Size Matters: Ingestion of Relatively Large Microplastics Contaminated with Environmental Pollutants Posed Little Risk for Fish Health and Fillet Quality

Occurrence and distribution of microplastics in the surface water and sediment of two typical estuaries in Bohai Bay, China

Estuaries are considered to be seriously polluted by microplastics. As the most important water body in North China, the pollution level of microplastics in two typical estuaries (Haihe Estuary (HHE) and Yondingxinhe Estuary (YDXE)) of Bohai Bay is not well understood. The occurrence and distribution of microplastics in the surface water and sediment of HHE and YDXE were investigated. The mean concentration of microplastics in surface-water samples was 1485.7 ± 819.9 items per m3 for HHE and 788.0 ± 464.2 items per m3 for YDXE, respectively, whereas the concentration of microplastics in sediment was 216.1 ± 92.1 items per kg dw for HHE and 85.0 ± 40.1 items per kg dw for YDXE, respectively. The concentration of microplastics in surface-water and sediment-samples of HHE was higher than that of YDXE, though YDXE is a typical sewage-received river. Anthropogenic activities and the river input were the main sources of microplastic pollution in estuarine areas. Sewage rivers could be point sources of microplastic pollution on a small scale. The small size (particle diameter < 1 mm) of microplastics was a dominant feature, the most abundant shape was fiber and colored microplastics were found widely in YDXE and HHE. We provided detailed information on microplastic pollution to support their control and management in HHE and YDXE.

Rainbow Trout Maintain Intestinal Transport and Barrier Functions Following Exposure to Polystyrene Microplastics

Ingestion has been proposed as a prominent exposure route for plastic debris in aquatic organisms, including fish. While the consequences of ingestion of large plastic litter are mostly understood, the impacts resulting from ingestion of microplastics (MPs) are largely unknown. We designed a study that aimed to assess impacts of MPs on fish intestinal physiology and examined integrity of extrinsic, physical and immunological barriers. Rainbow trout were exposed to polystyrene (PS) MPs (100-400 μm) via feed for a period of 4 weeks. Fish were fed four types of diets: control, diets containing virgin PS particles, or particles exposed to two different environmental matrices (sewage or harbor effluent). Extrinsic barrier disturbance in intestinal tissue was evaluated via histology. The paracellular permeability toward ions and molecules was examined using Ussing chambers and mRNA expression analysis of tight junction proteins. Active transport was monitored as transepithelial potential difference, short-circuits current and uptake rate of amino acid ³H-lysine. Immune status parameters were measured through mRNA expression level of cytokines, lysozyme activity, and hematological analysis of immune cells. We could not show that PS MPs induced inflammatory responses or acted as physical or chemical hazards upon ingestion. No measurable effects were exerted on fish intestinal permeability, active transport or electrophysiology.