The impact and potential distribution of exotic New Zealand mud snails in Grand Teton National Park

Authors(s): R. Hall

Publication:

Publisher:

Publication Date: 0000-00-00

Type: annual report

Location:

Abstract: Objectives We had 2 objectives: 1. Examine impact of New Zealand mud snails in Polecat Creek in JDR Parkway. For this project we measured impact of snails on algae, and we compared consumption rates of organic matter and excretion of ammonium with whole-stream estimates of primary production and ammonium uptake, which is part of R. O. Hall's nitrogen cycling project within GTNP. 2. Use a comparative approach to develop an assessment of the risk of invasion of GTNP streams. We will base our assessment on the relationship between abiotic conditions and snail density and pattern of successful invasion in the GYE, and on empirical data already in hand on the relationship between temperature, pH, conductivity, and snail life-history traits. Additionally we sampled several streams within GTNP to get pre-invasion invertebrate abundance in case of later mud snail invasion. We lack these data from streams in Yellowstone, and by sampling before invasion will be more able to assess impact. Findings and Status Objective 1. Polecat Creek has among the highest primary production rates and nitrogen demand for any stream, presumably because of its warm temperature, high P loading and constant discharge. Despite this high productivity we found that mud snails consume about 60% of daily gross primary productivity, which means that snails consume nearly all of the algae in the stream as fast as it can grow. Excretion of ammonium by snails was 4 times higher than the net uptake rate by benthic microbes, suggesting that snails drive ammonium cycling within this stream. Interestingly, we found a small impact of snails on algal biomass in small experimental chambers, but no impact on primary production. It is possible that snails recycle ammonium at a high enough rate to actually stimulate primary production, so that their grazing rates are counteracted by higher productivity. Objective 2. We sampled 5 stream locations within GTNP last summer that we believe to be the highest risk for snail invasion. They are: Cottonwood Creek, Jenny lake outlet, Kelly Warm Springs, Ditch Creek and the Bar BC spring creek. We found no exotic New Zealand mud snails at those sites, but we believe Kelly Warm Springs is particularly susceptible to invasion. We are currently analyzing data from growth in streams in the GYE where snails have invaded to develop an empirical model to estimate snail invasion success in streams with varying abiotic conditions.

Keywords: animal, population, mortality, Jackson Lake, Grand Teton National Park, Polecat Creek, John D Rockefeller Memorial Parkway, Cottonwood Creek, Jenny Lake, Kelly Warm Springs, Ditch Creek, food, forage, springsnail, Jackson Lake springsnail, Pyrgulopsis robusta (Walker) , mudsnail, New Zealand mudsnail, Potamopyrgus antipodarum (Gray), entomology, insect, Insecta