Rotifer Hatching from the Sediments of a Fluctuating Mainstem Reservoir

Abstract

Rotifer hatching was examined for moist sediments collected from three benthic environments in a mainstem reservoir embayment, Kentucky Lake, KY: a drawdown zone with an established annual drying and wetting cycle, a floodplain that is only rarely inundated, and the permanently inundated embayment. Hatching data were compared with previous published data for laboratory-dried sediments from the same sites and with bi-weekly water-column samples over a one-year period. Of the total 44 taxa now recorded from Kentucky Lake, 18 species hatched from moist sediments and six from completely dried sediments. Taxa that emerged from moist and dried sediments were common to temporary and littoral habitats indicating that they may be better adapted for surviving diapause in a fluctuating reservoir environment. Evidence further suggests that the degree of sediment drying in drawdown and floodplain zones may affect egg hatching and that human-induced reservoir water level fluctuations may play a role in rotifer community dynamics by increasing or reducing rotifer community diversity in a single year.