Effect of food quantity and quality on egg production of Acartia tonsa Dana from East Lagoon,Galveston, Texas

The nutritional value of natural particle diets on egg production of Acartia tonsa from subtropical East Lagoon was studied from April to November 1981. During the summer, monospecific blooms of dinoflagelates and chloromonads dominated the natural particle assemblages. But during the spring and fall, the inorganic fraction was dominant and chlorophyll concentrations were lower. At ambient concentrations of natural particles from East Lagoon, specific egg production rates were correlated in stepwise multiple regressions with temperature, salinity, and C:N ratio but not phytoplankton pigment concentrations. For stepwise multiple regression including all natural particle concentrations, specific egg production rates were correlated with C:N ratio, average particle diameter, percent nanoparticles (5–20 μm), and percent phytoplankton picoparticles. A nonlinear regression developed for the entire data set revealed that above the critical chlorophyll concentration (∼ 5 μg 1⁻¹ at all temperatures), an increase in temperature of 4°C caused about the same increase in specific egg production rates as a decrease in salinity from 30 to 10‰, or a decrease in C:N ratio from 10 to 5. On a seasonal scale, temperature is the dominant influence on egg production of A. tonsa in East Lagoon where temperature ranges from 10 to 30°C but on shorter time scales food quality, food quantity or salinity may influence egg production rates as much as temperature.