A carrier ship releasing ballast water in the 1990s (CSIRO/Wikimedia Commons)
Warren Cornwall, Anthropocene, March 16, 2022
North America’s Great Lakes have long been a poster child for the damage caused by aquatic invasive species, and the difficulty of stopping them.
In the chain of lakes that together form the world’s largest freshwater ecosystem, zebra mussels from Russia and Ukraine choke intake pipes for drinking water systems, swarms of spiny waterfleas from Europe and Asia devour native zooplankton, and voracious ruffe (a kind of fish) feast on the eggs and young of native fish.
The number of invasive species in the lakes has climbed inexorably for decades, to roughly 190 species today. Efforts to halt new arrivals seemed to make little difference. Until now.
Over the last 15 years, the number of new invasive species showing up in the lakes has plunged. New research points to one strategy for much of the success: Quite literally, giving invasive species the flush.
Photo and description from Minnesota DNR
The spiny waterflea is native to Europe and Asia. The species was unintentionally introduced into the United States’ Great Lakes through the discharge of contaminated cargo ship ballast water. They were first discovered in Lake Ontario in 1982, and spread to Lake Superior by 1987.
Spiny waterfleas are predatory zooplankton that eat other zooplankton. They migrate into deeper waters during the day to hide from predators, and return to shallower water at night to find food. During the spring and summer, they reproduce by cloning. In the fall, or when conditions in the lake are cold or there is less food, they will reproduce sexually and produce tough eggs that are resistant to drying and freezing. Females carry their eggs and young on their back.