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Investigating the Effect of Habitat Availability and Stream Morphology on Macroinvertebrate Demographics in Red Bud/Catalpa Creek of Northeastern Miss
Proceedings of the 2019 Mississippi Water Resources Conference
Year: 2019 Authors: Richardson B., Musser S., Ortega-Achury S., Ramirez-Avila J., Martin J.
Rapid bioassessments using macroinvertebrates is one of the most popular ways to gather large amounts of data on stream health in a very short amount of time. A wide variety of indices have been developed to score and weight macroinvertebrate communities for the purposes of evaluating water quality, and many of these are state- or region-specific. However, the use of these indices can often bias results toward better water quality when taken at face-value, as the presence of only one individual of a certain group or species can significantly raise the water quality score of many indices. This study investigated the macroinvertebrate demographics of Red Bud/Catalpa Creek in northeastern Mississippi. The Pollution Tolerance Index (PTI) of the sampled stream reaches reported, almost exclusively, an "excellent" rating. However, community abundances showed that many samples were dominated tolerant taxa while the most intolerant taxa (indicators of good water quality) were represented by 1 or 2 individuals. Community analysis also showed that many stream reaches were vacant, or nearly so, of important functional groups such as scrapers and predators. The absence of these functional groups is likely due, in part, to the absence of adequate habitat and other resources. In one study stream, forested riparian vegetation is restricted to approximately a 200-m section in the upper reaches while the rest of the stream is flanked by thick grasses and invasive shrubs. This restriction of forest vegetation reduces the availability of sufficient food resources for shredders in downstream sections of the stream. The results of this study highlight the importance of ecological metrics and community demographics in the evaluation of stream health. Water quality and stream health indices using macroinvertebrates should be used to support these results of these metrics, not supplant them.