Date: Wed, 25 Feb 1998 10:08:34 -0600

Greetings from the R/V Roger Revelle! We found a carrier albatross to bring you our report since e-mail is not operating for this cruise. Its name was fax. After 11 days of Process Cruise 2 we are leaving Station 6, having completed 3 two-day stations and 3 Hydro stations. We are presently steaming toward Mooring #4 at 63deg.S having crossed the 60-61deg.S region where the front has been during past cruises and where we deployed two optics buoys for Mark Abbott. Surface temperatures have been slightly warmer than during previous cruises, but the front showed no distinctive surface temperature signature during Survey 2 and the same has been true for our crossing. Salinity drops south of the front as melt water increases. We made hydro stations "at" the front and south of the front despite 30+-kt winds with gusts to 40 kts. From Mooring 4 we will proceed south to Mooring 5 and on to find the bloom "burning" toward the end of the earth as described last month by Ken Coale. Based on the southward spread during the last three cruises the bloom should be between 67 and 68deg.S when we arrive. This assumes a uniform southward progression of melting ice and the ensuing bloom. As we left Lyttleton, however, the report was that ice-free waters extended to 74deg.S, which is in the Ross Sea. If the ice cleared rapidly from a large region and exposed the ocean surface to the patchiness of wind, waves, sun and eddies, the steady southward march of the bloom could break down into the sort of patchiness seen in the North Atlantic spring bloom as eddies spun up and various areas stratified with a mixed layer shallower than the critical depth for sustaining phytoplankton blooms. We are not equipped to determine such patchiness without extensive steaming, so we ask that we receive a written description of any SeaWiFS images that might become available south of 65 in the next two weeks. We have seen the sun only briefly since we arrived on the first station, so we aren't holding our breath for clear images. Fog and clouds abound, with occasional rain. Without further information, we will steam south until we find evidence of the bloom and then a little further south to see if "pre-bloom" surface waters are at all uniform based on underway data. We'll do a long station in "pre-bloom" waters and then in "bloom" waters and make our way back north. Past cruises show that in addition to the strong silica and fluorescence signals in post-bloom/bloom waters, the underway pCO2 measurements being made by Stephany Rubin and Heather Anderson on P2 should show a strong drawdown as a result of the bloom. We have many veterans of previous AESOPS or other JGOFS cruises, so everyone seems to know what to do. We have frequently had winds above 30 kts, but have lost only 10 hours of wire time to weather. Even then, experiments were incubating, so the time was not wasted. The Revelle rides so remarkably well that inside the lab you wouldn't think there should be any problem deploying equipment over the side. On deck, however, you quickly see that large swells change the water level next to the ship by 15-20 feet in a matter of seconds, which can be disastrous for equipment. Res. Techs Tammy Koonce and Scott Hiller have been extremely professional in orchestrating deployment and recovery of gear in any weather the operator was willing to try. Captain Desjardins and his mates keep the ship right on station with their impressive dynamic positioning system and make it seem much calmer than the view out the porthole should warrant. The biggest weather casualty has been the in situ primary productivity measurements, which have yet to yield results. The array parted at the top shackle sometime during the first deployment and we chased the buoy bobbing rapidly southward in the strong wind for a day. Some backup equipment was located and parts fabricated, but the three subsequent attempts at deployment have been scrubbed due to dropping barometric pressures and increasing winds at deployment time. Meanwhile, the fantail is filled with incubators cooking away at 2.5deg.C, very close to present surface water temperatures. Plankton concentrations dropped in half between stations at Moorings 1 and 2. At Mooring 2 there were two species of rhizoselinia, one which made chains 0.5 cm in length based on water samples. These large chains are probably responsible for the spikiness of the fluorometer and transmissometer signals in the euphotic zone near Mooring 2. Phaeocystis was also present in single colony form. The TAMU/OSU Particle and Optics Profiling System (POPS) has a working camera run by Sarah Searson for this cruise and showed chains 2-3 cm long in the euphotic zone at Mooring 2, but the chains rapidly disappeared below that depth, though large particles (> 0.5 mm) were still abundant even at 400 m. The LISST instrument on POPS is showing large differences in the size distribution of particles between 1-250 microns at different stations. Unfortunately the Optics part of POPS (2 ac9's and an ac3), which worked so well during Process 1, is refusing to send signals over the wire despite constant efforts by Jan Gundersen, aided by Scott Hiller. We hope a shortened wire will solve the problem. Similar problems have plagued the Optics package of Rick Reynolds and John Wieland, but they are getting some ac9 data via a hand-held cable attached to their package. Plenty of water samples for particle size distribution and fluorescence measurements round out their work. Heidi Sosik is obtaining numerous casts and underway measurements with a Fast Repetition Rate Fluorometer to measure photosynthetic rates of individual cells. She and Rob Olson are also making single cell measurements with their PDP flow cytometer. Mary-Lynn Dickson and Joe Orchado have completed net community oxygen production and respiration rate measurements at stations 1 and 2 (Moorings 1 and 2) and found them to be roughly equivalent. At station 1 net community production and respiration rates integrated to the 1% light level were 78 and -85 mmol O2m2d-1, respectively. Net production and respiration rates at station 2 were approximately half of those measured at station 1; 45 and -50 mmol O2m2d-1. Converting their oxygen-based measurements to carbon they estimate a gross carbon and net carbon production rate at station 1 to be 133 and 56 mmolC m-2d-1, respectively, compared to 70 and 32 mmolC m-2d-1 at station 2. Comparison of these data with integrated 14C measurements provided by John Marra, Mike Hiscock and Ann-Marie White indicates that 14C production (112 mmolC m-2d-1 with chlorophyll averaging about 0.6 mg m-3 in a mixed layer (and euphotic zone) of 85 m) was 10-20% less than gross O2 production, where they are supposed to be according to theory. At the second station chlorophyll declined by about half and so did the productivity. The high degree of temporal and spatial variability in production and respiration rates is apparent when the data are compared for the two Process cruises. Net production and respiration rates at station 1 during P1 were 330 and -66 mmol O2m2d-1 in early December but only 40 and -69 mmol O2m2d-1 at the same site at the end of December. At station 2 during P1 net production was negative or net heterotrophic (-20 mmol O2m2d-1) and coincided with high respiration rates (-99 mmol O2m2d-1). Marra notes that it is interesting that stations 1 and 2 have so much mixing and high nutrients, yet have the same euphotic zone depths as the North Pacific Central Gyre. However, the productivity is much higher here than in the NPCG. Dave Nelson and Julie Arrington have been collecting and incubating numerous samples to measure uptake rates of 32Si, but won't have results for a while. The same is true of the nitrogen measurements of Bonnie Mace and Lois Breger. Sarah Searson is collecting DOC samples for later analysis in Bermuda. Helen Quinby and Dawn Castle have taken numerous water samples to measure bacteria, DNA and to conduct bacterial experiments. Epifluorescent microscopy measurement by Landry's group revealed a diverse community of microzooplankton at Mooring 1. Unlike P1, few large diatoms were found at this station. The dilution experiments of Karen Selph and Hector Nolla yielded phytoplankton specific growth rates of 0.2 - 0.3 d-1 and specific mortality rates of 0.1 - 0.2 d-1 at Mooring 1. These rates were roughly 50% lower than found on P1. Results at Mooring 2 were similar for both cruises with specific growth rates of 0.3 - 0.4 d-1, and mortality rates roughly 50% of the growth rates. Juanita Urban-Rich and Jay Peterson continue their relentless net towing and grazing experiments. (Will there be anything left for higher trophic levels to eat when they are through?) Mesozooplankton grazing by individual copepods (determined by fecal pellet production rates) at the first two long stations during P2 has decreased by approximately 50% from that measured in P1. The mesozooplankton community now appears to be dominated by young copedites compared to the adults that were common in P1. John Andrews and Glenn Crossin keep the Thorium pumps whirring to measure export from surface waters and they always finish their wire work in less than the allotted time. The hydro team of Bob Williams, Dennis Guffy, Kathy Krogslund, and Rob Masserini are keeping up with the onslaught of water from two rosettes and underway sampling. The data look excellent. Eric Quiroz and Mark Cook keep the CTD data streaming in and Marc Silver keeps all the computers and ADCP running, logging data and spitting out plots. Section data made during P1 by Ian Walsh and during S2 with the SeaSoar have helped in our station planning. Further underway sampling is conducted by Chris Measures and Paolo Rossini and their Wee Fish, streaming along side of the ship. Iron values seem to be slightly lower than during S2, but need further refining. There is always lots of rosette water to sample as well. We have the luxury of having all four winches working well so far. There are six different instrument packages for the four wires, so two winches service two packages each, and all four share the same block at the aft end of the boom. One has to be careful when switching out operations to be sure your tag lines are over or under the proper wires flaked out on the deck. Mustang suits are becoming the attire of the day as we move south. The ship's crew has been helpful, supportive and pleasant in everyway. Everyone hates to miss a meal because of the excellent food, but that means there is a whole lot of exercising going on so we don't personally carry home more than we came with. Hey, the sun just popped out the clouds have disappeared! Send SeaWiFS now! Wilf Gardner Chief Scientist