The Invisible Majority – How single cells make Earth habitable

Quelle: 17 June 2015
A. Fong, M. Kędra, and C. Mӓrz
We are at our 6th ice station and the fog has rolled in. Standing out on the back deck, you feel almost like you are enclosed inside one of those tiny snow globes, the scenery blanketed in snow and the Polarstern wrapped in a foggy mist. Looking out over the rail of the Polarstern, into the depths of the Arctic Ocean there appears little life to the naked eye. But, if you could see all the life teeming in a single drop of seawater, you might be reminded of a clear night sky filled with a million stars. Unbeknownst to most, the ocean’s most rail numerous organisms are tiny single cells. Though small and somewhat invisible, together these cells drive many of the important processes controlling biological productivity, geochemical fluxes, and ultimately Earth’s climate. How do such small organisms regulate such large and broad processes? We are here in search of clues that will help us better understand which organisms and what processes are important during the Arctic spring, as ice begins to melt, and light becomes available again after a long, dark winter. At this time of year, we are searching for the awakening of these small organisms, and when they bloom, they are no longer invisible. We can sense their presence using a range of instruments we deploy into the water, and onto and under the ice. At first, it may not seem all that impressive to find a piece of ice slightly discolored to light greenish-brown, but within this ice and the sea below, are the building blocks for the whole Arctic food web. But algae cannot grow on light alone. Just as us humans, they require a number of essential nutrients to build up their biomass and grow. The Arctic Ocean is not very nutrient-rich, so primary productivity should very quickly come to a halt, but it does not. Bacteria renew nutrients in the water by degrading dying algae cells, and the cycle continues. By this simple process, these single cells, in great abundance throughout the world’s oceans, make Earth habitable.