Microplastic accumulation in marine organisms across trophic levels along the west coast of India

Plastic pollution is a growing global concern, posing a significant threat to marine organisms as well as a health concern in commercial fisheries. However, there is a lack of research on microplastic accumulation and biomagnification across trophic levels. This study aimed to compare the abundance and diversity of microplastics (MPs) across trophic levels and habitats at two locations on the west coast of India with varying anthropogenic pressure. We compared MPs levels in different tissues of the sampled organisms and investigated potential biomagnification across two trophic levels and differences across habitat types (benthic and pelagic) at these locations. A total of 215 individuals from both locations were sampled and analysed for MPs. We found three types of MPs in our samples - fibres (92.16 %), fragments (1.19 %), and films (6.65 %) - which were of a variety of colours. Transparent fibres, likely derived from degraded fishing lines and nets, were the most abundant type of MP. A negative binomial generalized linear model showed no difference in MP concentrations between benthic and pelagic sharks or between locations, suggesting a similar level of exposure. However, lower trophic levels contained on average two to two-and-a-half times more MPs than higher trophic levels at both sites. Tissue-specific differences were also apparent: in lower trophic levels, the liver accumulated 58 % more MPs than the GI tract, whereas in higher trophic levels, the GI tract accumulated 40 % more MPs than the liver. While there was no evidence for biomagnification at the two locations, the differential accumulation in tissues provides insights that are relevant for both human and fish health.