Examining How Tributaries Contribute to Anthropogenic Microfiber and Microplastic Pollution in an Urban Watershed in Nashville, TN, USA

Recent research has shown that urban rivers often have large amounts of anthropogenic microfiber pollution (i.e. small thread-like pieces of litter that are most often microplastics and are <5 mm in size). However, there is often a limited understanding of how tributaries and streams that flow into urban rivers contribute to these amounts. This study examined how the presence and abundance of anthropogenic microfiber pollution varied in six tributaries of the Cumberland River in Nashville, TN, USA which is a growing city with more than 2 million residents in the metropolitan area. To examine how anthropogenic microfiber pollution levels varied, surface water samples were collected over the course of two months in Spring 2022 from six tributaries in the Richland Creek Watershed ( n = 96 samples total). Over the course of the study, anthropogenic microfibers were found in all tributaries and at all time points and at abundances that are similar to many other smaller tributaries and creeks that have been previously studied (mean of 96 samples = 17.4 microfibers/L or 17,400/m 3 ). Interestingly, there were no significant differences between the individual tributaries or across the four sampling time periods in anthropogenic microfiber pollution abundance. However, the consistent levels of anthropogenic microfibers found supports recent research which suggests that this type of pollution represents an important threat in urban aquatic ecosystems.