Marine environmental research最新文献

Natural stressors, including predation risk, can affect the response of organisms to anthropogenic contamination. Copper, used as an antifouling agent, can affect non-target organisms. We tested for effects of excess copper on survival with and without predator cues in five species of coastal copepods. We exposed adult copepods to four copper concentrations (0-1350 μg L^-1, 48h) on an automated imaging platform and analysed the data using the reduced General Unified Threshold model for Survival (GUTS) to detect potential species differences in underlying toxico-kinetics and -dynamics. Calanoid copepods had elevated mortality during early copper exposure compared to a harpacticoid and a cyclopoid species. Species-specific dominant rate constants, which represents the time it takes for damage to reach a steady state, best explained the time-dependent toxicity. Over time, most predicted mortalities converged to a similar level regardless of species. Predation risk reduced mortality at the intermediate copper concentration, potentially explained by reduced copper bioavailability by binding of copper to kairomone molecules, or other intrinsic and extrinsic factors. Models like GUTS can reveal the underlying toxicity mechanisms and improve toxicity predictions in a multi-stressor world.

This study investigates the individual and combined effects of cadmium (Cd²⁺) and poly (butylene adipate-co-terephthalate) (PBAT), a biodegradable macroplastic, on the marine diatom Phaeodactylum tricornutum (P. tricornutum). Interestingly, co-exposure with PBAT mitigates Cd²⁺ toxicity, except at high Cd²⁺ concentrations. Using a non-invasive Fourier-transform infrared (FTIR) spectroscopy protocol with robust acquisition parameters and principal component analysis, specific biochemical changes in membrane composition were monitored, with notable decreases in carbohydrate and lipid contents, while protein levels remained unaltered. Morphological observations revealed a shift toward the oval morphotype under exposure to Cd²⁺ and PBAT, alone and in combination, featuring a stress response. Additionally, the light-harvesting pigments, chlorophyll-a and fucoxanthin, increased in a dose-dependent manner upon Cd²⁺ exposure, while no significant β-carotene changes were observed, except at high Cd²⁺ concentrations in the presence of PBAT. This effect is further amplified under co-exposure conditions, the presence of PBAT leading to a marked increase in all three pigments, β-carotene included. The experimental protocol, which involved the aging of PBAT macroplastics in seawater for a short period, suggests that the degradation products of PBAT themselves are responsible for these observed biological effects. It is worth noting that morphotype shifts occur at lower Cd²⁺ concentrations than those affecting photosynthesis and photoprotective systems. These findings highlight the potential of P. tricornutum membrane fingerprints and morphotype shifts as sensitive ecotoxicological indicators of metal and plastic pollution, particularly in relation to degradation by-products in marine environments.

In tropical coastal ecosystems, monsoonal rainfall is a critical driver of seasonal variability, inducing shifts in hydrological parameters such as temperature, salinity, and nutrient concentrations, which subsequently regulate zooplankton community structure. This study investigated the influence of the southwest monsoon on coastal water quality and zooplankton composition along the Mumbai coast, India. Sampling was conducted in the pre-monsoon (May 2022) and post-monsoon (September 2022) periods, corresponding to early (EMP) and later (LMP) monsoonal phases, during which the region receives 1500-2000 mm of precipitation. Analyses revealed distinct hydrological changes and a significant reorganisation of the zooplankton assemblage between phases. Total zooplankton abundance was lower in the EMP compared to the LMP. Among the 25 taxonomic groups identified, Copepoda dominated the community, represented by 27 species (23 Calanoida, 2 Harpacticoida, and 2 Cyclopoida), with families Acartidae and Paracalanidae comprising 70 % of the copepod population. Statistical and biological trait-based analyses demonstrated significant temporal shifts in copepod community composition and functional structure. Temperature, salinity, and nutrient levels were identified as the primary environmental factors shaping the distribution of copepod functional groups. Eleven copepod taxa served as indicator species for specific monsoonal phases. Trophic structure analysis showed a prevalence of omnivorous copepods during the EMP, likely due to reduced phytoplankton availability under lower nutrient concentrations and fluctuating salinity, favouring opportunistic feeding. In contrast, the LMP, characterised by elevated nutrient inputs and stabilised salinity, supported a more complex food web with a balanced representation of herbivorous, omnivorous, carnivorous, and detritivorous functional groups. Herbivores were numerically dominant in both periods. The increased co-dominance of meroplankton (pelagic larvae of benthic invertebrates) during the LMP highlighted their ecological role in coupling benthic and pelagic subsystems. These findings elucidate the mechanistic links between monsoonal hydrography and zooplankton functional ecology, providing a scientific basis for informed conservation and management of monsoon-influenced coastal ecosystems.

In summer, the East China Sea (ECS) faces ecological challenges like harmful algal blooms, hypoxia, and jellyfish blooms, linked to nutrient distributions influenced by Changjiang Diluted Water (CDW), Kuroshio intrusion, and Zhejiang Coastal Upwelling (ZCU). The inconsistent interannual variations of these processes complicate nutrient dynamics. This study used the Empirical Orthogonal Function (EOF) analysis to reveal the interannual variations (1993-2022) of summer dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) concentrations in the ECS. We demonstrated that interannual variability in southerly wind strength was a key regulator controlling the relative influence of CDW and ZCU on surface nutrients. Weaker southerly wind combined with stronger Changjiang discharge (e.g., 1999, 2002, 2020) enhanced the nearshore influence of CDW and reduced the ZCU intensity. This suppressed DIP supply and biological consumption of DIN, leading to accumulated surface DIN but depleted surface DIP in the Zhejiang Coastal (ZC) region. Conversely, stronger southerly wind combined with stronger Changjiang discharge drove the CDW moving offshore that increased offshore DIN concentrations. Simultaneously, the stronger southerly wind also intensified ZCU that enhanced coastal DIP supply and biological DIN uptake, resulting in reduced coastal surface DIN. Critically, we identify the distinct drivers for bottom DIP. Weaker ZCU led to increasing (decreasing) of bottom DIP concentrations in an area deeper (shallower) than 20 m, while stronger Kuroshio intrusion substantially boosted bottom DIP, influencing productivity in both ZC region and the East Zhejiang coastal (EZC) region. The intricate interplay of these physically driven nutrient fluxes, characterized by differing N/P ratios, underpinned the ECS's complex and variable summer nutrient structures with profound implications for understanding its ecological responses.

Marine Protected Areas (MPAs) aim to preserve species, habitats, and the Nature Contributions to People they support. In the sub-Antarctic MPAs Namuncurá - Burdwood Bank I and II, the primary conservation features are the rich and abundant benthic assemblages across two distinct habitats: the plateau and the slope of the bank. Currently, these MPAs face significant threats from anthropogenic CO₂ emissions, which drive climate change and ocean acidification processes. Here, we establish an ecological baseline by analysing the diversity and structural patterns of benthic assemblages to evaluate MPA effectiveness, monitor climate change impacts, and inform management strategies. Comparisons were performed across three areas: the MPA, the Beagle Channel, and the Atlantic shelf of Tierra del Fuego, and between zones and habitats within the MPA. Sampling was conducted at depths of 90-710 m using bottom trawls, with megafauna identified to the lowest possible taxonomic level. Uni- and multivariate analyses revealed marked differences across areas. A total of 236 taxa were distinguished, but only 16 were shared among all the three areas, while 167 were unique to the MPAs. The habitats were characterized by different biotas, with sponges (mainly Demospongiae) dominating shallower environments and calcifying taxa, such as corals and echinoderms, predominating in deeper habitats. High β-diversity turnover within the MPAs suggests that the current zonation may inadequately protect benthic habitats, which is further exacerbated by ocean acidification predictions. Our findings highlight the biodiversity and conservation value in two opensea sub-Antarctic MPAs, providing a basis for effective management and the assessment of ecological responses to environmental change.

Riverine is the most vital ecosystem, which serves numerous important benefits to their locality, and it undergoes various chemical reactions that influence coastal water composition, nutrient cycling and broader geochemical processes. In this research, geochemical fractionation of metals with respect to the spatial distribution in the Miri River was examined. Initially, pXRF survey was conducted to understand the spatial variability of metal concentrations in the river sediments. Subsequently, selected sediment samples in the vulnerable zones (upstream, mid-stream and downstream) were collected and extracted into different geochemical phases via sequential extraction method, and analysed for metal concentrations. From the pXRF results, the order of dominance of metals are as follows: Fe > Zn > Pb > Cr > Ni > Cu > Mn > Cd, in which the higher concentration of metals was observed in the downstream and upstream sections of the river. From the sequential extraction, most of the metals are associated with residual, Fe-Mn oxides and organic matter fractions, as absorbed phases with less mobile and less readily available condition. Factor analysis also confirms that Fe-Mn oxyhydroxides was the major geochemical phase to absorb metals from various sources including anthropogenic activities and chemical weathering. Various pollution indices have been used to assess the potential ecological risk of the river sediments. All the indices revealed the contamination level of river sediments, particularly the elevated concentration of Cd and Ni. From this study, sequential extraction offers insights into the fractionation, availability, and mobility of metals, which can aid in evaluating environmental contamination in the river.