High tolerance of the calanoid copepod Acartia steueri to the abrupt food concentration changes in an embayment

The calanoid copepod Acartia steueri Smirnov, 1936 is one of the most dominant embayment species in temperate coastal waters where abrupt variations in food concentration may occur. In this study, their biological responses to abrupt changes in food concentration were examined in the laboratory. Four experimental conditions were designed by combining 2- or 5-day periods of high food concentration (1.0 μg C mL−1) at the beginning of the experiment with a subsequent 15-day period of low food concentration (0.09 μg C mL−1) or starvation. Egg production and fecal pellet production were measured every 24 h. A. steueri produced eggs and fecal pellets under all conditions, even when the food concentration drastically decreased from a high to a low concentration or to starvation conditions. Rapid energy accumulation during the high-food condition contributed to egg and fecal pellet productions under the low-food and starvation conditions. In the field, A. steueri accumulates energy during short-term, sporadic high-food conditions. They are then able to endure low-food conditions using the stored energy until they encounter favorable food conditions again.