New study illuminates how diatoms thrive in—and light up—the Southern Ocean

According to a new study, an area of the distant southern ocean which is a long confused ocean light light by reflecting large amounts of turquoise light is full of diatoms rich in silica, according to a new study. Surprisingly, there is also evidence in these polar waters of coccolithophores, a type of marine microalgae with elaborate calcium carbonate shells that plays an essential role in the world carbon cycle.

The study helps to respond to a long -standing mystery for satellite oceanographers as to what microbes dominate in this part of the ocean which have proven to be largely inaccessible, enlightening the way in which the plankton community changes in response to the evolution of temperature and seawater chemistry. This, in turn, has important implications for carbon cycling in the ocean and tools remote sensing that scientists use to study it.

“This work takes a large brush to understand the biological and geochemical dynamics of this distant water body in a way that had not been possible before,” said the main author of the Barney Balch study, emeritus of principal researcher at the Bigelow Laboratory for Ocean Sciences.

The study was published this week in the journal Global biogeochemical cycles.

In the early 2000s, Balch and his colleagues identified a strip of seawater surrounding Antarctica, which became known as the large calcite belt. This area is marked by unusual levels high of particulate inorganic carbon, such as calcium carbonate and limestone, which reflects light to satellites. Scientists finally confirmed that this was due to the shiny calcium carbonate shells of vast coccolithophore flowers.

At the same time, however, they identified an area well south of the calcite belt which also seemed unusually brilliant in satellite images, even if the water was considered too cold for cocolithophores. This mystery was more difficult to explain with heavy cloud cover, icebergs and difficult seas, which makes it difficult to monitor this far south with ships or satellites. So far.

The researchers sailed aboard the R / V Roger Revelle From Hawaii, up to 60 degrees latitude, taking a brief detour to the east to monitor where southern water seems to be pinched in several whirlwinds. Along the transect, the team measured the color of the ocean; calcification and photosynthesis rate; And the concentrations of carbon and inorganic silica, two minerals which reflect light and are essential to help to kidnap organic carbon in the deep ocean.

“The satellites only see the high meters of the ocean, but we were able to break through several measures at several depths,” said Balch. “We have never had such a complete follow -up of integrated measures through the water column in this part of the ocean.”

The approach at several levels – the combination of biogeochemical measures, optical data and even visual accounts from microscopy to microscopy – allowed scientists to observe how the plankton community moves south: dinoflagellates in the warmer and stratified belt of the subtop, towards the rich of coconut, the south of the calcite belt and finally the diatomy in the rich SIELIST, in the south of the calcite belt and and finally to diatoms in the SIELICE RICH, in the Calcite waters, and finally to the diatomas of the Sielice Rich, of the South of the Calcite, and finally in Diatoms in the rich of the SIEC in front.

This combination of complementary methods provides a “smoking pistol”, said Balch, that the high reflectance levels have observed in satellite images south of the calcite belt can be explained by frustles. These silica structures that diatoms build, resembling microscopic pullers, reflect light in the same way as coccolithophore shells (it takes much more frustles to produce the same optical effect as coccolithores, however – a testimony of the dense of their concentration).

Surprisingly, however, the team has also observed small concentrations of inorganic carbon, a certain amount of calcification occurs – a first – visual evidence of coccolithophores in the waters far from the south. This said Balch, suggests that Coccolithophores can survive in colder than expected waters. Perhaps, he said, the whirlwinds from the south are even used as “seed populations”, offering a small but coherent of coccolithophores in the large calcite belt.

The presence of Coccolithophores through a larger geographical beach than expected could influence the way in which carbon moves in the South Ocean, which is considered one of the most critical sinks on the planet for atmospheric carbon. Meanwhile, the domination of diatoms south of the polar front highlights the need to improve the algorithms that scientists use to translate satellite data into significant predictions of ocean biology. This potentially means combining the measures of other variables derived from satellites to help make the distinction between diatoms and coccolithophores in satellite images.

“We are expanding our vision of the place where Coccolithophores live and finally start to understand the models we see in the satellite images of this part of the ocean that we can rarely go,” said Balch. “There is nothing like measuring something in several ways to tell a more complete story.”

In addition to Balch, the interdisciplinary team includes the Bigelow Dave Dave Drapeau, Bruce Bowler and Sunny Pinkham laboratory researchers, as well as scientists from Woods Hole Oceanographic Institute, Arizona State University, Texas A & M University and Bermuda Institute of Ocean Sciences.