Aquatic ecosystems provide habitats for many organisms. Historically, riverbanks have always been inhabited and exploited for subsistence and navigation. The present study evaluates the contamination and ecological risks caused by potentially toxic elements in surface sediments of the Paraguaçu River, Bahia, Brazil. Seven sediments samples were collected, and eight heavy metals were determined employing inductively coupled plasma spectrometry mass (ICP-MS). The concentrations range as (mg kg⁻¹) found were 6.78–18.68 for lead, 14.21–42.16 for zinc, 27.61–48.63 for nickel, 2.03–6.50 for chromium, 6.06–12.90 for vanadium, 5.99–13.33 for cupper, 1.25–3.19 for cobalt, and 79.52–286.08 for manganese. Nickel showed significant enrichment (EF: 5.75; 7.62, and 14.11), followed by zinc, which showed moderate enrichment (EF: 2.16; 2.19, and 4.52). These enrichment levels are possible of anthropogenic origin. When the pollution index (PI) was evaluated, the elements V, Ni, Zn, Mn, Co, and Cu were strongly polluted (PI ≥3). In general, the pollution index (PI), geoaccumulation index (Igₑₒ), enrichment factor (EF), and potential ecological risk indices (Eᵣ and PERI) show that contaminated sediments have adverse effects on aquatic environments, especially for o Mn, Ni, Pb, V, and Zn.

The community composition and distribution of early-stage (24 h) biofilm-forming bacteria on two different surfaces (glass slide and polystyrene plastic slide) at three different locations (Diu, Alang and Sikka) were studied using a culture-dependent and next-generation sequencing (NGS) approach in the Arabian Sea, Gujarat, India. The most dominant phyla observed using the NGS approach were the Proteobacteria among the sampling sites. Gammaproteobacteria class dominated both the surfaces among the sites and accounted for 46.7% to 89.2% of total abundance. The culture-dependent analysis showed Proteobacteria and Firmicutes as the dominant phyla on the surfaces within the sampling sites. During the initial colonization, hydrocarbon-degrading bacterial strains have also attached to the surfaces. The outcome of this study would be of great importance for targeting the early stage biofilm-forming and hydrocarbon-degrading bacterial isolates may help to degrade plastic in the marine environment.

The world production of farmed Whiteleg shrimp was 5,812,180 t in 2020. Ecuador, Mexico, and Brazil produced 1,012,830 in that year according to data FishStatJ. Environmental impact studies were scarce given the rapid growth of this activity, mainly on cummulative impacts, loss of ecosystems services or resilience of wetlands and mangroves. Aspects of the management of environmental impacts published on American studies during 1986–2020 are analyzed. The main impacts included the loss of mangroves and their transformation of these ecosystems and their water bodies by receiving enriched effluents from shrimp farms. Different management measures are discussed between Ecuador, which contributes 63.76 % of American production of white leg shrimp; Brazil which published 46.2 % of the environmental studies of the analyzed period, and Mexico, in an intermediate situation. Finally, alternatives are discussed to improve the management of shrimp aquaculture with emphasis on the Ecuadorian context.

In this study selected marine species from north Persian Gulf ecosystems were collected to investigate the concentration of 15 trace elements (Al, As, Co, Cr, Cu, Fe, Li, Mo, Ni, Pb, Se, Sr, V, Zn and Hg) in muscle and liver tissues for the purpose of evaluating potential health risks for human consumers. The results indicated that Fe, Zn, Sr, Cu and As are the most abundant TEs in the tissues of the species. The concentration of Cu in P. semisulcatus and As in most investigated species pose the highest risk of exposure. The carcinogenic risk values indicate that As and Ni concentrations in the species are above the acceptable lifetime risk for adults and children in most of the species. The margin of exposure risk approach indicated that the risk of detrimental effects due to dietary Pb intake for age groups is low, except for consumers of T. tonggol.

Microplastics pretreatment of prior to biodegradation is an efficient approach for their bioremediation. We isolated Achromobacter denitrificans from compost and used it for biodegradation of thermo-oxidative pretreated polyvinyl chloride (PVC) and low-density polyethylene (LDPE). About 12.3 % and 6.5 % weight loss, and 326.4 and 112.32 mg L⁻¹ extracellular protein were observed in bacterial flasks with PVC and LDPE, respectively. The pH in treated PVC reached to 5.12 and the thermal stability increased by 29 °C. The chemical modification in LDPE was demonstrated through oxidation of antioxidants (Phenol group), formation of new groups (Aldehyde group), and chain fracture in the main backbone by Fourier transform infrared spectroscopy. Formation of peaks at the range of 1700–1850 cm⁻¹ in LDPE attributed to formation of carbonyl groups as the degradation result. Scanning electron microscopy confirmed LDPE and PVC degradation by surface alterations. Consequently, thermo-oxidative pretreatment can be considered as a suitable strategy for improving microplastics biodegradation.

Microplastics (MPs) are a ubiquitous contaminant worldwide, damaging the environment and human health. These particles have been identified in important seafood species, which are a possible source of contamination for humans and must be investigated. This study therefore aimed to identify the concentrations of microplastics in four important species of bivalves commercialized in Brazilian markets. The presence of microplastics was identified in all bivalves, with an average concentration of 1.64 MPs/g and 10.69 MPs/ind. We concluded that bivalves are a source of microplastics for the Brazilian population. However, further studies must evaluate other species sold in different regions of the country, estimating microplastics ingested by this population through bivalves. Finally, this contamination must be controlled by regulations such as mandatory depuration, in which can effectively minimize this problem.

Geographical and temporal differences of microplastic occurrence were documented in water and fish collected in 2017 and 2019 from the Giglio Island (North Tyrrhenian Sea) close to the area where the Costa Concordia sank in January 2012. Results on water samples showed a site-dependent difference, suggesting the role of surface current dynamics in the microplastic local distribution, while tested Neuston nets (200 μm and 330 μm mesh size) did not influence microplastic retention efficiency. Fish exhibited in 2019 a higher frequency of specimens positive to microplastic ingestion with respect to 2017, with an occurrence higher than those typically observed in other Mediterranean areas. Both in water and fish, fragments were the dominating shape, polypropylene and polyethylene were the prevalent polymers, without particular difference between sites and years. This study highlights the importance of applying microplastic investigation in biotic and abiotic matrices for an effective monitoring of this pollution in the marine environment.

Heavy metals contamination level and their ecological risk of the Burullus lagoon were estimated using four cores and twelve surficial sediment samples. The distributions maps of Fe, Mn, Zn, Hg, Cu, and Pb indicate an increase toward drains areas, whereas Cd rises toward the Boughaz El-Burullus. The geoaccumulation index (Igₑₒ) and contamination factor (CF) for heavy metal displayed the following order: Cd > Zn > Fe > Cu > Pb > Mn > Hg. The degree of contamination (Cd) indicates a considerable degree of contamination for 81.25% of the studied stations, and the pollution load index (PLI) suggested deterioration in 100% of sediments. Regarding the potential ecological risk (RI), the metals were arranged as: Cd > Hg > Cu > Pb > Zn, with considerable risk at the eastern part. According to sediment quality guidelines (SQGs), Zn concentrations suggest frequently adverse impacts on biota while Cu and Cd indicating an occasional adverse impact. Periodic monitoring of heavy metals in aquatic organisms is recommended to assess their toxic risk.

This study focuses on the presence of MPs in the sediment beds around coral reefs of MPNPs in Baja California Sur, México. Based on seasonal sampling results, comparison of MPs from Cabo Pulmo (avg. 680.25 items/100 g⁻¹ d.w) recorded higher values than Espiritu Santo Island (avg. 321.75 items/100 g⁻¹ d.w) from backshore/foreshore regions. Fibrous MPs are the dominant morphotypes followed by fragments and spheres. SEM/EDS analysis revealed that the MPs are altered texturally in surface and is bioavailable to marine organisms independent of size/shape. FTIR analysis indicate different polymers (in %) in the form of PP (70), PET (65), HDPE (59), LDPE (50), PS (30), PC (18), PU (10) and RYN (10). Most of the MPs are secondary in origin resulting from man-made and tourist's activities controlled by wave transportation and tidal currents. Existence of MPs in sediment beds around the coral reefs signals the ways for future investigations.