7/1/2008 - 6/30/2010
- Robert Stelzer, UW-Oshkosh
Nitrate concentration is elevated in many parts of Wisconsin and throughout the world yet the toxic effects of nitrate on aquatic invertebrates, particularly those that inhabit shallow sediments, are poorly known. We propose to investigate the lethal and sublethal effects of nitrate in ground water on Gammarus pseudolimnaeus amphipods, which are common and locally abundant in the infaunal habitats of Wisconsin streams. The first stage of the research will include a set of laboratory experiments that will used established toxicological protocols to determine lethal nitrate concentrations (LC10, LC50) for Gammarus and concentrations at which sublethal effects on physiological processes (growth rates, respiration rates, tissue nitrogen) occur. Amphipods will be exposed to nitrate concentrations ranging from 1 to 512 mg NO3-N/L in these experiments. The second stage will assess the influence of elevated porewater nitrate concentrations in Radley Creek, a stream in the Central Sand Plains, on mortality and physiological processes of amphipods including growth and respiration. Radley Creek has high and spatially variable porewater nitrate concentration which will allow us to expose amphipods in situ to porewater nitrate concentration ranging from 0.3 to 100 mg NO3-N/L. This research will fill important gaps in the understanding of the effects of elevated nitrate concentrations on sediment-dwelling aquatic invertebrates. Because infaunal invertebrates are important components of stream food webs our results will contribute to the understanding of how elevated nitrate concentrations affect stream ecosystems. Our results will also have implications for the design of best management practices in nitrogen-rich watersheds.