ANTHROPOGENIC MARINE DEBRIS ACCUMULATION IN MANGROVES ON PENANG ISLAND, MALAYSIA

Knowledge on anthropogenic marine debris (AMD) distribution and accumulation dynamics in mangroves is limited. To address this shortfall, abundance, sorting, and diversity parameters of AMD were evaluated in Penang’s urban and peri-urban mangroves. Debris were counted and classified across transects parallel to the coastline at progressively higher water marks. Plastic percentages make most of the AMD across all sites. More AMD were retained in the urban sites, consistent with larger population density. Diversity of debris was consistent with land use and livelihood of the population in each area. The greatest differences in abundance, diversity, and evenness were recorded between the lower intertidal zones and the remaining inner transects consistent with sorting towards the coastal edge in favour of plastic items. Differences across transects and sites suggested: 1) the main body of the mangrove efficiently retained debris with little sorting; and 2) debris deposited closer to the edge are increasingly sorted and lost to the water body in favour of smaller plastic items. The findings show that mangroves are vulnerable to accumulation and retention of potentially harmful debris, with evidence of a less efficient retention and selective sorting of materials back to the water body closer to their coastal edges.