Timing of diapause in relation to the onset of winter in the high-latitude copepods Pseudocalanus acuspes and Acartia longiremis

Abstract

It is proposed that the timing of overwintering diapause inmultivoltine, marine copepods is optimised as in insects and limnic copepods.Theoretical models state that resting should begin a period equivalent to 1generation before the environment becomes unfavourable. Computer simulationsand field studies have shown this to apply to insects and limnic copepods.The present paper tests and discusses the model predictions in relation toseasonal environmental changes and life history events for populations ofPseudocalanus acuspes (Giesbrecht, 1881) and Acartia longiremis Lilljeborg inNorth Norwegian fjords. These copepods switch from developing populations,with normally developing gonads, to resting populations, with immaturegonads, within a few weeks in early fall. Phytoplankton abundance and primaryproduction decline later in the fall.