Early development of Calanus hyperboreus nauplii: Response to a changing ocean

To forecast effects of temperature changes on recruitment and population dynamics of the Arctic copepod Calanus hyperboreus, laboratory experiments investigating temperature and food effects on early development were performed in Disko Bay, western Greenland, in 2009, and ascent rates of C. hyperboreus eggs collected in east Greenland were measured in the laboratory. Ascent rates were highly variable both between and within clutches, ranging from 0.7 to 27.7 m d21, suggesting variability in the biochemical composition of the egg. Development of eggs were investigated between 0.8uC and 6.6uC, and hatching was fitted to a Beleˇhra´dek temperature function (r2 . 0.99) with mean development time (MDT) of eggs ranging from 2.8 to 5.8 d. MDT of fed and starved nauplii was calculated for nauplii raised at 5uC. Fed nauplii developed through the first five nauplius stages (N1–N5) during 40 d of incubation, whereas development of starved nauplii ceased at N3. Nauplii were able to survive at least 30 d of starvation. Respiration rate was measured for N1 and N3 at 0uC, 5uC, and 10uC, and it increased with development stage and temperature from 0.05 6 0.01 to 0.29 6 0.08 nmol O2 nauplii21 h21 for N1 at 0uC and N3 at 10uC, respectively. A decrease in carbon and lipid content from egg to N3 indicates that nauplii are using stored lipids to cover their metabolic costs during the nonfeeding stages. Early stages of C. hyperboreus seem more affected by temperature than later stages, a vulnerability that might affect future recruitment.