Flexing Our Mussels

Invasive zebra mussels continue their full-scale assault on native species of freshwater mussels, but northern Michigan’s indigenous clams have found human allies to help them fight back:  young scientists at the University of Michigan’s Biological Station on Douglas Lake.  This battle holds symbolic weight if the natives are to survive the invasion.

Native to the Caspian Sea and the Ural River of southeast Russia, the zebra mussel uses its strong byssal threads to attach to any hard surface.  By latching on to anchors and the bottoms of ships traveling through international waterways, the mussels spread west into Europe and, eventually, across the Atlantic Ocean.  Ships entering the St. Lawrence Seaway introduced the invasive species to the Great Lakes in 1988, and zebra mussels have since extended throughout much of North America.  The exotics pose a serious ecological threat to the biodiversity of aquatic ecosystems.  By reproducing in greater numbers than native species and using them as a substrate, the zebra mussel colonies outcompete the local species of unionid bivalves.  The suffocated victims cannot move, gather food, or close their shells to protect from dehydration.

Without help, death is inevitable.

On July 8 I went out with twenty-five others to clean the invasives off four species of clams native to Douglas Lake.  In the graveyard of empty shells, a few living natives still resisted their attackers.  Each clam we cleaned might reproduce in great numbers, giving the population a meaningful shot at survival.  I saved about thirty native mussels; our modest team collectively saved over three hundred.  I accidentally killed one, however, when I tried to free her from her living shackles.  The shell broke and punctured my skin.  The soft, vulnerable tissues inside were now exposed to the world.  I finished shucking anyway to provide her with a decent burial.

By Stefanie Trout