Forests of the sea
An interview with marine biogeochemist, Dr. Adam Kustka
Assistant Professor in the Department of Earth and Environmental Sciences, Rutgers University, Newark
My name is Adam Kustka, I’m a professor in the Earth and Environmental Sciences Department at Rutgers. I work on phytoplankton and interactions between phytoplankton and trace metals.
The Ross Sea is part of a bigger Southern Ocean ecosystem. Large expanses of the Southern Ocean have plenty of plant food in the waters. Basically when you think of plant food you can think of the components of Miracle-gro: nitrogen, phosphorous, all of the things plants need to combine with carbon to make little phytoplankton bodies. It turns out that most of the Southern Ocean has very high levels of nitrogen and phosphorous, so for years this has been interesting to oceanographers to figure out why is it that there is plenty of plant nutrients and not a lot of phytoplankton. It turns out that iron has turned out to be a key limiting nutrient in these ecosystems.
We’re interested in looking at a specific part of the Ross Sea where the plant biomass seems to be a bit higher. We hypothesize that perhaps there is an iron supply in this very small region of the Ross Sea coming from something called Modified Circumpolar Deep Water. We will be conducting on-deck incubation experiments where we add iron to large bottles of the seawater and measure the response of the phytoplankton by measuring production of chlorophyll over time.
What’s also interesting about the Ross Sea is that there tends to be two groups of phytoplankton that dominate. Either diatoms or a group of organisms called phaeocystis. When diatoms bloom, there is a more robust food chain leading up to krill and seals and penguins and whales. And when phaeocystis blooms the food chain is not as robust. Phaeocystis doesn’t taste good to many organisms.
We’re interested in factors that drive diatom abundance versus phaeocystis abundance. When you think about phytoplankton in one cup of water you have representatives from very diverse evolutionary pathways. Diatoms are very very different from green algae, and those are very different from dinoflagellates, that is another group of algae that cause paralytic shellfish poisoning and other harmful events. So in one cup of water you can have organisms that are competing for the same nutrients and the same light that couldn’t be more different in terms of their evolutionary trajectory. They’re all in that single cup of water duking it out for the nutrients and the light. That’s actually another component that we’re interested in. Using the molecular methods we can figure out who is winning in that cup of water. In this case the cup of water is the Ross Sea ecosystem.
Phytoplankton are very important for global climate because they are just as important as the oak trees and maple trees and the grasses and prairies that we are all familiar with in terrestrial biomes we just don’t think about phytoplankton every day because we’re not underwater all the time. Phytoplankton basically carry out the same function as all the land plants, removing almost the same amount of carbon dioxide from the atmosphere every year.
Most of the work that I’ve done has been in tropical ocean environments so I’m used to going out on deck in shorts and a t-shirt and obviously I don’t think I’ll be doing very much of that on this cruise. And we’ve never really had to worry about ice off the coast of Barbados or northern Australia but in this case I think ice could be a potential problem. But other than that we have a great group of people going, a very tight-knit group of scientists and I think it’s going to be a great trip.