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• to different methods of collecting, ;;ith several of the studies not crp- <br />luring the small chi onomids. <br />5,P,p Density & Biomass <br />Density of organisms ranged from app_~oximately 350 to 23,000 per meter <br />considering all stations, dates, and samples. Table 5-1 &- 12 present <br />density data for the samples taken. Over the study area as a whole the most <br />abundant group xas the chironomids, and fluctuations in the L density strongly <br />influenced the total densities observed. Total densities were often 50q or more <br />chironomids and xere at times 90% or more. These are shown on Table 5- 2 . <br />Chironomid densities ranged to nearly 9,000 organisms per m 2. Groups xhich <br />showed moderately high densities were caddisflies, mayflies, ceratopogonids, and <br />snails. Groups xhich shored very lox densities xere the odonates, (dragonflies, <br />• damselflies), the true bugs and leeches. <br />By collection date, average densities for N~azch xere considerably higher than <br />for late July and October, as would be expected because of emergence. Average <br />densities per station of March samples ranged from approximately 6,000 to 12,000 <br />organisms per m2. While average October densities ranged from 700-1500 and <br />July samples from 550- 2200 organisms per .;. <br />* rounded to two significant figures <br />• <br />5-6 <br />