Science

What exactly are we doing over here?
In the lab at Stanford we study algae (phytoplankton) that grow in the Southern Ocean, because they take up CO2 from the atmosphere and take part of it down to the deep sea, or even the seafloor where it gets buried and removed from the carbon cycle for a while.
That’s pretty neat, but of course we want to know if it remains that way during global warming in the future. We are now in the Amundsen Sea, where the Pine Island glacier reaches the sea. This is the fastest flowing glacier in Antarctica, and the Amundsen Sea is an Antarctic area that is warming up very fast. So it is an interesting area to study and possibly predict the future using the results. The sea system is pretty simple here, there are no rivers that supply nutrients, there are only a few large animals that eat stuff, there are few bacteria and viruses, and there are only two different groups of algae that grow in the water: Phaeocystis and diatoms. These two groups have very different characteristics. In short, Phaeocystis is very good in taking up of CO2 and diatoms are more tasty for krill, the small shrimp that are eaten by penguins and whales. Factors important for growth of algae here are iron content of the water, and light. There is only little iron in the water here and algae need a bit to grow. They also need light, but to much light and UV radiation can be harmful, so the algae need to protect themselves against it.

We study which factors determine whether either Phaeocystis or diatoms grow, and how much CO2 they take up. And also if the adaptations to low-iron concentrations affect the way they deal with light. The ideas we are testing are the results of computer models that mimic the growth of algae and work that we did in the labs in Stanford and Groningen.
And now we test for real if it works in the water in the Southern Ocean they way we think it works. So far all our analyses and experiments work and we have not encountered any big surprises. We are now sampling at the Pine Island glacier and detect that the glacier melt water carries iron into the water. North of the glacier, many algae are growing and they deplete that iron pretty quickly. We have two incubators on deck for the algae to determine whether their growth is limited by iron and if they can use iron from other dissolved particles. Finally, it seems that when the algae are iron-limited, they use the available light less efficiently, and on top of that they are more stressed when they get too much light. We are now in the vicinity of the glacier to see whether we can get something out of the effect of the melting water on the algae. Unfortunately, that is easier said then done. Two samples that were taken 2 km apart vary wildly in properties, and also if you test the next day, there are large differences. We have to see how we can fit the results in the larger picture. For now there are algae to filter, incubate and results to be produced. We already try to make sense of the data on the fly, but the final interpretation has to wait until we are home and can sit back and look at it from a distance.

Anna