Polyhydroxyalkanoate (PHA) Straws and Grazers (Cerithium atratum) in Tampa Bay Marine Environment 

Abstract

Microplastic pollution poses a risk to ecosystems within Tampa Bay. Consequently, plastic alternatives are becoming increasingly popular, including a polyhydroxyalkanoate-based (PHA) straw that is certified as marine biodegradable. However, our previous studies have found that these straws remain largely intact after 58 days, regardless of light exposure conditions. As PHA straws are designed to sink, they may persist for long time periods on the sea floor, where benthic organisms may interact with them. The aim of this study was to evaluate the influence of the Florida Cerith (Cerithium atratum), a local benthic grazing snail, on the degradation of PHA straws and to determine if plastic particles are being ingested by the snails. Straws were held, both with and without snails, in jars of 5µm-filtered seawater replicating Tampa Bay summer conditions. After 104 days—including 88 days of grazing exposure—measurements of the mass and thickness of straws indicated degradation. Additionally, fluorescent microscopy comparisons of fecal pellets from snails held with and without straws demonstrated that the feces of snails exposed to straws contained PHA microplastics. This work suggests that while PHA straws remain largely undegraded in marine environments, marine grazers are exposed to these straws and can ingest microplastic particles. These findings can inform local policy regarding the implications of using PHA-based products.