Although smaller than a grain of rice, just one New Zealand mud snail can wreak havoc on an entire body of water, as seen with Capitol Lake in Olympia.
Discovered in the lake in 2009, the invasive freshwater mollusks — which have no known predators or parasites in Washington — outcompete native aquatic snails and insects for food such as algae. Measuring between 4 and 6 millimeters, each mud snail reproduces asexually and releases up to 300 baby clones every year.
The 260-acre Capitol Lake has been closed to boating and recreational activities to prevent the spread of the resilient mud snails. Anyone who comes in contact with the water must undergo a decontamination process, such as washing boots with hot water or chemicals.
Salish Middle School teacher Erica Baker brought 23 sixth-graders to Capitol Lake for a mud snail lesson Friday afternoon. The North Thurston School District students viewed the mollusks through little magnification boxes and sketched their elongated cone-shaped shells.
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Jesse Schultz, a biologist with the state Department of Fish and Wildlife, gathered several mud snails from the lake’s shore and put the tiny critters on a flat white pan. Although the mud snail has been contained within a 5-mile radius of the lake, he warned that one mud snail in the tread of a shoe could be enough to infest another lake.
The students had a number of observations about the adaptable mud snails, such as their ability to reproduce without needing to find a male counterpart.
“It’s interesting how they’re so small, but can populate the water so rapidly,” said Anna Tracy, 12, as she made a pencil drawing of a mud snail.
The students from Baker’s accelerated science class are studying how organisms affect food chains and ecosystems.
“I really try to get the kids thinking beyond ‘what is this critter’ and considering the impact they have,” Baker said of the opportunity to see the mud snails up close. “We’re bringing it home to a place where they may come with their families and get a chance to see that they’re right here in our backyard.”
The mud snail will play a key role in the long-term management of Capitol Lake as a committee of local stakeholders determines whether to convert the lake to its natural state as a saltwater estuary. The mud snail’s presence means that dredging and sediment disposal will be more costly, according to the state Department of Enterprise Services, which manages the lake.