Methods for quantitative sampling of epiphytic microinvertebrates in lake vegetation

Two methods were developed for the quantitative sampling of rotifers and cladocerans attached to aquatic macrophytes while separating them from plankton. We named them the "covering method" and the "picking-up method." We consider the covering method to be better for estimating the abundance of animals on plants, but it requires hard work on a boat. In contrast, the picking-up method is simple and easy to perform, but it seems to estimate animal abundance with some errors. The densities of rotifers and cladocerans on emergent and submerged plants in two Japanese lakes were estimated by the two methods, and the results were compared. The densities of most animals (e.g., the rotiferans Brachionus, Mytilina, Lepadella, and Colurella, and the cladoceran Alona) estimated by the picking-up method did not differ from those estimated by the covering method. In contrast, the densities of the rotiferans Monostyla, Euchlanis, and Trichocerca estimated by the picking-up method tended to be lower than those estimated by the covering method. These suggest that the picking-up method is suitable for estimating many densities, except for some rotiferan genera.