Under eutrophication background, the increasing dinoflagellates blooms relative to diatoms blooms off the Changjiang Estuary has caused much concern. We have provided sediment evidence for the first time that the time window of diatoms-to-dinoflagellates shift off the Changjiang Estuary in the East China Sea is early 1990s. Investigations to the water column revealed different surface-bottom concentration matchup patterns between peridinin (dinoflagellates) and fucoxanthin (diatoms), which suggests that the diatoms-dinoflagellates shift recorded in the sediment may have come from more dinoflagellate blooms since 1990s. Physical-biogeochemical 3D numerical simulations for the past decades suggest that the effect of increasing spring sea surface temperature and increasing N/P ratio on the diatoms-dinoflagellates shift is dominant and recessive, respectively.

Biotic resistance is considered an important driver in the establishment of non-indigenous species (NIS), but experiments in the marine environment have led to contradictory results. In this context, a transplant experiment of fouling communities was carried out over five months. Settlement panels were moved from low impact (species-rich native communities) to high impact sites by NIS in two Italian areas to test the biotic resistance hypothesis. Fouling communities displayed significant differences among treatments before and after the transplant, thus indicating the maintenance of a peculiar fouling community in transplanted panels. On the other hand, newly recruited species were similar between treatments and neither a facilitation nor a mitigation role from native fouling communities on NIS was observed. Our results highlight the importance to better investigate the factors affecting the high variability obtained in experiments testing this hypothesis, with the aim to identify potential solutions for NIS management in ports.

This study assessed the concentrations of nine trace metals from juvenile C. falciformis caught from Indian Ocean. This study also discussed the metal pollution index (MPI) and bioconcentration factor (BCF) of each element, and their correlations. Further, the potential health risks of consuming shark muscles (THI) were evaluated. Results showed the mean concentrations of 9 elements as follows: Cu (0.36 ± 0.17), Zn (5.19 ± 16.6), Pb (0.12 ± 0.23), Cd (0.17 ± 0.21), Cr (0.57 ± 1.61), Ni (0.086 ± 0.51), As (1.36 ± 0.83), Co (0.000073 ± 0.0074), and V (0.0024 ± 0.0094) mg/kg ww. The BCF values of the elements were higher than 1, with Co and V being the lowest indicating their bioaccumulative behavior. Correlation analysis showed MPI to be highly correlated with Cu, indicating its greater contributions to the total pollution load. Principal components analysis explained 81.0% of the variability in biometric characteristics and metal concentrations. Health risk assessment for consuming shark muscle in Taiwanese male and female adults suggests potential chronic non-carcinogenic health hazards.

Coral diseases contribute to the rapid degradation of coral reefs on a global scale. Although widespread in tropical and subtropical reefs, disease outbreaks have not been described in warm temperate areas. Here, we report the outbreak of a new coral disease in a warm temperate marginal coral community in Japan. Outbreaks of the disease have been observed during the summer and autumn months since 2014. It affects the coral species Porites heronensis and was tentatively named “White Mat Syndrome” (WMS) as it consists of a white microbial mat dominated by Thiothrix sp., a sulfide oxidizing bacteria. Outbreaks followed high seasonal temperatures and were associated with the macroalga Gelidium elegans, which acts as a pathogen reservoir. With ocean warming and the anticipated increase in novel coral-algae interactions as some coral species shift poleward, WMS and emerging diseases could hinder the role of temperate areas as a future coral refuge.

Underwater radiated noise from shipping is globally pervasive and can cause deleterious effects on marine life, ranging from behavioural responses to physiological effects. Acoustic modelling makes it possible to map this noise over large areas and long timescales, and to test mitigation scenarios such as ship speed reduction or spatial restrictions. However, such maps must be validated against measurements to ensure confidence in their predictions. This study carried out a multi-site validation of the monthly and annual shipping noise maps for 2019 produced as part of the Joint Monitoring of Ambient Noise in the North Sea (JOMOPANS) programme. Spectral, spatial, and temporal differences between predictions and measurements were analysed, with differences linked to uncertainty in model input data and additional sources of anthropogenic noise in the measurements. Validating shipping noise models in this way ensures they can be applied with confidence in future management decisions to address shipping noise pollution.

Ocean acidification and warming are two major environmental stressors; however, the generality of how warming will alter growth responses of phytoplankton to ocean acidification is less known. Here, enhancement of growth by high CO₂ (HC) in Phaeodactylum tricornutum and Thalassiosira weissflogii was most prominent at optimum temperature. The extent to which growth rates in HC cultures were raised compared to low CO₂ (LC) cultures tended to decrease with increasing or decreasing temperature, compared to the optimum. Further mechanistic studies in P. tricornutum revealed that cellular carbon and nitrogen content, superoxide dismutase activity, and respiration were generally higher in HC than those in LC at high and low temperatures, whereas PSII photochemical parameters were generally lower in HC than in LC at high and low temperatures. These results indicate that HC-grown cells needed to invest more energy and materials to maintain intracellular homeostasis and repair damage induced by the unsuitable temperatures.

Small microplastics (SMPs) in the gulf of Cadiz was sampled at 5 m depth by pumping it through the ship's pipe system and filtered through a 45 μm mesh size net. Our study reveals that higher densities have been found (130 mg·m⁻³) compared to other regions worldwide and these densities decreased from the coastline to the outer stations, showing a general coastal gradient influenced by estuarine outflows. SMPs with a size range between 45 and 193 μm were predominant and most of them composed by polyethylene and polypropylene. The metals associated with the MPs were mainly Na (21.1%), K (11.3%), Fe (8.5%), Ca (2.1%), Cr (1.8%), Zr (13.3%) and Hf (0.7%). The high proportion of Zr compared to Fe, which is different from what can be found in the environment, suggests that this metal is intrinsic to the materials used in catalytic processes during plastic production.

The control of macroalgal bloom development is central for protecting estuarine ecosystems. The identification of the nutrients limiting the development of macroalgal blooms, and their most likely sources is crucial for management strategies. Three Irish estuaries (Argideen, Clonakilty and Tolka) affected by green tides were monitored from June 2016 to August 2017. During each sampling occasion, biomass abundances, tissue N and P contents, and δ¹⁵N were determined for tubular and laminar morphologies of Ulva. All estuaries showed maximum biomass during summer and minimum during winter. Tissue nutrient contents revealed P rather than N limitation. The δ¹⁵N during the peak bloom indicated agriculture as the most likely source of nitrogen in the Argideen and Clonakilty, and urban wastewaters in the Tolka. No differences in the δ¹⁵N, and the tissue nutrients content were observed between morphologies. The period between May and July is most suitable for bioassessment of green tides.

Carbon fixation by chemoautotrophic microorganisms in the dark ocean has a major impact on global carbon cycling and ecological relationships in the ocean's interior. At present, six pathways of autotrophic carbon fixation have been found: the Calvin cycle, the reductive Acetyl-CoA or Wood-Ljungdahl pathway (rAcCoA), the reductive tricarboxylic acid cycle (rTCA), the 3-hydroxypropionate bicycle (3HP), the 3-hydroxypropionate/4-hydroxybutyrate cycle (3HP/4HB), and the dicarboxylate/4-hydroxybutyrate cycle (DC/4HB). Although our knowledge about carbon fixation pathways in the ocean has increased significantly, carbon fixation pathways in the cold seeps are still unknown. In this study, we collected sediment samples from two cold seeps and one trough in the south China sea (SCS), and investigated with metagenomic and metagenome assembled genomes (MAGs). We found that six autotrophic carbon fixation pathways present in the cold seeps and trough with rTCA cycle was the most common pathway, whose genes were particularly high in the cold seeps and increased with sediment depths; the rAcCoA cycle mainly occurred in the cold seep regions, and the abundance of module genes increased with sediment depths. We also elucidated members of chemoautotrophic microorganisms involved in these six carbon-fixation pathways. The rAcCoA, rTCA and DC/4-HB cycles required significantly less energy probably play an important role in the deep-sea environments, especially in the cold seeps. This study provided metabolic insights into the carbon fixation pathways in the cold seeps, and laid the foundation for future detailed study on processes and rates of carbon fixation in the deep-sea ecosystems.

Distribution and ecological risk assessment of trace metals were carried out in the core sediments of a highly urbanized tropical mangrove ecosystem along the Southwest coast of India. The metal distribution pattern was as follows: Co, Cu, Ni and Pb adsorbed onto Fe oxyhydroxides and fine grained sediments; Cd and Zn preferential adsorption by organic matter and Cr scavenging by Mn oxyhydroxides. Cd, Pb and Zn were significantly enriched in upper sediments, while Cd, Ni and Zn were present in metal exchangeable fractions. Geoaccumulation index (Igₑₒ) suggested that the study area showed moderate to strong pollution of Cd and Zn, whereas unpolluted to moderately polluted with respect to Co, Cr, Cu, Mn, Ni and Pb. Cd enrichment caused high ecological risk, primarily attributed to anthropogenic activities. Mangrove ecosystems are efficient sequester of trace metals but anthropogenic addition can cause significant fraction of exchangeable metals and pose high ecological risk.