To comprehend mangrove crab responses to predicted global climate changes, we assessed submersion and desiccation survival durations and salinity tolerances and upper thermal limits in fiddler crabs from Isla del Carmen, Yucatán Peninsula. Based on their tolerances of extreme ambient conditions, we also calculated safety margins using abiotic monitoring data. The two most terrestrial species, Minuca rapax and Leptuca panacea, exhibited submersion tolerances of from 22 to 40 h, and desiccation tolerances of from 30 to 55 h; LC₅₀'s were ≈45‰S and UT₅₀'s were ≈40 °C. The two least terrestrial species, M. vocator and L. speciosa, were less tolerant of all experimental challenges, showing submersion and desiccation tolerances of <6 h, and LC₅₀'s of 36‰S and UT₅₀'s of 38 °C. While these fiddler crabs inhabit niches closer to their salinity and desiccation/submersion tolerances than to their temperature limits, all are clearly vulnerable to the multiple stressors that accompany anticipated global climate change.

The spatio-seasonal variation, bioaccumulation and potential ecological risk of four metals (Co, Ni, Cu and Zn) in the multi-media of the Pearl River Estuary (PRE) were assessed. The degree of contamination and ecological risk of the four metals followed this pattern: Cu > Zn > Ni > Co, upstream > downstream, wet season > dry season. There were non-linear and linear correlations for Co, linear and non-linear correlations for Ni, and non-linear and no correlation for both Cu and Zn, between metals in bottom water or bioavailable concentrations in sediment and fish muscle. Co and Ni showed lightly polluted levels; Cu and Zn showed heavily polluted levels. This study demonstrates a tendency of cross-accumulation in fish of these four transition metals within specific habitats of the PRE.

Here we assessed the subsurface ultraphytoplanktonic (< 10 μm) community along a North-South round-trip Mediterranean transect as part of a MERITE-HIPPOCAMPE cruise campaign in April–May 2019. Temperature, salinity, and nutrient concentrations in subsurface waters (2–5 m depth) were also measured along the transect. The subsurface ultraphytoplankton community structure was resolved with a spatial resolution of few kilometers and temporal resolution of 30-min intervals using automated pulse shape recording flow cytometry. The subsurface waters were clustered into seven areas based on temperature and salinity characteristics. Synechococcus were by far the most abundant group in all prospected zones, and nanoeukaryotes were the main biomass component, representing up to 51 % of ultraphytoplanktonic carbon biomass. Apparent net primary productivity (NPP) followed a decreasing gradient along the transect from north to south and was mostly sustained by Synechococcus in all zones. These findings are likely to have implications in terms of the trophic transfer of contaminants in planktonic food webs, as they highlight the potential role of nanoplankton in contaminants bioaccumulation processes and the potential role of Synechococcus in a likely transfer via grazing activities.

Movement of marine debris is transboundary and complex, travelling vast distances and accumulating on shorelines. These marine debris wash ashore as stranded beach litter. The objective of this work is to identify release sources of marine debris accumulated along the Singapore coastlines collected by applying a time-backward adjoint marginal sensitivity method and citizen science data of stranded beach litter by a voluntary beach clean-up group. A popular tourist hotspot on the opposite shore was estimated as a possible release source contributing to the marine debris accumulation. This analytical result was validated by population density, industry types, rainfall, and inference from product packaging labels. The use of the citizen science data also illustrated potential as a data source for baseline monitoring and long-term cross-border research that influence policymaking. Future research can be conducted in an expanded domain, considering monsoon effects and instantaneous release events.

Although nanoplastic (NP) pollution across aquatic environments has elicited widespread attention in recent years, its associated risks remain unclear. Using intertidal Monodonta labio as the test organism, RNA-Seq was performed to analyze the expression levels of genes under acute exposure to different concentrations of NPs in this study. A large quantity of differentially expressed genes (DEGs) were detected in response to three concentrations (0.1, 1, and 10 mg/L) of NPs. The expression levels of genes related to immunity, oxidative stress, and apoptosis were altered after NP exposure, and most of them were suppressed. These findings establish the foundation for future research on the biological effects of NP ingestion among aquatic organisms and their potential effects on humans via the consumption of these marine resources. However, further research on DEGs is needed to gain a better understanding of the molecular mechanisms behind their responses to NP toxicity in aquatic organisms.

Ulva prolifera, a common species of green macroalgae, is often harmful-algal-bloom causative and significantly impacts local marine ecosystems. Previous studies on the physiological characteristics of U. prolifera have been conducted under constant light (CL). However, light in the natural environment continually changes, and little is known about fluctuating light (FL). Ocean acidification (OA) has been proposed to interact with dynamic surrounding environments to affect the physiological performance of macroalgae. Therefore, we investigated the combined effects of FL (80/300, alternating between 80 μmol photons m⁻² s⁻¹ for 2.5 h and 300 μmol photons m⁻² s⁻¹ for 1.5 h, with an average light intensity of 160 μmol photons m⁻² s⁻¹ and OA (1000 ppm CO₂) on U. prolifera. The results clearly showed that FL had no significant effect on the relative growth rate (RGR), whereas OA obviously improved RGR. However, under FL-OA combination conditions, RGR was inhibited significantly, accompanied by a concomitant downgraded photosynthetic performance, while the photoprotective abilities were enhanced. The results would help us accurately predict the primary productivity of macroalgae in coastal waters under future OA conditions with irradiance fluctuations.

Heavy metal concentrations in surface sediments collected from 17 stations samples in Bizerte coastal line were determined in order to evaluate the contamination status in the region. Heavy metal concentrations (mg/kg) of Bizerte coast line followed the decreasing trend of Fe > Pb > Zn > Mn > Cu > Cr > Ni > Co > Cd. The pollution degree of the surface sediment collected from 17 samples station in Bizerte coast line by heavy metals was evaluated on the basis of pollution indices (EF, Igeo, CF, PLI and CD). Results of Igeo, EF, CF, PLI and DC demonstrated that pollution levels of Pb and Cd were moderate, which should require more attentiveness as main pollution factors. However, no pollution was found for Zn, Cu, Ni, Cr, Co and Mn. Hierarchical cluster analysis was used to identify the influence of anthropogenic activities on the surface sediment.

Human activities have changed the global concentration of potentially toxic elements (PTEs) and significantly altered the marine ecosystem. Little is known about the concentrations of these PTEs around Hainan Island in China, or their distribution and human health risks. Understanding the variability of PTEs in marine sediments and how they accumulate is important not only for biodiversity and ecological conservation, but also for management of aquatic natural resources and human health risk assessments. This study showed that the concentrations of six PTEs (Cd, Cu, Zn, As, Pb, and Hg), sampled in nine different cities, were linked to human activities. In order to understand the ecological risks associated with PTE pollution, we calculated the contamination factor (CF), enrichment factor (EF), pollution load index (PLI), and geo-accumulation index (Igeo) of each element in each city. These indicators suggest that the pollution of Cd and Zn in the sediments of these cities is higher than that of the other PTEs. We also carried out a human health risk assessment which demonstrated the carcinogenic effects of Zn on children and adults in ChengMai, while Pb showed non-carcinogenic effects at all the studied sites, suggesting that Zn pollution in the sediments of ChengMai may pose human health risks. We would therefore advise that follow-up studies endeavor to monitor the levels of PTEs in the flora and fauna of these cities.

Maritime traffic is increasing globally, with a four-fold increase in commercial vessel movements between 1992 and 2012. Vessels contribute to noise and air pollution, provide pathways for non-native species, and collide with marine wildlife. While knowledge of shipping trends and potential environmental impacts exists at both local and global levels, key information on vessel density for regional-scale management is lacking. This study presents the first in-depth spatio-temporal analysis of shipping in the north-east Atlantic region, over three years in a five-year period. Densities increased by 34%, including in 73% of Marine Protected Areas. Western Scotland and the Bay of Biscay experienced the largest increases in vessel density, predominantly from small and slow vessels. Given well-documented impacts that shipping can have on the marine environment, it is crucial that this situation continues to be monitored – particularly in areas designated to protect vulnerable species and ecosystems which may already be under pressure.

The history of metal pollution in the semi-enclosed and human-influenced marine system of the Boka Kotorska Bay (Southern Adriatic) was studied considering geological composition of the surrounding catchment, the sedimentation rate and the mineralogical and early diagenetic processes in the recent sediments. The determination of background concentrations of metals, undertaken for the first time in this environment, proved to be particularly important for Ni and Cr, which are naturally enriched in the sediments of the southern Adriatic. The results showed widespread moderate contamination with Pb and Sn since the 1970s, while the upper layers of sediments near shipyards, marinas and urban areas were more contaminated with Sn, Cu, Pb, Zn, Cd, As, Sb and Mo. The transport of material through the narrow straits separating different parts of Boka Kotorska Bay resulted in a different geochemical composition of the smaller bays and a limited distribution of contaminated sediments from local sources.