The Project

Half of the oxygen in the Earth’s atmosphere is produced by phytoplankton, the drifting plants of the ocean. Phytoplankton (along with bacteria) also make up the basis of the oceanic food web. These microscopic plants live near the surface of the ocean because, like all plants, they need light for photosynthesis. In order to grow, phytoplankton also need nutrients. The main nutrients they use are nitrogen, phosphorus, and silicate. When phytoplankton grow in large numbers, or “bloom”, these groups of plants can be seen by satellites in space.

Many years ago, however, oceanographers found places in the world’s oceans where there were a lot of nutrients, but not much phytoplankton. What could cause that? Research has shown that the ocean water in these areas is low in dissolved iron. If plants don’t have enough iron, they can’t absorb nitrogen well. However, if there is enough iron in the ocean water, phytoplankton can bloom.

A section of the Southern Ocean is a great place to investigate this process because something unusual happens there. In the eastern Drake Passage near the edges of the Antarctic continental shelf and near the Scotia Sea, there are great numbers of phytoplankton. West of that area, however, the water is barren of phytoplankton. And, there is more iron in the water where there is more plankton! How did that iron get there?