Microplastic distribution and ecological risk in water and sediments of marine ranching area in Haizhou Bay

The widespread existence of microplastics (MPs) in marine environment and organisms is always an undeniable fact, and more attention should be paid to its ecological risk. In this study, four areas (natural area (NA), comprehensive effective area (CEA), artificial area reef (AR), and aquaculture area (AA)) in the marine ranching area of Haizhou Bay (Lianyungang City, Jiangsu Province) were selected as a case study to quantitatively analyze the distribution and potential ecological risks of MPs in the surface water and sediment. The mean abundance of MPs in the surface water and sediment was 5.05 +/- 1.05 n/m(3) and 0.47 +/- 0.18 n/g, respectively. MPs were mostly < 5 mm (>98%), fibrous (water: 74%; sediment: 64%), blue (water: 41%; sediment: 47%), and polyethylene terephthalate (PET) (water: 42%; sediment: 52%). CEA had the highest MP abundance (P < 0.05) and MPs in CEA significantly correlated with other areas (P < 0.05). Under the effect of currents or tides, we judge that MPs in AA and AR will accumulate in CEA from the surface water and sediment, and their transfer process will be blocked in sediments of AR. According to the hazard score (H score) and pollution loading index (PLI), the MPs in this region have middle and upper levels of ecological risk. We believe that the ecological risks of MPs should be closely monitored, and some assessment indicators should be added to help control and mitigate MP pollution.