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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Disturbance Ecology III
COMPARISON OF INVERTEBRATE ASSEMBLAGES OF FOUR INTERMITTENT OUACHITA MOUNTAIN STREAMS.
R.K. Heth1 and A.V. Brown2. 1Department of Biology, Missouri Southern State College, Joplin, Missouri 64801, 2Department of Biology, University of Arkansas, Fayetteville, Arkansas 72701
Benthic invertebrate assemblages were surveyed in four streams representing a gradient of flow permanence. Reaches consisting of a three riffle-pool sequence were sampled from May 1998 to May 1999. Quantitative benthic samples, light traps, and hand collections were taken on 18 dates when water was present. Invertebrates >0.20 mm were collected, identified, and measured. A total of 222 taxa were identified (109 to species), including 25 Plecoptera, 21 Ephemeroptera, 30 Trichoptera, 19 Coleoptera, 54 Diptera, and 15 Crustacea. Richness declined from 159 in the most permanent stream to 72 in the driest. Similarity among streams was low with Jaccard coefficients ranging from 0.41 to 0.34. Densities in the wettest stream were highest in late spring (18,200 m-2) augmented by copepod and daphnid populations (14,400 m-2) and low in late winter (2,850 m-2). Streams that dried in summer reached maximum density in December (5,050 m-2). Biomass was significantly higher (p<0.05) in the most permanent stream (2,643 mg DW m-2) compared to the drier streams (504 mg DW m-2). Crayfish (70%) and isopods (17%), along with other collector-gatherers and shredders, dominated biomass in more ephemeral streams. Reduced richness and increasing dominance of crustaceans characterized drier streams.
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