Following another season of shrinking sea ice Arctic Ocean life has been blessed with a doubling of plankton bloom cycles.
Historically, phyto-plankton began to bloom in the spring in the Arctic Ocean as daylight returned to shine even through the thinning and disappearing ice. Spectacular spring blooming created a rich ocean pasture that would sustain a feeding frenzy among zooplankton, fish and all of ocean life in the Arctic. Now the Arctic ocean is blooming again a second time in the fall.
“The entire ocean system is linked to this massive input of carbon,” said lead author of a new study Mathieu Ardyna, a marine biologist at Laval University’s Takuvik Joint International Laboratory in Quebec, Canada.
But more recently as the Arctic sea ice has declined dramatically a second bloom also appears in the fall, according to a new analysis of satellite records, published Sept. 2 in the journal Geophysical Research Letters. The fall bloom could have widespread ripple effects on marine life and the Arctic climate.
Other studies have shown that phyto-plankton are immensely effective at capturing carbon dioxide from the atmosphere through photosynthesis and storing it as ocean floating and sunken biomass much like a forest does on land. Plankton however grow 1000 times faster than land plants, thus a season of growth on an ocean pasture provides the equivalent to the growth stored in an old growth forest.
In 2011 a Stanford research group reported the discovery of vast amounts of phyto-plankton beneath Arctic ice, made during a Chukchi Sea expedition led by Stanford scientist Kevin Arrigo, contradicted past assumptions that blooms were possible only in open waters.
Arrigo and his research colleagues concluded that thinning of the ice layer and more widespread melt ponds atop the sea ice is allowing more sunlight to penetrate to the water underneath, likely simulating phyto-plankton growth. Findings were described in a study published in 2012 in the journal Science.
Blooms beneath the ice are probably much more widespread than earlier believed and may have been underestimated by a tenfold magnitude, the Arrigo study noted. This new field of Arctic ocean pasture study is now blossoming further with the report of Ardyna et al.
Ardyna said the double Arctic blooms may herald a shift of the Arctic ocean from a polar to a more temperate ecosystem.
These trends are still newly observed, and varied across the Arctic. As such the researchers can only speculate what the final impact will be.
“For sure, the carbon cycling will change a little bit, but the question now is to understand how the rest of the plankton and fish will respond to this new pulse of phyto-plankton,” says Ardyna.
Ardyna and his co-authors charted phytoplankton blooms between 1998 and 2012 with satellite data that measures ocean color (a proxy for phyto-plankton levels). The researchers also looked at sea ice extent and wind speeds.
The results showed that fall plankton explosions are becoming more frequent throughout the Arctic Ocean up to 80 degrees north latitude. Above these high latitudes, there are no plankton blooms at all because of permanent sea ice.
The largest increases were seen in the Eastern Arctic Ocean, especially north of Russia, where ice once prevented plankton blooms. “The percentage change is really high here because this is where there used to be ice,” Ardyna said. The western Arctic includes Alaska and Canada, while the eastern Arctic encompasses northern Europe and Russia.
The researchers said the plankton is likely thriving in fall for two reasons: delayed freezing and strong winds. In the fall, new sea ice starts to form when ocean temperatures fall below about 29 degrees Fahrenheit (minus 1.9 degrees Celsius). But as the Arctic sea ice shrinks, the ocean absorbs more of the sun’s heat in summer, postponing the freeze until all the warmth dissipates. There were also a greater number of strong fall storms in the last decade, which can stir up nutrients to feed a phyto-plankton bloom.
Read more about how ocean pastures are tied to and very much like pastures on land here…
Feeling like a Polar bear? Take a deep breath and come for a swim and see plankton bloom beneath the ice.
Read more on plankton blooming beneath the ice here…