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Little Topashaw Creek - Effects on Macroinvertebrate Community
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Identification and enumeration of aquatic invertebrates in the laboratory

Hyallela azteca, a common benthic macroinvertebrate that uses POM for food

   Collection of benthic macroinvertebrate samples from Little Topashaw Creek
Collections of invertebrates were made in five 150-meter-long reaches during three seasons before and three seasons following stream treatment with large woody debris structures. Sampled reaches included one site upstream of treatment, two within the treatment area, and two downstream of treatment.  Invertebrate samples were taken in June and October of each year using a variety of techniques, including; large woody debris brushings, coarse particulate organic matter (leafpack) grabs, quantitative streambed (Surber) samples, and aquatic net sweepings. Samples represented all major habitats: large woody debris, leaf packs / coarse particulate organic matter and streambed sand substrate.

Overall, numbers of individuals were very similar following rehabilitation efforts. A total of 149 macroinvertebrate taxa were identified, with 91 taxa observed before treatment and 118 taxa observed following treatment; the number of shared taxa was only 60. Jaccard and Sorenson incidence-based similarity indices both indicated a large change from before to after treatment. The Shannon index and Fisher's log series alpha index indicated low overall diversity before treatment and much higher diversity after structure placement. Overall sample evenness also increased substantially in collections after treatment. Despite many debris structure failures, several positive macroinvertebrate community responses to rehabilitation efforts were observed.