Southern Ocean Iron Experiment (SOFeX) Cruise
January 5 - February 26, 2002
Logbook
Skip to Log Entry from the R/V Melville
January 31, 2002: Day 27
R/V Revelle:
Ship: -66 19.3428, -171 55.0638
So. Patch In Drifter @ 1/31/02 04:13Z, -66 18.4824, -171 44.4258
So. Patch Out Drifter @ 1/31/02 04:13Z, -66 36.0612, -171 47.4306
No. Patch In Drifter @ 1/29/02 20:00Z, -54 32.58, -170 33.42
No. Patch Out Drifter @ 1/29/02 18:20Z, -55 25.2, -172 35.52
R/V Revelle Log Entry: Whoa, what a night! Remind me never to say the weather is moderating in an update, which I think I did yesterday. By midnight, the wind had picked up to a steady 40 knots and we were seeing gusts to 60 knots by the time I gave up trying to sleep around 0330. The seas grew rapidly and they were over 10 m by breakfast. Ouch! But there seems to be one rule about the weather down here: if its bad today, it will be nicer tomorrow and, well, you know the other side of that. So now, after dinner, its much nicer outside, just cold, snowing hard, but not too windy.Were tempted to blame last nights wind on MELVILLE, but were saving that for a really big storm. Second Officer Eric predicts well see 20 meter seas before were back in port.
We had to delay our morning work schedule, but we were on station and operating again by 1300 with the heavier equipment, some of our lighter instruments wont sink fast enough when the ship is rolling hard to avoid slack wires. Since the wire that suspends the instruments comes off a big drum, it wants to coil back up when the line goes slack. If it does that and the ship rolls back, it kinks the cable - thats called a hozzle and its bad because it breaks the wire and electrical conductors inside the wire.
We were concerned that the big blow would smear the patch and mix phytoplankton down to depths where there wasnt enough sun for them to grow.But that hasnt happened. The temperature profile shows the really uniform layer from the surface down to about 40 meters: we call that the mixed layer. The mixed layer has deepened only 5 more meters over night from the previous value of 35. The SF6 values are about what we were seeing yesterday: a little lower, but thats to be expected from all the waves. That really cold layer in the profile at 60 m is near the freezing point of salt water - its the remnant of the winter mixed layer when ice was forming here. Summer has warmed the surface waters from -1.8C to a balmy -0.6C. But summer winds arent strong enough to mix down as deep as the winter storms.
Not much specific news to report on the progress of the plankton community in the patch. Sue Brown continues to analyze the phytoplankton.Her epifluorescence microscope has captured this image of Chaetocerous in the patch.Lots of diatoms are coming up. People are having a hard time filtering samples as too many phytoplankton are clogging the filters now. Bye for now.
- Ken J.
R/V Melville:
Position: 66 degrees, 35 minutes South, 171 degrees, 53 minutes West
R/V Melville Log Entry: Although yesterdays station got off to a rocky start, for the first time this trip it appears that all systems were operational.before we got to station!! Unfortunately, Mother Nature has different plans for us. Throughout the night the wind shifted from the west and is now blowing out of the north. Since about 0400, winds have been steady above 40 kts. At 0600, winds were steady at 48 gusting to 58 kts, and the seas are building. I have suspended the morning deck operations and the captain and I will reevaluate the situation at noon.
So, what are we finding? The water column south of the Polar Fronts Zone is characterized by high silicate above 60 micromolar, nitrate of about 30 micromolar, water temperature that is cold (about -0.5 degrees C) and a mixed layer about 35 m deep.There is a subsurface fluorescence maximum just below the mixed layer so it appears there are some phytoplanktors hanging out on a density gradient where the water gets heavy but there is still enough light. The organisms there are largely diatoms of all kinds but they seem to be functioning below their optimal physiological level. They have large vacuoles (empty spaces) inside their cells and small amounts of chlorophyll (see photo). From a cell physiological perspective, they are built like big warehouses without a lot of materials and machinery that a working factory would have. In addition, their inventories are lownot much stock on hand. This seems to be due to the fact that they cannot efficiently harvest light energy (hook up to city power) and take up nitrate and carbon (bring in raw materials). Nonetheless, it appears they are there and ready to bloom, we just havent seen it happen yet.Except where we added iron.Here the efficiency of light energy harvesting has more than doubled and the phytoplankton are beginning to utilize raw materials and crank out product. How can we tell?
The clever people from Paul Falkowskis lab at Rutgers University have developed a way of titrating the light harvesting centers in phytoplankton with photons and measuring how efficiently they are utilized by the tiny algae. They rapidly flash saturating pulses of light at the phytoplankton. Very simply, the number of pulses before the phytoplankton begin to fluoresce is a measure of their light harvesting efficiency. What?
Here is the parental analogy: You put your little daughter in a highchair with her favorite cereal. Then you start loading her up and counting the spoonfuls that you can pack in before she fills up and pablum starts to come back up. The larger the number of spoonfuls, the more efficient the harvesting. (You can be sure that respectable biophysicists and parents alike take some offense at this analogy, but this is the basic idea). Back to the phytoplankton: how does a phytoplankton blow pablum all over the kitchen?.by fluorescing. That is, they absorb incoming radiation and would normally use this energy to run the equipment in the plant (reducing NADP+, phosphorylating ADP, fixing carbon, reducing nitrate, etc). When their reaction centers become overloaded with incoming light, they re-emit light at a lower wavelengththis is fluorescence. The more they can absorb without fluorescing, the more can go into the cell for metabolic purposes. In cases where iron is lacking, phytoplankton cells do not have the ability to swallow all the photons that they are fed. Max Gorbunov and Michal Koblizek on Melville (picture) are making continuous measurements of the Fast Repetition Rate Fluorometry (FRRF) response of natural assemblages of phytoplankton and on single cells. They use microsecond spoonfuls of photons and can make a single measurement in a matter of milliseconds. As such FRRF has become a very useful tool for understanding phytoplankton physiology and nutrition, and mapping the iron enriched area. In addition, iron enrichment has become a very useful way to understand the biophysical state and adaptability of phytoplankton. Unlike chlorophyll that takes days or weeks to increase, the fluorescent response develops within a very short time (several hours to a day or so).
The Southern Patch native:Corethron spp.One of many diatom species coming up in the Southern Patch. This picture was taken by Karen Selph under epifluorescence microscopy after staining with DAPI (stains nuclear material yellow in this picture), and proflavin (stains proteins greenish), the red dots are chloroplasts. This is a single cell centric diatom with lots of crazy spines (makes em hard to eat). The red bar with dots is 100 microns long.