Phytoplankton Under Threat From Climate Change

Tiny planktonic plants known as phytoplankton that are of crucial importance to the Arctic ecosystem could be under threat because of climate change. Due to changes in temperature in the oceans around the Arctic, phytoplankton could find it more difficult to bloom.

The result of this could have serious consequences for biodiversity in the region."Ice-edge phytoplankton blooms in the Arctic Ocean provide food for planktonic animals called zooplankton, which are in turn exploited by animals higher up the food chain such as fish," explained Dr Andrew Yool, who a team member of the researchers from the UK’s National Oceanography Centre that conducted the study on phytoplankton blooms.

Phytoplankton blooms occur on the edge of the ice. When ice water melts and breaks up it forms a layer over the saltier and denser ocean water. This causes the water to stratify into columns and with seasonal sunshine this triggers the phytoplankton blooms that normally occur in bands along the receding edges of the ice.

The Arctic has not been studied in detail, but satellite technology can be now used to monitor and view ice edge blooms at high spatial resolution over large areas from space. The SeaWiFs satellite, which was launched by NASA in 1997 looks at the discoloration in the oceans and this has given researches increased data and knowledge of planktonic blooms.

“Our aim was to use satellite data to get a synoptic view of ice-edge blooms across the whole Arctic region. The bloom peak is most often located close to the ice edge. We observed blooms propagating in a wave-like fashion behind the receding ice edge over hundreds of kilometers and over several months, while others remained stationary. Our findings demonstrate strong biophysical linkage between bloom propagation and sea-ice melt back, which is independent of the actual direction of retreat," said Dr Yool.

The research could prove to be significant in determining the prospects for the ecosystem in the Arctic and in predicting the likely outcome of continuous ice melting in the region, which could impact on phytoplankton and as a result other species. The blooms play an important role in the carbon cycle by drawing it down from the atmosphere and exporting it into the ocean. However, it is still unclear what large scale melting of the Arctic will do and how important blooms could be.

"It is quite possible that ongoing climate change will lead to ice-free summers in the Arctic within the next few decades. As the melt season becomes longer, ice-edge blooms may propagate over larger distances, stripping out surface nutrients as they go. However, whether the Arctic becomes more or less productive will ultimately depend on complex factors affecting ocean stratification and mixing, and thus the availability of nutrients in sunlit surface waters," said Dr Yool.

Photo credit: Originalwana