Mangrove mud clam as an effective sentinel species for monitoring changes in coastal microplastic pollution

Abstract

The worldwide mangrove shorelines are experiencing considerable contamination from microplastics (MPs). Finding an effective sentinel species in the mangrove ecosystem is crucial for early warning of ecological and human health risks posed by coastal microplastic pollution. This study collected 186 specimens of the widely distributed mangrove clam (Geloina expansa, Solander, 1786) from 18 stations along the Leizhou Peninsula, the largest mangrove coast in Southern China. This study discovered that mangrove mud clams accumulated a relatively high abundance of MPs (2.96 [1.61 – 6.03] items · g-1) in their soft tissue, wet weight, as compared to previously reported levels in bivalves. MPs abundance is significantly (p < 0.05 or 0.0001) influenced by coastal urban development, aquaculture, and shell size. Furthermore, the aggregated MPs exhibit a significantly high polymer risk index (Level III, H = 353.83). The estimated annual intake risk (EAI) from resident consumption, as calculated via a specific questionnaire survey, was at a moderate level (990 – 2,475, items ·g -1 ·Capita -1). However, the EAI based on suggested nutritional standards is very high, reaching 113,990 (79,298 – 148,681), items · g -1 · Capita -1. We recommend utilizing the mangrove mud clam as sentinel species for the monitoring of MPs pollution changing across global coastlines. Environmental ImplicationMicroplastics are pervasive pollutants in the marine environment, posing a threat to ecological and human food safety. In addition to physical impacts such as gut blockage, there is growing evidence of the cytotoxic and genotoxic effects of microplastics. The mangrove mud clam, which lives in the landward frontiers of coastlines around the world, is exposed to relatively high environmental concentrations of microplastics. This study found significant effects of coastal human activities on the accumulation of microplastics in mangrove mud clams. The mangrove mud clam can serve as an effective sentinel species for early detection of microplastic accumulation risks in coastlines worldwide.