PROCESSES CONTROLLING RECRUITMENT OF THE MARINE CALANOID COPEPOD TEMORA-LONGICORNIS IN LONG-ISLAND SOUND - EGG-PRODUCTION, EGG MORTALITY, AND COHORT SURVIVAL RATES

Three phytoplankton blooms were observed during our 6-month study period and each resulted in increased rates of egg production (EPR) by female Temora longicornis. An EPR of 50 eggs female(-1) d(-1) was observed during the first bloom (spring bloom, March). The maximum EPR observed during the other blooms (May and July) was 20 and 30 eggs female(-1) d(-1). At all other times the EPR was nearly zero. Each pulse in egg production initiated a distinct cohort. Survivorship from egg to adult was low: 3% for the first cohort and 0.8% for the second. The third cohort did not reach maturity. Mortality was highest in the egg stage-only 10% of the eggs produced survived to first nauplius. Rates of egg mortality were positively correlated with clearance rates of T. longicornis, suggesting cannibalism as a cause of high mortality. However, the clearance rates required would be similar to 34-fold too high, suggesting a different density-dependent factor, such as disease, viruses, ecto-parasitism or consumption by dinoflagellates. Advection and resting egg production do not appear to explain high rates of egg loss.