We report the Sabella spallanzanii mucus bacterial agglutination response after inorganic arsenic (As) exposure. As is actively adsorbed from the surrounding environment and accumulated at high concentrations in tissues as an anti-predatory strategy. Here we investigated the effect of high As concentrations on its immunobiological response. It may act on mucus lectins and on its ability to agglutinate bacteria. We concluded that As at high concentrations leads to the inhibition of pathogen recognition. Nevertheless, although its biological activity is significant reduced in winter, responses to As concentrations are very similar, and below a certain threshold do not induce alterations, supporting the hypothesis of adaptation to high As concentrations related to involvement in predation defence.

Ocean acidification resulting from increased CO₂ and pollution from land-sourced toxicants such as copper have been linked to coral cover declines in coastal reef ecosystems. The impacts of ocean acidification and copper pollution on corals have been intensively investigated, whereas research on their effects on coral endosymbiont Symbiodiniaceae is limited. In this study, reproduction, photosynthetic parameters, nutrient accumulation and metabolome of Symbiodiniaceae Cladocopium goreaui were investigated after a weeklong treatment with acute CO₂-induced acidification and copper ion. Acidification promoted algal reproduction through increased nutrients assimilation, upregulated citrate cycle and biomolecular biosynthesis pathway, while copper exposure repressed algal reproduction through toxic effects. The combined acidification and copper exposure caused the same decline in algal reproduction as copper exposure alone, but the upregulation of pentose phosphate pathway and the downregulation of aromatic amino acid biosynthesis. These results suggest that copper pollution could override the positive effects of acidification on the symbiodiniacean reproduction.

This study aims to evaluate the seasonal and spatial characteristics of hydrochemistry and DO isotopes and identify the eco-environmental threats under the background of saline intrusion and human activities in Yellow River Delta (YRD). Analyses for major ions (i.e., K⁺, Na⁺, Ca²⁺, Mg²⁺, SO₄²⁻, HCO₃⁻ and Cl⁻), nitrate ion (NO₃⁻) and isotopic composition are performed for precipitation, river water, wetland water and sea water. Based on the range of δ²H and δ¹⁸O as well as their relations, the mixing between multiple sources and evaporation are confirmed. Electrical conductivity (EC), concentration of NO₃⁻, soluble sodium percentage (SSP) and magnesium hazard (MH) are employed as indicators to reflect the ecological risks from salinity, agricultural pollutants, sodium and magnesium. By hierarchical cluster analysis (HCA), the samples of wetland water are grouped associated with those of river water. The characteristic reflects 3 patterns of risks in wetlands, including saline intrusion, human activities and their mixed influence.

The community composition and distribution of early-stage (24 h) biofilm-forming bacteria on two different surfaces (glass slide and polystyrene plastic slide) at three different locations (Diu, Alang and Sikka) were studied using a culture-dependent and next-generation sequencing (NGS) approach in the Arabian Sea, Gujarat, India. The most dominant phyla observed using the NGS approach were the Proteobacteria among the sampling sites. Gammaproteobacteria class dominated both the surfaces among the sites and accounted for 46.7% to 89.2% of total abundance. The culture-dependent analysis showed Proteobacteria and Firmicutes as the dominant phyla on the surfaces within the sampling sites. During the initial colonization, hydrocarbon-degrading bacterial strains have also attached to the surfaces. The outcome of this study would be of great importance for targeting the early stage biofilm-forming and hydrocarbon-degrading bacterial isolates may help to degrade plastic in the marine environment.

Single-use plastics (SUPs) represent a major threat to marine environments and require proactive policies to reduce consumption and mismanagement. Many SUP management strategies exist to reduce SUP use and mitigate environmental impacts, including extended producer responsibility (EPR), deposit-return schemes, SUP bans or taxes, and public outreach and education. This study analyzed brand audit and beach cleanup data in four densely populated Canadian cities (Vancouver, Toronto, Montréal, Halifax) and a remote island (Sable Island) to determine efficacy of ongoing SUP mitigation measures. Cities were found to have similar litter type proportions, and six brands were found to disproportionally contribute to Canadian SUP litter, comprising 39% of branded litter collected. Results confirm that current Canadian SUP management appears to be insufficient to address leakage of SUPs into the environment. Recommendations to strengthen SUP management strategies and mitigate plastic pollution are recommended to improve future Canadian SUP reduction policies.

Responses of different sexes of farmed Strongylocentrotus intermedius to chronic CO₂-induced seawater acidification were investigated in 120-day lab-based experiments. Four experimental groups were set up as one control group and three seawater acidification groups. The results showed that 1) Specific growth rate and the numbers of mature gamete cells declined in a pH-dependent way in both sexes of adult S. intermedius. 2) There were differences in SDMs identified in females and males reared in acidified seawater reflecting sex-specific response variation in adult S. intermedius. 3) The number of altered metabolic pathways exhibited a linear increasing trend as seawater pH declined in both sexes of adult S. intermedius. Meanwhile seawater acidification might affect metabolic processes via changing the relative expression and activity of key enzymes controlling the corresponding metabolic pathways of adult S. intermedius.

It is generally believed that the enhancement of phytoplankton appears only in shallow and intermediate depth seamounts, while the phenomenon has also been observed in some deep seamounts by satellites recently. To figure out what effect do deep seamounts have on phytoplankton and the relevant mechanisms, the phytoplankton biomass and community on the Kocebu Seamount (depth: 1198 m) were studied. The results showed that the average Chl a concentration of the seamount was 0.09 mg·m⁻³, and the Chl a maximum layer was mainly located at 150 m, and picophytoplankton such as prochlorophytes and cyanobacteria were the dominant groups. High Chl a patches (>0.2 mg·m⁻³) were mainly distributed within 20 km of the peak, and both nitrate and orthophosphate were obviously uplifted at the peak. The physical data indicated the uplifted of nutrients could be caused by the internal tides, which generated by the interaction of topography and tide. This is the first time that the promotion of phytoplankton was observed in situ on a deep seamount, and this study expounded relevant mechanisms and suggested that the ecological functions of deep seamounts may have been previously neglected.

There is scarce information on the current importance of oyster beds as fishing grounds in the United Arab Emirates (UAE). This study aims to understand the socio-economic value of oyster bed fisheries through questionnaire-based surveys with fishers. Of 106 Emirati fishers interviewed, 67 % use oyster beds due to the proximity to shore, better catch quality, and species abundance. Oyster bed fisheries are recreational and commercial, with handline and fish traps the most common used gears. They provide food for local consumption and cash income. All respondents noticed a fish abundance and size decrease throughout the last decade. Fishers suggest establishing marine protected areas and updating fishing regulations to improve fishing stock status. During the Covid-19 pandemic, oyster fisheries increased, highlighting the value of these fishing grounds for food availability. These fisheries support the local economy and heritage, and urgently need management to ensure the protection of these often-overlooked habitats.

Since 2015, green tides have impacted the coastal waters of Qinhuangdao, particularly at Jinmenghaiwan bath. Micro-propagules are considered the “seed bank” of algal blooms and play an important role in the formation of green tides. To investigate the spatial and temporal distributions of micro-propagules of green algae and associated environmental factors, a field survey was carried out in the coastal waters of Jinmenghaiwan, Qinhuangdao, China. The results showed that the NO₃-N concentration was the most important impact factor of the abundance of micro-propagules and explained 42.9% of the total variance. Furthermore, the number of micro-propagules was significantly and positively correlated with the biomass of attached and floating macroalgae. Therefore, reducing the NO₃-N concentration by controlling the NO₃-N input from Tang River is expected to be an effective measure to prevent and control green tides in the coastal waters of Qinhuangdao.

Microplastics (MPs) are emerging contaminants in aquatic and terrestrial ecosystems and have caused substantial concern worldwide. This study surveyed the presence of MPs in surface water and sediments across the coastal area of Saint Martin Island in the Bay of Bengal. MPs were collected following the standard protocol and identified as various types like expanded polystyrene, foam, filaments, fragments, lines, fibres, and paint flakes. Total MPs pollution in beach sediment was 317 particles/kg across 14 sampling sites, varied from 11 to 10589 particles/m² of dry sediment and 0.95 particles/m³, having ~2 to 19 particles/30 min trawl in coastal surface water samples. Most of the frequent MPs in beach sediments ranged from 1.0 to 2.0 mm, whereas the fragments were predominant in sediment and surface water samples. MPs distribution revealed that different shapes were dominant at different sites within the Island. The calculated pollution risk index due to the presence of MPs indicated that the sediment and surface water samples were under the low-risk category. However, polymeric risk assessment and contamination factors suggest that the coastline is significantly polluted, as high pollution load indices (PLI >1) were observed for sediments and coastal surface water samples. This work provides the detailed MPs data in the coastal environment of Saint Martin Island for the first time; hence it may be helpful to develop proper strategies to deal with environmental problems.