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comparison with backwater benthic numbers. Grabowski and Hiebert (1989) reported <br />plankton densities of 1051/m3 for backwaters located near Ouray and up to 16,600/m3 <br />for backwater near Jensen in June. Their estimates included 88 °lo rotifers, and rotifers <br />were not quantified in the present study. Adjusting their numbers to reflect <br />microcrustaceans only gives a range of 100/m3 for Ouray backwaters and 2000/m3 <br />near Jensen. Our Ouray site was more similar to their Jensen site. The high densities <br />of microcrustaceans in Intersection Wash could be due to either the flooded vegetation <br />that enriched the waters or the earlier sample date. <br />River. Densities of river plankton ranged from 317-1,312/m3, benthic river <br />densities ranged from 948-6,318/m2. The benthic densities were 5-7 times greater than <br />plankton densities per square meter. The densities of both benthic and planktonic <br />microcrustaceans were 4-6 times greater in July than August. This decline may reflect <br />the utilization of nutrients left after high water or may be due to reduced source <br />areas, such as floodplains for plankton in August. There does not appear to be a <br />cohort shift since all life stages experience a sharp decline. Both the Ouray backwater <br />and the river site showed similar trends. The backwater decreased five fold while the <br />river decreased four fold. This supports the idea that river plankton is dependent on <br />source areas. Grabowski and Heibert (1989) report river plankton densities of 100/m3 <br />in June, with no plankton reported at later dates. The difference here may have been <br />the sample location. This study collected samples near the bank with some degree of <br />protection by a submerged sandbar whereas, Grawbosld and Hiebert may have <br />sampled a midchannel location which may not have had as many planktonic <br />15 <br />