Microplastics (MPs) are a global environmental concern and pose a serious threat to marine ecosystems. This study aimed to determine the abundance and distribution of MPs in beach sediments (12 beaches), marine biota (6 beaches) and the influence of microbes on MPs degradation in eco-sensitive Palk Bay and Gulf of Mannar coast. The mean MP abundance 65.4 ± 39.8 particles/m² in beach sediments; 0.19 ± 1.3 particles/individual fish and 0.22 ± 0.11 particles g⁻¹ wet weight in barnacles. Polyethylene fragments (33.4%) and fibres (48%) were the most abundant MPs identified in sediments and finfish, respectively. Histopathological examination of fish has revealed health consequences such as respiratory system damage, epithelial degradation and enterocyte vacuolization. In addition, eight bacterial and seventeen fungal strains were isolated from the beached MPs. The results also indicated weathering of MPs due to microbial interactions. Model simulations helped in tracking the fate and transboundary landfall of spilled MPs across the Indian Ocean coastline after the X-Press Pearl disaster. Due to regional circulations induced by the monsoonal wind fields, a potential dispersal of pellets has occurred along the coast of Sri Lanka, but no landfall and ecological damage are predicted along the coast of India.

Halogenated polycyclic aromatic hydrocarbon (HPAH) concentrations in tissues from three tuna species Thunnus albacares (yellowfin tuna), Katsuwonus pelamis (skipjack tuna), and Auxis thazard (frigate tuna) were determined by high-resolution gas chromatography Orbitrap mass spectrometry. The tuna samples were collected from the Indian Ocean. The instrument conditions gave high mass accuracy at 0.9 m/z isolation width of the mass filter and a mass error of <±1.0 ppm for many HPAHs. A total of 29 of the 30 targets chlorinated PAHs (ClPAHs) and 20 of the 21 targets brominated PAHs (BrPAHs) were detected in the tuna muscle samples. The mean total ClPAH, BrPAH and PAH concentrations for tuna were 127.2, 156.6 and 682.8 ng/g lipid weight, respectively. The mean total ClPAH and BrPAH concentrations (ng/g lipid weight) in the tuna were considerably lower than that of PAH concentrations. The mean total ClPAH, BrPAH and PAH concentrations in T. albacares respectively were 185.8, 249.2 and 784.1 ng/g lipid weight, irrespective of the body sizes. The mean total ClPAH, BrPAH and PAH concentrations in K. pelamis respectively were 45.1, 24.8 and 555.6 ng/g lipid weight. The mean total ClPAH, BrPAH and PAH concentrations in A. thazard respectively were 34.09, 4.73 and 433.24 ng/g lipid weight. The total ClPAH concentrations and body weights significantly positively correlated for T. albacares. The mean total ClPAH concentration in white muscles was significantly higher (p < 0.05) for large than for small T. albacares. This suggests ClPAHs could bioaccumulate in T. albacares, possibly because they are poorly metabolized. The chlorinated phenanthrene and pyrene concentrations indicated tuna accumulate these compounds increasingly effectively as the tuna grow. This was the first time large numbers of HPAHs were found in biological samples. HPAHs may adversely affect the health of humans consuming tuna.

The objective of the research was to assess the spatio-temporal variation of plastic pellets dispersion in the coastline of Sri Lanka concerning the most tragic maritime accident of the cargo vessel; MV X-Press Pearl. Field sampling was carried in three intensive surveys during May and July 2021. A dry sieving procedure was employed to separate pellets followed by a chemical characterization using Fourier transform infrared spectroscopic analysis. A pellet pollution index (PPI) was determined to compare the degree of pellet pollution. The dispersion peaked two weeks after the spill, with severe pollution levels (PPI: Extreme) found in about 40 % of the coastal stretch from Matara to Kalpitiya. The occurrence of pellets was lower on the Northeast coast of the island compared to the South-west coast. No pellets were recorded from the Northern coast (PPI: Very low). The connection between pollution levels and upper ocean dynamics were explored, with the findings being utilized to track plastic pellets for future spills.

Tributyltin (TBT) is a toxic organotin compound that belongs to the group of Persistent Organic Pollutants (POPs) and it is documented to cause severe sexual disorders development in aquatic fauna. According to the present study, The TBT concentration in coastal water ranged from 303 ± 7.4 ngL⁻¹ to 25 ± 4.2 ngL⁻¹ wherein sediment was from 107 ± 4.1 ngKg⁻¹ to 17 ± 1.4 ngKg⁻¹. TBT in Perna viridis was found to range from 4 ± 1.2 ngKg⁻¹ to 42 ± 2.2 ngKg⁻¹ wet weight and in ascending order of the body weight. The highest TBT level in water and sediment was found in the Colombo port where the highest level of TBT in P. viridis (42 ± 2.2 ngKg⁻¹) was recorded from the Dikkowita fishery harbor. A positive correlation between the number of male P. viridis and TBT level (p < 0.05) suggests possible reproductive impairment in aquatic animals exposed continuously to a high concentration of TBT.

The abundance of microplastics (MPs) in surface water and beach sediment in Southern Sri Lanka covering a distance of 91 km of coastline is reported. MPs were classified according to polymer type, geometry and color of the sites tested 60% showed MP contamination in sand and 70% in surface waters off the coast. The size range of MPs from surface waters and beaches were to 1.5–2.5 mm and 3–4.5 mm, respectively. Majority of these were identified as polyethylene (PE) and polypropylene (PP) with some polystyrene (PS) foam at a few sites. Fragments derived from larger debris appears to be the dominant type of MP at most sites and only 2 sites showed virgin pellets that accounted for 14% of the samples collected.

This study provides the first analysis and quantification of MPs in salt products in Sri Lanka. Commercial table salt brands, rock salt, lab-grade NaCl and raw salt from three salterns were analysed using microscopy and Fourier transform infrared spectroscopy. All salt samples were contaminated with MPs: in commercial salts products it ranged from 11 to 193 items/kg, rock salts had 64 items/kg and lab grade NaCl had 253 ± 8.9 items/kg. The MP levels in salterns varied significantly: Hambantota 3345.7 ± 311.4 items/kg, Puttalam 272.3 ± 10.6 items/kg, and Elephant Pass 36.3 ± 4.5 items/kg. Predominantly, MPs were presented as fibres, followed by fragments. Of the 23 polymer types identified; low-density polyethylene (LDPE; 17%), resin dispersion (15%) and high-density polyethylene (HDPE; 12%) were notable. This study provides the first comparison of MPs in raw salt and commercial salt. This information is important to trace the pollutant sources and then to take steps to eliminate MPs in food products consumed.

We present a viewpoint regarding the prospects in Sri Lanka (a tropical island nation) to depend on mangroves in the remediation of heavy metal laden coastal environments. Sri Lanka has a rich array of lagoons and estuaries (total extent of 1580.17 km²) with ideal brackish water habitats to allow mangrove proliferation and for more restoration works. Furthermore, our estimates of Total Potential Ecological Risk (PER < 150) indicate that ecological risk from metallic contamination of coastal sediments is low, which means mangrove ecosystems would be ideal natural treatment systems for such low polluting environments (but as final cum tertiary treatment systems only). Mangroves are neither metal hyperaccumulators nor good phytoremediators (no ability to take up more than 5000 mg/kg dry weight of a given metal or exhibit a bioconcentration factor ≥ 1000), which means not very effective for high polluting environments.

Abundance of buried microplastics in sand profiles and pellet pollution index at Sarakkuwa beach, at west-coast of Sri Lanka was studied as a case study due to the receival of plastic nurdles and debris from the MV X-Press Pearl ship disaster in May 2021. Sand collected at 7 locations to a depth of 2 m in different depths for a beach segment of 200 × 25 m² during October 2021 and sand samples obtained from beach surface during March 2020 from the same location were analyzed for microplastics. Beach was contaminated with 2–5 mm sized partially pyrolyzed LDPE fragments and nurdles demonstrating a peak abundance of 13.3702 g/kg and1 mm-500 μm sized LDPE fragments up to 2.0 m depth. High concentrations of Mo and Cr were observed in the sand collected in 2021. Sarakkuwa beach is critically polluted by nurdles, partially pyrolyzed microplastics, and toxic elements from ship disaster.

Sri Lanka is positioned as an important hub for international shipping. The recent naval accidents of MT New Diamond (in 2020) and MV X-Press Pearl (in 2021) suggest that the country is at risk for future maritime environmental disasters. However, Sri Lanka still has no adequate planning and regulation at the national policy level. Therefore, the objective of the current study is to formulate a national policy and contingency plan to augment maritime safety. This paper proposed the framework for the integrated coastal zone management in Sri Lanka, based on the national acts and laws, existing regulations, and analysis of international experiences. The integrated coastal zone management framework is proposed into four hierarchical levels. The proposed framework establishes a permanent coordination and management system for environmental assessment and sustainability of the coastal zone. This article describes requirements for coastal zone management, reasons for failures during recent naval accidents, possible drawbacks of implementing an integrated coastal zone management framework in Sri Lanka, and ways to overcome these challenges.

Microplastics (MPs) are ubiquitous in marine environment. The prevalence of MPs in coastal and lagoon sediments, and water were studied in two Marine Protected Areas (MPAs); Bundala National Park (BNP) and Hikkaduwa Marine National Park (HNP) in Sri Lanka. Both areas are important for turtles, birds and coral ecosystems, all of which are particularly threatened by MPs. Abundance of MPs was generally higher in both coastal sediments and waters in HNP (111±29 MPs/m² for sediments and 0.515±0.054 MPs/m³ for water) than in the BNP (102±16 MPs/m² for sediments and 0.276±0.077 MPs/m³ for water). The most common shape and polymer type of MPs were fragments and Polyethylene respectively. This research is the first to survey MPs in MPAs in Sri Lanka and provides a baseline of MPs pollution in these environments for future research and management.