Disintegration of portions of the ice shelves and a decrease in the frequency of strong recruitment of young krill from seasonal spawning may be the first evidence, he said. Using satellite data available from the National Snow and Ice Data Center, scientists analyzed seasonal sea ice cover off the northwestern side of the Antarctic Peninsula from 1979 through 1996, the length of the passive microwave data record. To correlate daily sea ice concentration data with annual population dynamics of immature and adult krill, they created an annual index that combines the temporal and spatial extent of sea ice. Salps prefer an open ocean environment and flourish in years with warmer temperatures and less sea ice. They obtain food by filtering water and extracting edible resources through the cylindrical gelatinous tubes that are their bodies.
Early spring determines the impact of salp population on krill.
In October or November, during periods of limited sea ice cover, salps rapidly increase their numbers by asexually budding little clones, creating long chains of salps. 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.