Lisa Kim Project Description
THE EFFECT OF PLASTIC ON LEAF LITTER BREAKDOWN IN URBAN STREAMS
The plastic component of anthropogenic litter (AL) is an emerging ecological concern and has been a focus of research, as it is long-lived, mobile, interacts with physical and chemical components of aquatic ecosystems, and breaks down into smaller pieces (i.e., microplastic, <5mm particles). Rivers are considered a major source of plastic to oceans, but little is known about its abundance, distribution, and effects on ecological processes in urban streams. Previous studies report plastic is abundant in these areas, especially in naturally occurring debris dam structure and overhanging vegetation that accumulate high quantities of AL, especially plastic items (i.e. bags, wrappers, packaging material), along with leaf litter and other coarse particulate organic matter. In temperate, forested streams, leaf litter is a critical food source and plays an essential role in the stream food web. The rate at which leaves break down is affected by many variables such as hydrology, water chemistry, and macroinvertebrate and microbial communities. Plastic accumulation along with leaf litter can slow leaf breakdown by reducing diversity and abundance of microbial decomposers, as well as macroinvertebrate consumers. We measured leaf breakdown, macroinvertebrate and microbial (i.e., bacterial, fungal, algal) communities in 3 litter bag treatments: leaves alone, plastic alone, and mixed. Although plastic did not reduce leaf breakdown rates or have a significant effect on macroinvertebrate consumer community, it showed distinct microbial communities compared to leaf substrates. Results will provide a new understanding of how plastic and microbial communities interact, and set the framework for future studies to look at microbial succession and macroinvertebrate diversity on other synthetic substrates in freshwater systems.