It has been thought that the packed sea ice of the Southern Ocean prevented light from reaching the sea beneath. The less light there is, the less the phytoplankton can photosynthesize and thus the less life there will be.
There is underestimated ecological variability under the ice according to research inspired by increasing under-ice blooms of phytoplankton.
As the sea ice begins to retreat, there are many blooms that can be seen. A team led by Dr. Christopher Horvat suspected that there would be blooms in the near future. They described how they used the BGC-Argo floats and the climate model to estimate light availability beneath the ice.
Horvat said that they found that almost all examples of profiling under the sea ice record increases in the ocean before it retreats. We observed a lot of blooms. Horvat pointed out that the floats only sample a small portion of the millions of square kilometers of sea ice that could host these under-ice blooms, so there may be many more hidden blooms with the potential to support other life out there.
There are laboratories floating in the water.
The floats are thrown away from research vessels and are left to take their own biogeochemical samples. The levels of chlorophyll-a and particulate backscatter can be used to estimate the amount of carbon in the water. The team used data from 51 floats that made 2,197 under-ice dives over the course of two years.
"We used a new data product derived from a new NASA satellite, the ICESat-2 laser altimeter, to understand the compactness of ice aroundAntarctica and with a suite of global climate models considered how much light reached the upper ocean."
In order for sea ice in the Southern Ocean to support under-ice blooms, there must be at least 50% of it under-ice.
Is there a hidden system?
The scientists were able to measure under the sea ice with complete or nearly complete coverage of the water below, as well as recording a rise in the number of plants.
The coordinates for sample locations are not completely precise due to the fact that the floats can sample under the ice but can't return data. Some of the high productivity events may be recorded in areas with low sea ice.
"Because the time we observe these blooms is close to when sea ice retreats, it is also possible some of the phytoplankton come from processes occurring outside of the sea ice zone, though we consider this unlikely given the sheer number of high-productivity measurement we found."
The implications for the environment in the South Pole. One might expect the food web to follow if the productivity is under the ice. There is more research that needs to be done to understand how the hidden ecosystems function and how the blooms of the phytoplankton attract prey.
There is evidence for Phytoplankton blooms under the sea ice. The DOI is 10.389/fmars.
Journal information: Frontiers in Marine Science
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