Anthropogenic microfiber pollution (small thread-like pieces of microplastic and organic material <5mm in size) can pose a significant threat to urban rivers. However, we often lack an understanding of how tributaries contribute to anthropogenic microfiber pollution in urban rivers. In this study, we examined how anthropogenic microfiber presence and abundance varied in six tributaries of the Cumberland River in Nashville, TN, USA in spring 2022. To do this, we collected grab samples from the six tributaries at four different time points and counted the number of anthropogenic microfibers found across sites and time (n=96 samples). For each of the 96 samples, we counted the number of anthropogenic microfibers by pouring our water samples into steel sieves with three different sizes (5.00, 1.02, and 0.38mm) and doing grid searches with both a dissecting scope and a Nightsea Microscope Adapter with royal blue excitation filter. Over the course of the study, there were anthropogenic microfibers present at all sites and all time points. These findings demonstrate that anthropogenic microfiber pollution is common in tributaries and can be an important source of pollution for urban rivers. 

We collected grab samples from six tributaries at four different time points (n=96 samples). We then counted the total number of anthropogenic microfibers for three different size categories (5.00, 1.02, and 0.38mm). We also did two experiments in the research to control for the number of anthropogenic microfibers that could have contaminated the study and used this to provided corrected values.  All of these raw and corrected values are provided here.