An empirical test of the impact of drying events and physical disturbance on wind erosion of zooplankton egg banks in temporary ponds

Abstract

Most temporary pond zooplankton species produce drought-resistant eggs that accumulate in the sediment and form an egg bank. When a pond dries and the egg bank is exposed, wind erodes eggs and wind action has been suggested as an important determinant of population demographics. While field observations suggest that egg bank erosion may be highest shortly after pond drying and physical disturbance of the sediment crust, this remains to be tested empirically. We performed a laboratory wind tunnel experiment to assess the effects of wind speed and sediment characteristics on egg pickup rates over time in a controlled environment. We used sediment samples in which an egg bank of the fairy shrimp Branchipodopsis wolfi was embedded and compared the number of eggs that blew away from dry, drying and disturbed egg banks as a function of time. Few eggs were picked up when the egg bank was dry prior to exposure, even at winds of 70 km h⁻¹. Most eggs were eroded when the egg bank was exposed to wind before it dried out, after the last water evaporated. Likewise, physical disturbance resulted in strong erosion fluxes. Overall, our results suggest that the state of the egg bank may be more important for egg bank erosion rates than the prevailing wind speed or the wind exposure time. Also, our findings are worrying in the context of climate change since they imply that predicted increases in drying events and reduced inundation lengths may compromise egg bank persistence in temporary ponds.