crabs at the end of each experiment. While crabs preferred moist sediment with lower salinity, changes in salinity alone had minimal direct effect compared to sediment water contents. Our results clarify crab movements under varying water and salinity conditions, offering valuable insights to support adaptive interventions for crab populations and inform adaptive conservation and management strategies in intertidal wetlands., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Global changes in the coastal ecosystems of oceans and seas, influenced by natural environmental factors and anthropogenic load, have led to a shift in the sexual structure of the mussel Mytilus galloprovincialis, a species cultivated in many countries. This paper is the first to study the effects of steroid hormones on sex inversion and mortality in the M. galloprovincialis. A unidirectional pattern of sex change from females to males was observed. A 100% sex change of females was achieved under the influence of the hormone testosterone during the period of post-spring restructuring of the gonads. No sex change occurred when males and females were exposed to 17β-estradiol. The mortality of mollusks did not exceed 5%., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Predator-prey interactions are important in shaping ecosystem structure. Consequently, impacts of accelerating global warming on predators will have notable implications. Effects are likely to be particularly marked for tropical organisms which are anticipated to be sensitive to further thermal stress. Here, we investigated effects of future ocean warming on the predatory dogwhelk Reishia clavigera and its predation of Saccostrea cucullata. Mortality of the predators rapidly increased under the extreme elevated temperature, while those exposed to moderate elevated temperature displayed similar mortality as the ambient. Predators that survived moderate temperature increases altered their oxygen consumption patterns, increased average feeding rates, and functional responses, although condition index and energy reserves were unchanged. Overall, we show extreme ocean warming scenarios can remove predators and their consumption of prey from an ecosystem, whereas moderate warming can intensify predator-prey interactions. Such temperature-dependent alterations to predator-prey interactions would lead to fundamental changes of ecosystem structure as the ocean warms., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Increased human demand on the marine environment and associated biodiversity threatens sustainable delivery of ecosystem goods and services, particularly for shallow shelf-sea habitats. As a result, more attention is being paid to quantifying the geographical range and distribution of seabed habitats and keystone species vulnerable to human pressures. In this study, we develop a workflow based on unsupervised K-Means classification units and Generalized Linear Models built from multi-frequency backscatter analyses (95, 300 kHz), bathymetry and bathymetry derivatives (slope) to predict different levels of sandeel densities in Hempton's Turbot Bank Special Area of Conservation (SAC). For Hyperoplus lanceolatus densities, the performance of single frequency verses multi-frequency models is compared. Relatively high agreement between K-Means clustering outputs (from 95 kHz and multi-frequency models) and ground-truthed sandeel densities is noted. Moreover, Root Mean Squared Error (RMSE) values in this instance demonstrate that single-frequency models are favoured over the multi-frequency model in terms of predictive ability. This is mostly linked to the species strong affinity for sedimentary environments whose variability is better captured by the lower frequency system. Generally, these results provide important information about species-habitat relationships and pinpoint bedform features where sandeels are likely to be found and whose variability is potentially linked to the bathymetry domain. The workflow developed in this study also provides a proof of concept to support the design of a robust species-specific monitoring plan in marine protected areas. Most importantly, we highlight how decisions made during sampling, data handling, analysis could impact the final outputs and interpretation of Species Distribution Models and benthic habitat mapping., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

To unravel the effects of environmental factors on fishery resources in the bay, we conducted six biological and environmental surveys in the Laizhou Bay between 2013 and 2020. The findings of our study illuminated several key aspects: (1) The annual discharge of water and sediment from the Yellow River to Laizhou Bay exhibited notable variations, while concurrently, environmental factors including temperature, salinity, and suspended particle matter underwent fluctuations, yet remained within a relatively stable range overall. (2) A total of 8318 eggs and larvae belonging to 10 orders, 16 families, and 19 genera were collected. Significant interannual fluctuations had been documented in the species composition, abundance, and biodiversity of ichthyoplankton. Notably, both Shannon-Wiener diversity index and Pielou evenness index were significantly negatively correlated with suspended particle matter concentration. (3) The water and sediment discharge significantly positively correlated with the number of cold-temperature species. However, the sediment input negatively correlated with the number of continental shelf benthopelagic fish. (4) Redundancy and correlation analyses confirmed the strong link between spatial and temporal distribution of fish communities and environmental factors, with salinity and dissolved oxygen key for ichthyoplankton abundance. Our research offers a scientific foundation for targeted fishery protection and management, which is crucial for preserving the ecological functions of spawning grounds in the bay., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

To explore the variation of phytoplankton community along the Bakkhali river estuary and its adjacent coastal water in the north of the Bay of Bengal, total Chl-a (TChl-a) concentrations and group-specific photosynthetic pigments were investigated during April 2017. Distinct spatial distribution was observed in temperature, turbidity and nutrient concentrations as well as in TChl-a concentrations, showing a seaward decreasing pattern. The different distribution of phytoplankton pigments and functional groups along the gradients was also observed. Chlorophyll-b and zeaxanthin showed their highest abundance in the turbid riverine water, while alloxanthin and prasinoxanthin dominated in the coastal water. High concentrations of fucoxanthin, peridinin and hex-fucoxanthin were associated with high-light availability and showed a seaward increasing trend. Three phytoplankton groups can be classified: the riverine group (chlorophytes and cyanobacteria), the coastal group (cryptophytes and prasinophytes) and the offshore group (diatoms, dinoflagellate and haptophytes&#95;type 6). The predominance of cryptophytes (avg. 48%) over diatoms (avg. 28%) was basically influenced by the scarcity of nitrogen and silicate relative to phosphate. Not only availability of nutrients, the photosynthetically active radiation also plays a key role in regulating TChl-a, photosynthetic pigments and functional groups in this tropical estuarine-coastal zone., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Aquaculture of bivalve shellfish and algae offers significant ecological benefits, yet the complex interactions between these organisms can substantially impact local carbon dynamics. This study investigated the effects of co-culturing four intertidal bivalve species Pacific oysters (Crassostrea gigas), Manila clams (Ruditapes philippinarum), Chinese clams (Cyclina sinensis), and hard clams (Mercenaria mercenaria) with microalgae (Isochrysis galbana) on specific water quality parameters, including total particulate matter (TPM), total organic matter (TOM), dissolved inorganic carbon (DIC), dissolved carbon dioxide (dCO 2 ), dissolved oxygen (DO), and ammonium (NH 4 + ) concentrations. The bivalves were divided into smaller and larger groups and cultured under two conditions: with algae (WP) and without (NP), along with matched controls. Total particulate matter (TPM), total organic matter (TOM), dissolved oxygen (DO), ammonium nitrogen (NH 4 + ), dissolved inorganic carbon (DIC), and CO 2 (dCO 2 ) were measured before and after 3-h cultivation. Results revealed species-specific impacts on water chemistry. C. gigas, C. sinensis and R. philippinarum showed the strongest reduction in DIC and dCO 2 in WP groups, indicating synergistic bioremediation with algae. M. mercenaria notably reduced TPM, highlighting its particle carbon sequestration potential. DO concentrations decreased in most WP or NP groups, reflecting respiration of the cultured bivalves or microalgae. NH 4 + levels also declined for most species, indicating nitrogen assimilation by these creatures. Overall, the bivalve size significantly impacted carbon and nitrogen processing capacities. These findings reveal species-specific capabilities in regulating water carbon dynamics. Further research should explore integrating these bivalves in carbon-negative aquaculture systems to mitigate environmental impacts. This study provides valuable insights underlying local carbon dynamics in shallow marine ecosystems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Climate and anthropogenic impacts are prevalent in marine and estuarine ecosystems. Rapid environmental changes have altered biological diversity and the ecological services associated with ecosystems around the world. The consequences of these impacts on estuarine ecosystems are worrying, given that estuaries are essential habitats for maintaining the diversity of species functions, as they act as sources for larger ecosystems through the recruitment and replacement of species. Through long-term standardized monitoring (1996-2019), we evaluated the temporal variability of the functional structure of fish species in a subtropical estuary using Principal Component Analysis (PCA), and their relationship with environmental, climatic, and anthropogenic variables using Generalized Additive Models (GAM). We investigate the hypothesis that natural disturbances associated with El Niño events and anthropogenic ones related with changes in the estuary morphology will lead to a decrease in the diversity of functions of the fish assemblage in the Patos Lagoon Estuary in south Brazil (32°S). Our findings suggest an overall downward trend in the fish functional structure, especially in the second half (2006-2019) of the time series, which seems to be associated with a combination of abiotic effects (salinity and temperature), global climate phenomena (ENSO phases) and anthropogenic impacts (changes in the morphology of the estuarine mouth and its connection with the sea). These findings rise concern considering the current climate change scenario, where phenomena such as El Niño may become more frequent and intense. Therefore, the evidence from this study suggests that extreme natural climatic events in synergy with anthropogenic disturbances may imply biodiversity losses over time and, consequently, loss of ecosystem processes in a subtropical estuary., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Archaea play a crucial role in the global biogeochemical cycling of elements and nutrients, helping to maintain the functional stability of estuarine systems. This study characterised the abundance and diversity of archaeal communities and identified the environmental conditions shaping these microbial communities within six temperate estuaries along approximately 500 km of the New South Wales coastline, Australia. Estuarine sediments were found to exhibit significantly higher species richness than planktonic communities, with representative sequences from the Crenarchaeota phylum characterising each environment. Ordinate analyses revealed catchment characteristics as the strongest drivers of community variability. Our results also provide evidence supporting distance-decay patterns of archaeal biogeography across intermediate scales within and between temperate estuaries, contributing to a growing body of evidence revealing the extent spatial scales play in shaping microbial communities. This study expands our understanding of microbial diversity in temperate estuaries, with a specific focus on archaeal community structure and their role in maintaining ecosystem stability., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Megan Huggett reports equipment, drugs, or supplies was provided by BioPlatforms Australia Ltd. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Global marine biodiversity loss impairs entire ecosystems and their stability. Robust biodiversity estimates are key to inform policies and management strategies, and need to consider the contribution of diverse habitats, including those for which estimates of biodiversity are scattered or totally absent. This study assessed the fish diversity associated with three main coastal habitats (rocky bottoms, Posidonia oceanica meadows, sandy bottoms), and their role in shaping the overall coastal fish diversity, also in relation to potential environmental and anthropogenic drivers affecting patterns of fish diversity in coastal areas. Using underwater visual census, we sampled 62 sites distributed on the three habitats, for a total of 496 replicates. We assessed the contribution of each habitat to β-diversity, divided into Local Contribution to β-diversity (LCBD), a comparative indicator of the contributions to β-diversity of each habitat, and Species Contribution to β-diversity (SCBD), which measures the relative importance of each species in affecting β-diversity. Finally, we modelled species diversity in relation to potential environmental and anthropogenic drivers. Overall, 72 species were recorded, with the highest species richness observed on rocky bottoms (56 species, 16 unique to this habitat), followed by P. oceanica (38 species, 0 unique) and sandy bottoms (32 species, 14 unique). Sandy bottom assemblages had a significantly higher contribution to LCBD than P. oceanica meadows and rocky bottoms, and two of the five species with the highest contribution to SCBD are exclusively associated with sandy bottoms. Finally, sea surface temperature, sea surface salinity, and habitat were highlighted as significant predictors of species richness. Our findings, aside from highlighting the environmental drivers of coastal fish diversity in the Mediterranean Sea, unravel the potential key role of sandy bottoms in contributing to overall coastal fish diversity and can inform conservation planning., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Coastal areas conservation strategies often left deeper habitats, such as mesophotic ones, unprotected and exposed to anthropogenic activities. In this context, an approach for including the mesophotic zone inside protection plans is proposed, considering 27 Italian Marine Protected Areas (MPAs) as a model. MPAs were classified considering their bathymetries, exposure to marine heat waves (MHWs), mass mortality events (MMEs) and, using a local ecological knowledge (LEK) approach, the estimated resilience of certain sessile species after MMEs. Only 8 MPAs contained considerable mesophotic areas, with stronger MHWs mainly occurring in shallower MPAs, and MMEs mostly affecting coralligenous assemblages. Even with only a 10% response rate, the LEK approach provided useful information on the resilience of certain species, allowing us to suggest that the presence of nearby mesophotic areas can help shallower habitats facing climate change, thus making the "deep refugia" hypothesis, usually related to tropical habitats, applicable also for the Mediterranean Sea., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Carlo Cerrano reports financial support was provided by European Commission. Joaquim Garrabou reports financial support was provided by EU Framework Programme for Research and Innovation Euratom. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The persistence of coral reefs globally is threatened by various forms of chemical pollution. Climbazole, an azole antibacterial agent extensively utilized in pharmaceuticals and personal care products (PPCPs) in everyday life, has been detected in various environment media and proved to have significant adverse effects on aquatic organism. However, the effects of climbazole on coral remain largely unknown. Therefore, in this study, we conducted a 42-day investigation to examine the effects of varying concentrations of climbazole on Galaxea fascicularis (G. fascicularis), a stress-tolerant coral species. Our investigations included coral color observations, physiological experiments, and assessments of microbial diversity. The results showed that, after 42 days of exposure, the coral color in the treatment group exposed to 100 μg/L climbazole significantly decreased by one color category on the reference chart (D6 shifted to D5), while there was no change in the control group. This was accompanied by an increase in oxidative stress and a decrease in photosynthetic capacity in coral specimens. Additionally, there was a notable alteration in microbial diversity, resulting in reduced community stability. Elevated levels of climbazole (100 μg/L) stress led to an increased abundance of potentially pathogenic bacteria such as unclassified Erysipelotrichaceae. However, at an environmentally relevant concentration of 1 μg/L, climbazole decreased the photosynthetic efficiency and induced oxidative stress in the stress-tolerant coral G. fascicularis, while not significantly impacting the microbial community diversity of the coral. The findings of our study have important implications for the protection and management of nearshore coral reefs and offer essential data for ecological risk assessment of climbazole., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)