Exploring the Presence of Microplastics in Salt Creek

Rising concerns of microplastics, defined as synthetic polymeric materials less than 5 mm in diameter, have emerged over the past several years, due to the many potential and known negative implications on the ecosystem. While a great deal of research has taken place in marine ecosystems, very little work has been done in watersheds. Therefore, studies were carried out in the Salt Creek (IN), Lake Michigan watershed in effort to determine the type and extent of synthetic polymers present. Sediment and water samples have been collected, screened, and processed mostly by wet peroxide oxidation (WPO) to isolate microplastics from natural organic matter (NOM). Water sampling for microplastics was performed using a 300 µm plankton net suspended on the surface of the waterway, after which the material was processes similar to the sediment collections. For nearly all the samples, plastic presence was confirmed using microscopic evidence, infrared spectroscopy, and/or Raman spectroscopy. The presence of microfibers in macroinvertebrates was also studied; blackfly and caddisfly larvae were collected above and below the wastewater treatment plant to assess the effects of wastewater discharge on filter feeders. Microfibers are found in the macroinvertebrates, and the effects of the watershed location are still underway. The longer term goal of the work is to assess the effects of microplastics on more aspects of the ecosystem.