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Microplastics (MPs) pose one of the major environmental threats to marine organisms and ecosystems on a global scale. The present study investigated MPs in surface water, beach sediments, and fish in two coastal areas of Bangladesh namely Cox's Bazar and Kuakata. The MPs were identified and characterized using three different techniques, including the binocular microscope, the ATR-FTIR (Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy), and SEM-EDS (Scanning Electron Microscopy- Energy Dispersive Spectroscopy). The number of MPs in seawater was 10.1 ± 3.10 and 8.52 ± 3.92 items/100 L and in beach sediment, 13.2 ± 3.68 and 9.48 ± 3.63 items/100 g in Cox's Bazar and Kuakata, respectively. In fish samples, the abundance of MPs was 7.82 ± 1.28 and 6.82 ± 1.87 items/individual species of Cox's Bazar and Kuakata, respectively, where the highest quantities of MP were found in Euthynnus affinis and Sillago sihama and the lowest in Terapon jarbua and Pampus chinensis in Cox's Bazar and Kuakata, respectively. The number of MPs in GITs (Gastrointestinal tracts) was 1.63 ± 0.991 and 1.25 ± 0.546 items/g GIT and in BW (Body Weight) were 0.042 ± 0.014 and 0.037 ± 0.014 items/g BW in Cox's Bazar and Kuakata, respectively. There revealed a positive correlation between MP abundance and GIT weight and body weight in fish species. MPs were predominantly fiber-shaped, white/transparent, and small size. The most common MP polymers were polyethylene and polypropylene. SEM images of MPs demonstrate surface roughness, cracks, mechanical weathering and oxidative weathering, demonstrating their ongoing environmental exposure. The EDS spectrum unearthed that the MPs contained several elements (C, N, O, Na, Al, Fe, and Si). Findings from this study might be useful in coastal plastic particle management and to mitigate the potential risks associated with them. [Display omitted] • MPs were investigated in water, sediment and fish along the coast of Bangladesh. • Concentration of MP in fish was positively correlated with GIT and body weight. • Fiber, white/transparent and small sizes MPs were most dominant in the samples. • Polyethylene and Polypropylene were the most common polymers. • MPs had rough surface, cracks, foreign materials and elements like Na, Al, Fe and Si etc. [ABSTRACT FROM AUTHOR]

This study was carried out to assess the levels of trace metals (Fe, Zn, Mn and Cu) in the macroalgae and sediment of the Sundarban mangrove estuary in Bangladesh. In this connection, macroalgae, water and sediment samples were collected seasonally (pre-monsoon, monsoon and post-monsoon) for a year from the study area. The surface water of the estuary was found to be quite rich in NO3, PO4 and NH4, which is more than that of the sediment pore water. Trace elements were determined using an atomic absorption spectrophotometer. The amount of trace metals in the samples were found in the order of Fe > Mn > Zn > Cu. Enrichment factor was done for trace metals in sediment and showed non-crustal origin of Zn and Cu in the monsoon period. Analysis of variance revealed the seasonal variation of trace metal concentration in sediment (except Mn; p > 0.05) and macroalgae (except Zn; p > 0.05). Iron in sediment showed significant positive correlation both with Fe (r = 0.84, p < 0.05) and Mn (r = 0.87, p < 0.01) in macroalgae. Similarly, Cu in sediment demonstrated a significant positive correlation with Cu in macroalgae (r = 0.81, p < 0.01). The findings reveal a significant communication of metals in sediment and macroalgae. [ABSTRACT FROM AUTHOR]

Being a resourceful ecosystem, mangrove estuaries have always been subjected to trace elements (TEs) contamination, and therefore, the biomonitoring approach holds immense potential for surveilling the aquatic environment. To investigate the potentiality of mangrove macroalgae as biomonitors, estuarine water, intertidal-sediment, and macroalgal samples were collected from the Pasur River estuary of Sundarbans mangrove ecosystem, Bangladesh, and afterward studied through Atomic Absorption Spectrometer to quantify the levels of six concerned TEs (Fe, Mn, Zn, Cu, Pb, and Cd). This study utilized the geo-environmental and ecological indices and sediment characterization approaches (sediment quality guidelines-SQGs) for assessing the contamination scenario of the adjacent environment to macroalgae whereas the performance of studied algal groups was evaluated using Bio-contamination factor, Comprehensive bio-concentration index, and Metal accumulation index. Metal occurrence scheme in the water followed the order of Fe > Zn > Mn > Pb > Cd while Fe > Mn > Zn > Cu > Pb > Cd for both sediment and macroalgae. Both Pb and Cd exceeded the guideline limit in estuarine water and the indices approach manifested low to moderate contamination with enrichment from anthropogenic origin of Mn, Zn, and Cu in sediment. Moreover, the SQGs revealed rare biological effects of Cu on an aquatic community. Within algal samples, Chlorophyta contributed the highest biomass production, followed by Phaeophyta and Rhodophyta. Statistical relationship disclosed the influence of environmental variables on TE's accumulation in Chlorophyta. By contrast, hydrochemical's association showed prevalence over the TEs accumulation process for Phaeophyta and Rhodophyta. Bioaccumulation performance analysis revealed that the ability to accumulate TEs in macroalgal groups varied with seasons. Therefore, biomonitoring with macroalgae for the region of interest might require further temporal considerations. [Display omitted] • Mangrove macroalgae were assessed as biomonitors for trace elements contamination. • Iron was abundant in estuarine water and sediment as well as in macroalgae. • Trace elements level was higher in algal taxa compared to water and sediment. • Seasonality was prevailing on the biomonitoring ability of algal taxa. [ABSTRACT FROM AUTHOR]