Seasonal variability and inter-specific differences in hatching of calanoid copepod resting eggs from sediments of the German Bight (North Sea)

Hatching experiments were conducted on sediment samples collectedon seven cruises between March 2002 and February 2003, at fourstations near Helgoland (54°11'N, 7°53'E). Samples wereincubated for up to 12 months and examined weekly for calanoidcopepod nauplii. 12807 nauplii hatched in total. Of these 36.43%were stage N1 (pooled), 44.08% were Temora longicornis (stageN2 and older), and 17.96% were Centropages hamatus (stage N2and older). Some Acartia spp. and an unidentified species werefound, too. Hatching varied significantly between sampling dates.At three stations, counts of all nauplii peaked in samples takenin April, while at one station the maximum was recorded in thesample collected in October. The seasonal pattern of hatchingwas similar in T. longicornis and C. hamatus. In March, April,October and February numbers of all nauplii were initially low,but increased over the following 2–3 weeks. In June, Augustand December, however, average numbers were comparatively highat first, but declined thereafter. In three of the four samplesthat were incubated for 12 months nauplii hatched from the sedimentfor the entire experimental period. Temora longicornis and C.hamatus displayed clearly distinct patterns of hatching in theselong-term incubations.