Aquatic Plant Control Research Program. Effects of Endothall Treatment on Phosphorus Concentration and Community Metabolism of Aquatic Communities.
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS ENVIRONMENTAL LAB
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Herbicide treatment and macrophyte senescence may results in the recycling of phosphorus from aquatic weeds to nontarget species because the nutrient is rapidly leached from plant tissue. A field study and two microcosm experiments were conducted to examine changes in phosphorus, oxygen, and chlorophyll a concentrations after the application of the herbicide and endothall. In each microcosm experiment, Potamogeton crispus communities were housed in 57-lambda aquaria containing known standing crops of the test plant and sediment with a specific phosphorus-adsorbing capacity. In the first microcosm experiment, the application of 2.0 ppm endothall caused plant death and a rapid, short-term increase in soluble reactive phosphorus, presumably from excessive leaching during senescence. A second microcosm experiment, which employed six control and six experimentally treated systems, differed from microcosm experiment I in that the sediment used had a weak phosphorus-adsorbing capacity. In addition, the metabolism of the total microcosm and three autotrophic components macrophyte-epiphyte, planktonic, and benthic were monitored to assess the effects of an herbicide perturbation on nontarget assemblages.