Showing papers by "Heidelberg University (Ohio) published in 1988"

Effects of herbicides on stream Aufwuchs productivity and nutrient uptake.

Abstract: The effects of atrazine and a combination of alachlor, atrazine, metolachlor, and metribuzin on the productivity and nutrient uptake rates of native streamAufwuchs communities were investigated in two separate artificial stream experiments. After an 8-day colonization period, the first experiment employed constant doses of atrazine at 0 Μg/L (control), 24 Μg/L and 134 Μg/L. The second experiment employed a pulsed dose having maximum concentrations of 35 Μg/L alachlor, 109 Μg/L atrazine, 90 Μg/L metolachlor, and 21 Μg/L metribuzin. Each 20-day experiment was run at both 10‡C and 25‡C. Constant exposure to 24 Μg/L atrazine yielded a significant reduction in both ash-free dry weight (AFDW) and chlorophylla at 25‡C but not at 10‡C. Constant exposure to 134 Μg/L atrazine yielded significantly less AFDW and chlorophylla at both temperatures. The pulsed exposure to four herbicides yielded significantly less AFDW at both temperatures, while chlorophylla was significantly less only at 10‡C. During continual exposure to 134 Μg/L atrazine, both NO2 + NO3 and silica uptake rates appeared to be reduced at both temperatures, although the differences were generally not statistically significant. At 10‡C uptake rates of soluble reactive phosphorus and NO2 + NO3 were depressed temporarily by exposure to the pulse of four herbicides, recovering to control rates within a few days, while no effect on uptake rates was discerned at 25‡C. The temperature difference between experimental runs had a greater effect on nutrient uptake rates than did the herbicide treatments during a run. The results indicate thatAufwuchs growth and nutrient uptake rates may be reduced temporarily by herbicide exposures in agricultural streams. However, greater effects on these processes may be exerted by other factors accompanying storm events, such as reduced temperatures.