Great Lakes Water Issues: Pollution & Invasive Species

Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

Making up the largest freshwater system on Earth, the Great Lakes are an impressive feature. But there are also great issues: those of pollution and invasive species.

The Great Lakes

I'm guessing you've heard of the Great Lakes, but how much do you actually know about them? Well to start, there are 5 of them: Lakes Superior, Michigan, Huron, Erie, and Ontario. They also have a collective volume of 6 quadrillion gallons of water - that's 1/5 of the fresh water on Earth's surface! They are also the largest freshwater system on Earth. They cover more than 94,000 square miles, touch 8 states (Minnesota, Wisconsin, Michigan, Illinois, Indiana, Ohio, Pennsylvania, and New York) in addition to the Canadian border, and have a total coastline of almost 11,000 miles. There are also shipping channels and lochs that allow vessels from the Atlantic to come inland and transfer goods. These lakes truly are great!

There are 5 Great Lakes, making up the largest freshwater system on Earth
Great Lakes

Pollution in the Great Lakes

But because the lakes are so extensive, border so many states (and two countries!), and provide recreation, commerce, and industry to so many, pollution is a major issue. Water wasn't always seen as a precious resource to protect. In fact, until the early 1970s both industry and individuals would dump waste into the Great Lakes thinking that it would simply be diluted without causing any harm.

This unfortunately led to large-scale pollution in the lakes, both from point source pollution (pollution from a specific location such as a sewage drainpipe) and non-point source pollution (runoff pollution that comes from many different sources and includes soil, litter etc). When a company that is placed along the shore of one of the Great Lakes dumps its waste into the water, this is point source. But runoff of land fertilizers and chemicals creates non-point source pollution, which is much harder to control.

The Cuyahoga River, which is connected to Lake Erie, has caught on fire multiple times from pollution. This photo from 1973 shows a city pump dumping sewage into the river (point source pollution).
Cuyahoga River

Water pollution leads to a number of issues. First, it directly affects our health because the Great Lakes and the rivers connected to them are the drinking water source for many, many people. Pollutants can also accumulate in animals that we eat, like fish and shellfish. These toxins and other pollutants not only affect us because we eat this food, but may also cause deformities and abnormalities in the animals themselves.

The good news is that there have been many grassroots groups and legislative changes that have helped to clean up the Great Lakes, and will also help prevent future pollution from occurring. For example, after a study determined an abnormally high level of phosphorous in the lakes, the U.S. and Canada signed the Great Lakes Water Quality Agreement (GLWQA) in 1972 and again in 1978 to combat pollution, specifically 'persistent organic pollutants' (a collection of synthetic chemical pollutants related to industry), pollution related to non-point sources, and air pollution.

Invasive Species

The Great Lakes are home to an incredible variety of native plants and animals. But they are also now home to a number of species that do not occur naturally. While many non-native species do not cause any problems, some do because they do not have any natural predators and they can eat a variety of food and live in a variety of environments. Without anything to keep them in check, their populations explode, which can drastically alter ecosystems and food webs.

Zebra mussels were likely brought into the area through ballast water, which is water held in the tanks of ships to help increase stability. This water is often taken on in one place, say the beginning of a trip, and then dumped in another place, maybe a port or harbor where the ship stops along the way. It's kind of like taking your bath water and dumping it into the washing machine - one clearly doesn't belong in the other! But the main problem is that it's not just water that gets moved; all the organisms in that water also take a ride. And they may find themselves in a place where they can thrive, which is exactly what the zebra mussel has done in the Great Lakes.

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