Population dynamics of Acartia pacifica (Copepoda: Calanoida): The importance of benthic-pelagic coupling

The seasonal occurrence of Acartia pacifica (Copepoda: Calanoida) and their resting eggs in the sediment of Xiamen Bay were documented between October 2002 and September 2003. The number of viable eggs in the sediment increased from January to May with tile increase in the number of planktonic females. When the population of A. pacifica disappeared from the water column, the number of eggs in the sediment began to decrease and reached a low value due to lack of input. The peak of nauplii abundance occurred when the hatching potential of eggs from the sediment was high under the natural environment from February to June. The hatching of resting eggs of A. pacifica was essentially temperature-dependent after suspension, while photoperiod regimes had no significant effect on the hatching. The mean density of subitaneous eggs was 1. 122 0 g/cm³ with a standard deviation (SD) of 0.000 2 g/cm³. The mean density of diapause eggs was 1. 151 2 g/cm³ with a SD of 0.000 1 g/cm³. The sinking rates of subitaneous eggs ranged from 19.55 to 26.17 m/d, while those of diapause eggs ranged from 30.29 to 31.28 m/d. The comparison of the egg deposition time and egg hatching time suggested that in most cases virtually all subitaneous eggs of A. pacifica would settle to the bottom before their hatching even though the eggs have high potential to hatch. The evidence was provided that the seasonal dynamics of A. pacifica is accompanied by benthic-pelagic coupling.