Estuaries receive the anthropogenic pollutants of their watershed area. Dhamra estuary, on the east coast of India, is such an estuary that receives a huge amount of pollutants, and it will eventually pose a threat to the ecological sensitive areas in its vicinity. Therefore, a study was carried out on physico-chemical parameters and chlorophyll-a to delineate the sources of variation during pre-monsoon and post-monsoon seasons. Surface water sampling was carried out from 12 stations in the estuarine and coastal area. Factor analysis and cluster analysis were applied to seasonal data to understand the sources of variation. From the study, it was observed that the chemical parameters are severely affected by anthropogenic influences such as sediment dredging, aquaculture effluent, and waste from industry and sewage from upstream. In the long run, this will affect the nearby nesting ground of vulnerable Olive Ridley turtles, high bio-diverse mangrove forests, and saltwater crocodile habitat.

This study initially investigated the coral status during the unexpected bleaching event in three coastal areas in Northwest Hainan coastal areas and analyzed changes in coral holobionts of the healthy and bleached Galaxea fascicularis. Coral coverage had declined severely, and the bleaching rate was extremely high during heat stress. The bleached corals had lower maximum photosynthetic yield, actual photosynthetic yield, zooxanthellae density, and chlorophyll a content than the healthy G. fascicularis, but there was no significant difference in protein, carbohydrate and lipid in eutrophic waters. The diversity and community composition of Symbiodiniaceae and symbiotic bacteria between healthy and bleached G. fascicularis showed no difference. Function prediction of the symbiotic bacteria revealed that the metabolism process was the main pathway of annotation. Present findings suggested that energy reserve functioning and high stability of the holobiont structure and might provide opportunities to G. fascicularis to adapt to eutrophication and heat stress.

To comprehensively understand the chemical changes over time of spilled oils subject to tropical climate conditions and the active weathering processes, a spill simulation experiment was conducted along 210 days with two distinct Brazilian oils (19 and 24 API) under irradiation and non-irradiation of sunlight. Isoprenoids and n-alkanes showed a great loss after 40 days for both oils under the two conditions due to evaporation. Diagnostic ratios of saturated biomarkers showed no changes, whereas the polycyclic aromatic hydrocarbons had a decreasing concentration under both conditions mainly due to evaporation. Furthermore, oxygenated polar compounds produced by photooxidation were investigated by ESI(−) FT-ICR MS and showed changes only for the oils exposed to sunlight irradiation. Based on the observed polar compositional changes, new parameters are suggested using heteroatom classes to estimate oil spill time under tropical conditions: NO₃/NO₂; NO₃/(NO + NO₂); ∑NOₓ/N₁; (O₄ + O₃)/(O₂ + O₁); O₄/(O₂ + O₁); and O₃/O₂.

This study investigates the influence of upwelling induced seasonal hypoxia in the sediment-water interface on the distribution, bioavailability and geochemical partitioning of selected trace metals in surficial sediments along the southwest coast of India based on two successive cruises. The first cruise was during the southwest monsoon (SWM) season when coastal waters exhibited intermittent bottom hypoxia due to upwelling. The second cruise during the northeast monsoon (NEM) season was characterised by a uniformly warm and well-oxygenated water column in the study region. The results showed that grain size, organic carbon and Fe are the major factors influencing the distribution of trace metals in the surface sediments. Based on the geochemical indices (contamination factor, enrichment factor and geo-accumulation factor), the study region appears to be moderately contaminated by Ni, Cr, and Pb. Based on the ecological risk assessment criteria, the enrichment of Pb, Cr and Ni may cause adverse effects on the benthic organisms. The fractionation studies demonstrated that the major pathway of metal deposition in the sediment is lithogenic. The data also showed that labile and organic fractions are the second dominant forms, while other fractions (exchangeable and carbonate) are insignificant. The consistency in the reactive Fe concentrations during SWM and NEM could be due to the absence of Fe dissolution in sediments under mild reducing condition (intermittent hypoxia). In addition to the above, an enrichment of organic matter also leads to increased deposition of trace metals in sediments. Conversely, the secondary phase enrichment factor and risk assessment code calculated based on the metal fractionation data indicated low risk and contamination along the southwest coast of India except for Zn that showed moderate contamination in some transects. The study provides the need for regular geochemical assessment to control metal pollution in the coastal environment, which is a major resource of the fishery.

We investigated the accumulation of litter along a transition gradient from the dunal beaches (B), to the backdunes (BD), to the channels of a coastal wetland (W), considering both the total litter and a sub-category represented by expanded polystyrene (EPS). Using a removal sampling technique carried out in spring (April and May), we hypothesized that: (i) the total accumulation of litter decreases progressively from the dunes to the backdunes to wet environments while (ii) the lighter polystyrene concentrates in the BD-W fringe where the Phragmites australis reedbeds can have a sink role for this polymer. The total litter density showed a significant decrease along the gradient B-BD-W in both months, with an evident collapse between BD and W. Analogously, EPS showed a significant difference in density along the B-BD-W gradient in both months, although with a different pattern: a maximum in the BD and a significant collapse between BD and W. The presence of backdune hygrophilous vegetation (Phragmites australis’ reedbeds) may act as a sink trapping all types of litter in both cases (total litter and EPS). The different accumulation pattern between total litter and the EPS is due to the lower specific weight of the latter polymer: while the generic litter tends to decrease quantitatively moving away from the sea, the lighter EPS is removed by the winds and pushed towards the land, beyond the dune, where it is trapped by the vegetation, thus showing a peak in density in the backdunes. No significant differences were observed between the litter density in the two months (before and after the removal) either considering the total litter and only EPS. This may suggest a continuous supply of litter from the sea, highlighting how clean-ups actions should be carried out with a higher frequency rather than monthly. This may be even more valid in the period of greater frequency of intense weather-marine events (autumn-winter) when a greater quantity of litter is deposited. These are the first data for the Mediterranean regarding a specific role of wetland hygrophilous vegetation as a sink for anthropogenic litter, mainly expanded polystyrene.

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.

This study quantified the distribution of Vibrio spp. by qPCR and pathogenic vibrio species by metagenomics, during 2 oceanographic cruises—XIXIMI-04 and XIXIMI-05 —in the southern Gulf of Mexico (GoMex). A total of 708 samples from various levels of the water column and 22 sediment samples were analyzed, according to a designed net of sampling lines. Sampling was focused on reported water masses with distinctive characteristics, to detect the presence-absence of vibrios. The results indicated that the genus Vibrio was detected along the entire water column and in sediments. Pathogenic vibrios, such as V, campbellii, V. parahaemolyticus, V. vulnificus or V. cholerae were also detected in the water column and in sediments, in both oceanographic cruises. Thus, the ecological conditions of the GoMex permit the growth of Vibrio spp. in deep water environments of the GoMex, despite continuous oil input from natural and anthropogenic sources.

Marine plastic pollution (MPP) is one of the most pressing issues especially for fast-growing economies in the Global South where addressing it involves both government and personal actions to achieve effective waste management policies. Alternative modelling strategies accounting for personal traits and beliefs (latent attitudes) which are unobservable characteristics are frequently overlooked in policy assessment studies. This study combines contingent valuation and latent traits questions to derive the willingness of Indonesian respondents to support MPP mitigation initiatives. One and two-step models are compared to test the sensitivity of results to modelling assumptions. Latent traits help to understand the willingness to pay (WTP) for MPP and one and two-step approaches produce comparable results. On average respondents are willing to pay £15, per person, per year to reduce MPP, or 2% of the average monthly salary. Local and international organizations should consider motivations and latent traits when designing MPP mitigation strategies.

This study investigates the concentration of heavy metals in the macroalgae, seagrasses, mangroves, and crabs collected from Hare Island, Gulf of Mannar Marine Biosphere Reserve. The concentration of heavy metals ranged between 0.06 (Hg)-259 (Fe) μg/g in macroalgae, 0.09 (Pb)-377 (Fe) μg/g in seagrasses, 0.112 (Cd)-122 (Fe) μg/g in mangroves, and 0.11 (Cd) -240 (Fe) μg/g in crabs. The levels of heavy metals in the analyzed samples were found below the maximum residual limits (MRLs) prescribed by various National and International agencies. The result suggests that exposure to the analyzed metals through macroalgae consumption does not cause potential health risks to consumers (target hazard quotient (THQ), estimated exposure dose (EED), and hazard index (HI) <1). Hence, this study concludes that macroalgae that grow in the Gulf of Mannar regions are safe for human consumption and are suitable to prepare food supplements and bioceutical products.

The heavy metal contents (Cr, Cu, Zn, Cd, Pb, Hg, and As) of 88 surface sediment samples from the western Sunda Shelf were analyzed to determine their spatial distribution patterns and contamination status. The results demonstrated that high enrichment regions of heavy metals were focused in the Kelantan, Pahang, and Ambat river estuaries, and deep water regions of the study area. These high enrichment regions were mainly controlled by riverine inputs and their hydrodynamic conditions. The enrichment factor (EF), geoaccumulation index (Igₑₒ), and potential ecological risk index (PERI) were used to assess heavy metal accumulation. The results indicated that the study area was not significantly contaminated overall at the time of the study; however, Cd, As, and Hg were at levels corresponding to moderate contamination at many stations located in the Pahang River estuary, Kelantan River estuary, and north-eastern region of the study area, primarily because of anthropogenic activities.