They efficiently consume the meager quantities of available phytoplankton, decreasing amounts available to krill. Insufficient quantities of food during the early spring inhibit krill reproductive development and spawning. During years of extensive ice cover krill seem to spawn early. According to research published by the Australian Antarctic Division female krill can lay up to ten thousand eggs, sometimes several times a season, that sink to a depth of two thousand meters before hatching. Krill larvae metamorphose through several stages as they move up the water column appearing about two or three weeks later in the ocean surface plankton.
Scientists believe that spring phytoplankton is the key in the salp and krill equation.
During the summer months, salp consumption of phytoplankton accounts for only 20 percent of total available phytoplankton. In years of limited sea ice cover when the Antarctic ocean waters open early encouraging early phytoplankton blooms, Hewitt said, the salp population explodes while the krill population declines. Combining passive microwave sea ice data with annual salp and krill densities, Hewitt and his colleagues correlated strength of krill population with sea ice extent. During years of poor sea ice development, open water conditions favor salps and krill do not seem to spawn nearly as aggressively nor do their young survive as well. The connection between krill, salps, sea ice and long-term warming has not been concretely proven, but the evidence suggests a dependency.