The Response of Macroinvertebrates to Aquatic Macrophyte Decomposition

The response of macroinvertebrates to the progressive decomposition of the American lotus Nelumbo lutea (Willd.) Pers. was examined. Macroinvertebrate densities increased significantly with the onset and progressive senescence of the leaves, as reflected by decreasing chlorophyll a concentrations. The chironomid Polypedilum nymphaeorum Maschwitz and three species of Naididae exhibited positive responses to presumably increasing levels of food as leaf decomposition progressed. P. nymphaeorum larvae probably switched from feeding on periphyton to utilization of decomposing plant tissue and associated microbial decomposers once the Nelumbo leaves began to decompose. Naididae did not become abundant on the leaves until the onset of initial leaf decomposition. Densities of the carnivorous chironomid Ablabesmyia philosphagnos Beck and Beck were more closely related to the age of the leaves than to prey availability, older leaves having been colonized by several generations of individuals while the younger leaves had been colonized by only one