MARINE CALANOID RESTING EGGS IN NORWAY - ABUNDANCE AND DISTRIBUTION OF 2 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 (Svartatjonn; western Norway). The basin undergoes rotenone treatment and draining every winter. Eggs densities were highest in autumn, when up to 2 x 10(6) 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 in Eurytemora affinis Poppe, 1880 and Acartia clausi Gurney, 1931 (present phenotype reclassified as A. 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.