A study of benthic macroinvertebrate community composition was conducted at eight sites along Shabakunk Creek, a small stream in Mercer County, New Jersey, which receives urban runoff. The relationship between changes in substrate composition and the nature of the benthic macroinvertebrate community has been examined. Organisms were collected seasonally from natural substrates in riffles. Attempts to employ artificial substrates for invertebrate collection proved unsuccessful, as the population on the samplers was not representative of that in the stream bed.
Number of total benthic macroinvertebrate taxa collected declined from 13 in relatively undeveloped upstream areas to four below heavily developed areas, while population density decreased simultaneously in the same areas. Periphyton samples collected from natural substrates were analyzed for selected heavy metals. Significantly higher heavy metal concentrations are reported from substrates sampled below heavily developed areas, and changes in these values are discussed with regard to changes in benthic macroinvertebrate distribution.
This experiment tested the effects of heavy metal contaminated sediment on emergence of chironomids. The number of adults emerging from test chambers containing an uncontaminated sediment and ones with sediment containing 1030 ppm cadmium (Cd), 17,300 ppm zinc (Zn), and1640 ppm chromium (Cr) were observed for rqdays. It was found that emergence was reduced by over three times and delayed for two days in the heavy metal contaminated sediment.
Chironomid larvae were maintained for 17 days in sediments with various heavy metal levels . The control sediment had levels of 0.6 ppm cadmium, 17 ppm chromium and 77 ppm zinc . The most contaminated sediment had levels of 1030 ppm cadmium, 1640 ppm chromium, and 17300 ppm zinc .The mean length and weight of the larvae from the control sediment were 1 .83 cm and 2 .86 mg. The mean length and weight of larvae from the most contaminated sediment were 0 .82 cm and 0 .20 mg. A linear relationship was found for the square root of length versus metal levels in the sediment .
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