freshwater mussel

Biodiversity at Drift Creek

In 2008 the Drift Creek Nature Center hosted a "Bioblitz" in the late successional forest surrounding its site at the Drift Creek Camp. During a 24-hour period of time, a team of educators, naturalists and nature enthusiasts identified just over 200 species in the 12-acre area. Return visits by many experts have revealed a multitude of other species, and the list has now grown to 700 species with the discovery of the Western Pearlshell, Margaritifera falcata, a freshwater mussel that can live to be over 100 years old.  

The Western Pearlshell lives on the bottom of streams throughout the western United States and filter feeds on suspended organic material. A single individual can filter up to 50 liters of water per day. The mussels then digest the particulates and make nutrients avalialable to bottom dwelling insects. In order to reproduce, mussels release larvae called glochidia into the water that then attach onto the gills of a host fish. Host species include cutthroat and rainbow trout as well as coho, sockeye and chinook salmon, among others. Once attached to the fish's gills or fins, the glochidia form a cyst and develop for several weeks to months, depending on water temperature. The larvae later release from the fish and burrow into sediment to grow and mature into full adults. It takes 7-10 years for the mussels to fully reach maturity.  

The Western Pearlshell's dependence on host populations of fish for dispersal, as well as its sensitivity to pollutants, has led it to become an indicator of stream health. Given that this mussel species is such long-lived, they are used in many monitoring programs as "bio-monitors." Through the analysis of physical and chemical variations in the shells of freshwater mussels, the cumulative effects of environmental conditions over time can be assessed (similar in nature to how the rings of a tree record information). In addition, the mussels can aid in the monitoring of contaminants such as mercury, lead, dioxin, poly chlorinated biphenyls, and polycyclic aromatic hydrocarbons. 

North America is considered a hotspot of freshwater mussel diversity.  However, it is estimated that up to 70% of these species are at risk.

The Drift Creek Nature Center has identified many rare and endangered species occurring in the coast range including the Marbled Murrelet, Spotted owl, Coho salmon, and red-legged frog.  These and the full list of species can be found here.

Article by Conrad Gowell - Photo courtesy of US Fish and Wildlife Service

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