Surprising results!

The Antarctic keeps surprising me! When we studied the phytoplankton in the Amundsen Sea Polynya in Antarctica in 2009, we discovered that melting glaciers release iron in the water and that phytoplankton can use that iron for growth and photosynthesis. So, melting glaciers support phytoplankton growth, and because phytoplankton take up CO₂ from the atmosphere this slows down global warming a teeny tiny little bit.

So when we returned to the Amundsen Sea in 2010 to further explore the properties of phytoplankton there, we did not expect to find any effects of iron in the water on phytoplankton. However, we were wrong! We confirmed that glaciers release iron in the water. And we confirmed that phytoplankton can use that. But if you give the phytoplankton even more iron, they grow even faster! Especially, the phytoplankton that was growing at distances of more than 30 miles from the glacier could use more iron. It is like growing tomatoes in your yard, they may grow rapidly and look great, but if you add extra fertilizer (nutrients) they might grow even bigger.

This was quite a surprise to us. Melting glaciers release iron in the Amundsen Sea, and the Amundsen Sea has the most phytoplankton growth in the whole Antarctica, how can iron availability still limit the phytoplankton? One of the clues is that iron is very insoluble in water that contains oxygen. Almost all iron will precipitate and sink out of surface waters, before phytoplankton can use it. So no matter how much iron is released by melting glaciers, most of it will likely not be used by phytoplankton. And, thus, the effects of melting glaciers on phytoplankton will likely be local and not expand very far into the Southern Ocean. Nevertheless, when glacier melting rates increase it is likely that some more iron will be used by phytoplankton, which means a little bit more phytoplankton growth to stop climate change.  However, while phytoplankton growth in Antarctica supports the entire Antarctic food web and is thus generally a good thing, too much phytoplankton growth may be harmful with unknown consequences. Meanwhile, we will keep studying to find more pieces of climate change effects in Antarctica.

http://elementascience.org/article/info:doi/10.12952/journal.elementa.000043