Tracking turds

Learn how DNA source tracking can be used to identify water quality concerns.

Local health officials have long been concerned about E.coli and other pathogenic bacteria because of their impacts on human health. When levels of E.coli in bodies of water are above what is determined to be safe, advisories are posted and regular recreation like swimming and fishing is discouraged. Michigan has an abundance of fresh water sources that are used for recreation and drinking water, but when those water sources are unsafe, it puts people's health and livelihoods at risk.

A couple of well-known sources that contribute to higher levels of E.coli and pathogenic bacteria in the water are failing septic systems, wildlife population booms, and improper manure management from livestock operations. DNA source tracking can be used to identify what animal is contributing to E.coli levels. Aaron Snell, a researcher from Streamside Ecological Services, has used DNA source tracking to provide detailed information about E.coli sources found in waterways throughout watersheds in the state of Michigan.

Sarah Fronczak and I had the opportunity to discuss some of these findings with Aaron. You can find the link to the recording below. We were able to chat about the Saginaw Bay region and learn a bit more about the work Aaron has done in Pine River. Located in mid-Michigan, the contamination of the Pine River has been a point of contention for both the agriculture sector and private landowners, with both sides claiming the other is responsible for the E.coli contamination.

When Snell analyzed samples collected in the Pine River, he found that sources the of E.coli were pigs, horses, cattle, and humans. He also was able to quantify how much DNA was found for each source as compared to the others. When asked about these findings, Snell said that he was surprised to find out that in a lot of cases, human was the prevalent source throughout our samples in that watershed.

Much of the human waste that ends up in the water is a result of failing septic systems. Septic systems at private homes - many around lakes, were not built for the load that they currently bear. Families are showering more and longer, washing their clothes more, and are using water softeners; all water intensive activities that may not have been expected when the home septic was initially installed. Many homeowners don’t know how to inspect the health of their septic system and this can lead to problems.

We discussed with Aaron, what impact his findings had on public perception. He mentioned that by revealing that the fecal contamination was coming from both humans and livestock, the residents should stop the finger pointing and realize this is something they must work on together. Unfortunately, this hasn’t been the case and the finger pointing has continued, making progress in the Pine River difficult.

To hear more about this podcast and others, listen to the Michigan Field Crops podcast channel for a new “In the Weeds” series exploring water quality farming. You will hear from farmers, agribusiness, and Michigan State University Extension educators. The podcast is available on Spotify, iTunes and embedded on the Field Crops Team website. New podcasts will be posted every week for this series. To receive notification on podcast posts, please subscribe to our channel: Michigan Field Crops.

This project is supported by the Environmental Protection Agency’s grant #00E02802, awarded to the Institute of Water Research at Michigan State University in partnership with The Nature Conservancy, Michigan Department of Agriculture and Rural Development (MDARD), Michigan Association of Conservation Districts (MACD), Michigan Farm Bureau (MFB), and Michigan State University Extension.

Did you find this article useful?