Antarctic warming has led to major changes in the weather of West Antarctica, altering the food chain. As reported in the journal Science, scientists examining thirty years of data on phytoplankton concentration have determined that major alterations to the food web have occurred due to warming. Even more troubling, the climate of the West Antarctic peninsula appears to be "undergoing a transition from a cold-dry polar-type climate to a warm-humid sub-Antarctic–type climate," according to the abstract for the Science article. The scientists examined satellite and other data to determine that concentrations of a certain type of phytoplankton had declined substantially along the peninsula, most likely due to stronger winds, increased cloud cover, and mixing of surface waters with deeper ocean water.
When phytoplankton moves, krill (who eat the phytoplankton) have to follow suit. Krill-dependent predators such as penguins then also must go where the krill are. So while there is less plankton in some areas, there is now more in others, particularly the southern regions of the peninsula. Penguin species not dependent on krill, such as Gentoo and Chinstrap penguins, have taken the place of krill-dependent Adelies. It remains to be seen what long-term consequences these shifts will have on penguins and krill, but if phytoplankton populations continue to decline, it could have disastrous consequences for penguins and other krill eaters.
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