| Popis: |
Sediment contamination and benthic macroinvertebrate distribution were studied in Palestine Lake, Indiana, a public 80-ha system contaminated by effluents from a nearby electroplating plant. Trace metal levels in the upper 3 cm of sediment ranged from a high of 969 ppm cadmium, 14,032 ppm zinc and 2106 ppm chromium (dry weight basis) near the influent ditch, to a low of 4 ppm cadmium, 139 ppm zinc and 38 ppm chromium in the uncontaminated eastern basin of the lake. The midge Chironomus tentans was absent from areas of highest contamination; how ver, midge numbers increased to an average of 28 individuals/grab sample in the eastern basin. Specimens of the aquatic oligochaete Limnodrilus sp. were abundant (89/sample) in the most heavily impacted areas of the lake and scarce (3·4/sample) in the eastern basin. |
