Earlier phytoplankton blooms in Arctic could affect food chain
Tiny phytoplankton are taking to warmer Arctic waters by blooming almost two months earlier in the spring season.
A new study published in the April edition of the journal Global Change Biology says that the earlier bloom has consequences for the Arctic food chain and carbon cycling.
It may sound like a good thing. Phytoplankton, the nutritive basis for much of ocean life, stimulates the production of zooplankton, which provides forage for larval fish, and so on. But more of it out there, at an earlier point in the season, could be disrupting the food web.
The researchers, led by Mati Kahru at the Scripps Institution of Oceanography at the University of California, San Diego, say there could develop a mismatch between the reproductive cycles of marine organisms. For example, shrimp may have adapted their egg hatching times to the spring bloom in phytoplankton.
The one to two week bloom creates a major influx of new organic carbon into the marine ecosystem. The earlier blooms seem to be timed to areas where sea ice concentrations have declined, according to satellite data. For the period of 1979-2007, the trend towards an earlier ice melt was up to 7.3 days.
The researchers say there’s a limit to how early phytoplankton blooms can appear, given that daylight is also a constraint. But the trend towards earlier blooms could spread to more areas of the ocean and impact the whole food chain. If other species do not or cannot adapt, excess phytoplankton could sink lower into the ocean and cause oxygen deficiency in poorly mixed bottom waters.