Over the past several years our lab at Saginaw Valley State University has tested public beaches in Bay County, MI for fecal contamination. A trend has been seen relating a high level of contamination after a rainfall event. This poster will encompass a beach’s level of contamination in response to rainfall events in the summers of 2019, 2020, 2021, 2022. South Linwood Beach is connected to a series of drains that collect runoff from farmers’ fields and border several dense housing areas. Two separate methods were used to quantify the levels of fecal indicator bacteria, specifically Escherichia coli, which is associated with the lower intestine of warm-blooded organisms. The first was the historical standard Colilert, a culture-based method that requires overnight incubation, resulting in slow-turnaround for beach closing determinations. The second test, digital drop PCR (ddPCR), was used to measure E. coli DNA within a few hours of sampling. ddPCR methods can also be used to determine the sources of contamination, known as microbial source tracking (MST) by exploiting genetic differences in Bacteroides and other enteric microbes originating from humans, ruminants, avians, etc., each of which were detected at the South Linwood Beach and its nearby inlets. Based on comparison of rainfall and E.coli levels, there was indeed a trend of high levels of fecal contamination following precipation events, with the sources of this microbial contamination appearing to be a majority of gull and bovine markers. More beach sites should be studied in relation to contamination due to rainfall events.

Effects of rainfall events on microbial contamination at South Linwood public beach

Where thousands of chemistry professionals meet to share ideas and advance scientific and technical knowledge. Spring 2023 abstracts, posters, and presentations will launch at the end of March.

ACS Spring 2023

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.