Species-specific microplastic ingestion responses to biofilm in Eastern Tropical Pacific zooplankton

Microplastics are pervasive in pelagic environments and overlap in size with zooplankton prey, resulting in widespread ingestion. Responses may vary among species due to feeding traits. We tested ingestion responses to surface conditioning (clean vs biofilm-covered) of fluorescent polyethylene microspheres (38-45 μm; 10 Ms mL^-1) under natural food conditions during short-term exposure (2 h) in three tropical zooplankton: Subeucalanus crassus, Centropages furcatus, and Euphausia distinguenda. We hypothesized species-specific responses, with copepods favoring biofilm-covered particles and the euphausiid showing no preference. In S. crassus, ingestion occurred in 50% of individuals with biofilm and 0% with clean particles (p = 0.063). In C. furcatus, ingestion occurred in 67% with clean and 0% with biofilm (p = 0.019). In E. distinguenda, ingestion was similar across treatments (p = 0.588). These results suggest species-specific differences in early-stage ingestion responses to particle surface condition, including responses that deviate from expected trait-based predictions.