Occurrence and significance of copepod resting egg accumulation in seagrass sediments

Abstract

The resting eggs produced by some species of marine calanoid copepods have been observed to accumulate on the seafloor in areas of high deposition and low resuspension. Seagrass beds are known to be environments that promote the accumulation of fine sestonic particles by inhibiting resuspension but have not been previously investigated as possible reservoirs for copepod resting eggs. Field sampling on a shallow reef in the northern Gulf of Mexico over 3 yr revealed that viable resting eggs of the copepod Acartia tonsa were significantly more abundant in seagrass-colo- nized sediment than in adjacent unvegetated sediment. Egg abundance differences between the 2 environment types occurred throughout each year. Differences tended to be greatest during the sum- mer when the seagrass canopy was highest. These results suggest that the unique effects seagrass blades and rhizomes have on sediment stabilization may make seagrass beds important accumula- tion sites for resting copepod eggs in shallow areas subject to frequent disturbance. Seagrass-medi- ated resuspension events could therefore influence the population dynamics of some copepod spe- cies and may be essential for local copepod populations reliant on recruitment from benthic eggs. The effects that seagrass presence may have on the benthic distribution of resting stages produced by other species of zooplankton and phytoplankton should be evaluated, and the possible effects of resting stage accumulation in seagrass on plankton communities and whole ecosystems should be considered.