Date: Wed, 3 Feb 1999 13:23:01 GMT To: ALSUTHER@nsf.gov, KERB@nsf.gov, mo-sciweekly@asa.org From: rossro@lmg.polar.org (Robin Ross) Subject: LMGould: SciWeekly 25-31 Jan 99 Cc: sanamowa@lmg.polar.org, asalmg@lmg.polar.org, shawca@lmg.polar.org, patterka@lmg.polar.org, duleype@lmg.polar.org, kozlowwe@lmg.polar.org, tupaslo@lmg.polar.org, langdon@icess.ucsb.edu, karen@icess.ucsb.edu, ray@icess.ucsb.edu, charleen@icess.ucsb.edu, dkarl@soest.hawaii.edu, mvernet@ucsd.edu, fraserbi@palmer.usap.nsf.gov, dgm@ldeo.columbia.edu Dear Colleagues, In the early morning hours of 25 Jan, we finished the segments of alongtrack data collection on the 600.* line missed a few days earlier, then steamed south. The bottom moored sediment trap, successfully retrieved from near Hugo I. on 20 Jan, was reconfigured and redeployed 25 Jan in fog. The array includes an ice sonar that senses both the presence and thickness of sea ice. This is the eighth deployment at the Hugo site. A new bottommoored sedment trap had been deployed on 23 Jan near Palmer Station. During the week of Jan 25 - 31, we occupied 13 stations, completing the 400.* line (north of Matha Strait and Adelaide I), and several of the inner shelf stations of the 200.* line, just south of Adelaide I. We also completed the alongtrack data collection between stations for the 400.*line. At this juncture in the cruise we have completed 4 of the 5 standard lines, and 4 on/offshore transects with alongtrack data collection for our study of the determinants of spatial variance. We broke off from sampling on the 200.* line to collect diet samples from Adelie penguins nesting on Avian Island at the southern tip of Adelaide I., and to make our scheduled visit to Rothera to further the ongoing interaction between the Palmer LTER and the British Antarctic Survey at Rothera. Both groups have established long-term sampling in the nearshore area (spring and summer for the LTER at Palmer Station and year-round at Rothera). The comparison of seasonal dynamics in the two areas separated by 400 km will be enlightening. We docked in mid-afternoon of 30 Jan. The Bonner Lab was open for tours before dinner and the LM Gould was open for tours after dinner. Live music and dancing followed, with a wonderful time had by all. On 31 Jan, 16 BAS personnel joined us for a day at sea, and 6 from the LM Gould stayed at Rothera. We accomplished 3 major objectives that day. 1) The diet sampling of Adelie penguins on Avian I. was successful, with 19 samples obtained. 2) We ferried the BAS gps team to Avian I. and they successfully completed their work. They were pleased, as for several years in a row they have been unable to get transport to Avian I. 3) We did a full water column station, with PRR/PUV, a CTD cast to 200 m with the HydroScat and the Chelsea CTD package used by BAS for the year-round sampling tied onto the frame, and a deep CTD cast. The vertical profiles of the Chelsea and SeaBird sensors will be compared for cross-calibration of the two sampling regimes. Two post-doctoral scientists at Rothera and working on biogenic N and S gases were pleased to sample from the deep cast, as their own CTD and bottle work is done by hand and limited to 100 metres maximum depth. We retrieved our own personnel and said goodbye to our British friends around 2130, and set off to find an area of sea ice to sample. Those few days were among a handful of bright sunny days during this entire cruise, and the overcast skies returned at the end of the day 31 Jan. Preliminary results from the primary production experiments on the 600.* line are emerging. Production was similar to that on the 300.* line, 0.39 gC/m2, with a high of 0.88 gC/m2. Production on the foraging grid, in the Lemaire and at the nearshore stations B and E was also low. On the 600.* line the diatom Corethron still dominated the net phytoplankton community. Krill were not actively spawning on the 600.* line, unlike krill found on the 300.*, 400.* and 500.* lines. The low 'greenness' ranking of the digestive glands of the krill matched the low chl a standing stock and low primary production on the shelf. A comparison of the oxygen profiles from discrete measurements and the CTD profiles in the upper 100 meters show that oxygen appears to be mixed deeper than either temperature or salinity, suggesting that the oxygen distribution is partly a function of biological activity. The deep station near Avian Island proved interesting. For most of the cruise, the depth of the 1% light level has been approximately 50 m or greater. The depth of the 1% light level at this deep station was approximately 10 m. Also near surface fluorometer readings from the CTD package were several times higher than we have seen previously, indicating much higher phytoplankton biomass. The spectral absorption of visible and ultraviolet radiation by colored dissolved organic matter proved especially interesting in this region. A distinct absorption peak was observed in the 300-350 nm range. Historically, samples exhibiting such peaks have often been discarded as contaminated samples. However, we have observed similar absorption peaks on a regular basis at another field site off California and have reason to believe that these types of absorption peaks may be related to a specific class of phytoplankton. Unfortunately last week we had two shutdowns of the uncontaminated seawater system, the third and fourth shutdowns of the cruise. When the seawater lines break, and the system has to be repaired we have no uncontaminated seawater for up to 7 hours, depending on how long it takes for the glue to dry. The ship's crew responds quickly to these emergencies, and repairs the breaks as fast as is humanly possible. They are doing a wonderful job with the system as it is. However these extensive shutdowns are not acceptable during cruises where incubations of primary production, microbial production, krill growth and spawning and alongtrack data collection are all dependent on the supply of uncontaminated seawater. We heartily endorse the recent decision to replace all the pvc pipe with the recommended green strand during the next maintenance period. The CTD package had another down period. Most of the problem was quickly remedied by ASA personnel on board. However, the Chelsea fluorometer took much longer to repair, and was out of commission for two days. The extra effort taken by ASA, in particular C. Weddle, the ET, to talk to technical representatives at Chelsea is greatly appreciated. >From below the Antarctic Circle, R. Ross (BP028), P. Duley (BP013), W. Kozlowski (BP016), K. Patterson (BP032), and L. Tupas (BP046)