Marine calanoid resting eggs in Norway: Abundance and distribution of two copepod species in the sediment of an enclosed marine basin

Abundance and distribution of calanoid resting eggs in sediment were examined in 1988–1989 in an enclosed marine basin (Svartatjønn; western Norway). The basin undergoes rotenone treatment and draining every winter. Egg densities were highest in autumn, when up to 2 × 10⁶ eggs m^–2 were found, and lowest in summer. Egg densities were also highest in the deeper parts of the basin and in the upper 1 cm of sediment. Hatching was initiated in late January by pumping warmer deep water from the outside area into the basin. Evidence is given for resting-egg formation inEurytemora affinis Poppe, 1880 andAcartia clausi Gurney, 1931 (present phenotype reclassified asA. teclae by Bradford 1976: N. Z. Jl mar. Freshwat. Res. 10: 159–202). Seasonal differences in inhibition of hatching, together with the longevity and tolerance of these eggs, strongly suggest that they are diapause eggs.