In the same biological class as krill and shrimp, these rice grain-sized crustaceans dwell on lake bottoms and feed on descending algal plankton. Their bodies contain 30 percent to 40 percent lipids like fats and oils, making them a vital energy and nutrient source for the entire food web.
They are already gone from many large areas of lakes Michigan, Huron, Erie and Ontario, said collaborating researcher Tom Nalepa. In Lake Michigan, there are almost no Diporeia found at depths shallower than 90 meters. Just 15 years ago, their density often exceeded 10,000 animals per square meter at such depths, said Nalepa, a research biologist with the Great Lakes Environmental Research Laboratory.
The spread of invasive zebra and quagga mussels - voracious filter feeders with an overlapping diet - largely coincides with Diporeia's decline and is widely believed to be at least partially responsible. But research cannot yet explain the link, Nalepa said.