Marine environmental research最新文献

Zooplankton are a key food source for fish and shellfish in the Arctic. One of the most valuable areas for fishing potential is the southern Barents Sea. To assess the productive capacity of this coastal area, we examined spatial variations in the summer zooplankton community. We recorded 44 different zooplankton taxa with the most common species being copepods Acartia longiremis, Calanus finmarchicus, Oithona similis, and Temora longicornis. The study revealed two distinct zooplankton groups, one in the fjords and the other in the open sea. These groups were noticeably different because of environmental factors, which aligned closely with the distribution of the zooplankton populations. Smaller neritic (coastal) species made up most of the zooplankton in shallow, inshore waters, while larger Calanus copepods were more common in deeper, offshore waters. Zooplankton biomass and daily production were generally higher in the open sea, reaching averages of 5.4 g (dry mass per m²) and 204 mg (dry mass per m² per day), compared to 0.9 g and 40 mg in inshore waters. The findings showed that water depth, temperature, and chlorophyll a levels were the main environmental factors influencing zooplankton abundance, biomass, and productivity. Zooplankton diversity was higher in the bays, likely due to the more varied environmental conditions found there. Comparative assessment of summer zooplankton biomass and production values underscores the considerable productive potential of the southern Barents Sea. Our findings provide novel insights into the structure and function of Arctic coastal zooplankton communities and offer a valuable baseline for ongoing pelagic ecosystem monitoring.

Intertidal environments are highly dynamic, exposing organisms to multiple physical stressors simultaneously. This study evaluates the physiological responses of encapsulated Acanthina monodon embryos to stressors associated with tidal cycles, using oxidative damage and antioxidant activity as indicators. Egg capsules collected from the rocky intertidal zone were subjected to a tidal cycle including 3 h of emersion followed by re-immersion. Environmental variables such as temperature, humidity, PAR and UV-B radiation were recorded. Samples were analyzed for lipid peroxidation, protein carbonyls, and total antioxidant capacity. Previous studies have shown that initial-stage embryos are particularly vulnerable to desiccation and thermal stress, yet little is known about their antioxidant responses under natural tidal fluctuations. Based on this, we hypothesize that embryos possess a developmentally regulated and environmentally responsive antioxidant defense system envolving an enzymes or non-enzymatic antioxidants that mitigates oxidative damage during emersion and activates repair mechanisms upon re-immersion. Results showed that early-stage embryos exhibited high antioxidant capacity, particularly during air exposure, suggesting an adaptive response to oxidative stress. Prolonged emersion increased oxidative damage markers, while re-immersion reduced them, indicating activation of repair mechanisms. No mortality was observed in any developmental stage. These findings support the hypothesis and highlight antioxidant capacity as a key strategy for survival during early ontogeny in fluctuating intertidal conditions. This study provides insight into the defense mechanisms of A. monodon embryos and their resilience to environmental stress during encapsulated development.

The southwestern continental shelf of the South China Sea (SCS), a vital fishing ground, lacks systematic studies on fish with different feeding habits as bioindicators of heavy metal(loid)s (HMs) pollution. This study combines stable isotope analysis and Monte Carlo simulation (MCS) to assess HMs, trophic dynamics, and human health risks in fish from this region. Results indicate that all HMs concentrations are below safety thresholds set by Chinese and FAO seafood standards. Trophic transfer analysis revealed significant biodilution of Cu, Zn, Cr, Cd, and Ni with increasing δ¹⁵N values, while Mn, As, and Pb showed no significant variation. Mixed feeding fish were significant correlated with Zn, Cd, and Cu; planktivorous species with Cr and Ni; and carnivorous species with Mn and Pb. Health risk assessment revealed significant differences in target hazard quotient (THQ) values for Cr, Zn, Cu, Ni, and Cd among trophic groups, while total THQ (TTHQ) showed no significant variation. Compared to 1D MCS, the two-dimensional MCS (2D MCS) produced lower estimated risks, except for higher carcinogenic risks observed in children. The combined multiple linear regression (MLR) and 2D MCS model estimated the maximum acceptable daily fish intake at 22.4 g/day for children, 93.1 g/day for adult females, and 104.7 g/day for adult males. This study revealed differences in HMs levels and health risks of human consumption among different feeding groups, providing a scientific basis for sustainable fisheries management and safe seafood consumption in the SCS.

The gut microbiota forms a complex symbiotic community that performs essential functions for the host, including metabolism, nutrient absorption, and environmental adaptation, while being shaped by both environmental and intrinsic host factors. This study represents the first comprehensive investigation of seasonal gut microbiota diversity in brittle stars, examining Ophiothrix exigua from the Yellow Sea using full-length 16S rRNA gene metabarcoding. A total of 565 amplicon sequence variants were identified from gut samples, distributed across 20 phyla, 135 genera, and 46 species. The dominant phyla included Proteobacteria, and Spirochaetota, with Salinispira identified as the core genus. Seasonal variations in microbiota diversity were evident, with Caulobacter predominating in summer, and Kistimonas and Trichococcus driving winter community shift. Corresponding seasonal changes in gut microbiota functions and functional pathways were observed. Fatty acid biosynthesis pathways were enriched in winter, while aromatic compound degradation pathways showed elevated activity in summer. Although seawater microbiota exerted relatively minor influence on gut microbial diversity, correlations with abiotic factors such as pH were observed. This study highlights the intricate relationship between gut microbiota, environmental microbiota, and abiotic factors in shaping the seasonal gut microbiota diversity of O. exigua, contributing to a better understanding of the host-microbiome ecology of invertebrates.

The Canadian Arctic is undergoing significant environmental changes. As climate change continues to drive the reduction in the extent and thickness of sea ice, this region is experiencing an increase in shipping and other industrial activity, notably mining. In addition to existing natural oil and gas seeps, greater industry has led to growing concerns about the release of oil and gas contamination into vulnerable Arctic ecosystems. Polycyclic aromatic compounds (PACs) are a broad class of organic contaminants that are associated with oil and gas, many of which are persistent, bioaccumulative and toxic. This study examines spatial and temporal PAC trends in thick-billed murre (Uria lomvia) eggs between 1993 and 2024 from Prince Leopold Island, Nunavut (high Arctic; 74°02'N, 90°00'W) and Appatuurjuaq (Coats Island), Nunavut (low Arctic; 62°51'N, 82°29'W). Forty-eight polycyclic aromatic hydrocarbons (PAHs) and alkylated polycyclic aromatic hydrocarbons (APAHs) were quantitated using gas chromatography-tandem mass spectrometry. Overall, concentrations of total PACs, alkylated high molecular weight (AHMW) PACs and high molecular weight (HMW) PACs were greater in eggs from birds breeding in the high versus low Arctic, suggesting potential spatial differences in PAC exposure. While concentrations of PACs did not change dramatically from 1993 to 2024 at either location, considerable variation among individual years was observed. As interest in Canada's northern shipping routes continues to grow, monitoring of PACs in seabird eggs will survey as a practical sentinel system to assess potential changes in contamination that may pose risks to Arctic wildlife and their environments.

The reproductive process plays a crucial role in the renewal of populations of marine bivalves and represents an economic issue for exploited species like the king scallop Pecten maximus. However, environmental phenomena, such as harmful microalgal blooms (HAB), can affect key reproductive life stages, such as gametes and embryos. This study examines the effects of exposure to three harmful microalgal species (Alexandrium minutum, Lingulodinium polyedra, and Pseudo-nitzschia australis) on spermatozoa and embryos of king scallops P. maximus. The physiological responses of spermatozoa were evaluated after exposure to low (LC) and high concentrations (HC) of each microalgal species. While none of the tested microalgal strains showed direct toxicity, oxidative stress was associated to HC of A. minutum, and morphological changes were observed after exposure to L. polyedra and P. australis. Embryos of P. maximus were also exposed to HC of the same three microalgae species and examined under a microscope after 4h, 24h, and 48h of exposure. Exposure to A. minutum hindered cell division of embryos within the first 4 hfour hours of development, leading to complete embryo lethality at 24 h. No significant changes in early development were noted during the initial 48 h of exposure to L. polyedra and P. australis. These findings underscore the diverse effects of harmful microalgal species, emphasizing the need for targeted fishery and shellfishery management, both spatially and temporally, especially when bivalves and harmful algal bloom species potentially coincide during bivalve reproduction and recruitment.

^{Microplastics (MPs) vary widely in size and shape, characteristics that critically influence} their biological interactions and toxicity in marine organisms. We exposed juvenile Ciona intestinalis type A to three MP shapes: aged fragments (afrPE-MP), fibers (fiPET-MP), and spheres (sPS-MP) for 168 h, with a size range of 2-200 μm and concentrations of 0.1-1.0 mg L^-1. Natural inorganic particles (IOPs) served as a reference. We quantified heart rates, squirting activity, and mucus secretion in relation to particle characteristics. Fibrous MPs exerted a highly significant depressive effect on cardiac activity. Heart rate declined significantly with increasing particle size. Squirting activity increased significantly with size and strongly with concentration, consistent with a clearance or rejection response. Mucus secretion was significantly elevated under fibrous MP exposure and strongly influenced by concentration, whereas IOPs produced minimal effects. Together, these results indicate that particle size and shape are key drivers of sublethal stress, with fibers imposing the greatest physiological burden. To the best of our knowledge, this study provides the first evidence in ascidians of concurrent MP-induced cardiac disruption heightened squirting, and increased mucus production, supporting C. intestinalis as a sensitive model for sublethal MP toxicity in marine filter feeders.