Online

Shore, Emily Ann

Biology

2020

M.S.

Microplastics (<5 mm) are ubiquitous in the global environment and are increasingly recognized as a biological hazard, particularly in the oceans. Due to the small and pervasive nature of these particles, zooplankton have been known to consume and egest microplastics. Though zooplankton play critical roles in marine food webs and in carbon storage through carbon rich fecal pellets, we know little about the effects of microplastics on early life stage growth, reproductive output, and carbon storage. Here, I investigated the effects of ingestion of low-density Polystyrene beads (5 [mu]m) by the copepod Acartia tonsa on (1) early life stage (naupliar) growth, (2) adult fecundity and egg quality, (3) and fecal characteristics. I further explore potential impacts on carbon storage and the biological pump. A. tonsa were reared in one of two treatments: a 1:1 ratio of microplastics to 501 [mu]g C L⁻¹ algae particles, or 501 [mu]g C L⁻¹ algae only. Nauplii exposed to microplastics had shorter body lengths; additionally, adults produced eggs with smaller diameters and excreted smaller, more fragmented fecal pellets. Contaminated fecal pellet sinking rates were calculated to be 3.73 times slower and 2.29 times smaller than without microplastics. These two factors resulted in 8.56 times less fecal volume settling in the benthos per day for contaminated fecal pellets compared to control fecal pellets. Shorter zooplankton body lengths could reduce zooplankton morphology and population sizes, and thus impact higher trophic levels that depend on zooplankton as the critical link to the energy generated by primary producers. Slower fecal sinking rates can result in lingering carbon in the euphotic zone and increase the chance of contaminated fecal pellet consumption by coprophagous organisms. Taken together, these results suggest that microplastic consumption by zooplankton can impact the oceanic food chain, and slow carbon storage.