Microplastics in the menu of Mediterranean zooplankton: Insights from the feeding response of the calanoid copepod Centropages typicus

Microplastic input into the ocean represents an increasing threat to marine biota and may endanger the functioning of marine ecosystems, especially in semi-enclosed basins, such as the Mediterranean Sea. The size spectrum of microplastics overlaps with that of nano-microplankton (2-200 mu m), thus potentially misleading suspension-feeding zooplankton, which represent a key trophic link in pelagic food webs. We investigated the effects of microplastics on the feeding performance of the copepod Centropages typicus in laboratory experiments. Adult females were incubated in natural prey assemblages under different conditions: without and with nutrient enrichment, and in the presence and absence of microplastics (20-1000 mu m). Non-significant changes were recorded in either copepod ingestion rates or daily rations upon microplastic addition. However, the copepod diet shifted significantly in the presence of microplastics, as the copepods fulfilled their individual carbon requirements by ingesting different protistan prey. The number of microplastic particles found in copepod guts (0.9 particles ind.(-1)) and fecal pellets (2.1 particles pellet(-1)) was low and particles occurred mostly in the lower size range (similar to 20 mu m). Overall, the exposure of C. typicus to microplastics did not affect the copepod daily intake of food, likely due to the avoidance of microplastics and flexible feeding habits.