A team of researchers recently observed evidence of potentially large blooms under the sea ice surrounding Antarctica. This discovery confirms the conclusions of an underwater scientific expedition which took place ten years ago and which already reported a massive population of phytoplankton in the region.
The study reporting this discovery was published in the scientific journal Frontiers. It comes as scientists believed that with the lack of light, the ice cover prevented phytoplankton growth for most of the year in the ocean around Antarctica.
However, the document shows that there are just enough “cracks and holes” in the area to allow enough daylight to pass through the sea ice.
“In wide views from most satellites, the ice cover can appear uniform and sheet-like, which reinforces the idea that light would be too scarce and weak to support plant life below,” says Chris Horvat. , a sea ice scientist at Brown University and lead author of the study.
But observed from and below the surface of the ocean – and through the use of a latest-generation NASA satellite – Antarctica’s sea ice is actually riddled with fractures and openings, says the study. “Sunlight filters through the cracks and provides energy for blooms under the ice in the Southern Ocean. »
Enough light under the ice
Experts point out that phytoplankton are to the ocean what grass is to land: these floating, plant-like organisms absorb the sun, absorb mineral nutrients and create their own food (energy) through photosynthesis. “Phytoplankton are an essential food source for other forms of life in the ocean and play a key role in recycling and eliminating carbon for the planet”, specifies the specialist adding that it develops approximately wherever there are open, sunny areas of ocean,” Horvat points out.
When conditions are right, these microscopic cells can grow to scales visible from space.Chris Horvat, lead author of the study
In addition to satellite images, Horvat and his colleagues have collected several sources of data such as those collected by floats. These instruments can detect the presence of chlorophyll and particulate carbon. These can indicate the presence of phytoplankton.
“Reviewing data from more than 2,000 ice dives over a seven-year period, the science team found that almost all measurements showed an accumulation of phytoplankton even before the sea ice retreated in the spring and in summer in the southern hemisphere,” the study states.
Experts also relied on ice cover models to estimate the location and thickness of the Southern Ocean’s ice cover, as well as how it was moving. They then found that 3 to 5 million square kilometers – an area larger than India – of the ice-covered Southern Ocean could let in enough light to support some blooms under the ice.
“Scientists have talked about the potential for these blooms before, but this is the first time we’ve seen them under the ice in Antarctic waters,” Horvat said. “This discovery opens the way to a whole new way of looking at life around and under the ice. Sea ice is more interesting and diverse than you might think, and it can support a wide range of ecological systems. »
With information from NASA’s Michael Carlowicz