CAREER: Anthropogenic litter reveals drivers of ecosystem processes in urban streams

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Accumulation of man-made trash in the oceans has received much public attention. Human trash includes plastic, fishing debris, and metal, which have negative effects on marine resources. For example, some trash can be ingested by organisms including birds and turtles, and plastic can break down into small particles that have unique toxic properties. The study of the origins, movement, and consumption of trash in the ocean has provided information about ocean currents and food webs. Research by this investigator has shown that trash in rivers can reach similar densities as in the oceans. However, the sources, movements, and influences on biological systems of human trash in rivers are unknown, and are needed to develop efficient prevention strategies and policies. Also, studying the ecology of trash in rivers may reveal previously unexplored controls on ecosystem structure and function. This study will be conducted in Chicago- and Baltimore-area rivers, and include students from high school, undergraduate, and graduate levels. Trash removal will be used by student teachers to develop lessons for teaching the scientific method across grade levels.This research will examine the ecosystem role of anthropogenic litter (AL) in 3 size classes by adapting fundamental tools used to measure communities of organisms and movement of organic matter. First, the role of large AL will be measured. Urban rivers typically have reduced channel complexity due to straightening and flood management. Large AL may act as an ?artificial reef,? providing habitat complexity and organic matter retention that is otherwise lacking, and thereby enhance biodiversity. Researchers will measure stream organism abundance at naturally occurring debris dams (i.e., wood) and at those generated by large AL. Next, this research will quantify interactions between AL and microbes. Bacteria, fungi, and algae carry out important biological activities in rivers, removing excess nutrients and providing food for insects and fish. Initial studies showed AL has unique microbial communities compared to natural surfaces. Experiments will test how microbes are affected by the structural and chemical properties of AL surfaces. Last, movement of intermediate-sized (e.g., shopping bags), and small AL (e.g., microplastic) will be examined. Initial research showed that AL in rivers is abundant and mobile, with some portion always moving downstream. Because AL attracts common toxic chemicals, its movement may be an overlooked pathway for delivery of toxins downstream and into food webs. This work will quantify inputs, outputs, and re-distribution of toxins on litter surfaces in urban streams.