HR: 09:30h
AN: NB31E-05    [Abstracts]
TI: Diel Drift Patterns and Spatio-temporal Distribution of Macroinvertebrates in the Blanco River, Texas: A Groundwater Dominated Stream Subject to Intermittent Flow
AU: * Pendergrass, D R
EM: dp1091@txstate.edu
AF: David Pendergrass, Department of Biology--Aquatic Station, Texas State University, San Marcos, TX 78666 United States
AU: Arsuffi, T L
EM: ta04@txstate.edu
AF: T.L. Arsuffi, Junction Field Research Station, Texas Tech University, Junction, TX 76849 United States
AB: The Blanco River is a relatively pristine karst stream in central Texas and designated a conservation target by The Nature Conservancy. It is fed primarily by groundwater in the upper reaches and dominated by runoff and intermittency downstream. The spatial and temporal structure of macroinvertebrates in the Blanco River was assessed with seasonal Hess and d-net samples during 2003-2004 and three diel drift samples from May to October 2004. Our downstream site showed a 47% drop in diversity, but comparable abundances to up- and mid-stream sites. Ephemeropteran and trichopteran taxa (e.g. Tricorythodes and Cheumatopsyche) comprised about 60% of drift and benthic samples alike, however, non-insect taxa were nearly absent from the drift. Some taxa not present in the benthic samples were present in the drift. Post-dusk and pre-dawn peaks in diel drift were discerned. No strong seasonal patterns were detected which may be attributable to an unusually wet year and asynchronous, multivoltinous life cycles associated with mild seasonality in subtropical regions. The Blanco River's historically variable hydrological regime may be further exacerbated by long-term flow alteration associated with increasing anthropogenic development and could alter the composition and distribution of macroinvertebrate assemblages.
DE: 1800 HYDROLOGY
DE: 9901 NABS Student Award - Basic Research
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly