Context: River regulation has altered the timing and magnitude of hydrological connectivity between rivers and their floodplains, with potential consequences for zooplankton that persist via diapausing eggs in sediment “egg banks”. Aims: We examined how water temperature and recent inundation history of riverbank versus floodplain sediments influence emergence, diversity and community composition of zooplankton. Methods: Dry riverbank and floodplain sediments from the lower Lachlan River (New South Wales, Australia) were rewetted and incubated in temperature-controlled cabinets at 10 °C (winter) and 21 °C (spring). Emerging zooplankton were sampled repeatedly over six weeks and identified to the lowest feasible taxonomic level. Key results: Greater abundance of zooplankton emerged at warmer temperatures, and that floodplain sediments supported a greater abundance and diversity of emerging zooplankton, whereas differences in community composition between habitats were relatively minor, perhaps because all collected sediments had been recently inundated by large-scale flooding. Conclusions: Seasonal temperature regime and the extent of floodplain inundation jointly regulate activation of sediment egg banks and zooplankton emergence dynamics in this regulated lowland river-floodplain system. Implications: Management that maintains lateral river-floodplain connectivity, particularly during warmer periods, is likely to support high zooplankton abundance with potential flow-on effects for the riverine food webs.
Maharjan et al. (Sat,) studied this question.