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Resources |  Water Quality
Algae and Water Quality


One of the things we least like when we go for a swim in the lake is coming out with green slime clinging to our hair. Algae is a regular occurrence on the Great Lakes. Too much algae on our beaches and nearshore waters, though, usually indicates a  problem with the local ecology.


Cladophera is a naturally occurring algae on the Great Lakes which provide shelter and nourishment to a wide variety of organisms including mollusks,  diatoms and young crayfish.  As with most plants, the addition of nutrients like phosphorous and nitrogen can accelerate growth rate of algae, and this can be a problem when the natural balance goes out of control.


Large amounts of algae are usually indicative of excessive nutrients like nitrogen and phosphorous entering the water from runoff.  Algae fouling along our beaches are an obvious example of an ecological imbalance due to excessive nutrients in the water.

What are the sources of these nutrients? The usual suspects… agricultural and stormwater runoff, faulty septic systems, and wildlife.


But compounding the issue in  recent years has been the emergence of Zebra Mussels, and their cousin the Quagga Mussels


These are the non-native, invasive species that have been implicated in contributing to some of our water quality woes on Lake Huron and the other Great Lakes.  The foreign invaders arrived in the Great Lakes around 1986 and were first  discovered in Lake St. Clair. Zebra Mussels can significantly change the nature of the lake bottom, affecting fish habitat and spawning.  Prolific breeders, Zebra and Quagga Mussels can produce millions of offspring per year.


Mussels eat by filtering algae from the water. This is the same food source for many species of native fish and other organisms. Overall, the impact is a reduction in the amount of food available to native species. The Mussels have caused drastic declines in the native Great Lakes mussels commonly called clams. They infest the clam’s habitat to the extent the clam cannot get enough food to survive.

Cladophera is nuisance algae that needs three things to florish – sunlight, nutrients and a hard underwater surface on which to grow. Nutrients come from land runoff from various sources (agriculture, septic systems, wildlife), but also from Zebra and Quagga Mussels. They filter the water making it clearer for sunlight to penetrate, and fertilize the algae with nutrient-rich excrement. Their shells provide a hard surface for the algae to grow. Storm waves will break off some of the algae and wash it ashore.


While this algae clings to rocks, it occasionally gets sloughed off and gets carried to shore by waves. When large amounts of algae pile up on our beaches, it can produce a powerful smell – not a pleasant experience for the average beach-goer.

Nutrients are part of the concern. The other is that scientists have identified an association between the mats of algae that we see washed up on our beaches and high levels of the bacteria E. coli. The algae may actually promote the growth of E. coli. These decaying mats of algae likely provide increased levels of nutrients, decrease the amount of ultraviolet radiation from the sun that tends to kill the bacteria, and likely provide a warmer, more moisture-stable environment than sand or rock beach environment.

Reducing phosphorus pollution is critical to controlling nuisance algae growth and the overall health of Lake Huron. One of the simplest things we can all do to help keep our lake clean is to reduce our contribution of nutrient pollution by reducing  fertilizer use, properly disposing of pet waste, reducing runoff of soil from construction activities and landscaping, and from agricultural runoff.

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