Effects of the microplastics in plastics feeding and fecal pellets sinking rates for the marine copepod Calanus sinicus

Abstract

Plastic debris is prevalent in marine across worldwide and it has been recognized that it affects marine ecosystem and organisms especially by consuming. Microplastics could be attached with harmful chemicals and carry to zooplankton by feeding. Depending on their sizes, microplastics might be bioaccumulation or be excreted by fecal pellets, and those pellets also could be ingested for marine organisms. Thus, we investigated the effects of microplastics for plastics feeding rates and fecal pellets sinking rates of marine copepod Calanus sinicus according to three diameters (0.5, 6.0, 20.0 μm) and two mass concentrations (500, 5000 mg/m³). We collected C. sinicus from The East Sea (35°03’32.4”N, 129°06’32.5”E) and feeding fluorescence labeled microplastics with three algae Thalassiosira weissiflogii, Chaetocerus simplex and Isocrysis galbana. After 18 hours, we calculated the feeding rates by counting the number of total pellets and microplastics in pellets. And then, we investigated sinking rates by dropping the pellets into filtered seawater and measuring sinking velocity. Subsequently, we measured length and diameter of pellets and calculated pellet density by Stoke’s law. The weight and number of microplastics were significantly higher at high than low concentration. The number of 0.5 μm diameter microplastics was detected the most, however the weight of 20.0 μm diameter was calculated the heaviest. Also, feeding rates were measured the highest at the low concentration of 20.0 μm diameter. Sinking rates were significantly decreased except at low concentration of 0.5 and 20.0 μm diameter microplastics and density was significantly decreased at high concentration of 0.5 and 20.0 μm diameter. In this study we could be suggested that C. sinicus could ingest microplastics and discharged by fecal pellets. Microplastics almost decrease fecal pellets sinking rates and it could cause other marine organisms more likely to feed and adverse effect would be appeared.