Keep It Going: Recycling in Phytoplankton Blooms
February 11, 2011 
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Dr. Adam Kustka has been wearing the same gray-and-black windbreaker for about two weeks. He doesn’t appear to sleep at all except for short naps, which consist of pulling his hood up and putting his head down on his desk in front of his computer monitor. His hands remain over the keyboard so that when he wakes up he can resume typing without interruption. His hair can assume any of the angles of a clock face, depending on the hour, and his eyes are puffy from being open so long.
If you ask him a question, he answers slowly at first and then accelerates, as if his brain is a voluminous hard drive that takes a few seconds to access the full stream of ideas inside. He told me he misses his breakfast routine back home, which is a glass of diet ginger ale mixed with a Red Bull. He gets a ‘frequent buyer’ discount on rare isotopes of carbon. He and his team have a lot going on.
They’re trying to understand the lifetime of a phytoplankton bloom—the give and take between organisms, the battles that go on for nutrients like iron, the ways that phytoplankton bodies get recycled as a bloom flourishes or dies away. At the moment, a bloom is kind of like a television: we don’t know what’s going on inside; all we can do is watch what comes out of it.
Dr. Kustka’s team is trying to change that, using subtle principles of chemistry, precise lab techniques, and hours and hours of painstaking preparation to set up controlled experiments on the ship. Read on through the slideshow to find out what they’ve been doing lately:
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- Dr. Kustka measures a precise amount of carbon-13-labeled food into 2.5 gallons of seawater for an experiment. His team uses isotopes of carbon and iron to understand how well these elements get recycled during a bloom, and which organisms are best at doing the recycling. (Isotopes are alternative forms of an element that have similar chemical properties but can be easily distinguished in analyses, making them useful as tracers.) Once scientists understand this recycling process better, they may be able to predict how long a phytoplankton bloom will last, or uncover differences between different kinds of blooms—for example, ones dominated by diatoms vs. by Phaeocystis (see Feb. 3 post).
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- The food Dr. Kustka is using in this incubation consists of broken-up pieces of diatoms and Phaeocystis. By adding these dead phytoplankton to a seawater sample, he simulates a bloom that has been going on for a while. Dr. Kustka grew these in the lab before coming to Antarctica, feeding them carbon-13 so that their bodies would be rich in this type of carbon. When organisms in the seawater eat these dead diatoms, they’ll use some of the carbon-13 to make more DNA. Then Dr. Kustka can isolate the DNA that contains carbon-13 and sequence it. It’s a clever way of separating out the organisms that are good at recycling carbon from ones that aren’t.
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- Menglei Chu, Dr. Kustka, and Ashley New meet to discuss the next round of experiments. Each set of incubations requires lots of water samples, which they have to get from Dr. Chris Measures’s ‘clean’ rosette to make sure they’re not contaminated with iron (see Jan. 26 post). The 12 bottles in the rosette yield about 25 gallons of water for experiments, so it takes careful planning to make the best use of it. Some of the larger experiments require more than 25 gallons so they have to send the rosette into the water twice in a row—which is why other teams have nicknamed them the ‘trace-metal water hogs.’
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- Graduate student Ashley New checks on seawater incubating in the Blue Room (see Jan. 27 post). Each 2.5-gallon pouch contains a different condition that the experiments are testing: water taken from different sampling stations, some of it mixed with iron, some with MCDW, some with carbon-13-labeled diatoms, some with carbon-13-labeled Phaeocystis, and a handful of other treatments. The team prepares two identical versions of each of these treatments. The duplication helps them spot errors or contamination when they analyze the results.
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- Several different students have written in to us with an excellent question: if the light outside is white, then why do we grow the phytoplankton in a room where all the lights are blue? This image and the next one show you the answer. It’s true that in our normal view of the outdoors, the light is mostly white. But that’s not where phytoplankton live…
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- Phytoplankton live underwater, and water is an excellent light filter. Most colors don’t make it very far past the surface before they’re absorbed. The main color that penetrates past the surface is blue. This photograph was taken just a few minutes after the previous one, but the light isn’t gray at all. In fact if you look back at the photo of the Blue Room, the light is a very similar shade (neither of these photos have had their color altered).
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- Ashley’s lab book shows columns of calculations to make sure she adds the right amount of each ingredient to her experiments. Carbon-13 is just one of three kinds of isotopes the team is using to understand how nutrients get recycled during a bloom. The other two are carbon-14 and iron-59. These two isotopes are used to measure how fast carbon and iron get recycled by all the organisms in the seawater. The technique can’t identify which species are doing the recycling, which is why Dr. Kustka’s team is using it alongside the carbon-13 technique.
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- Because carbon-14 and iron-59 are mildly radioactive, those experiments must be incubated in seawater tanks kept outside on an upper deck. Here, Menglei Chu checks on a separate project he’s been conducting involving Phaeocystis. You can barely see 6 clear plastic bottles that are still in the water. They contain Dr. Cecile Mioni’s iron-59 experiments. A few hours after this photo was taken, around midnight, Dr. Mioni brought the bottles back into her Rad Van for analysis (see Jan. 27 post). By tomorrow, we should know how much iron got recycled by the seawater organisms in her sample—and we’ll be one small step closer to understanding how phytoplankton blooms work.
I’m sure you noticed the Adélie penguin that was swimming around in the ‘Gray light’ photo in today’s slideshow. I’ll admit it: we didn’t have to use that photo—we have plenty of great photos showing white sky and gray water uncluttered by penguins. But we’re in Antarctica, and to tell the truth at least one of us is kind of crazy about penguins. Maybe you are too. At any rate, here’s a close-up look at Chris’s amazing penguin-in-the-water shot:
Read more in the following posts:
- A Little Iron Goes a Long Way (Jan 26)
- Where Biology and Chemistry Meet (Jan 27)
- A Cupful of Smelly Gooey Phytoplankton (Feb 3)
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