Monster Seminar JAM - From physiology to ecosystem function: Three ways to measure impacts of exotic New Zealand mud snails in rivers
Dr. Robert O. Hall, Jr., Department of Zoology and Physiology, University of Wyoming
Many animal species can affect ecosystem function and exotic animals, in particular, may demonstrate this linkage clearly because they acheive high biomass and/or have novel traits relative to native taxa. Exotic New Zealand mud snails (Potamopyrgus antipodarum) achieve very high densities in several rivers in and around Yellowstone National Park, and their impacts to native assemblages and ecosystem functions are unclear. We took a three-way approach that related snail energetics to carbon and nitrogen cycling at small and large spatial scales. Mud snails constituted 65-92% of total invertebrate production in three rivers suggesting that this exotic snail is sequestering a large fraction of the available carbon for invertebrate production. In one river their production was one of the highest recorded for an invertebrate. Small scale experiments showed that snails consumed most algae production, yet their interaction strength varied among rivers, with no impact on primary production in one location. At the whole-river scale, snails dominated carbon and nitrogen fluxes, despite very high primary productivity and fast rates of nitrogen cycling. Exotic snails consumed 75% of gross primary productivity, and their excretion accounted for two-thirds of
ammonium demand. These large fluxes were due to high snail biomass rather than high per-biomass rates of excretion or consumption. We
suggest that snails have altered element cycling in rivers because their large biomass.
Date and Time:
February 5, 2004,
11:00 am - 12:30 pm