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1995J MACROINVERTEBRATES OF THE GREEN RIVER 215 TABLE 1. Mean:t standard deviation water chemistry values from Green River sample sites, June-August 1991 (n = 3, temperature in oC, salinity in percent, conductivity in p,mhos, turbidity in NTUs, hardness and alkalinity in ppm CaC03), Habitat type Date Min./max pH Salinity Conductivity Turbidity Hardness Alkalinity temp. River channel 7/15 * 8,14:t ,09 .04 :t .0 753 :t 6 183 :t 318 411 :t 0 183:t 10 8/12 20,5/26,5 8,48 :t .10 .04:t ,01 7l8:t8 402 :t 41 320 :t 20 205:t 17 Ephemeral side channel 6/3 20.5/30.5 9,0 :t 0 ,03:t ,06 326:t 10 57 :t 6 183 :t 20 171:t0 7/1 16/30,5 9,14:t ,16 ,12:t ,03 445 :t 5 127 :t 21 228 :t 10 240 :t 17 River backwater 7/10 20,5/29,5 7.98 :t .23 .01 :t .01 523 :t 23 57:t 9 228 :t 10 183 :t 20 8/8 19/26.5 8.59 :t .12 ,03:t ,0 730:t III 45 :t II 268 :t 40 228 :t 26 Seasonally inundated wetland 6/10 19.5/26,5 9,0 :t 0 ,02 :t ,0 314:t 8 52 :t 8 154 :t 0 143:t 10 7/12 22/32 8,37:t ,ll .02 :t .01 446 :t 20 36:t 8 205 :t 0 223 :t 0 8/15 22/29,5 8,93:t ,1 .01 :t .0 345 :t 13 195:t 17 171:t17 154 :t 0 *Thermometer lost , . River Backwater River backwaters are submerged during high flows and do not emerge as distinct entities until the river drops. For this reason the river backwater was not sampled during peak flow Gune). The river backwater we sampled, located just upstream of the river channel site described above, was approximately 10 m wide X 50 m long and 1.3 m deep, Turbidity, alkalinity, and pH were highest during the August sample. Substrate consisted mostly of loose silt and detritus with virtually no sand. Silt and detritus were constantly being deposited during the study period. Seasonally Inundated Wetland This site, commonly called "Old Charlie's Wash," is a shallow floodplain wetland man- aged by the USFWS for waterfowl and is located approximately 4.3 km south of the USFWS hatchery. As the river rises in the spring, water enters Old Charlie's Wash and, at peak flow, retaining structures are put in place to create a 43-ha pond and to prevent the impounded water from receding as rapidly as the river. By early fall the water in Old Charlie's Wash is nearly depleted by seepage and evaporation, Turbidity increased dramati- cally during the August sample, and conduc- tivity, hardness, and alkalinity peaked during the July sample. Substrate consisted of firm silt, detritus, and sand. METHODS Sampling Samples were collected during the summer of 1991 (Tables 2-5). Initial sampling of the ephemeral side channel and seasonally inun- dated wetland occurred just after river flow peaked in early June, but samples for the river channel and backwater habitats were not col- lected because the water level was too high. All four habitats were sampled during July and all but the ephemeral side channel during August. Fifty core samples were taken along a 30-m transect at each site. Each sample was collect- ed with a clear acrylic tube, 450 mm long X 47 mm in diameter (Shiozawa 1985), which was pushed into the substrate to a depth of 60-80 mm. Sediment from each sample was preserved in 5% formalin with rose bengal stain added to aid in sample sorting. Sample Processing In the laboratory we washed each sample to separate organisms from sediments using the following procedure. First, the formalin was drained and replaced with tap water. The sample was then gently stirred to resuspend the sediments and poured into a plastic tray (36.5 cm X 31.5 cm X 6 cm) through which a small volume of warm water flowed. The out- flowing water, laden with small sand and clay particles, detritus, and benthic invertebrates, was filtered through a 63-lLm screen. Larger