Macroalgae and their rocky substrates both support diverse and abundant microbiota, performing essential ecological functions in marine ecosystem. However, the differences in the epiphytic microbial communities on macroalgae and rocky substrate are still poorly understood. In this study, the epiphytic microbial communities on four macroalgae (Corallina officinalis, Rhodomela confervoides, Sargassum thunbergii, and Ulva linza) and their rocky substrates from Weihai coast zone were characterized using high-throughput sequencing technology. The results showed that the alpha diversity indices were greater in rocky substrates than that in macroalgae. The microbial similarities among macroalgae and rocky substrate groups tended to decrease from the high taxonomic ranks to lower ranks, only 22.69% of the total amplicon sequence variants (ASVs) were shared between them. The functional analysis revealed that the microbiotas were mainly involved in metabolic activities. This study would provide the theoretical foundation for macroalgal cultivation and algal reef applications.

Solutions are being sought to ameliorate the impacts of anthropogenic climate change. Seagrass may be a solution to provide refugia from climate change for marine organisms. This study aimed to determine if the seagrass Zostera muelleri sub spp. capricorni benefits the Sydney rock oyster Saccostrea glomerata, and if these benefits can modify any anticipated negative impacts of ocean acidification. Future and ambient ocean acidification conditions were simulated in 52 L mesocosms at control (381 μatm) and elevated (848 μatm) CO₂ with and without Z. muelleri. Oyster growth, physiology and microbiomes of oysters and seagrass were measured. Seagrass was beneficial to oyster growth at ambient pCO₂, but did not positively modify the impacts of ocean acidification on oysters at elevated pCO₂. Oyster microbiomes were altered by the presence of seagrass but not by elevated pCO₂. Our results indicate seagrasses may not be a panacea for the impacts of climate change.

To explore the influence of tidal events on protozoan periphyton fauna along tidelines, a 1-month baseline survey for bioassessment was conducted in an intertidal zone of the Yellow Sea, Northern China. A total of 27 protozoans species were identified among five sampling sites along five tidelines (sites A–E). The periphytic protozoans showed a significant variation in species distribution and community pattern along five tidelines. Species richness decreased from the high tideline (site A) and reached the minimum value at the middle tideline (site C), followed by an increase up to the low tideline (site E). Individual abundances peaked at site C and leveled off at the other four tidelines. Species richness, evenness, and diversity showed low value at site C compared with those at the other four sites. These findings suggest that periphytic protozoan fauna was shaped by tidal events along the tidelines of marine ecosystems.

The presence of floating marine anthropogenic litter in marine environments increase the possibility of transportation of fouling organisms using these substrates as a vector, mainly for those species with close affinities to artificial substrates. The objectives were to qualitatively and quantitatively report anthropogenic litter and its associated fouling groups arround Ilha Grande Bay (IGB). Litter was collected, classified and examined for the presence of fouling organisms on beaches located at two different levels of wave exposure during rainy and dry seasons. The types of litter do not differ among beaches, and the highest density and cover of fouling were reported on exposed beaches due the currents, winds, and storm waves. Bryozoans, barnacles, polychaetes, and mollusks were the most frequent fouling groups observed in litter and represents a potential vector for the dispersion of species in the IGB and adjacent coastal areas.

Horseshoe crabs (HSCs) are a group of ancient chelicerates with great ecological and biomedical importance. Food poisonings caused by the consumption of Asian HSCs have significant impacts on public health and safety. This study measured tetrodotoxin (TTX) concentrations in two HSC species across various life stages in May 2020 from the northern Beibu Gulf, their most important spawning and nursery habitats in China. The average TTX contents in both Carcinoscorpius rotundicauda and Tachypleus tridentatus ranged 6.2–8.0 μg/kg and 3.8–8.4 μg/kg, respectively. While sampling location, growth and molt stages have little influence on TTX distribution in both species, significantly higher levels of TTX were detected in hemolymph, but lower in pooled tissues of early-instar juvenile T. tridentatus. These results provide a regional view of TTX occurrence and distribution in HSCs during their spawning season, which are critical for future studies to enhance understanding of TTX dynamics and formation in HSCs.

The present study aims to analyze the level and total toxicity of the most common pollutants in surface sediments and assess their impact on the occurrence of antibiotic resistance genes (ARGs) in the Sea of Azov. Biotesting using the whole-cell bacterial lux-biosensors showed high integral toxicity of surface sediments and the presence of genotoxicants and substances that cause oxidative stress and protein damage. Using cluster analysis, it was shown that the distribution of pollutants in the Sea of Azov depends on the type of surface sediments. The relative abundance and distribution of 14 ARGs in surface sediments were shown. Principle component analyses results suggest that non-corresponding contaminants do not exert direct influence on the ARGs abundance in the surface sediments of the Sea of Azov. Thus, the need to investigate the significance of non-corresponding pollutants in the selection and distribution of ARGs in the aquatic environment remains a pressing problem.

The water quality of the northern Caspian Sea has not been well-known, and its contamination can adversely affect the health of swimmers and seashore residents. The study sought to determine the contamination state of the Caspian Sea in Kazakhstan and quantify human health risks coming from the existing heavy metals concentration. The Caspian Sea was found to be “fairly to marginally” contaminated (24 < CCME-WQI < 64), with Cd influencing the index significantly. Concentrations of Cd and Pb increase over time (seasonal Kendall test, p-values = 2–4 %) in sites near oil fields and ports, suggesting the significant role of anthropogenic sources in causing diverse pollution events. Pb demonstrated the highest variability and number of outliers (4.3 % of all samples with coefficients of variation reaching up to 175 %). The principal component analysis further revealed that various discharges from oilfields and upstream transport could contribute to the contamination by heavy metals and their concentrations. Contamination is associated with up to 6 % cancer risk for adults. The long exposure duration of swimmers in water increases risks by up to 18 %, indicating the local population is at a higher risk. In conclusion, statistical tests and analysis indicate the presence of anthropogenic sources, and risk assessment reveals swimming can contribute to cancer risk.

Krossfjord-Kongsfjord system in the European Arctic has been assessed for abundance, source and distribution of microplastics in the surface sediments. The average abundance of microplastics in Krossfjord and Kongsfjord is 721.42 ± 217.89 (n = 5) pieces/kg and 783 ± 530.28 (n = 8) pieces/kg. Polymers like polyethylene and polypropylene are abundant in the sediment samples. Fibers are the most common shape of plastic particles. A high abundance of smaller plastic particles in the sediment may be due to the fragmentation of larger plastic particles during transportation. The microplastics' spatial distribution, shape, size, and composition suggest that the long-range transport by west Spitsbergen current and local inputs from anthropogenic activities are possible sources of microplastics found in the study area. Our results exhibit the presence of microplastic pollution, suggesting the influence of anthropogenic activity in the Arctic fjord and the need to control/reduce marine pollution which has become a potential threat to marine organisms.

A quinquennial seasonal study (2015–2019) has been conducted to evaluate the bioaccumulation pattern of trace metals in Meretrix meretrix. The concentration of trace metals in the clam was observed as Cr > Cu > Ni > Zn > Pb > Cd > Hg, (Body> Mantle > Gills), similar to sediments. Contamination Factor of Cu and Cr in sediments showed strong association with the corresponding metal concentration in the body (r = 0.687, r = 0.962), mantle (r = 0.880, r = 0.956) and gills (r = 0.937, r = 0.863). Bioconcentration Factor was high for Cr followed by Ni. Mean Metal Concentration Rate (MMCR) of Cr was high and Hg was low (Body>Mantle>Gills). Our study establishes that the trace metal intake by Meretrix meretrix is associated with seasonal variation, physicochemical factors, sediment texture, chemical speciation and the metabolic stress created within the species induced from increased demand for protein synthesis. The latter resulted in the augmented rate of accumulation of Cu and Cr.

This introduction to a special issue on approaches to managing underwater noise in Canada provides a brief overview of recent efforts to better understand and reduce anthropogenic underwater noise. Recent programs have aimed to increase understanding of anthropogenic noise in the habitats of highly endangered whales and have supported management actions such as vessel slow downs. Technical workshops have advanced the development of quiet ship design and associated technologies. Collaborative research examined noise levels in the St. Lawrence Estuary and the Arctic Ocean. Efforts to better manage noise have gone beyond shipping: enhanced mitigation measures have been put in place for naval exercises near habitats used by southern resident killer whales, while other work has focused on the identification of appropriate metrics for measuring noise. To coordinate and advance these and other efforts, the Government of Canada is developing a national Ocean Noise Strategy.