Here’s the latest representation of the patch - derived from Kevin Sullivan and Craig Neill’s measurements of SF₆ over the last two days and hot off Steve Pierce’s computer not 10 minutes ago

Jump to the log entry from the RV Melville

REVELLE @ 2/2/02 05:10Z, 

-66 9.3312, -172 2.1192

So. Patch In Drifter @ 2/2/02 04:54Z, 

-66 11.154, -171 47.0034

So. Patch Out Drifter – no fix today

No. Patch In Drifter @ 1/31/02 1900Z, 

-54 21.84, -170 9.78

No. Patch Out Drifter @ 1/31/02 2345Z, 

1810 February 2, 2002

Hello again. We finished adding iron for the third time at midnight. We then have 65 hours until we head north, first of the North Patch, then for Lyttelton. The schedule for our remaining time here is full (over full actually by 5 hours – work fast folks). A last SeaSoar survey, an In and Out station, service the drifting buoys – one of which has not reported its position for several days - and a final dose of iron.   

The Out drifter must have suffered some damage in the storm of a few days ago.  We can still talk to it by packet radio, but its GPS receiver can’t compute the drifter’s position. The GPS antenna is broken or a cable has come loose. The RDF (Radio Direction Finding) beacon on it also is now not operating. Where to look?  After a little head scratching and then Eric conferring with Captain Tom, we found an old RDF unit up on the bridge that will tune in to the packet radio frequency. So, hopefully, with a little triangulating, we will be able to track it down. The Out drifter is beyond range right now, but we found that we could use the system to track down the In drifter, so there is hope.  

We’ve been building maps of the patch over the past few days, but the weather has not been cooperating. We’ve had fog so thick that the ship couldn’t move (can’t see small icebergs on RADAR). We’ve had wind and seas so high that we could barely move. And then, when we finally did go, the ship was pitching in the large seas so much that the scientific seawater intake (at the bottom and a fair way back from the bow) would come out of the water, suck in air, and vapor lock the pump: no water, no data. But, we’re persistent. Here’s the latest representation of the patch - derived from Kevin Sullivan and Craig Neill’s measurements of SF₆ over the last two days and hot off Steve Pierce’s computer not 10 minutes ago. From its original dimensions of 15x15 km, the patch has spread out to 25x25 km. Variable fluorescence is maximal over the entire region with elevated SF₆ - we’ll send that map tomorrow. 

MELVILLE informs us that chlorophyll in the patch has continued to increase and is now about 6 times greater than the concentrations that we observed just before iron was added eight days ago. Kenneth Coale over on the MELVILLE told me today that the waves, which are drenching them on deck, are green, not blue. Hopefully Ron Nicolayson, who is photographing the expedition, can capture that color shift. 

Now that is a distinct advantage of being on the REVELLE: it’s bigger, wider, heavier, newer and, most importantly, drier.  We’re here, on the big ship although there are fewer of us, because it can carry a much larger deckload - and we have a mighty big one, over 50 tons of gear out on deck that we brought along. Big winches, 10,000 gallons of tankage for the iron and SF₆, containers - just a bunch of stuff. And now we have to start thinking about getting it off the deck in 1.5 days in Lyttelton. Oww! I’m tired already.

Latest contestant in the Shackleton lookalike contest - Kevin Sullivan, artiste of the SF₆ machines.

Bye for now.

February 2-3, 2002

Local time: 1500

Ship’s Position: 66 degrees, 9 minutes South, 171 degrees, 41 minutes West

            Yesterday we conducted an Outside Patch station, southwest of the enriched area.  Here in these waters, the chlorophyll is somewhat elevated but the cells don’t seem to be very healthy (pablum blown all over the kitchen). The zooplankton tow came up full of phytoplankton mostly Rhizoselenia, Chaetocerous and our friend Chorethron - a few zooplankton, a few pteropods and some lonesome copepods. Maybe we should have used a phytoplankton net to catch zooplankton. Anyway there does seem to be some growth happening outside the Southern Patch in un-enriched waters. It will be interesting to see if any geochemical signal develops there. What I mean is that we think that blooms are very normal for these waters but the ability for phytoplankton to really draw down nutrients and carbon dioxide to significant levels, requires iron. Things are rarely simple and this experiment has both that which is easy to understand, and that which we may never understand. This is why we need so many different ways of looking at the system.

            One set of eyes we have are really the beam of a powerful blue laser and detectors at four separate wavelengths. Zachary Johnson from Penny Chisholm’s Lab of MIT is using flow cytometry to look at several optical properties of the phytoplankton community. Some of these properties have to do with the color of light that the objects in the light path emit when blasted with a laser beam. Different phytoplankton groups have different fluorescent characteristics (pigments) that will give off light of a color characteristic of their taxa.  Phytoplankton also have different shapes and sizes that scatter light to different angles when blasted with a powerful beam. 

Imagine you’ve got the hose and you are squirting it at things to distinguish their shape. The image that you get when you splatter a hubcap differs from the image you would get from squirting your little brother, or a tennis ball.  I know, for all its sophistication, a flow cytometer is still a crude instrument. But it does tell us a lot. When you put all these things together, certain phytoplankton have a certain set of scatter angle/fluorescent parameters that can be used as a fingerprint for certain cells.  It is really more tricky that this, the fluorescent patterns and scatter angle can change as the cells grow, change their chlorophyll content, or divide and very little sample is needed for an analysis. So what is Zack doing with his light hose? Well, he is trying to keep it from burning up. The laser is high powered and needs to be cooled by a constant supply of seawater. This has been a little problematic, but it has kept Zack on his toes and actually he has some pretty interesting results. Zachary Johnson of MIT with his flow cytometer (note blue laser light above red tie-down strap)

What Zack is finding is that, for the smaller cells that his instrument can accurately detect, the amount of chlorophyll per cell for different cell types is changing. Inside the Southern Patch, chlorophyll per cell is increasing significantly. Does this make sense?  Well, iron is needed for chlorophyll synthesis. This means that each cell is making more chlorophyll than their counterparts outside the patch. When considered together with the increased efficiency of the light harvesting reaction (see Max and Michal’s results), it seems to us that we now have a population of very healthy cells that are ready to take off and grow like crazy.