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<br />Elevated concentrations of selenium in bottom sediment 'occurred at four <br />of five reservoir sites and at one tributary site. The maximum concentration <br />was 5.4 micrograms per gram in Lake Meredith near Ordway, Colo. <br /> <br />Geometric mean selenium concentrations in livers from bird species <br />collected at reservoirs during the spring were highest in killdeer (9.9 to <br />42 micrograms per gram dry weight), intermediate in mallards (9.7 to 24 micro- <br />grams per gram), and lowest in American coots (12 to 15 micrograms per gram). <br />The maximum selenium concentration (56 micrograms per gram) was detected in <br />the liver of a black-necked stilt from Lake Meredith in Colorado. <br /> <br />Five species of fish from the Arkansas River had selenium concentrations <br />ranging from 2.1 to 18.5 micrograms per gram dry weight, and three species <br />from the tributaries had selenium concentrations ranging from 3.6 to 16.9 micro- <br />grams per gram. Thirteen species of fish in the reservoirs had selenium <br />concentrations ranging from 2.2 to 20 micrograms per gram. Selenium concentra- <br />tions in invertebrates from the Arkansas River, tributaries, and reservoirs <br />ranged from 2.7 to 8.7 micrograms per gram. The maximum concentration of <br />. <br />selenium detected in plants was 14 micrograms per gram in a sample of algae <br />from Lake Meredith in Colorado. Eight organochlorine pesticides were detected <br />in some samples of bird livers and eggs and in fish from the reservoirs, but <br />all concentrations were within the ranges of reported background concentra- <br />tions. No evidence of deformity or reproductive failure was observed for any <br />bird or fish species; however, the study was not designed to assess reproduc- <br />tion or to determine the extent of embryonic deformities. <br /> <br />Selenium concentrations in some samples of food organisms (small fish, <br />invertebrates, and aquatic plants) exceeded the dietary concentration of <br />10 micrograms per gram wet weight demonstrated to alter reproduction in <br />mallards. Nearly all fish samples had selenium concentrations exceeding the <br />85th percentile established by a national survey. Nearly all fish samples <br />from three reservoirs and almost none from two other reservoirs had whole-fish <br />concentrations of selenium exceeding the concentration that correlated with <br />reproductive impairment in bluegills. <br /> <br />Selenium concentrations in fish collected from reservoir sites were <br />positively correlated to selenium concentrations in the reservoir water. No <br />other relations between abiotic and biotic matrices were identified. <br /> <br />Elevated concentrations of aluminum, arsenic, copper, lead, mercury, and <br />zinc also were determined in at least one matrix (water, sediment, or biota) <br />at one or more sites. The source of lead, mercury, and zinc may be mine <br />drainage upstream from the study area. <br /> <br />2 <br />