Abstract

The accumulation of plastic debris in waterways is an increasingly complex environmental problem due to the ubiquity and magnitude of plastic debris across freshwater ecosystems, along with the unknown impacts on ecosystems and public health. However, “plastic” is a catchall term for numerous polymers with unique physical and chemical properties. Further complicating the prediction of risk, plastic characteristics may change from environmental exposure, with changes in density, adsorption or leaching of toxins, and accumulation of biofilms that further influence material properties, fate and impact. Recent studies suggest that a substantial proportion of plastic entering freshwater systems is deposited in the benthos, where organisms may be exposed to plastic-associated toxins indirectly or through consumption by invertebrates and higher trophic levels. The presence of toxic materials may hinder crucial ecosystem functions carried out by microbes and invertebrates that are key drivers of benthic ecosystem function and benthic-pelagic coupling. This research addresses the diversity that exists among plastic polymers, and studies how the ecotoxicology of plastic varies both spatially and temporally in the environment. Using toxicity bioassays with the oligochaete Lumbriculus variegatus and microcosm experiments, I investigated the eco-toxicity and impacts on biogeochemistry of 6 common consumer plastics in pristine form and after aging in Lake Ontario and a stormwater pond in the watershed, and how the impacts of plastic on benthic organisms extends to impact ecosystem function. While all polymers studied had sublethal impacts on L. variegatus, there were unique impacts on nitrogen and phosphorus cycling and ecosystem metabolism among polymers. These effects shifted after environmental exposure and varied between sites, with some materials losing toxicity and others gaining, and unique impacts to biogeochemistry persisting over time. These results suggest that ecological impacts of plastic pollution are complex, varying among polymers, water bodies and exposure time.

Library of Congress Subject Headings

Microplastics--Environmental aspects; Microplastics--Toxicology; Freshwater ecology; Benthic ecology; Lumbriculus variegatus

Publication Date

7-22-2021

Document Type

Thesis

Student Type

Graduate

Degree Name

Environmental Science (MS)

Department, Program, or Center

Thomas H. Gosnell School of Life Sciences (COS)

Advisor

Anna Christina Tyler

Advisor/Committee Member

Matthew Hoffman

Advisor/Committee Member

Nathan Eddingsaas

Campus

RIT – Main Campus

Plan Codes

ENVS-MS

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