Macroinvertebrate Recolonization Dynamics in Response to the Level of Urbanization, Drought and Flood in Three Austin, Texas, Streams




Chhopel, G. Karma

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Impervious cover of urbanized areas exaggerates the hydrologic disturbance (intensity of spates and duration of dry periods) common in central Texas. The objective of this study was to determine how benthic macroinvertebrate community composition, diversity, resilience, and recolonization in three Austin, Texas, streams that vary in degree of impervious cover are affected by drought and flood. The least urbanized watershed (Onion Creek, 1.6% impervious cover) was used as reference. Walnut Creek is in the most urbanized with 30% impervious cover followed by Barton Creek at 7%. Benthic macroinvertebrates were quantified in three riffles in each of the three streams. Recovery from drought and flood were determined by: 1) Two bi-weekly samples after flow resumed in September 2001, and monthly sampling thereafter until flood disturbance; 2) Two bi-weekly samples after flows receded in November 2001, and monthly sampling thereafter for three months. Among the three streams, Walnut Creek had the greatest overall abundance with 41% of the total organisms; Barton Creek had 30% and Onion Creek 29%. Walnut Creek had the maximum abundance (3,774 individuals/m2) and Barton Creek had the least abundance (1,914 individuals/m2) during the post-drought. During post-flood, the greatest abundance occurred at Barton Creek (1,410 individuals/m2) and Onion Creek had the least abundance (527 individuals/m2). Overall, Chironomidae made up the bulk of the total organisms at all sites comprising 33.7% followed by Szmulium (19%) and Baetis (17.1 %). Chironomidae and Baetis were the dominants at all study streams. Relative abundance of macroinvertebrate was 2 times greater during the postdrought than during post-flood. Greatest species richness occurred at the moderately disturbed stream where Baetis, Caenis, Stene/mis and Chironomidae were dominant. Results indicated that rate of recolonization following disturbance was inversely related to degree of impervious cover. Impervious cover appears to interact with natural hydrologic disturbances in determining structure and function of the benthic community in urbanized streams.



Invertebrates, Benthos, Texas


Chhopel, G. K. (2003). <i>Macroinvertebrate recolonization dynamics in response to the level of urbanization, drought and flood in three Austin, Texas, streams</i> (Unpublished thesis). Texas State University-San Marcos, San Marcos, Texas.


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