Copepod egg production and food resources in Exmouth Gulf, Western Australia

Abstract

Measurements of plankton community structure, copepod egg production and potential copepod trophic resources were made in Exmouth Gulf, north-westem Australia. Egg production rates by four of the dominant copepod species-Acartia fossae, Parvocalanus crassirostris, Oithona attenuata and O. simplex-were measured by bottle incubations and the egg-ratio technique. Plankton abundance and biomass did not differ greatly within the gulf; however, highest values of chlorophyll a, particulate carbon and nitrogen, and copepod egg production rates occurred in the south-east of the gulf. Though egg production rates were low and apparently severely food-limited, resuspension of bottom sediments or export of material from adjacent salt flats may fuel production in shallow inshore areas of the gulf. P. crassirostris appeared to be omnivorous and O. attenuata primarily herbivorous, but the trophic resources used by O. simplex and A. fossae could not be identified. From the egg production data, it was calculated that adult females of the four dominant copepod species graze 12% of the total particulate carbon each day.