The Effects Of Specific Conductivity On The Distribution Of New Zealand Mud Snails (Potamopyrgus Antipodarum) From Redwood Creek Estuary, California

The New Zealand mud snail (NZMS) is an invasive mollusk that has become numerous in many waterways of the western United States. In 2009, NZMSs were detected in Redwood National Park (RWNP) in Northern California. Although NZMSs are noted for their ability to rapidly colonize new habitats, after 3 years in the park their distribution remains limited to a ca. 300 m reach of Redwood Creek estuary. Recent literature suggests that low specific conductivity (SC) can limit NZMS distribution within watersheds. We are conducting experiments to determine if NZMS distribution in RWNP is limited by low SC. Snails were collected from the estuary and placed in petri dishes containing either estuary water (SC= 123 µS/cm) or water from one of 3 other tributaries in the Redwood Creek watershed that encompass a range of SC (range= 61.3-77.4 µS/cm). In addition to the natural water treatments, we established additional treatments using purified (reverse osmosis) water with SC manipulated to 20.6, 50, 100, 150, and 200 µS/cm using a salt solution. Treatments were established April 1, 2012 and are ongoing. Response variables to be measured include mortality, growth, and fecundity. Preliminary data shows that NZMS mortality is much higher in low-SC treatments than high-SC treatments. However, snails can persist for long periods (> 14 weeks) in the lowest SC natural waters from Redwood Creek tributaries. Additional data on fecundity will be necessary to determine whether low SC is likely to keep NZMS from expanding their distribution in RWNP.