A Cupful of Smelly Gooey Phytoplankton
February 3, 2011 
16 Comments
It was the color of the ocean from space that brought us here. We knew it was a gamble, a dogleg away from our main sampling plan. But satellites were telling us that phytoplankton were flourishing here, over deep water, where no one could explain it and no one had ever been to study it before.
To come here and still get the rest of our work done would require long shifts at the pumps and filters and spectrophotometers and microscopes. But it might turn up something unexpected. And I guess that’s why these people are scientists. They are drawn toward the unknown.
When we got here the water, which is normally blue in the open ocean, was green with phytoplankton. The first net over the side brought up cloudy water that people described as smelling like broccoli, seaweed, sulfur, or brussels sprouts. To me it was briny and sharp and smelled like freshly shucked oysters. That’s the smell of the ocean—a gas called dimethyl sulfide—and it meant we had stumbled on a different kind of phytoplankton bloom. Read on through the slideshow to find out more about our day:
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- Dr. Cecile Mioni of the University of California, Santa Cruz decorates a styrofoam cup for her sister, Amandine, who is turning 30 today. That may seem like a strange present, but we’re going to do something cool with these cups—you can see Ashley New, Menglei Chu, and Dr. Angelicque White decorating their own cups in the background.
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- Able-bodied Seaman Louis Andrada keeps his eyes on the CTD rosette as he maneuvers it out of the Baltic Room. With both hands guiding a control stick, he keeps the winch cable steady while extending a heavy hydraulic arm out over the sea. In rolling seas this is a tricky procedure, as the 750-pound rosette can swing dangerously with the ship’s motion. Louis is from Mindanao, Philippines, where his wife and children live, but he spends about 10 months of the year on the Palmer.
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- Marine technician Mark Harris, just visible at right, guides the CTD rosette out of the Baltic Room. Dangling out of view beneath the rosette is a mesh bag with 34 decorated styrofoam cups in it. In about 45 minutes they will be 1,900 meters (1.2 miles) deep. Because of the tremendous pressure of all the water on top of them, each square inch of styrofoam will have the weight of a car pressing down on it. What do you think will happen to the cups?
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- Meanwhile, up in the sunlight, biologists were complaining. Almost everything we’d seen so far had been delicate, glass-walled diatoms (see Jan. 26 post). But the phytoplankton that make this water so green are something different. They’re tiny creatures called Phaeocystis that live in colonies surrounded by a sticky, snot-like substance. That snot clogged everyone’s filters: Dr. Walker Smith’s 45-minute procedure took 6 hours; Dr. Allen Milligan had to use 3 times the number of filter pads to get a sample; and 2 of Dr. Phoebe Lam’s particle pumps simply shut down after 15 minutes.
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- The dusty spheres you see here are Phaeocystis colonies. They look like dandelion seedheads just before you blow on them, and each one of the little points of light is an individual Phaeocystis. Those spiky, stars scattered across the image are one end of a Corethron diatom (see Jan. 26 post and next image). You can see that individual Phaeocystis are much smaller than the diatoms, but they live in colonies that are larger than a diatom. The bright-white dots are bubbles of gas—much of it dimethyl sulfide, or DMS (see Jan. 27 post).
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- We put our sample of Phaeocystis under a microscope. Here’s a single colony—a sphere pocked with dark dots like craters on a moon. Each little dot is a Phaeocystis individual, and they’re all held in this arrangement by their gooey secretions. A pretty Corethron diatom has wound up inside (or perhaps on top of) the Phaeocystis colony, giving another look at how the two compare in size. That dark oval to the left of the diatom is another tiny organism called a dinoflagellate. And it’s hiding a secret…
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- This is the same image seen with the microscope’s fluorescent light, so all the chloroplasts light up red. You can see that everything—the little Phaeocystis, the long, skinny Corethron diatom, and the dinoflagellate—has chloroplasts. But the dinoflagellate doesn’t make its own chloroplasts—it steals them from Phaeocystis. This one individual shines so red because it has the chloroplasts of probably 15 Phaeocystis individuals inside it, Dr. Rebecca Gast told me. The thief can keep its stolen chloroplasts alive for several months, but it can’t make the chloroplasts divide. So the dinoflagellate is locked into a life of crime—attacking Phaeocystis and stealing its chloroplasts again and again.
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- When the CTD rosette came back on deck, Ana Filipa Carvalho, Ashley New, Xiao Liu, and the rest of us checked the mesh bag of decorated cups. Compare how big the cups were in the first photo to how big they are now. They shrank down to less than half their size, but kept their shape. The growing pressure as the CTD sank squashed the cups, but it didn’t squash them flat. That’s because the water surrounded the cups on all sides and pressed in roughly equally at every point. So now everyone has a miniaturized keepsake cup.
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- Penguins were the dominant symbolic touchstone for most of our cup decorators. The artists worked in varying degrees of realism, from Dr. Scott Fay’s eager Adélie at the top, to Filipa’s adorable cartoons (top right, next to the glider; these were the group’s favorite), to more bowling-pin inspired talking penguins—doubtless an allusion to the fondness with which our own culture views penguins. A vaguely owlish representation (not shown) may have been one artist’s wistful allusion to the underappreciated wisdom of the penguin. Other recurring themes were orcas, diatoms, skuas, petrels, and the Nathaniel B. Palmer herself. What would you draw on your own cup if you were here?
Throughout the Ross Sea, the two major kinds of phytoplankton are Phaeocystis and diatoms. But wherever blooms happen, they tend to be made up mostly of one of these types, with far fewer of the other. Before today, our expedition had found blooms dominated by diatoms. This is the first mostly Phaeocystis bloom we have seen.
Scientists aren’t sure why the two types don’t occur in more equal proportions in all blooms. Some think that Phaeocystis blooms earlier, beating out the diatoms but requiring more iron, and perhaps performing better in low light. Then, later in the summer when less iron is available and there’s more sunlight, the diatoms take over. But these ideas have not been thoroughly researched yet.
The Phaeocystis bloom we found will make an interesting comparison to the diatom blooms we’ve been finding. It’s happening at the same time, in the same light conditions as the diatom blooms. And the iron measurements Dr. Chris Measures and Dr. Lam are making will tell the scientists whether this Phaeocystis bloom has more iron in it than the diatom blooms. Perhaps they’ll find enough new information that they’ll come back and test a new hypothesis… and make some more keepsake cups.
Read more in these related posts:
- A Little Iron Goes a Long Way (Jan 26)
- Where Biology and Chemistry Meet (Jan 27)
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