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Phytoplankton bloom in the Barents Sea.
TagsBiogeosciences, Arctic Sea-ice, Phytoplankton bloom
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Plankton blooms around polar sea ice - Article in BG
26.02.2011, Age: 813 days
A new study in the open-access journal Biogeosciences reports on belts of phytoplankton blooms that appear when sea ice retreats during summer melt. Ongoing degradation of Arctic sea ice will have consequences for the food production of higher organisms and ultimately fish.
When sea ice disappears during the spring and summer, phytoplankton (microscopic plant-like organisms) start to bloom along its margins. Phytoplankton is food for zooplankton, which in turn is eaten by higher animals such as fish. Fish production in higher latitudes is therefore directly dependent on the seasonal phytoplankton blooms.
The study by Perrette and colleagues shows that the blooms, which may form belts of more than 100 km in length, closely follow the seasonal retreat of the sea ice. Complete, or almost complete breakdown of the Arctic sea ice will have an effect on temperature, salt content and layering of the ocean water and therefore affect the inetensity of the phytoplankton blooms. The exact mechanism is not yet completely understood. It is possible that the blooms will cover larger areas and thus increase Arctic food production. Other factors may counter this trend however.
Ice-edge blooms are significant features of Arctic primary production, yet have received relatively little attention. Here we combine satellite ocean colour and sea-ice data in a pan-Arctic study. Ice-edge blooms occur in all seasonally ice-covered areas and from spring to late summer, being observed in 77–89% of locations for which adequate data exist, and usually peaking within 20 days of ice retreat. They sometimes form long belts along the ice-edge (greater than 100 km), although smaller structures were also found. The bloom peak is on average more than 1 mg m−3, with major blooms more than 10 mg m−3, and is usually located close to the ice-edge, though not always. Some propagate behind the receding ice-edge over hundreds of kilometres and over several months, while others remain stationary. The strong connection between ice retreat and productivity suggests that the ongoing changes in Arctic sea-ice may have a significant impact on higher trophic levels and local fish stocks.
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