Bottom-dwelling algae is a side effect of invasive mussels

A recent column I wrote for Michigan Outdoor News highlighted research ongoing at Good Harbor Reef near the Sleeping Bear Dunes National Lakeshore. These studies could be the precursor of efforts to suppress or possibly even eliminate the zebra and quagga mussel scourge that has befallen the Great Lakes.

More than 25 years ago, when these closely related mussels invaded the lake, their populations proliferated to incalculable numbers and immediately began to affect the lake’s food web. The mussels filter feed on plankton and phytoplankton in the water and compete directly with fish and other organisms for food and vital nutrients. The result has been a nearly complete reordering of fish populations since the mussels arrived.

There are other indirect consequences to the ecology of mussel-infested lakes.

One is increased sunlight penetration as the water becoming clearer from the reduction in plankton and phytoplankton. Lake Michigan has now taken over from Lake Superior as the Great Lake with the clearest water for no other reason than zebra and quagga mussels.

Another consequence is the “fertilization affect” from massive amounts of mussel doo-doo being deposited at the lake’s bottom.

The increased light penetration and fertilized substrate combine to encourage bottom-dwelling filamentous algae to grow, spread, and sometimes proliferate into massive mats.

Before the zebes and quaggas showed up this type of algae was seldom encountered. Now, it’s relatively common, sometimes clogging on fishing lures and lines, interfering with fishing nets set by commercial fishermen or fish biologists and worse.

Outbreaks of avian botulism are becoming a regular occurrence in some areas where it was previously rare or non-existent. Avian botulism is a disease caused by a neurotoxin released by the botulinum bacteria. It can kill birds that eat invasive round goby fish, which in turn feed on zebra mussels that eat the bacteria and accumulate the toxin within them. There’s a direct link between the presence of botulism bacteria and filamentous algae infestations.

Currently, there’s no solution to control or eradicate zebra or quagga mussels completely from the Great Lakes. It’s hoped research projects such as the ones ongoing at Good Harbor Reef can form a foundation on which other plans and projects can be built to eventually come up with a workable solution.

Categories: Michigan – Mike Schoonveld

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