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Methods <br />Sampling <br />Sampling was conducted monthly from June through August 1991. The first <br />backwater sampled was Intersection Wash which was only sampled in June while it <br />was still connected to the main channel. The Ouray backwater emerged in July after <br />high water receded. Sampling of the floodplain began in June while flooding was <br />underway. Sampling of the river began in July after the high water receded. Follow- <br />up samples were taken to detect temporal changes in the community (see Table 1 for <br />dates and number of samples processed). Fifty 1.27 cm diameter benthic cores and <br />five vertical plankton tows were taken at each location. Five benthic cores were taken <br />every three meters along a 30-meter transect and a vertical plankton tow was taken <br />every six meters. The core sampler consisted of a 19 cm long plastic tube attached to <br />a 120 cm long pipe. The pipe had an attached plunger and a stopper to cover the <br />plastic pipe. The coring device was lowered to the benthos in the unstoppered position <br />to reduce the pressure wave in front of the sampler. After the core was pushed into <br />the substrate to a depth of four cm the stopper was used to seal the top of the tube to <br />prevent loss of sediment as the core was retrieved to the surface. The plastic tube had <br />a total volume of 24 ml excluding the four centimeters displaced by the sample. The <br />plankton tows were taken with a Wisconsin plankton net of 63 micron niter with a 29 <br />cm diameter opening. The net was lowered vertically in the water to the substrate, the <br />depth was then recorded and after waiting one minute to minimize bias created by <br />lowering the net, it was retrieved. Samples were washed in the field into 20-m1 vials <br />7 <br />