Zorinsky Lake drained for infestation

In November, the first zebra mussel spotted at Zorinsky Lake was attached to a beer can. In December, after realizing the lake was infested with a potentially harmful population of zebra mussels, the lake was drained 20 feet below its typical depth to combat overgrowth of the species.

The draining is intended to expose and free the mussels living on rocks at the bottom of the lake, said Karie Decker, Invasive Species Project Coordinator at UNL. Zorinsky Lake will remain drained through next year, and the Nebraska Game and Parks Commission will rehabilitate fisheries upon complete eradication.

The mussels in question are striped, thumbnail-sized invertebrates that reproduce rapidly, feed on photoplankton, and are known for their expedient migration. The plankton they consume is a key component in the diet of many fish — when mussel populations rise, fish populations plummet.

The bivalves are also notorious for blocking power plant and water system pipes, causing millions of dollars in damage, and for riddling lake beaches with their glass-like shells.

Chris Wiehl, chief of natural resources for the Corps of Engineers in the Midwest, and state officials agreed mussels posed a substantial threat to Zorinsky Lake's ecosystem as well as those of surrounding lakes.

Draining the lake was their strongest offensive to combat the infestation. The decision to drain Zorinsky Lake was a strategy to quarantine the mussel expansion before populations spread to neighboring lakes like Cunningham and Standing Bear.

"The nature of this species is such that they quickly reproduce," Decker said. "Each female can produce up to 1 million eggs each year."

When mussel masses occur, damages accrue.

"What they are most notorious for is their ability to attach to and cause damage to substrates in the water," Decker said in an Oct. 19 interview. "These mussels will attach and colonize inside water intake pipes, wells and screen systems. This level of infestation requires millions of dollars a year for treatment and control."

They've become problems in Colorado and Kansas lakes. Isolating the zebra mussel colonization is vital in their prevention. The U.S. Corps of Engineers designed Zorinsky Lake as a flood control structure so the Corps of Engineers can regulate the outlet structure to increase water flow to the Missouri River. Draining the lake was achieved by adjusting the structure.

The hope is to stunt the growth of these invasive mollusks before they become a greater threat to the region, Decker said.