We report a high-spatial-resolution study on the distributions, characteristics, and environmental risks of microplastics in surface sediments of the southern East China Sea. Microplastics were omnipresent in the sediments (concentration range: 53.3–246.7; mean: 138.4 particles/kg dry-weight sediment) and enriched in nearshore areas close to urban centers relative to lower offshore concentrations. The microplastics identified were dominated by polyethylene (41.2%) and polyethylene terephthalate (19.9%) in polymer type, fibers (45.8%) and fragments (40.3%) in shape, 0.1–0.5 mm (61.0%) in size, and black (52.0%) in color. The benthic environment experienced low to moderate microplastic pollution, with polyvinylchloride exhibiting the highest ecological risk index. The high-resolution sampling revealed highly diverse polymer types and strongly patchy distributions of microplastic abundance and pollution indices in sediments. Results from this study imply that complex physical, biological, and topographic interactions control the distribution of microplastics and the associated environmental risks in coastal sediments.

Nanoparticles (NP) are potentially reprotoxic, which may compromise the success of populations. However, the reprotoxicity of NP is still scarcely addressed in marine fish. Therefore, we evaluated the impacts of environmentally relevant and supra environmental concentrations of titanium dioxide (TiO₂: 10 to 10,000 μg·L⁻¹) and silver NP (Ag: 0.25 to 250 μg·L⁻¹) on the sperm of gilthead seabream (Sparus aurata). We performed short-term direct exposures (ex vivo) and evaluated sperm motility, head morphometry, mitochondrial function, antioxidant responses and DNA integrity. No alteration in sperm motility (except for supra environmental Ag NP concentration), head morphometry, mitochondrial function, and DNA integrity occurred. However, depletion of all antioxidants occurred after exposure to TiO₂ NP, whereas SOD decreased after exposure to Ag NP (lowest and intermediate concentration). Considering our results, the decrease in antioxidants did not indicate vulnerability towards oxidative stress. TiO₂ NP and Ag NP induced low spermiotoxicity, without proven relevant ecological impacts.

Invasive, fouling species increase management costs and reduce mussel growth, which jeopardizes mariculture. We studied the distribution of eight invasive species in Santa Catarina, the leading mussel producer in Brazil. Our goals were to determine their spatial distribution and prevalence on farm structures (buoys, long lines, and mussel socks), as well as understand the relevance of propagule pressure (recruitment), port distance, and area of the farm in this distribution. Although present in all sites, adult and recruits distribution were spatially restricted, showing that species might have a metapopulation structure. The most prevalent species were the ascidian Styela plicata, the barnacle Megabalanus coccopoma, the bryozoan Schizoporella errata, and the polychaete Branchiomma luctuosum. Recruitment was the main driver of three species distribution while distance to port explained only one species distribution. Based on those results, we discuss policy options, management, and regulation enforcement, that can be used in the mussel aquaculture elsewhere.

Increased Rare earth elements (REE) usage culminates in discharges into the environment. Mussels have been chosen as models in biomonitoring, hence, REE concentrations in Mytilus galloprovincialis from six locations on the Portuguese coast were accessed to determine natural concentrations and possible linkage to local ecosystem characteristics and temporal variations, by determining them in distinct seasons (autumn and spring). Samples from Porto Brandão (located on the south bank of the Tagus estuary) exhibited the highest REE concentrations, while mussels from Aljezur (the southernmost point on the Portuguese coast) exhibited the lowest, in both seasons. Overall, ∑REE concentration was greater in the spring. LREE enrichment relative to HREE occurs and a negative Ce and Eu anomaly was observed. This study constitutes the first assessment of REE composition on this model species in the Portuguese coast, in two distinct seasons and contributes to a better understanding of REE uptake for future biomonitoring studies.

Free-living nematodes were investigated in three Mediterranean commercial ports (Ancona and Trieste, Italy; Koper, Slovenia) in terms of abundance, diversity and functionality. Results indicated that r-strategist genera were dominant in all ports and that a more diverse assemblage characterized Trieste, despite the high contamination levels, suggesting a potential adaptation to long-standing contamination. The main environmental factor that shaped the assemblage in all ports were Total Polycyclic Aromatic Hydrocarbons, while Total Organic Carbon and the grain-size were less relevant. A co-occurrence analysis was applied for identifying which genera cohesively respond to site-specific environmental conditions in order to recalibrate and implement the sets of bioindicator genera in relation to their different opportunistic behaviour. Finally, we provided some suggestions for a proper application of the nematode indices (Maturity Index, Index of Trophic Diversity, Shannon diversity) in order to encourage the use of free-living nematodes for the environmental quality assessment of commercial ports.

The pollution characteristics, potential sources, and potential ecological risk of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were investigated in the Hangzhou Bay (HZB) and East China Sea (ECS). Total OCPs concentration ranged from 2.62 to 102.07 ng/L and 4.41 to 75.79 μg/kg in the seawater and sediment samples, with PCBs concentration in the range of 0.40–51.75 ng/L and 0.80–45.54 μg/kg, respectively. The OCPs were positively correlated with nutrients, whereas PCBs presented a negative correlation. The newly imported dichlorodiphenyltrichloroethane (DDT) in HZB is mainly the mixing of technical DDT and dicofol sources. The PCB source composition is more likely related to the mixture of Kanechlor 300, 400, Aroclor 1016, 1242, and Aroclor 1248. Risk assessment results indicate that OCPs posed low risk in seawater. The potential risk of DDTs in the sediments is a cause of concern.

As an important biological indicator, multivariate dispersion in homogeneity of an observed community is a useful parameter for bioassessment of environmental heterogeneity. To identify the influence of tidal events on homogeneity of protozoan periphyton fauna from the highest tideline to the lowest, a 1-month baseline survey was carried out along five tidelines (sites A–E) in an intertidal zone of the Yellow Sea, northern China. There was a significant influence of tidal events on the homogeneity in both compositional and community structure among five tidelines. The β-diversity measures generally decreased from the highest tideline to the lowest. The biodiversity indices of the protozoans dropped sharply from the highest to the middle tidelines, followed by an increase until to the lowest tideline. These findings suggest that the homogeneity of protozoan periphyton in both species composition and relative abundance was significantly shaped by the environmental heterogeneity in intertidal zones of marine ecosystems.

The effects of reduced forms of nitrogen (NH₄⁺ and dissolved organic nitrogen (DON)) on the spatial distribution of diatoms and dinoflagellates in an estuarine-coastal water continuum were investigated from 2015 to 2019. The proportion of non-DIN in total nitrogen was utilized as an indicator of DON along with direct measurements of DON. While NO₃⁻ originated from Seomjin River, the abundant NH₄⁺ and DON occurred from Gwangyang Bay through Namhae. Diatoms were mostly confined to the upper estuarine system and dinoflagellates dominated in the regions with high levels of NH₄⁺ and DON. Generalized additive models also presented the different responses of diatoms and dinoflagellates to increases in NH₄⁺ and DON. Thus, our results highlight that diatoms dominate in NO₃⁻-replete water with full access to the source and dinoflagellates take over the ecologically open niche in an anthropogenically polluted estuary with full access to reduced forms of nitrogen.

A ridge-to-reef framework was developed for 26 watersheds around Guam. Dissolved inorganic nitrogen (DIN) data were collected for one year at the base of streams while coral and fish surveys were conducted on adjacent reefs. Two independent analyses revealed a similar 0.10 mg/l DIN threshold beyond which negative impacts to water quality and coral reefs existed. The influence of DIN was next partitioned with respect to a second primary stressor, fishing pressure. While coral diversity was negatively influenced by DIN, the cover of some stress-tolerant corals increased, such as Porites rus, making coral cover alone a poor indicator of watershed pollution. Less intuitive, DIN predicted increased food-fish biomass that was accounted for by generalist herbivores/detritivores, representing homogenized assemblages, while fishing pressure reduced biomass. Our DIN thresholds resonated with a similar study in American Samoa suggesting broader guidance for water quality legislation may be emerging.

Oil spill discharges from operational maritime activities like ships, oil rigs and other structures, leaking pipelines, as well as natural hydrocarbon seepage pose serious threats to marine ecosystems and fisheries. Satellite synthetic aperture radar (SAR) is a unique microwave instrument for marine oil spill monitoring, as it is not dependent on weather or sunlight conditions. Existing SAR oil spill detection approaches are limited by algorithm complexity, imbalanced data sets, uncertainties in selecting optimal features, and relatively slow detection speed. To overcome these restrictions, a fast and effective SAR oil spill detection method is presented, based a novel deep learning model, named the Faster Region-based Convolutional Neural Network (Faster R-CNN). This approach is capable of achieving fast end-to-end oil spill detection with reasonable accuracy. A large data set consisting of 15,774 labeled oil spill samples derived from 1786C-band Sentinel-1 and RADARSAT-2 vertical polarization SAR images is used to train, validate and test the Faster R-CNN model. Our experimental results show that the proposed method exhibits good performance for detection of oil spills with wide swath SAR imagery. The Precision and Recall metrics are 89.23% and 89.14%, respectively. The average Precision is 92.56%. The effects of environmental conditions and sensor parameters on oil spill detection are analyzed. The expected detection results are obtained when wind speeds and incidence angles are between 3 m/s and 10 m/s, and 21° and 45°, respectively. Furthermore, the computer runtime for oil spill detection is less than 0.05 s for each full SAR image, using a workstation with NVIDIA GeForce RTX 3090 GPU. This suggests that the present approach has potential for applications that require fast oil spill detection from spaceborne SAR images.