We love our lakes and rivers, but how can we avoid getting sick while recreating?
Cody Sheik, a microbial ecologist at the Large Lakes Observatory at the University of Minnesota, joined the KAXE Morning Show to discuss how aquatic microorganisms, particularly cyanobacteria, can impact the health of humans and domestic animals.
Green scum on the surface of the water is one easy indicator to reconsider your swimming plans (or tossing the ball in for your dog).
“I use my common sense,” Shiek said. “If it’s green, if it doesn’t look right, maybe I don’t go in that day.”
During cyanobacterial harmful algal blooms (charmingly called cHABs), water turns green because cyanobacteria use green chlorophyll to photosynthesize. When the population of cyanobacteria grows out of control, the pigment becomes visible to the naked eye.
Native harmful microorganisms
Like all photosynthetic organisms, cyanobacteria take in carbon dioxide and water to create energy, and release oxygen. They are a natural part of freshwater ecosystems across the world, and foundational components of aquatic webs.
A few cyanobacteria, however, can have harmful effects on humans and domestic animals. These harmful microorganisms are much more likely to proliferate to toxic levels in polluted bodies of water containing an excess of fertilizer, phosphorus or nitrogen, Shiek stated. Effects of cHABs range from itching to liver damage or even neurotoxicity.
Water quality control is important to reduce populations of these harmful microorganisms, Shiek said. Efforts to reduce runoff from lawns, agricultural fields and septic systems, for instance, can have a great effect. Buffer areas of native plants between aquatic systems and fields or lawns also work to filter out pollutants before they reach the lake or river.
Replacing lawns altogether with native plants can benefit not just water quality, but also provide habitat for insects, birds, mammals and other desirable wildlife that help to balance and control aquatic ecosystems.
Non-native microorganisms
While invasive species tend to be thought of as relatively large organisms like zebra mussels or buckthorn, there is also potential for microorganisms to be introduced to novel habitats and spread out of control. Some of those new microorganisms are harmful to humans or cause massive fish die-offs.
To reduce the spread of non-native microorganisms (and larger invasive species), Shiek and other experts recommend cleaning, draining and drying boats before moving between lakes or rivers. Water in bait buckets should also be replaced with bottled or tap water before leaving.
Learn more
Cody Sheik was August’s presenter for Itasca Waters’ Practical Water Wisdom virtual learning series. You can view his presentation and others here.
Shiek became interested in aquatic systems during his frequent childhood trips to the Boundary Waters. After studying ocean microbiology for a number of years, he jumped at the opportunity to move to Duluth and study Lake Superior and freshwater systems. After the Lake Superior algal bloom of 2018, he became more interested in researching toxic cyanobacterial blooms.
