By: Carrie La Seur,
Legal Director —
Hey there, water lovers. It’s time for a little more plain talk about the mess that is the Pine River of central Michigan. No sooner had it begun to recover from toxic contamination than tens of thousands of cattle moved in upstream. Every year, millions of gallons of their waste is spread on farm fields that couldn’t possibly absorb that much untreated sewage. It can only go one place: downstream.
Researchers at Alma College under the leadership of Professor Murray Borrello have been tracking this problem for decades. One recent study demonstrates the public health risk to people who live, play, and fish along the Pine. They wondered about potential for Escherichia coli (E. coli, you may have heard of it? Nasty little bug.) exposure among anglers in the watershed, in light of all the agricultural runoff documented by earlier studies. This investigation sought to quantify the presence of fecal coliforms and E. coli on fish and from there to anglers’ hands, their lunch, their kids, their pets … you get the picture.
The Pine, in the headwaters of the Saginaw River Basin, has exhibited E. coli counts exceeding safe human contact levels since 2005, according to state environmental and health agencies. This study aimed to bridge the gap in existing research.
A close up look at E.coli at the celular level. Photo Credit: CDC
This study aimed to bridge a gap in existing research, which largely focuses on source and end-point contamination (e.g., livestock operations, drinking water), by examining the potential for bacterial transfer through recreational fishing.
The researchers began with a caged fish pilot study, deploying hatchery-raised bluegill at three sites along the Pine. Over 21 days, they detected E. coli in the mucus of these fish at frequencies ranging from 16% at the confluence of a heavily impacted tributary, to 56.5% at a downstream site. E. coli colony-forming units (CFUs) increased moving downstream, suggesting a complex interplay of bacterial dynamics within the river system.
Then the study shifted to resident fish populations. In other words, the researchers went fishing, pulling in sunfish, bluegill, suckers, and largemouth bass. Of these fish, 88% tested positive for fecal coliforms, with 73% specifically positive for E. coli. CFUs of E. coli were significantly higher in fish angled from the shoreline, although the frequency of E. coli detection was slightly higher in fish caught from a boat (67%) compared to the shore (60%). This data suggests that bacteria accumulate in different ways in different spots along the river, a possible topic for further study, and a warning for shoreline anglers.
To measure human exposure, hand swabs were collected before, during, and after fishing. Results demonstrated that 50% of anglers had E. coli on their hands after catching their first and last fish of the day, while 31% showed E. coli presence at 30-minute intervals, regardless of fish handling.
Dipping hands directly into the Pine resulted in 78% positive tests for E. coli, emphasizing the danger of contaminated water.
The study went on to look at cross-contamination risks by analyzing fish fillets. Eight fish from the caged study were filleted and swabbed, revealing at least 1 CFU of E. coli on each fillet – meaning contaminated surfaces or improperly cooked fish could deliver E. coli directly to your digestive tract.
The study acknowledges limitations. The human health risk associated with direct contact with elevated E. coli levels in fish mucus isn’t completely clear. The study also highlights the need for further research on the connection between bacterial levels in water and fish mucus, and the influence of fish species and size on bacterial accumulation.
The findings underscore the need for better monitoring and risk assessment to safeguard public health along the Pine. Be careful out there, kids.
