GROWTH AND SURVIVAL RATES OF EARLY DEVELOPMENTAL STAGES OF ACARTIA-GRANI (COPEPODA, CALANOIDA) IN RELATION TO FOOD CONCENTRATION AND FLUCTUATIONS IN FOOD-SUPPLY

The scales of temporal and spatial variability of food resources in ma rine systems are determinant factors in the control of zooplankton pop ulations. For adult copepods, egg production rates are dependent on th e frequency of fluctuating food availability. However, very little is known about the effects of food fluctuations on the life-history param eters for early developmental stages of copepods. The growth and survi val rates for naupliar stages of the marine copepod Acartia grani were studied in relation to food concentration and to experimentally induc ed fluctuations in food availability. Growth rates of early nauplii we re highly dependent on food abundance, and were comparable to simultan eously estimated rates of adult production (egg production rates). Tol erance to starving conditions (survival time) increased through the co hort development. For short-time fluctuations in food abundance (alter nating, 12 h high food / 12 h low food conditions), growth rates of na upliar stages depended on the light conditions at which food was avail able. Lower frequency fluctuations (alternating, 24 or 48 h high food / low food conditions) significantly reduced both naupliar growth and survival rates. The sensitivity of growth rates to food fluctuation fo r naupliar stages, and their low tolerance to starving conditions, are further evidence to explain the confinement of A. grani to coastal ha bitats.