BLOOMINGTON, Ind., May 11 (UPI) — U.S. biologists say they’ve discovered the shape of a lake basin is a key factor in supporting plankton disease epidemics in Midwestern states.
The researchers, led by Assistant Professor Spencer Hall of Indiana University-Bloomington, said they discovered U-shaped lake bottoms promote disease hot spots more than V-shaped ones.
The scientists said the disease studied is caused by a fungus in the water that infects the filter-feeder Daphnia dentifera, a water flea that plays a critical “grazer” role in many Midwestern freshwater lakes. The fungus slowly consumes the tiny crustacean’s blood and produces spores that fill all that remains.
For the fungal spores to make it to the next potential host, the researchers said Daphnia host’s exoskeleton must be opened in an area where the spores are exposed to living, uninfected Daphnia dentifera.
Whether that happens, the researchers discovered, can be predicted by the lake basin’s shape.
Lakes with U-shaped bottoms have fewer near-shore nursery areas, and, as a result, bluegill fish populations tend to be lower. Bluegill are a major Daphnia dentifera predator. And with fewer bluegill, Daphnia tend to be larger, and larger Daphnia have a greater chance of eating spores and becoming infected, the scientists said.
The study that included researchers from the University of Illinois, the University of California-Santa Barbara and the Georgia Institute of Technology appears in the journal BioScience.
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