Date: Tue, 03 Mar 1998 15:18:39 -0500

The following was received via fax from the Revelle this morning: Feb. 28 As we were sending our last report the skies cleared and the winds died. We enjoyed almost 36 h of winds of only a few knots and clear, and a few hours of sunny skies for parts of two days. If this doesn't fuel a bloom, what will? As we left Mooring 4 (St. 7 for us), a BLOOMIN' CONTEST was started to guess the latitude of the peak of the bloom as determined from the underway fluorometer. That night the Aurora Austrailus put on a show for us as the pale lights waxed and waned rapidly across the sky. It was still calm the morning of 2/27 as we started to sample at Mooring 5 (St. 9; 66S), but we started to get a few snow flakes that grew to a light flurry and then the snow ceased. It is definitely surreal to deploy equipment when it is snowing, the sun is faintly piercing through the clouds in the distance, a huge iceberg is nearby, air temp is 0, the water is 1C, and we are looking for a plankton bloom! In the afternoon the winds kicked up to 20 kts, and by the next afternoon the winds were back up to our familiar 30-40 kts. Giant icebergs hovered nearby at moorings 4 & 5. Particle concentrations increased markedly at mooring 5 - the highest we have had for the cruise, although fluorescence didn't exceed the values measured at mooring 1. Everyone reported more phytoplankton and zooplankton in the water. Yet the surface silica was up to 50 umol/kg at this station. S. Rubin's plot of the underway pCO2 showed much higher surface values than along any of the 4 Survey II transects, and values at mooring 5 (350 uatm) were as high as those reached south of the bloom during Survey II. It seemed possible that the bloom had ended and that our task was to monitor the system as it progressed after the bloom. Still, we felt it was important to head further south to see if there were any indications of blooming waters and to then to do a long station in what appeared to be prebloom waters. Why hydrographic conditions prevail there? What species and abundance of phytoplankton, bacteria and zooplankton could be found and what were their growth and grazing rates? Why wasn't it blooming? After Mooring 5 plans were to do hydro stations at 67.5, 69 and 70.5S to assess conditions. With our first report went a request to look at SeaWiFS images to check for bloom conditions to the south since we had some open skies. This afternoon (2/28) Greg Mitchell sent a cartoon of conditions from 160-180W and 50-72S, and it appeared that the best was yet to come (thanks Greg and Walker!). We are finishing the Mooring 5 station and will head south, although it seems that we will not get to prebloom waters before we have to turn around. It is great to see that the chlorophyll highs and lows in the SeaWiFS image match so well the highs and lows in the locations we have sampled so far. it is also reassuring to have information about what lies ahead. Evening We have suspended over the side sampling at this site as winds are gusting over 40 kts and the seas are heavy, so we are heading south. A sad note is that the primary productivity array was being recovered under these rough conditions a few hours ago and only some of the surface bottles and a PAR sensor were recovered before the line was severed by the screw and Neptune extracted his dues. One good in situ deployment has been obtained and there is still enough equipment left to try another floating array. Most incubations, however, will be restricted to the deck for the remaining stations, and right now we have to request permission from the bridge to retrieve bottles from the incubators due to the rough seas. 3/1, St. 10 We left St. 9 early because the weather was so bad we couldn't work over the side. It was rough all night. They used night glasses on the bridge to look for ice. We came to the next hydro station (67.5S) just after breakfast. it was marginal for the CTD, but we got it in and out, and didn't try the TMR. The mixed layer was only 50 m. Beam attenuation was low and pCO2 high, yet silica was also still high (55 umol/kg). According to the SeaWiFS image this should be in an area of moderate (0.1-0.5 mg/m3) chlorophyll concentrations, but the image was a composite from 10-15 days ago. The icebergs at the last two stations had been moving NE, so we assumed that the water in the SeaWiFS image was moving ion the same direction and decided to steam SSE to look for the bloom. As we headed for 69S there were a couple of 20 km patches with higher particle concentrations and lower pCO2. Icebergs were becoming abundant and Sunday morning we passed 1 mile from one very tall berg we called the Cathedral because of the tall spire on one side. As night approached, visibility became very limited and the sudden appearance of several small pieces of ice led us to stop for the night and do what sampling we could with the intent of moving southeast at daylight. 3/2 Daylight came along with pea soup fog- low visibility. After waiting a while for it to burn off, we steamed on a course of 145 deg. The fog cleared and we moved faster. Fluorescence and beam attenuation started to increase and pCO2 dropped. Things really changed around noon and by 1500 fluorescence was twice as high as anything we had seen south of the front. pCO2 drooped to 270 uatm- by far the lowest of the cruise. Surely this was the bloom. However, our fourth rapid "bloom barometer" was Helen Quinby's fluorescence microscope evaluations of the plankton assemblage from the underway water samples. "This is not the bloom" she announced, and we moved on. Fluorescence started to decrease, and the fog had thickened, slowing us to 5 kts. It was an opportune time to start a long station, so measurements began at 70 deg., 24'S, 165deg, 55'W. There are plenty of Phaeocystis in the water, and some healthy diatoms, but no species dominate as one might expect in a bloom. Silica, nitrate and phosphate have dropped slightly, but are still high (silica is still at 55 umol/l). The area is clearly patchy as we sit here and the surface 50 m of water moves E or NE (based on the ADCP), but all values are more extreme than anything else seen south of the front. As we speculated earlier, it may be that when large areas of water suddenly were freed of ice, the bloom became much more patchy rather than "burning" steadily southward. Based on the nutrients, fluorescence, and plankton assemblages, the system seems more complicated than on earlier cruises. Fortunately, the weather has been excellent for 2 days (10-20 kt winds) and we hope to sneak south a few more miles to see what is on the other side of the peak before we return north. Lots of good measurements are being made and report some of those next time. Wilf Gardner Chief Scientist