Tiny Water Flea Has Large Effect On Lake Huron; 'A Key Predator On Zooplankton'

An invasive species, the spiny water flea, is likely a primary driver of changes in Lake Huron's food web over the past decade, according to a new U.S. Geological Survey study.

The USGS research suggests that consumption of prey by invertebrates is outweighing consumption by fish in Lake Huron, and one invertebrate in particular â€" the invasive Bythotrephes, or spiny water flea â€" is likely a primary driver of changes in the food web. This predator ate 78 percent of all zooplankton prey consumed at the study sites, said Dr. David B. Bunnell, USGS scientist and lead author of the report.

"These findings shine a spotlight on the role of the invasive spiny water flea as a key predator on zooplankton in Lake Huron," Bunnell said. "Our study suggests that a better understanding of the role of invertebrates, and the spiny water flea in particular, is essential to fully comprehend the food web changes we've seen in Lake Huron since 2002."

Zooplankton feed the prey fish that support key recreational and commercial fish species in Lake Huron. Bunnell and his colleagues estimated densities of zooplankton prey and their fish and invertebrate predators in Lake Huron between May and October 2007, using models to determine which predators were having the greatest impact on zooplankton dynamics.

"Lake Huron has undergone dramatic changes at multiple levels of the food web since the early 2000s," Bunnell said. "Some changes have been quite visible, such as the collapse of alewife and Chinook salmon, whereas other changes have received less attention."