Bruce Beach Cottagers' Association

Sudden Impact 

Diporeia (die-por-ia) is a tiny, shrimp-like organism that is at the base of the Great Lakes food chain. Studies have identified that this animal is in a rapid state of decline in Lake Huron. 

Diporeia is environmentally sensitive, requiring clean, cold, well oxygenated water for growth and survival. It is native to the Great Lakes, having been present since the receding of the glaciers. Diporeia have a high fat content, with lipid fats often exceeding 30% of its total weight. As a result, it is rich in calories and a good source of energy for fish. 

Since Diporeia normally make up over 70 percent of the living biomass in healthy lake bottoms in offshore areas, their decline in the Great Lakes is negatively affecting a variety of fish species that depend heavily on them for food.

“Exact mechanisms are unclear, but the decline of Diporeia is related to the introduction and expansion of the Zebra and Quaggamussels,” says Tom Nalepa, a US biologist who has been sampling sediments in Lakes Michigan and Huron since the early 1980s. Tom was a featured speaker at the Coastal Centre’s “Is the Coast Clear?” conference in 2006. One of his theories is that mussels are out-competing Diporeia for available food. Diporeia live in the bottom mud and feed mostly on algae settling from the water column. Now, large concentrations of mussels residing on the lake bottom may be filtering out algae and thereby depriving food to amphipods, according to Nalepa.

While many species of fish will readily eat Diporeia, few species can use Zebra and Quagga mussels for food. Moreover, even if a fish species does eat these mussels, they are provided with a food value much lower than that of Diporeia. Evidence suggests that declines in Diporeia are having a significant impact on fish populations throughout the Great Lakes.



"The loss of Diporeia is one of several changes that are occurring in response to the expansion of the Quagga mussel population," Nalepa said. "People have to realize that the lakes are no longer going to be what they were 20 years ago, or even 10 years ago, because of the Quagga mussel.

"We're still in the explosive-growth stage of the Quagga mussel expansion, and we're in uncharted territory in terms of what's eventually going to happen," he said. "But there's a delay between what the mussels do and how it affects the fish populations, so we haven't seen the worst of the impacts yet, in my opinion." 

Nearly every fish species in the Great Lakes feeds on Diporeia at some point in its life cycle. The Diporeia downturn is already impacting Great Lakes commercial fisheries and a sport-fishing valued at more than $4 billion per year.  Lake Huron is going to become less productive, and that translates into fewer fish as well as different types of fish. 

For more information on Diporeia, see:
Science Daily - http://www.sciencedaily.com/releases/2008/05/080528172001.htm


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Green Tip

Bathing in the lake doesn't mean take a bath. Don’t use soap in the lake, ever. Even if a soap says it’s phosphate-free and biodegradable, don’t assume it’s safe for the lake. The soap can be harmful to fish and other aquatic animals. All “biodegradable” means is that it’s capable of breaking down (with the help of soil bacteria) into its constituent parts. However, do use this type of soap when bathing at the cottage. It's better for the septic system.


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Project Donor Opportunities

For The Sake of the Lake project donors direct their dollars directly to the Centre's community project costs.  Consider becoming a Shore Protector ($500), Beach Benefactor ($250) or Dune Builder ($100)!  Your support will help us accomplish our environmental and conservation efforts along the Lake. Consider making a donation as a gift to a family member or friend. A donation card is sent to them, a tax receipt is sent to you!
 
All donations above $10 will receive a charitable tax receipt. 
 
Call Kristin at (519) 955-6269 for more information.

Other ways to support the Coastal Centre - see our "How you can help" webpage.

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About the Coastal Centre

The Coastal Centre is a non-governmental organization dedicated to the conservation and wise stewardship of Lake Huron's coastal ecosystems. Our environmental priorities include coastal water quality, biodiversity, coastal processes and climate change. For more information on the Centre, its Board of Directors, Board of Technical Advisors and staff, go to our website or contact us at (519) 523-4478, P.O. Box 178, Blyth, Ontario, N0M 1H0.

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The monthly e-news from the Lake Huron Centre for Coastal Conservation (The Coastal Centre) provides you with a feature story about an issue concerning Lake Huron, ways you can be a steward to the Lake and upcoming projects and events.  Please pass this information forward to anyone interested. 

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