Nutrient release and community metabolism following application of herbicide to macrophytes in microcosms.
The macrophyte Egeria densa was introduced into plastic-lined pools of dechlorinated tap-water and allowed to grow for 17 days. A mixture of diquat + endothal was applied to the water to give concns. of 0.2 and 0.3 mg/litre respectively. Egeria died rapidly and 64% of the original o.m. had decomposed within one month. The N and P content of the water increased slightly after treatment, but the increase was less than the amount removed by the plants during the first five days after introduction into the pools. During decomposition, CO2 production exceeded O2 consumption by a factor of 10 and far more o.m. was lost than could be explained by aerobic respiration. This suggests that decomposition of the plants was principally anaerobic, despite the continued presence of O2 in the water column. From summary.