RECOLONIZATION OF AQUATIC INVERTEBRATES FOLLOWING AN EXTREME DROUGHT IN A PERENNIAL STREAM AND LIFE HISTORY ATTRIBUTES OF SPECIES RESTRICTED TO LOTIC HABITATS

Burk, R. A.; Kennedy, J. H.;

Extreme climatic events such as droughts eliminate aquatic biota and alter community structure and function. Perennial headwater springs provide essential drought refugia to benthic macroinvertebrates and are an important source of post-drought colonists via drift or aerial adults to intermittent streams. Ash Creek (north-central Texas) is a perennial groundwater-dependent stream that maintained flow for 2.0 km in contrast to regional streams with minimal surface water and no flow. A recolonization study on Ash Creek was conducted comparing the perennial headwaters’ benthic macroinvertebrate communities and trophic ecology with a downstream intermittent site’s. The headwaters supported higher mean taxa richness than the intermittent site until 9 months post-flow at the intermittent site (ANOVA p<0.001). Declining taxa richness at the perennial headwater site from August 2006 to April 2008 appears to reflect lag effects of the drought combined with effects of multiple spates in 2007. Adult emergence and life history attributes of species restricted to these perennial refugia reveal variable future vulnerabilities of these populations to loss of surface flow linked to recurring drought and groundwater overabstraction.