Progress report for
Assessment of microplastics in coral reef ecosystem of Gulf of Mannar, India
Achievement at a glance
Samples of sediment and water, 130 numbers each, were collected from 21 locations along the 160 km long coast covering the coral reef areas (mainland and islands) of Gulf of Mannar, Southern India to study the abundance, characteristics and surface degradation features of microplastics (MP). Analysis of the samples from the southern Gulf of Mannar area show that the mean abundance of MP varies from 6054 to 126.697 items/L in subsurface water, and from 5029to 103.8 87 items/kg in sediment. The highest MP concentrations were observed in the mainland samples. MP distributions in the shoreward direction of the islands closely reflect those of mainland. Ten different types of polymers were identified across all samples collected, with polyethylene (PE) being the most common. MP fibres (1-3 mm) were the most abundant form in water samples, while MP fragments (3-5 mm) were the most abundant in sediment samples. Analysis of selected MPs using scanning electron microscopy combined with energy dispersive X-ray spectroscopy (SEM-EDAX) highlights the presence of cracks, protrusions and depositions on the surface of many MPs, indicating their partial degradation through weathering processes. EDAX analysis frequently showed the presence of Ni, Cd, Pb, Zn and Fe associated with MP surfaces.We also carried out an investigation of microplastics in the clam (Donax sp.), and water and sediment from its habitat (inter-tidal area) from 11 sites in the study area. Clams were grouped under three categories [Type 1 (<1 cm), Type 2 (1-2 cm), Type 3 (3-4 cm)]. Microplastics were found at concentrations ranging from 0.9-6.5 items/g and 0.6-1.3 items/individual) in clam species, 10-30 items/l in water and 24-235 items/kg in sediment. Fibres were the most dominant MP types accounting for 40-100% in clams across all sampling sites.
The analysis of the remaining water and sediment samples is in progress.
Challenges faced in implementation
The major challenges are 1). Collection of voluminous samples along the 160 km long coast; and 2). Analysis of samples involves much labour.Beneficiaries
This study offers an insight into the level of MP (and associated elements) exposure to which the filter-feeding corals in the region are subjected, suggesting that the current MP contamination represents an exposure risk and that corals may facilitate their uptake. The results will suggest appropriate management practices to conservation managers and policy-makers in order to reduce the impacts of microplastics in the coral reef areas.