The Impact of Polystyrene Microplastics on Feeding, Function and Fecundity in the Marine Copepod <i>Calanus helgolandicus</i>

TLDR

Microplastics are an escalating environmental concern, with zooplankton such as copepods known to ingest them, and copepods serve as a key trophic link between primary producers and higher marine organisms. A conceptual energetic (carbon) budget indicates that microplastic exposure leads to progressive energetic depletion in copepods. Exposure to 20 µm polystyrene beads reduced algal ingestion by 11 % and carbon biomass by 40 %, shifted prey size toward smaller cells, increased ingestion of the smallest size class, and over prolonged exposure lowered reproductive output without affecting egg production, respiration, or survival, demonstrating that microplastics impair feeding and may sustain reductions in ingested carbon biomass.

Abstract

Microscopic plastic debris, termed “microplastics”, are of increasing environmental concern. Recent studies have demonstrated that a range of zooplankton, including copepods, can ingest microplastics. Copepods are a globally abundant class of zooplankton that form a key trophic link between primary producers and higher trophic marine organisms. Here we demonstrate that ingestion of microplastics can significantly alter the feeding capacity of the pelagic copepod Calanus helgolandicus. Exposed to 20 μm polystyrene beads (75 microplastics mL(–1)) and cultured algae ([250 μg C L(–1)) for 24 h, C. helgolandicus ingested 11% fewer algal cells (P = 0.33) and 40% less carbon biomass (P < 0.01). There was a net downward shift in the mean size of algal prey consumed (P < 0.001), with a 3.6 fold increase in ingestion rate for the smallest size class of algal prey (11.6–12.6 μm), suggestive of postcapture or postingestion rejection. Prolonged exposure to polystyrene microplastics significantly decreased reproductive output, but there were no significant differences in egg production rates, respiration or survival. We constructed a conceptual energetic (carbon) budget showing that microplastic-exposed copepods suffer energetic depletion over time. We conclude that microplastics impede feeding in copepods, which over time could lead to sustained reductions in ingested carbon biomass.