Search

Microplastic (MP) pollution is an ongoing problem in coastal systems, where wastewater treatment plants (WWTPs) deposit particles daily. This study examined MP characteristics at WWTP outflow and control sites in St. Andrew Bay in Northwestern Florida, USA. WWTP sites contained mostly polypropylene fragments (180.1 μm avg. size), while reference sites contained polypropylene fragments, and polyethylene and polyester fibers (315.3 μm avg. size). MP sizes were strongly linked to distance from the nearest WWTP, while shape and polymer compositions were more closely related to dissolved oxygen concentrations and distance to the nearest water input source. The prevalence of polypropylene fragments at WWTP sites suggests that extreme weather events during the study flushed land-based debris into the system, where it was buried in the sediments. Increased abundances of polyester and polyethylene terephthalate in the winter at WWTP sites are indicative of the role that laundering synthetic textiles plays in coastal MP pollution., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Aaron Ridall reports financial support was provided by PADI Foundation. Aaron Ridall reports financial support was provided by Friends of Gumbo Limbo. Aaron Ridall reports financial support was provided by Southern Association of Marine Laboratories., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Wastewater treatment plants (WWTPs) cause approximately 25 % of microplastics (MPs) in the marine environment. While research on MPs in WWTP effluent has demonstrated that an abundance of particles enter the marine environment, little effort has gone to assessing MP abundances in coastal sediments to determine their seasonal and spatial variability. Here, we assessed MP abundances in sediments at sites of WWTP outflow and at non-polluted sites over six consecutive seasons within the St. Andrew Bay system in Northwestern Florida. We showed that MP abundances were highest at one of the WWTP sites, where they increased with increasing distance away from the input source (3.16 ± 1.59 MP/kg to 34.03 ± 11.69 MP/kg sediment dry weight). We also found that mean MP abundances were highest in the winter (12.41 ± 3.56 MPs/kg sediment dry weight) and lowest in the spring (2.17 ± 0.63 MPs/kg sediment dry weight). Therefore, while WWTPs differentially retain MPs in their removal processes, MP pollution in the St. Andrew Bay system shows seasonal dynamics like other studies. Although average MP abundance in surface sediments (0-5 cm) was higher than in subsurface sediments (5-10 cm) at all sites, this difference was not as substantial as has been found in other studies. Based on mean MP abundance in surface sediments, we estimate that there are 30 billion MPs within the surface layer of sediment in the St. Andrew Bay system, and that the particles export to the Gulf of Mexico because of seasonal flushing between the winter and spring. The distributions of MPs in the system were also likely driven by extreme weather events that occurred in the bay system during 2018 and 2020, which acts as a cautionary tale for coastal urban ecosystems in the face of sea level rise and climate change., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)