Mechanisms for copepod resting egg accumulation in seagrass sediments

Abstract

We identify several mechanisms by which seagrass presence can enhance the retention and benthic abundance of copepod eggs on a shallow reef in Florida: (1) benthic macrofauna are more abundant in seagrass patches than in bare sediment and bioturbation by these animals may contribute to egg retention through burial; (2) the physical presence of the seagrass canopy inhibits the resuspension of fine particles and thereby promotes egg accumulation; (3) the persistent low oxygen conditions at the sediment surface sustained in seagrass patches during warm summer months promote egg retention by inhibiting the hatch of newly settled eggs. Understanding how these factors contribute to copepod egg accumulation in the seagrass beds of other areas could give valuable insights into how seagrass presence may influence local copepod populations.

A field experiment demonstrating risk on the seafloor for planktonic embryos

“…Mortality from deposition on the seafloor to hatching as nauplii is difficult to estimate, but for some coastal planktonic copepods, sufficient numbers of solitary benthic resting eggs survive to hatch and repopulate the plankton after seasons when planktonic larvae, juveniles, and adults are absent. Solitary benthic embryos of copepods arrest development, tolerate anoxia, and resume development when returned to oxygenated water (Marcus and Schmidt‐Gengenbach ; Hairston and Cáceres ; Scheef and Marcus ; Broman et al ). Mortality rates estimated for buried resting eggs are extraordinarily low (Sichlau et al ), but these estimates do not include mortality before burial, as a result of permanent burial, or after emergence at the sediment surface.…”