Oozing with Life, and Maybe Iron

The Palmer has an ample supply of Dutch hot chocolate mix to warm people as they come in from the wind, spray, and snow on deck. Today I fixed my cup as normal, but I walked away from the galley without a spoon.

As I sloshed and swirled my cup, hoping the hot chocolate powder would mix with the hot water, I realized I was facing the same problem that phytoplankton face in the Ross Sea. At the bottom of my cup were a whole bunch of particles that I wanted, while at the top there was only clear water.

If I could get just some of the powder up to the top, the water would be sweet and chocolatey, and I’d be happy. But even though I was adding a considerable amount of energy in the form of swirling, I still had to go back and get a spoon. If all that work couldn’t mix the chocolate just a few inches in my cup, how does mixing happen at sea, where nutrients have to move up through thousands of feet of water?

This is one question that Dr. Phoebe Lam has spent much of this voyage thinking about—and it has prompted her to start looking at what lies on the bottom of the Ross Sea in more detail. We’ve been looking over her shoulder. Read on through the slideshow to see what she has found:

For the rest of our expedition, the Palmer is going to crisscross two shallow parts of the Ross Sea: Mawson Bank and Pennell Bank. Dr. Lam will be sampling the seafloor as we cross, and Dr. Kohut’s and Bruce Huber’s teams will measure the currents that flow along the seafloor. Here’s a map of the area to help you keep straight the parts of the Ross Sea we’re studying:

If the Ross Sea is getting mixed like a giant cup of hot chocolate, how is it happening? Dr. Lam’s analyses will tell us about the particles on the seafloor: how much iron is there, and whether particles of it might be reaching the phytoplankton.

To move that iron up to the surface waters will take a lot of energy. Dr. Kohut’s and Bruce’s measurements will help decide if the bottom currents are providing enough. And the terrain of the seafloor, as shown on the map, might be acting like that spoon I needed today—a hard surface that deflects the swirling currents upwards. That’s why the scientists are focusing on these two shallow banks and their sloping sides.

Many thanks to Dr. Angelicque White and Dr. Scott Fay for help with the seafloor creatures, and to Kathleen Gavahan for plotting the map.

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Profile photo of Hugh Powell

About Hugh Powell

Hugh is a staff writer at the Cornell Lab of Ornithology and is on special assignment with the Rutgers University Institute of Marine and Coastal Sciences. He has previously written for the Woods Hole Oceanographic Institution.

12 Responses to “Oozing with Life, and Maybe Iron”

  1. Profile photo of Loris Chen

    Great analogy. Dr. Lam talked about iron particles on the February 2 Live Call when she explained the effect of salinity and temperature on iron solubility.

  2. That really puzzled me. How far down does the mud-grabber have to go to get to the bottom???

    • Profile photo of Hugh Powell

      Hi Emily, the answer is all the way. Sorry, that’s a bad joke. I think you’re asking how deep the water is here? It’s between about 250 and 500 meters (825-1650 feet) deep in the sampling stations we’ve been visiting over the last couple days. Check out the map at the end of this post to see water depths in more detail.

  3. James and Dan from Harborfields High School February 9, 2011 at 9:53 am

    Do you find a realtionship between tmeperature of the water and where phytoplankton are blooming?

    Is genetic testing being conducted on the different types of phytoplankton being collected?

    • Profile photo of Hugh Powell

      Hi James & Dan, thanks for writing. Those are good questions—ones that scientists have been studying for a while.

      Dr. Adam Kustka said that there is a relationship between water temperature and phytoplankton blooms, but it’s complicated. When water warms up it also becomes less dense, so it doesn’t mix as well with the water below it. This can mean that the phytoplankton becomes more concentrated close to the surface, where it gets more light. But depending on other factors such as where in the world they are, that can also mean that nutrients in the surface water get depleted, hindering growth.

      As for genetic testing, Dr. Kustka’s group as well as Dr. Bob Sanders’s and Dr. Rebecca Gast’s group are analyzing phytoplankton DNA. They want to find out what kinds of phytoplankton species live in the specific conditions they have found in their samples across the Ross Sea (And Dr. Sanders’s group wants to find out which species eat bacteria.) This information will help them learn about the microscopic food chain here, as well as understand the way carbon dioxide moves between the atmosphere and ocean.

  4. Charlie from Mrs. Worth's 7th Grade Class February 9, 2011 at 4:55 pm

    Staghorn coral with White-band disease. That’s what I think you found. Scientists say it is an endangered species of coral hopefully I helped.

    • Profile photo of Hugh Powell

      Hi Charlie, thanks for the help! I don’t think this is a typical reef coral because it came from much deeper water, but we are checking with coral experts back home and hopefully we’ll learn the answer.

  5. Profile photo of cworth
    Kimberly from Intermediate South Toms River February 9, 2011 at 5:14 pm

    Hi, I have a question. How fast would the underwater currents have to be moving to get the nutrient at the bottom of the Ross Sea to get to the surface? how heavy or how many gallons would the take? and what direction would the currents be moving?
    God Bless.

    • Profile photo of Hugh Powell

      Hi Kimberly, that’s a great question—in fact it’s one of the things the scientists on this trip are trying to figure out. The hard part to figure out is not how fast the currents would have to move, but how much energy would be required to overcome the differences in density between the water at the bottom of the sea and the much less dense water at the surface, as well as where that energy might come from.

  6. Profile photo of cworth
    Mrs. Worth's 7th Grade Class February 9, 2011 at 9:56 pm

    Do upwelling’s occur in the Ross Sea? If they do, would they contain enough energy to carry iron up to the surface a long with the other nutrients that upwellings carry?

    • Profile photo of Hugh Powell

      Hi Mrs. Worth’s seventh graders. Good question. That’s what we’re trying to find out: does water such as MCDW make it all the way to the surface as upwelling or other mixing, and how much iron does it contain? It does make sense that upwellings would provide this, but the scientists need to gather evidence to find out for sure.

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