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Presented at the NABS Annual meeting, Anchorage, Alaska, 2006
in Disturbance Ecology
Macroinvertebrate spatio-temporal structure and drift in a karst Texas stream
D.R. Pendergrass1 and T.L. Arsuffi2.1Aquatic Station, Texas State University, San Marcos, TX 78666, 2Field Station, Texas Tech University, Junction, TX 76849
We assayed macroinvertebrates seasonally at ten sites from Fall 2003 through Summer 2005 in the Blanco River, Texas: a karst stream subject to intermittent flow and flash flooding. Sampling at up, mid and downstream sites permitted spatial analysis of the assemblages across gradients of flow permanence, distance downstream, and local versus regional land-use impacts. A total of 166 genera have been identified, although dipteran richness is likely underestimated. Ephemeroptera and Trichoptera genera were ubiquitous and accounted for 50% of all individuals collected. Uncommon taxa (<1%) totaled 20%. Collector–gatherers and filterers were dominant at most sites and common throughout the river, while shredders were nearly absent. Canonical Correspondence Analysis indicated longitudinal spatial variation in macroinvertebrate composition related to antecedent hydrological disturbance. Drift assemblages exhibited strong diel periodicity and were dominated by Ephemeroptera and Trichoptera taxa, some of which were unique to the drift samples. Understanding macroinvertebrate ecology and life history in relation to antecedent hydrology and flood and drought disturbance regimes in conjunction with watershed development and aquifer levels will be critical to informed Blanco River watershed management.
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