ABSTRACT: The scales of temporal and spatial variability of food resources in marine systems are determinant factors in the control of zooplankton populations. For adult copepods, egg production rates are dependent on the frequency of fluctuating food availability. However, very little is known about the effects of food fluctuations on the life-history parameters for early developmental stages of copepods. The growth and survival rates for naupliar stages of the marine copepod Acartia grani were studied in relation to food concentration and to experimentally induced fluctuations in food availability. Growth rates of early nauplii were highly dependent on food abundance, and were comparable to simultaneously estimated rates of adult production (egg production rates). Tolerance to starving conditions (survival time) increased through the cohort development. For short-time fluctuations in food abundance (alternating, 12 h high food / 12 h low food conditions), growth rates of naupliar stages depended on the light conditions at which food was available. 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 for naupliar stages, and their low tolerance to starving conditions, are further evidence to explain the confinement of A. grani to coastal habitats.

KEY WORDS: Growth rates · Food availability · Copepods · Nauplius · Acartia grani

Published in MEPS Vol. 147 (1997) on February 27
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1997