Predation, production and the organization of an estuarine copepod community

Abstract

The copepod community of the estuaries near Beaufort, NC underwent a consistent seasonal succession from a spring assemblage dominated by the medium-sized copepod Acartia tonsa (1 mm) to a summer—fall assemblage dominated by the small-bodied copepods Parvocalanus crizsrirostris and Oithona colcarva (both 0.5 mm). However, in enclosure experiments during this period, A. tonsa dominated the community, due to higher growth rates and its predation on the nauplii of other species. Nutrient additions enhanced the dominance by A. tonsa . The decline in abundance of A. tonsa in the estuary was associated with increased abundance of planktivorous anchovies and silversides. In other enclosure experiments, planktivorous fish eliminated A. tonsa and other large copepods, although they persisted in enclosures lacking fish. I conclude that predation by size-selective planktivorous fish prevents dominance by A. tonsa during summer—fall.