A review on sea cucumber (Bengali: Somuddro Sosha) as a bioindicator of heavy metal contamination and toxicity.

This review paper exhibits the underexplored realm of heavy metal contamination and associated risks in sea cucumbers (SCs), which hold significant importance in traditional Asian marine diets and are globally harvested for the Asian market. The assessment focuses on heavy metals (HMs) presence in various SC species, revealing a global trend in HMs concentrations across anatomical parts: Fe > Zn > As > Cu > Hg > Pb > Mn > Cr > Ni > Cd. Specific species, such as Eupentacta fraudatrix, Holothuria mammata, Holothuria polii, Holothuria tubulosa, and Holothuria atra, exhibit heightened arsenic levels, while Stichopus herrmanni raises concerns with mercury levels, notably reaching 3.75 mg/kg in some instances, posing potential risks, particularly for children. The study sheds light on anthropogenic activities such as cultivation, fishing, and shipping, releasing HMs into marine ecosystems and thereby threatening ocean and coastal environments due to the accumulation and toxicity of these elements. In response to these findings, the paper suggests SCs as promising bioindicator species for assessing metal pollution in marine environments. It underscores the adverse effects of human actions on sediment composition and advocates for ongoing monitoring efforts both at sea and along coastlines.

Coastal and nearshore sediment data along the eastern coastal zone of Bangladesh of the northern Bay of Bengal.

A seafloor sediment dataset of 42 samples has been collected from the coastal and nearshore areas of the northern Bay of Bengal, which is situated in the southern part of the eastern coastal zone of Bangladesh. From February 2018 to March 2019, Van Veen grab samplers were employed to gather samples at a depth of 4 m and 23 m. The unconsolidated bottom surface has been sampled, taking bathymetry and fishing boat accessibility into account. Using the dry sieving technique, grain size distribution analysis was performed on the obtained sediments. The retrieved dataset was measured to identify seafloor sediment grain size distribution and determine the sediment dynamics. This data can be used to delineate sediment characteristics, depositional processes, and the environment.

Spatiotemporal trends and characteristics of microplastic contamination in a large river-dominated estuary.

Microplastic (MP) pollution is a major global issue that poses serious threats to aquatic organisms. Although research on MP pollution has been extensive, the relationship between MPs and water quality parameters in estuarine water systems is unclear. This work studied the spatiotemporal distribution and characteristics of MPs in the Karnaphuli River estuary, Bangladesh. MP abundance was calculated by towing with a plankton net (300 µm mesh size) at three river gradients (up-, mid- and downstream) and the association between physicochemical parameters of water (temperature, pH, salinity, electrical conductivity, total dissolved solids, and dissolved oxygen) and MP distribution patterns was also investigated. Mean MP abundance in water was higher during the wet season (April) (4.33 ± 2.45 items per m3) compared to the dry season (September) (3.65 ± 2.54 items per m3). In descending order, the highest MP abundance was observed downstream (6.60 items per m3) > midstream (3.15 items per m3) > upstream (2.22 items per m3). pH during the wet season (April) and temperature during the dry season (September) were key physicochemical parameters that correlated with river MP abundance (r = -0.74 and 0.74 respectively). Indicating that if the Karnaphuli River water has low pH or high temperature, there is likely to be high MPs present in the water. Most MP particles were film-shaped, white in color, and 1-5 mm in size. Of the six polymers detected, polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), and cellulose were predominant, comprising roughly 17-19% each. These results can be used to model MP transport in the freshwater ecosystem of the Karnaphuli River estuary in Bangladesh to help develop future mitigation strategies.

Distribution, characteristics, and risk assessments analysis of microplastics in shore sediments and surface water of Moheshkhali channel of Bay of Bengal, Bangladesh.

Microplastic pollution in various ecosystems has gained significant attention across the globe. Due to ubiquitous abundance, terrestrial and aquatic ecosystems at regional scales are polluted via uncontrolled anthropogenic actions. Therefore, this study investigates microplastic pollution and distribution in sediments and surface water of the Moheshkhali channel of Bangladesh, Bay of Bengal, along with their shape, size, color, and polymeric analysis. It has been observed that both sediments and surface water are significantly contaminated with microplastics at 14 sediments and 12 surface water sampling sites. 291 particles of microplastic were observed in two quadrants, separated 10-m away from each other, across 14 sediment sampling sites, with average concentrations registered in the range of 6.66 to 138.33 particles/m2. At the same time, 163 particles were observed across 12 sampling sites in the surface water, ranging from 0 to ~0.1 particles/m3. Various shapes, like films, fragments, fiber/lines, foams, and pellets (resins), were observed extensively in the Moheshkhali channel. Besides, various risk assessments, like contamination factors, polymeric risk assessment, pollution risk index, and pollution load index, were analyzed for each sampling site across the channel. Pollution load index (PLI) of shore sediments and surface water were 2.51 and 1.67, respectively, indicating significant pollution in the Moheshkhali channel. This research investigation provides insight into anthropogenic activities and baseline microplastic pollution in the Moheshkhali channel of Bangladesh, which helps to prepare robust strategies for conservation and management to deal with such environmental issues.

Baseline marine litter abundance and distribution on Saint Martin Island, Bay of Bengal, Bangladesh.

Baseline marine litter abundance and distribution on Saint Martin Island, Bay of Bengal, were assessed. Seventy-two transects (100-150 m) along 12 km of coastline were surveyed for litter items every two weeks for two months. The most abundant items were polythene bags, food wrappers, plastic bottles/caps, straws, styrofoam, plastic cups, plastic fragments, fishing nets, clothes, and rubber buoys. Tourism, local markets, hotels, domestic waste, and fishing activities were primary sources of marine litter. According to the mean clean coast index (CCI), all transects were clean, of which 11.3 % and 14.1 % of sandy beaches and rocky shores with sandy beaches were reported dirty, respectively. Northern Saint Martin Island comprised sandy beaches (2.8 %) and was extremely dirty. In addition, plastic abundance index (PAI) analysis showed that 24 % of sites, out of 72 sites, were under "very high abundance", 33 % were "high abundance", 33 % showed "moderate abundance", and 4 % were classified as "low abundance". Establishing baseline results of marine litter abundance and distribution on Saint Martin Island may help improve island conservation and mitigation strategies (e.g., improved waste management, beach cleaning activities to raise public awareness, local government litter reduction policies, and increase local pro-environmental behavioral change).

Occurrence, spatial distribution, and risk assessment of microplastics in surface water and sediments of Saint Martin Island in the Bay of Bengal.

Microplastics (MPs) are emerging contaminants in aquatic and terrestrial ecosystems and have caused substantial concern worldwide. This study surveyed the presence of MPs in surface water and sediments across the coastal area of Saint Martin Island in the Bay of Bengal. MPs were collected following the standard protocol and identified as various types like expanded polystyrene, foam, filaments, fragments, lines, fibres, and paint flakes. Total MPs pollution in beach sediment was 317 particles/kg across 14 sampling sites, varied from 11 to 10589 particles/m2 of dry sediment and 0.95 particles/m3, having ~2 to 19 particles/30 min trawl in coastal surface water samples. Most of the frequent MPs in beach sediments ranged from 1.0 to 2.0 mm, whereas the fragments were predominant in sediment and surface water samples. MPs distribution revealed that different shapes were dominant at different sites within the Island. The calculated pollution risk index due to the presence of MPs indicated that the sediment and surface water samples were under the low-risk category. However, polymeric risk assessment and contamination factors suggest that the coastline is significantly polluted, as high pollution load indices (PLI >1) were observed for sediments and coastal surface water samples. This work provides the detailed MPs data in the coastal environment of Saint Martin Island for the first time; hence it may be helpful to develop proper strategies to deal with environmental problems.