Nutrient Release and Community Metabolism Following Application of Herbicide to Macrophytes in Microcosms

Abstract

A diquat-endothall mixture was applied to replicated pools stocked with the macrophyte Egeria densa. Egeria died rapidly and 64% of the original organic matter had decomposed within 1 mo. 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 1st 5 days after introduction into the pools. During decomposition, CO2 production exceeded O2 consumption by a factor of 10 and far more organic matter was lost than could be explained by aerobic respiration. This suggests that decomposition of plants was principally anaerobic, despite the continued presence of O2 in the water column.