Did You Know Lake Michigan Has a Reef System?

The world's most famous reef is the Great Barrier Reef, a massive underwater structure built by living organisms in Australia's Coral Sea. This coral reef is gorgeous and is known primarily for its high biodiversity. The image of the colorful corals and organisms living there is easily etched into one's mind.

Get our free mobile app

However, what few people know (even Wikipedia doesn't have a page about this) is that Lake Michigan has its own reef, although it is very different from the coral reefs typically thought of when considering a reef. It lacks the color and wonder that come with the Great Barrier Reef. While it may not be flashy, it serves a unique and vital role in the lake's ecosystem.

What is a reef?

National Geographic defines a reef as "a ridge of rocks, coral, or sand rising from the ocean floor all the way to or near the ocean's surface." While the more iconic reefs around the globe are made of coral, the reefs in the Great Lakes are made of rocks. While there are natural and artificial reefs in Lake Michigan and other Great Lakes, Lake Michigan's four largest reefs, known as the Midlake Reef Complex, are natural.

These reefs have varying levels, with the Northeast Reef and the East Reef both having summits at ~50m, and the Sheboygan Reef having a summit at ~40m. We'll arrive at the Milwaukee Reef shortly, but these reefs serve as essential spawning and habitat locations for Lake Trout and other fish.

The Milwaukee Reef's Unique Function

In his book Lake Michigan Passenger Steamers, author and Professor Emeritus of Economics at the University of California, Los Angeles, George W. Hilton detailed the "rise, fall, and extinction of steam passenger transportation in Lake Michigan." If you're wondering what steamboats have to do with reefs, it's related to currents. 

The Milwaukee Reef, described as "the most important geological formation" in Lake Michigan, runs from Milwaukee to a point between Grand Haven and Muskegon. The reef has a unique function in that it divides Lake Michigan into two pools, with the northern pool flowing counter-clockwise from a point 5 miles north of Muskegon.

READ MORE: Only Been Since 1985 That We Reached The Deepest Part of Lake Michigan

The southern pool also flows counter-clockwise, centering on a point south of Holland. These pools were important to boats as the currents were the sources of strong boat travel. However, these currents also play a role in lake-effect weather, according to Hilton.

There isn't much information about the Milwaukee Reef itself, but the Midlake Reef Complex plays a vital role in Lake Michigan. You can learn more about it by reading Hilton's book or further exploring the Department of Environment, Great Lakes, and Energy's mission to restore and protect the reefs throughout the state.