Invasive Quagga Mussels Could Eat Lake Michigan Ecosystem to Point of Collapse


photo: Wikipedia

Forget about the potential damage by invasive Asian carp, another invasive species, the quagga mussel is likely to destroy the Lake Michigan ecosystem long before the bottom-feeding fish do. That's the word of Michigan Tech biologist W. Charles Kerfoot, who says the proliferating mussels are eating up so much phytoplankton that, through an interesting chain of events, hypoxic dead zones could be created, with disastrous results.That's the quick version. The more complex version, published in the Journal of the Great Lakes, goes like this:

Back in the late 1990s, Kerfoot's research team discovered in the southern end of Lake Michigan a roughly circular movement of phytoplankton rotating counterclockwise. They determined that seasonal doughnut-shaped bloom (pictured at left) was being fed upon by zooplankton, which were in turn eaten my smaller fish, and on up the food chain.

However, since 2001 the doughnut has been declining, eaten away at the edges by the quagga mussels, which at the worst are found in concentrations along the lake bottom of 10,000-15,000 per square meter.

Here's the connection to phytoplankton: These mussels are eating five to seven times as much phytoplankton as is being produced--so much that between 2001 and 2008 there's been a 75% decline in phytoplankton abundance.

Moving on, the resultant mussel poop stimulates the growth of Cladophora algae, which upon death and decomposition can cause the water to be depleted of oxygen.

Kerfoot describes what happens next: "When things go anaerobic, that kills off everything, including the quaggas, and creates conditions for botulism. We've had massive kills of fish-eating birds." Along with that, zooplankton will decline as well, and with them the fish that depend upon them. "A high percent of the fish biomass could be lost in the next couple years," Kerfoot notes.

Read the original study: Approaching storm: Disappearing winter bloom in Lake Michigan
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Tags: Ecology | United States