Blooms of Arctic Plankton Occurring Far Earlier as Sea Ice Retreats

The steady disappearance of summer sea ice in the Arctic Ocean is causing annual blooms of phytoplankton to occur as much as 50 days earlier now than in the late 1990s, a major shift that could have profound consequences for the Arctic Ocean food chain. Researchers at the Scripps Institution of Oceanography in San Diego used satellite images taken from 1997 to 2009 to analyze blooms of the tiny marine algae and plants, known as phytoplankton, whose appearance can be detected from space. The researchers found that in a 396,000-square-mile area, where melting of Arctic sea ice was most pronounced, phytoplankton blooms that once peaked in September in the late-1990s now peak in early July. The Arctic’s annual phytoplankton blooms, which last for up to two weeks, occur when sea ice melts, exposing the surface of the ocean to sunlight, which triggers the blooms. The phytoplankton are consumed by tiny zooplankton, which are in turn eaten by fish, whose reproductive cycles are often timed to match peak numbers of zooplankton. Reporting in the journal Global Change Biology, the Scripps researchers said the advance in phytoplankton blooms and zooplankton peaks could adversely effect populations of Arctic fish, shellfish, birds, and marine mammals.