HR: 11:00h
AN: NB52B-03    [Abstracts]
TI: Influence of Geology on Benthic Macroinvertebrate Assemblages: a Field Experiment Examining Differences in Fitness With Water Hardness
AU: * Olson, J R
EM: jrolson@cc.usu.edu
AF: Department of Aquatic, Watershed, and Earth Resources, and Ecology Center, 5210 Old Main Hill, Utah State University, Logan, UT 84322-5210 United States
AU: * Olson, J R
EM: jrolson@cc.usu.edu
AF: Western Center for Monitoring and Assessment of Freshwater Ecosystems, 5210 Old Main Hill, Utah State University, Logan, UT 84322-5210 United States
AU: Hawkins, C P
EM: chuck.hawkins@usu.edu
AF: Department of Aquatic, Watershed, and Earth Resources, and Ecology Center, 5210 Old Main Hill, Utah State University, Logan, UT 84322-5210 United States
AU: Hawkins, C P
EM: chuck.hawkins@usu.edu
AF: Western Center for Monitoring and Assessment of Freshwater Ecosystems, 5210 Old Main Hill, Utah State University, Logan, UT 84322-5210 United States
AB: The composition of benthic macroinvertebrate assemblages is associated with catchment geology, with soft-water streams having restricted fauna and hard-water streams having greater diversity and abundance. We hypothesized that these patterns arise because of differences between taxa in osmoregulatory ability, with taxa found primarily in hard water having lower fitness in soft water, and taxa found in soft water having similar fitness in both types of water. To test this hypothesis, we exposed 13 taxa found across a range of water hardness to naturally occurring soft and hard water in streamside microcosms for three months. For each taxon, we measured 3 components of fitness (survival, growth rates, and adult emergence success). Responses of most species were consistent with our hypothesis. However, the hard-water taxon Hydroptila had equal survival between treatments and 50% greater emergence success in soft water. In this case, we suspect that osmoregulatory effects on fitness occur in earlier instars than used in this experiment. Although more information is needed to conclude osmoregulation limits the distribution of taxa, the direct effect of water chemistry on fitness provides a mechanism for the influence of catchment geology on stream invertebrate taxa.
DE: 0400 Biogeosciences
DE: 1806 Chemistry of fresh water
DE: 1871 Surface water quality
DE: 9901 NABS Student Award - Basic Research
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly