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Presented at the NABS Annual meeting, Vancouver, British Columbia, 2004
in Bioassessment
Analysis of benthic macroinvertebrates associations in low gradient streams of the Kisatchie National Forest (central Louisiana, USA).
V.E. Alley1, A.M. Hill2, M.D. Farr1, and F.L. Pezold2. 1USACE Waterways Experiment Station, Aquatic Ecology and Invasive Species Branch, 3909 Halls Ferry Rd. Vicksburg, MS 39180, 2Department of Biology,The University of Lousiana at Monroe, Monroe, La 71209
Kisatchie National Forest (KNF) has six ranger districts within three ecoregions (central Louisiana, USA). In 2000-2001, 57 3rd - 6th order low-gradient, sandy substrate streams were sampled for macroinvertebrates and physicochemical parameters to characterize stream quality using standard bioassessment metrics and diversity calculations. Macroinvertebrates were enumerated and identified to lowest practical taxon. Shannon-Wiener diversity scores were 0.38-2.83. Taxa richness ranged from 2-30. North Carolina Biotic Index scores were 4.9-6.6, yielding water quality designations of “good-fair” to “excellent”. Most streams fell within the “good” designation. Streams were compared by ecoregion, stream order, and ranger district groupings. Preliminary non-parametric statistics suggested differences among variables at the ecoregion level. However, principal components analysis (PCA) did not readily group streams by ecoregion. Analyses yielded no differences when comparing streams among stream orders. Statistics suggested differences among some variables when comparing among ranger districts. PCA grouped some ranger districts as having lower water quality than others; but groupings were not consistent among axes. While results suggest KNF streams generally have “good” water quality, macroinvertebrate sampling methods were coarse, requiring use of non-parametric statistics. This study highlights the need to refine macroinvertebrate sampling protocols for stream bioassessment, particularly where results may be used in management decisions.
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