PURPOSE OF REVIEW: Microplastic (MP) pollution is a global concern due to its prevalence and persistence in the environment. Aquatic sediments, particularly marine sediments, are considered as the potential final sink of this pollution. This review summarizes (1) the fate and transport of microplastics (MPs) in waters and aquatic sediments and (2) the ecological impact of MPs, including the interactions between MPs and microbiome, and the effects of MPs on living organisms in aquatic sediments. RECENT FINDINGS: Characteristics of MPs, water movement, and weathering conditions determine the fate and transport of MPs. These factors influence MPs’ travel and inclination to settle. The interactions of MPs and microbiome can alter bacterial communities, cause MPs’ biodegradation, and facilitate biofouling that subsequently changes the fate and transport of MPs. MP presence poses exposure risks to benthic organisms through direct ingestion or trophic transfer, negatively affecting not only individual organisms but also the fauna. The destiny of MPs is affected by many factors, from MPs’ characteristics to water movement and weathering. Thus, future research is warranted to develop comprehensive modeling tools that include all the key factors to better understand and predict the fate and transport of MPs in aquatic environments and sediments. The potential impact from the exposure to MPs on the ecosystem of aquatic sediments is relatively less studied. More research is needed in this area, particularly from a systematic level, to understand how different biotic and abiotic factors will interact together and what the consequential impact of these interactions on ecological and human health are.

The baseline study of Microplastics (MPs) in zooplankton (copepods, chaetognaths, decapods, and fish larvae) from six different zones along India's west coast (off Kanyakumari/Cape Comorin, Kochi, Mangalore, Goa, Mumbai, and Okha) in the Eastern Arabian Sea (EAS) is presented here with their vast ecosystem impacts. This investigation revealed that zooplankton in all six zones accumulated MPs pellets (52.14%), fibres (28.40%), films (10.51%), and fragments (8.95%). The highest average retention of MPs (MPs/individual) was found in fish larvae (av. 0.57 ± 0.18) while copepods had the lowest (av. 0.03 ± 0.01). The presence of low-density polyethylene, polypropylene, polystyrene, and polyethylene terephthalate was confirmed by Raman Spectra of MPs. The MPs in zooplankton found in this study (av. 22 ± 7 pieces/m³) were nearly 2-fold greater than those found in some of the world's most densely populated areas. It is shown that the strong southerly coastal currents could advect the MPs contaminated water mass too far away, having the potential to affect the fish and corals.

Nickel bioaccumulation capacity of a marine Brevibacterium sp., designated as X6, was evaluated to explore its potential application in the bioremediation of Ni²⁺ pollutants in marine environments. The minimum Ni²⁺ inhibitory concentration and maximum Ni²⁺ bioaccumulation of X6 were 1000 mg/L and 100.95 mg/g, respectively, higher than most reported strains. Among the co-existing metal ions in seawater, K⁺ caused a slight adverse impact on Ni²⁺ uptake, followed by Na⁺ and Ca²⁺, whereas Mg²⁺ drastically inhibited Ni²⁺ bioaccumulation. Other heavy metals such as Co²⁺, Zn²⁺ and Cd²⁺ moderately affected Ni²⁺ binding, but the adverse effect of Cu²⁺ was severe. The investigation of the mechanism of Ni²⁺ bioaccumulation revealed that 66.34% of the accumulated Ni²⁺ was bound to the cell surface. Carboxylic, hydroxyl, amino and thiol groups participated in Ni²⁺ binding, while carboxylic group contributed the most, while thiol group may be more involved in Ni²⁺ binding at low Ni²⁺ concentrations.

Although seagrass ecosystems provide various ecosystem services, the implications in correspondence with temporal changes of the meadows is lacking. In this study, we analyzed two-decade changes of the seagrass area with the organic carbon storage and the sources at Libong island in Thailand. The seagrass area covered 841 ha in 2019, after two decades of decline (3.2 and 0.6% yr⁻¹ between 2004 and 2009 and 2009–2019, respectively). Although δ¹³C was not significant between depth layers (p > 0.05), the general trend suggested that the terrestrial source of carbon is dominating bottom depth layer (31.7–37.2%), mixture of terrestrial (19.7–30.3%), seagrass (22.9–29.6%), mangrove (16.8–43.0%) and CPOM (11.2–25.4%) in the middle, and mangroves and seagrasses are dominating surface layer (28.3–66.2 and 29.3–36.5%, respectively). These trends approximately correspond to the areal changes of the meadows, as well as changes of urban area and water quality, providing detailed information on the meadow changes and possible causes.

This work aimed to investigate the contamination pattern in Kongsfjorden marine environment (Svalbard, 79°N 12°E) and to disentangle primary and secondary emissions. Surface seawater, sampled in two seasons, was analysed by GC–MS and LC-MS/MS to detect polychlorobiphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), nonylphenols (NPs), bisphenol A (BPA) and perfluoroalkyl and polyfluoroalkyl substances (PFASs). In summer, average ΣPAHs, BPA, ΣNPs, ΣPFASs and ΣPCBs concentrations were 17.3 ± 11.1 ng/L, 0.9 ± 0.3 ng/L, 10.0 ± 6.9 ng/L, 0.4 ± 0.7 ng/L and 1.8 ± 1.3 pg/L, respectively; while in winter, they were 13.6 ± 10.1 ng/L, 0.5 ± 0.2 ng/L, 6.8 ± 3.3 ng/L, <LOD and 0.6 ± 0.4 pg/L, respectively. The application of generalized linear models (GLMs) highlighted that: PFAS pattern agrees their predominant long-range hydrospheric transport; the additive effect of the distance to glacier and harbour affected PAH, NP and BPA distributions; the additive effect of season and distance from the glacier, but not their interaction, influenced PCBs distribution, indicating melting glaciers as potential secondary POP sources.

In this study, recent and aged inputs of five classes of organic contaminants (i.e. PCBs, OCPs, PCDD/Fs, PAHs, and n-Alkanes) were evaluated in eight deep sediment cores of the Venice Lagoon, collected along the path of a new waterway whose excavation is under evaluation by local authorities, to assess the environmental quality status of the area. Diagnostic indices were calculated for identifying pollutant distribution patterns and their major emission sources, whose relative contribution was quantified by a Positive Matrix Factorization source apportionment model. Sedimentary depth profiles highlighted higher contamination in the top layer, mainly related to ship traffic combustion and vehicular/industrial emissions from the mainland. Nevertheless, a significant level of pollution has been detected also in the deeper layers, probably due to the transport of particulate matter through the aquifers underlying the lagoon seabed. The results underlined the threat posed by the possible resuspension of pollutants in the water column during contaminated sediment dredging.

The Sanchi oil tanker collision has attracted worldwide attention for its uniqueness in history. This study investigates the contamination level, spatial distribution, sources, and ecological risk level of polycyclic aromatic hydrocarbons (PAHs) present in the surface sediments collected from around the sunken tanker. The results indicated that the total PAH contents in the study area were in the range of 26.42–226.94 ngˑg⁻¹, with an average of 106.86 ngˑg⁻¹. The highest PAH concentration was observed at the station closest to the Sanchi wreckage, indicating potential PAH contamination due to the accident. The PAH ratios and statistical analysis revealed that the PAHs were mainly generated by coal and fuel oil combustion, with certain petrogenic inputs. The ecological risk assessment results suggested that adverse ecological effects to the benthic ecosystem due to PAH contamination was rare. However, long-term monitoring of the local sedimentary environment is highly recommended because of the prominent presence of high molecular weight PAHs.

A total of seventy surface sediments were collected from fourteen estuaries of South China to investigate the distribution of polybrominated diphenyl ethers (PBDEs), decabromodiphenyl ethane (DBDPE), 1,2-bis (2,4,6-tribromophenoxy) ethane (BTBPE) and dechlorane plus (DP). The concentrations of Σ₁₆PBDEs, DBDPE, BTBPE and DP in estuarine sediments ranged from 0.39 to 81.2, 0.18 to 49.9, not detected to 0.62, and 0.025 to 1.66 ng/g dry weight, respectively. Significant differences for levels of Σ₁₆PBDEs, DBDPE, BTBPE and DP were found among the sediments from fourteen estuaries. Sediments from the Pearl River Estuary had the highest concentrations of Σ₁₆PBDEs, DBDPE and DP. PBDEs and DBDPE were the main halogenated flame retardants in estuarine sediments. BDE 209 was predominant congener of PBDEs with an average contribution of 88.1% to the total PBDEs. 32.9% sediment samples from South China had fₐₙₜᵢ values lower than 0.65, suggesting that stereoselective enrichment of syn-DP occurred in estuarine sediments.

The coral diseases are recognized as serious threats to coral reef ecosystems and a major contributor to the reduction of zooxanthellate scleractinian populations worldwide. Quantitative disease surveys can provide important information on the status and trends of coral reef health over the time. In this study, coral disease surveys were carried out during August 2014 and 2015 at designated sites located in the northern Persian Gulf. Seven different diseases affecting eight scleractinian genera were documented: Black Band Disease (BBD), Skeletal Growth Anomaly (SGA), Arabian Yellow Band Disease (AYBD), White Mat Disease (WMD), White Syndrome (WS), Porites Pink Spot (PPS), and Porites Bleached Patches (PBP). Additionally, it should be noted that this is the first report of SGA in Acropora sp. found in the Persian Gulf. The results of this study generated a baseline dataset of various related diseases in the northern Persian Gulf which can be utilized for future studies.

Biodiversity plays a key role for our planet by buffering ongoing and future changes in environmental conditions. We tested if canopy-forming algae enhancing biodiversity (CEB) in a Mediterranean intertidal reef ecological community could alleviate the effect of stressors (heat waves and pollution from sewage) on community metabolic rates (as expressed by oxygen consumption) used as a proxy of community functioning. CEB exerted a buffering effect related to the properties of stressor: physical-pulsing (heat wave) and chronic-trophic (sewage). After a simulated heat wave, CEB was effective in buffering the impacts of detrimental temperatures on the functioning of the community. In reefs exposed to chronic sewage effluents, benefits derived from CEB were less evident, which is likely due to the stressor's contextual action. The results support the hypothesis that ecological responses depend on stressor typology acting at local level and provide insights for improving management measures to mitigate anthropogenic disturbance.