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Section 779.20 (c) Continued. <br />• <br />Tub ificid wormy were the dominant group found in the Ekman grab <br />samplPS. These worms comprised over 63 percent of the total mean <br />density or 12 organisms/ft2. Midge larvae represented 21 percent <br />of the total mean density and consisted of 2 specimens each of the <br />species Microtendipes sp. and Glyptotendipes sp. A few specimens <br />of the mayfly species Caenis sp. were also collected. <br />Comparison of 1979 data to the 1975 baseline data show somewhat <br />similar results. Seven taxa and a total density of 18 organisms/ft2 <br />were found from one Surber collected in the 1975 baseline st~~dy. <br />This compares to a mean number of nine taxa and 28.5 organisms/ft2 <br />found in the recent 1979 survey. Diversities were nearly the same <br />in both studies. In the 1975 baseline study the Falculated diversity <br />was 2.2 for one Surber sample as compared to 2.0 in the 1979 study. <br />While mayflies also dominated in the 1975 baseline study, the most <br />dominant group reported was the family Baetidae. No baetid mayflies <br />• were collected in 1979, however the species Paremele~us sp. and <br />Siphlonurus sp. of the family Siphlonuridae were collected. These <br />were not among the taxa reported ir, the 1975 baseline study. The <br />reasons for this discrepancy may be due either to a taxonomic error <br />or a true shift in the community structure. Siphlonurids and <br />baetids occupy very similar niches indicating a possible misidenti- <br />fication in the 1975 study, since most other data and stream conditions <br />are similar. <br />Ecological Notes. Aquatic macroinvertebrates collected from the <br />four sampling stations were representative of natural corditiors <br />found within this type of aquatic habitat in the region. The <br />generally low densities found in July are probably due to early <br />emergence by dipterans and mayflies, with the next generation in <br />the egg or very early instar stage. The stream's habitat is vari- <br />able due to the highly fluctuating flows and temperatures experienced <br />throughout the year. Flow in upper r-oidel Creek usually dries up <br />• in late summer, while floras in the middle and lower portion become <br />minimal. Substrate in most of Foidel Creek is conducive to those <br />779-233 <br />