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HARSHNESS: CHARACTERIZATION OF INTERMITTENT STREAM HABITAT OVER SPACE AND TIME
Citation:
Fritz, K M. AND W. K. Dodds. HARSHNESS: CHARACTERIZATION OF INTERMITTENT STREAM HABITAT OVER SPACE AND TIME. Presented at North American Benthological Society, Athens, GA, May 27-31, 2003.
Impact/Purpose:
The goal of this research is to develop methods and indicators that are useful for evaluating the condition of aquatic communities, for assessing the restoration of aquatic communities in response to mitigation and best management practices, and for determining the exposure of aquatic communities to different classes of stressors (i.e., pesticides, sedimentation, habitat alteration).
Description:
Frequently disturbed environments, such as intermittent streams, are ecologically useful for studying how disturbance characteristics (e.g., frequency, magnitude) affect community structure and succession. A harshness index summarizing spatial and temporal characteristics of prairie intermittent streams was developed to predict benthic macroinvertebrate assemblage measures. The index incorporates 11 variables that describe recent and historical hydrologic regime (e.g., average flow, flow variability, drying, and flooding) and surface water connectivity. Relationships between index values and annual assemblage characteristics (taxonomic richness, diversity, evenness, and abundance) were tested over 2 years using 7 sites across a range of flow permanence. Total macroinvertebrate abundance was significantly related to harshness values in both years, whereas taxonomic richness and species diversity were significantly related to harshness index values only for the year with lower flood frequency. The results suggest that temporal and spatial aspects of habitat harshness constrain community structure in intermittent streams. It is important to consider both short-term factors (e.g., floods, distance from colonization sources) that can alter abundance and colonization immediately, and historical factors (e.g., probability of drying, average duration of dry periods) that may be relevant over longer timescales.