The effect of temperature on egg development rate and hatching success in Calanus glacialis and C. finmarchicus

The pelagic copepods Calanus glacialis and C. finmarchicus are important components of Arctic marine ecosystems. Projected climate warming may influence the roles they play in the ecosystem. Arctic C. glacialis and boreal C. finmarchicus eggs were incubated at temperatures of 0, 2.5, 5, 7.5 and 10°C to investigate the effects of increasing temperature on egg development rate and hatching success. The effect of increasing temperature on median development time, described by B[ebreve]lehrádek's temperature function, was examined using a Bayesian approach. For the studied temperature range, we observed the increase of egg development rates with the increasing temperature, although there was no change in hatching success. Calanus finmarchicus eggs hatched significantly faster than C. glacialis above approximately 2°C; the difference was progressively larger at higher temperatures. This may indicate that the boreal species have physiological advantages in areas where ambient temperatures increase, which may lead to C. finmarchicus outcompeting the Arctic species in situations where timing is important, for example, in relation to spring bloom dynamics. Development time to hatching (DH) was evaluated using B[ebreve]lehrádek's model and a set of different assumptions. The models that best fitted our data were those with species-specific parameters: DH (h)=5940 (T+9.7)−1.63 for C. finmarchicus and DH (h)=14168 (T+14)−1.75 for C. glacialis.