Viability of Calanus finmarchicus eggs in situ:: does the presence of intact phytoplankton reduce hatching success?

In order to test whether or not the presence of intact diatoms land other phytoplankton) inhibits hatching of copepod eggs, hatching success was measured for Calanus finmarchicus eggs collected from freshly captured females incubated in filtered seawater (FSW), in natural phytoplankton mixtures (collected at the depth of the chlorophyll maximum), and in a culture of Thalassiosira weissflogii. When compared with eggs incubated in FSW, hatching success was generally the same in the natural phytoplankton mixtures, but lower for eggs incubated in the T, weissflogii culture. Hatching success was also uncorrelated with the abundance of phytoplankton available in situ. The results suggest that hatching success is generally high for eggs produced by female C. finmarchicus feeding during spring bloom conditions in the Northwest Atlantic, and also that it is not generally reduced by toxins exuded by natural phytoplankton assemblages in situ. (C) 2000 International Council for the Exploration of the Sea.