The importance of Iron
The Fitzsimmons lab in the Department of Oceanography at Texas A&M studies the global iron cycle, and they visited the coast of the Western Antarctic Peninsula in the austral summer of 2016. As we discussed in last week’s show, the waters near the Antarctic continent are filled with iron coming from sediments near shore, yielding a lot of phytoplankton, or microscopic “plant” growth. However, as we moved away from land we expected to find more evidence of iron limitation, as we were moving away from the continental iron source, and thus the phytoplankton should have become iron limited. As expected, by the time we got ~200 km off the shelf, we found “blue” waters devoid of phytoplankton life. We also did experiments where we added iron to these waters to see whether more phytoplankton would grow compared to control experiments that received no extra iron. As expected, these organisms did in fact need iron! Finding evidence of iron limitation in this area is significant because the Southern Ocean accounts for so much of the carbon uptake from the atmosphere for long-term storage in the deep ocean. In light of today’s rising carbon dioxide levels in the atmosphere, studying areas known to be integral in carbon uptake and yet also limited in phytoplankton activity is absolutely crucial. While determining trace metal distribution from the coast to the open ocean was our main goal on this cruise, iron limitation poses a threat to all marine organisms as it targets the base of the marine food web: phytoplankton. Further research needs to be done in this area to elucidate the full effect of iron limitation on carbon cycling and climate in this region. This highlights the importance of maintaining funding for the well-established scientific research stations in these regions, such as the United States Palmer Research Station that helped this Texas A&M team gather their oceanographic data. This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links, please go to ocean.tamu.edu and click “On the Ocean”.
Script Author: Laramie Jensen
Filters with obvious growth response to an iron dose after incubation of a few days
C’s are control with no iron added, F’s are iron added. The more color, the more growth was seen.