The Southern Ocean The vast shelves of floating glaciers appear to conceal sprawling phytoplankton blooms, which could dramatically change our understanding of Antarctica’s marine ecosystem.
Key to phytoplankton growth is photosynthesis, and key to photosynthesis is sunlight – and so up to this point experts didn’t think there was much opportunity for the plankton to thrive in the dark conditions under Antarctic ice shelves.
However, recent research has shown that Under Arctic ice, phytoplankton bloomsAs the glaciers become less cohesive, they also become more seasonal. ThickerIt is more vulnerable to melting water. Researchers were inspired to reexamine Antarctica.
The field work was done using floating measuring devices, which were combined with satellite data on sea ice coverage, and outputs of climate models to estimate how much phytoplankton might be hidden beneath the ice.
“We found that almost all examples of floats profiling beneath Antarctic sea ice record increases phytoplankton prior to sea ice retreats.” Christopher Horvat, polar oceanographerFrom the University of Auckland, New Zealand.
“We observed significant blooms in many cases.”
These floats can independently take measurements and take evasive action when approaching ice sheet. They were assigned to measure levels of the pigment chlorophyll-A. Particulate backscatterBoth are indicators of phytoplankton.
Between 2014 and 2021, 51 floats collected data during 2,197 underwater dives. The data was then compiled into 79 sequences for further analysis. Satellite imagery also provided information about ice cover.
“We found that 50% or more of Antarctic’s under-ice could support under-ice flowers, as sea ice in Southern Ocean is composed of discrete floes and small areas open water allow light and photosynthetic life to flourish.” Horvat.
In those cases where sea water coverage was complete or near-complete, 88 per cent of the sequences measured a rise of phytoplankton prior to any seasonal retreats of sea ice. This is when plankton tends to pick it up.
There is some uncertainty over the data due to occasional lag between sampling and position logging – uncertainty that future studies should remove – but the scientists behind the study say there’s good, solid evidence that these blooms are happening.
As Phytoplankton communities contain significant quantities of tiny algae, they typically represent the very bottom of the food chain in the ocean – variations in their availability and coverage can have a significant effect on the rest of the aquatic life in the area.
Researchers will now need to collect more data and determine how plankton blooms may impact other forms under the ice. It will help us to understand how the global warming effect on ice cover will affect other forms of life under the ice.
“Higher levels of trophic level migrate to areas where productivity is high, and if the ice is below the ice, one might assume that the food web follows.” Horvat.
The research has been published in Marine Science Frontiers.
