Bivalves are the focus of experimental research as they can filtrate a broad size range of microplastics (MPs) with negative consequences for their physiology. Studies use a range of MP shapes, materials, sizes and concentrations raising the question on whether these reflect environmental observations. We review experimental studies on the effects of MPs on marine bivalves and contrast the MP characteristics used with corresponding data from the environment. Mussels were the most common bivalve across experiments which reflect their high abundance and broad distribution in the field. Although fibres are the dominant shape of MPs in coastal systems, most studies focus on spherules and beads, and MP concentrations are often orders of magnitude higher than environmental levels. For higher relevance of experimental findings we recommend that maximum experimental concentrations of MPs are in the range of 100–1000 particles/L, that there is more focus on microfibers and that concentration is reported in particles/volume.

Negative human actions on seagrasses affect habitat condition and its associated fauna. Epiphytic hydroid's assemblage response to seagrass condition, water quality, and human impacts was evaluated in two bays of the Sabana-Camagüey Ecosystem of Cuba, using the presence of contamination, causeways, and trawling fishing as impact level proxies to the seagrass meadows. Thirty-eight species composed the hydroid's assemblage including five new records. Symmetroscyphus intermedius was the most abundant species and sensitive to indicators of the seagrass condition. Dynamena disticha and Gastroblasta sp. were sensitive to water quality predictors. Obelia bidentata was exclusive to the most impacted sites. Species richness and abundance were low in impacted sites and were highly affected by fishing trawling and causeways construction. Salinity, depth, NO2, pH, SSV, macroalgae cover, shoot density, and wet weight of Thalassia testudinum were the best predictors for hydroid's assemblages. Results suggest epiphytic hydroids on tropical seagrass meadows as sentinel organisms.

The quantity of floating plastic debris (FPD) is continuously being increased in the oceans. To assess their size, structure, and composition along the eastern Arabian Sea (EAS), FPD samples were collected by using a surface plankton net. The microplastic size fraction (0.5–5 mm) was the most prevalent accounting for >50% of the total, followed by mesoplastics (5–25 mm; ~40%) and macroplastics (>25 mm; ~10%). The collected FPDs were categorized into five different types and eight colours. Attenuated Total Reflectance-Fourier Transform Infrared Spectrometry (ATR-FTIR) analysis of the plastics revealed that polypropylene, polyethylene, and nylon were the most dominant polymers, and these comprised mostly of fibre/fishing line. The abundance of FPD in the EAS (0.013 ± 0.012 no.s/m³) was found to be very low compared to elsewhere. The prevalent microplastics presence in the oceans might have occurred mainly by the degradation of larger items. It increases bioavailability, and hence, is a risk to marine ecosystems.

The Southern Hemisphere long-finned pilot whale (Globicephala melas edwardii) is a top predator in the New Zealand pelagic food web, feeding predominantly on arrow squids. This study quantified trace element concentrations (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Ni, Mn, Pb, Se, V, Zn) in four tissues (blubber, kidney, liver, muscle) from 21 individuals from stranding sites in New Zealand. Maximum Cd and Hg concentrations were measured in liver and kidney, respectively. Selenium had a positive correlation with Cd and Hg, suggesting the involvement of Se in Cd and Hg detoxification. Arrow squids from the whales' stomach contents were DNA barcoded and identified as Nototodarus sloanii. Trace element concentrations were measured in squid samples from the whale stomach contents. The significant correlation for Hg between the squid tissue and the whale tissue suggests that arrow squids play a major role in trace element uptake by G. m. edwardii.

Pharmaceuticals and personal care products in wastewater discharge can be stressors to estuarine species. We transplanted juvenile Pacific oysters at varying distances within sites near wastewater treatment plant outfalls or oyster aquaculture control sites to assess small scale spatial variation in contaminant uptake and oyster condition. Oysters were transplanted to sites in Coos and Netarts Bays, Oregon and Grays Harbor, Washington, then collected after 9 and 12 months. Two pharmaceuticals (miconazole and virginiamycin M1) were detected in spring samples and four alkylphenols (NP1EO, NP2EO, NP and OP) were detected in summer samples, with more frequent detections at wastewater sites. Contaminant concentrations were similar across site types, indicating that even in sparsely populated coastal areas (<25,000 in the watershed), shellfish are exposed to and uptake wastewater contaminants. Additionally, oyster condition was lower at wastewater sites compared to aquaculture sites, indicating a need to better understand whether contaminant exposure affects oyster condition.

Nurdles, the pre-production plastic pellets, are a major source of plastic pollution in marine environments due to unregulated spills during production and transportation. We analyzed the types of plastics and associated organic pollutants on nurdles collected along the shoreline of Gulf of Mexico in Texas. Our results showed that the nurdles were made from polyethylene (81.9%) and polypropylene (18.1%). Polycyclic aromatic hydrocarbons (PAHs, 16 US EPA priority) and polychlorinated biphenyls (PCBs, 7 commercial congeners) sorbed to the nurdles were in concentration ranges of 1.6–14,700 ng/ g and 0–642 ng/ g, respectively. Heavily weathered nurdles tended to have higher concentrations of PAHs and PCBs than lightly weathered ones. The bioaccessibility of sorbed contaminants was evaluated using a simulated intestinal fluid. The results showed that the associated PAHs were more bioaccessible in lightly weathered nurdles (13.1 ± 2.3%) than heavily weathered one (5.3 ± 0.1%), and that no PCBs were bioaccessible. These findings are informative for toxicity evaluation and resource management of plastic debris in coastal environments.

This study in the Kochi backwaters (KBW) presents the distribution of 9 trace metals (Fe, Zn, Cu, Mn, Ni, Co, Cr, Cd, Pb) in different parts (root, stolon and leaf) of the common water hyacinth Eichhornia crassipes during three different seasons [Pre-Monsoon (PRM), Southwest Monsoon (SWM), and Northeast Monsoon (NEM)]. The hyacinth was collected from 4 sections upstream of the KBW where a saltwater barrage [Thannermukkom Barrage (TB)] prevents saltwater intrusion. Results showed that regardless of seasons, all the trace metals concentration in different parts of Eichhornia varied in the following order: roots > stolon > leaves. All the trace metals except Fe showed their highest concentration during the PRM when TB introduces stagnancy of the water upstream through flow restrictions. Instead, Fe was high during the SWM associated with increased river influx at that time. Overall results showed that the hydrographical alterations of TB upstream of KBW have clear imprints on the trace metals concentrated in the hyacinth Eichhornia crassipes.

This study presents the first data relating to debris ingestion by diving seabirds wintering in the south-eastern Baltic Sea, sets baselines for further studies and presents the first global record of plastic ingestion in Long-tailed Duck (Clangula hyemalis). Three of the six studied seabird species, and 2.1% of all 524 examined individuals collected from fishery bycatch, had ingested marine debris. Frequency of ingestion of Long-tailed Duck, Common Murre (Uria aalge) and Red-throated Loon (Gavia stellata) were 5.0%, 4.5% and 3.0% debris respectively, dominated by plastic objects. Providing detailed information about the studied individuals and the debris, this initiates discussion about diving birds' sensitivity to marine debris - it may depend on the feeding preferences of the birds, expressed as isotopic niches in this paper.

The present work aimed to evaluate the sources and ecological risks of heavy metal (HM) contamination in the soils of marine origin in central Saudi Arabia. HM concentrations were determined in 30 soil samples in October 2020, from Al Uyaynah–Al Jubailah region and their averages were in the following order: Al > Fe > Zn > Cr > Pb > Ni > As > Cu > Se > Cd > Hg > Sb. Average values of Zn, Ni, Co, Cr, and Cu in the investigated soils were less than averages of the continental crust, worldwide soils, and European soils, in contrast to the average values of As, Hg, Cd, and Se which were greater than the continental crust and worldwide soils. Enrichment factor, contamination factor, and degree of contamination revealed minor enriched and moderate contamination factors with As, Se, Hg, and Pb. Potential ecological risk index indicated that 93.33% of the soil samples fell under no-to-low risk, whereas 6.67% were categorized as moderate risk. Multivariate statistical analyses determined natural processes for Pb, Al, Cr, Sb, Zn, Fe, and Ni, while anthropogenic processes for As, Hg, and Se, mainly attributed to the chemicals used in agricultural applications and P fertilizers.

Characteristics of macrofaunal assemblages and their relationships with environmental factors in a semi-enclosed bay were studied seasonally in China. A total of 251 species were identified, including polychaetes (104 species), crustaceans (73 species), mollusks (51 species), and other phyla (23 species). Mean values of macrofaunal abundance were 1210, 2483, 3209, 3600 ind./m² while those of biomass were 56.88, 176.15, 136.28, 265.55 g/m², respectively. Ranges of species richness index, evenness index, Shannon-Wiener index were 1.54–8.16, 0.17–0.90, 0.69–4.78, respectively. The diversity indices were affected by bottom water salinity and pH. BIOENV analysis showed that water depth, phaeophorbide, and silt-clay proportion had important impacts on macrofaunal assemblages while abundance and biomass were affected by bottom water temperature, salinity, and water depth. Compared with historical data, macrofaunal species number, abundance and biomass showed a slight increasing trend, which may be due to the water quality improvement of this bay.