New Zealand mud snails (Potamopyrgus antipodarum ) have invaded rivers in Yellowstone National Park, and their abundances, biomass, and production are alarmingly high.  Summer abundance in Polecat Creek (near Flagg Ranch, JDR Parkway)  as high as 750,000 / m2 in 2000, with biomass near 30 g/m2.   Annual secondary production in Polecat Creek,  194 g m-2 y-1,  is one of the highest rates of invertebrate production ever measured.
 

How many snails is that?
Below are snails at only 90,000/m2.  They are small, but they get very dense.

Together with Mark Dybdahl and Billie Kerans we are examining invasion and impact of these snails.  Using measures of secondary production we show that these sanil dominate the invertebrate assemblages and can constitute up to 93% of annual production in Polecat Creek.  Even though mudsnail production is much lower in Gibbon River, Yellowstone,  native invertebrates are only 15% of total production.  

These snails live in geothermal streams which are hydrologically stable and have really high primary production; Polecat Creek has 4.5 g C m^-2 d^-1 of primary production.  We have estimated that snails consume 80% of daily gross primary production.  Additionally, excretion rates of ammonium by snails is the largeest inorganic N transformation in the stream.      

Publications from this project:

Hall, R. O., M. F. Dybdahl, and M. C. VanderLoop.  In press.  Extremely high secondary production of introduced snails in rivers.  Ecological Applications.

Hall, R. O., J. L. Tank, and M. F. Dybdahl. 2003. Invasive snails dominate nitrogen and carbon cycling in a highly productive stream. Frontiers in Ecology and the Environment 1:407-411.               

Firehole River and hotspring                                                                                 Algae and mud snails