The role of egg cannibalism for the Calanus succession in the Disko Bay, Western Greenland

AbstractThe present study is the first to describe egg cannibalism in the key Arctic copepod species Calanus finmarchicus, Calanus glacialis, and Calanus hyperboreus. Initially, a series of staining experiments evaluated the application of Neutral Red for staining Calanus eggs. The method was effective and applied in subsequent feeding experiments, where adult females were incubated in bottles with their own eggs. The results showed that all Calanus spp. ingested C. finmarchicus and C. glacialis eggs. However, consumers showed a slight preference for C. finmarchicus eggs when incubated with those of both species. The addition of phytoplankton even at high concentrations did not decrease clearance rates for eggs, suggesting that the presence of alternative food does not afford eggs any protection from cannibalism. To evaluate the potential impact of egg cannibalism on the succession of the three species, we calculated and compared field egg mortality rates with potential egg clearance rates for the Calanus complex based on rates from the experiments. Our results show that in Disko Bay cannibalism by Calanus spp., even at its highest level just before the spring bloom, could only account for about 10% of observed in situ egg mortality, and much less for most of the season.