Weekly Science Report 5: LMG01-04 Southern Ocean GLOBEC

(Jose Torres, Chief Scientist)

Science days 26 May to 29 May inclusive


I. LMG 01-04

a. Mission statement:

Overall goal is to elucidate shelf circulation processes and their effect on sea ice formation and Antarctic krill distribution, and to examine the factors that govern krill survivorship and availability to higher trophic levels, including seals, penguins, and whales.

b. Projects represented on the process cruise

    BG-232-0 Dan Costa and Jennifer Burns - seal ecology

    BG-234-0 Bill Fraser - seabird ecology
    BG-235-0 Chris Fritsen - SIMCO and water column phytoplankton communities
    BG-236-0 Kendra Daly - Krill ecology and physiology
    BG-245-0 Jose Torres - krill and fish ecology, krill physiology
    BG-248-0 Meng Zhou - krill ecology, behavior, and modeling
c. Cruise overview to date

    20 APR 01 LMG departed PA
    24 APR 01 LMG arrived at KGI to pick up field party (O-196 :Dr. Brenda Hall) and began transit to Livingston Island.
    25 APR 01 LMG arrived at Livingston Island. Lost a day to weather.
    26 APR 01 dropped off Dr. Hall's team began transit to Palmer Station
    27 APR 01 Arrive Palmer Station
    28 APR 01 Depart Palmer Station for study site
    29 APR 01 Began sampling at process station 1.
    5 MAY 01 Concluded sampling at process station 1, transited to process station 5 and initiated sampling.
    12 MAY 01 Concluded sampling at process station 5, transited to process station 4.
    13 MAY 01 Arrived process station 4 and initiated sampling
    17 MAY 01 Departed station 4
    18 MAY 01 Arrived process station 2 and initiated sampling
    20 MAY 01 Departed process station 2 due to extreme weather
    21 MAY 01 Arrive process station 3, Lazarev Bay.
    25 MAY 01 Depart process station 3
    26 MAY 01 Arrive in George VI Sound for Penguin survey in A.M.
    26 MAY 01 Depart George VI Sound - transit to Neny Fjord - MOC 1 in transit
    27 MAY 01 Arrive Neny Fjord A.M.
    27 MAY 01 Depart Neny Fjord P.M. - transit to S end of Adelaide for ADCP survey
    28 MAY 01 A.M. Arrive vic Day Island for seal survey
    28 MAY 01 P.M. Continue N through The Gullet and Tickle Channel into Hanusse Bay for ADCP survey of Hanusse Bay
    29 MAY 01 A.M. Seal survey , HTI drift station
    29 MAY 01 P.M. MOC 10, MOC 1
    30 MAY 01 01:30 End of science. Transit to Palmer Station
    31 MAY 01 08:00 Arrive Palmer Station
    31 MAY 01 13:30 Depart Palmer Station - transit to Livingston Island
    01 JUNE 01 08:00 Arrive Livingston Island for pick up of field party (O-196 Dr. Brenda Hall)
    01 JUNE 01 11:30 Depart LI - transit to Punta Arenas
    05 JUNE 01 08:00 Anticipated arrival in PA
d. Acknowledgements

A grateful scientific party would like to extend their sincere thanks to our friends on the Lawrence M. Gould for making our cruise a successful one. To Skip Owen, Christian McDonald, and Josh Spillane for help on deck, in the zodiacs, under the ocean, in the shop, with logistics and damn near everything else. To Sheldon Blackman and Bruce Felix for keeping our MOCNESS nets running, emails flowing, DAS system recording, and CTD's dunking. To Captain Warren Sanamo, chief mate Jesse Gans, 2nd mate Tracy Ruhl, and 3rd mate John Snyder for plain and fancy boat driving, even in unsurveyed areas, putting up with our schedule changes, and generally keeping us all safe. To Chief Engineer Mike Murphy, 1st engineer Paul Waters, 2nd engineer Russ Lesser, and our two oilers Noli Tamayo, and Donde Dasoy for keeping us afloat and moving, even when declutched on the starboard side. To Rudy Lucas, Romeo Agonias, and Luciano Albornoz for 45 days of great meals and great desserts. To Fernando Naraga and Roy Ninon for all their help on the winches, and Rafael Sabino and Dionito Sabinas for their general help on deck and keeping our boat spotless. We thank you one and all.

e. Synopsis of the last four science days and the creation of mini-stations 6 and 7

Our primary goal for the last 4d of the cruise was to locate concentrations of penguins and seals for diet analyses. To this end we departed Lazarev Bay 25 May and returned to George VI Sound. Observations during our occupation of station 4 suggested that very high numbers of Adelies were residing in the sound. We arrived 26 May at first light, intending to make our way to the Rhyolite Islands, but were stymied by newly formed ice, ca 6 inches in thickness, and a sound peppered with growlers, bergie bits, and icebergs. It became clear that the Rhyolites were unreachable in a reasonable amount of time. We surveyed the N margin of George VI Sound and decided to move on to Neny Fjord about midway up the eastern shore of Marguerite Bay. We did a MOC 1 on a trackline southwest of Neny Fjord to get a snapshot of krill abundance in its vicinity and arrived in the fjord proper at first light on the 27th.
Neny Fjord was free of new ice and sea surface temperatures were hovering in the -1.0o range. We did a zodiac- based penguin survey of the bay and attempted a blue water dive to survey the upper 1 m of the water column for evidence of krill furcilia in an ice-free environment. The dive was cut short by equipment problems but no krill were observed. Neny Fjord was dubbed process station 6.

At nightfall on the 27th the LMG transited to the S end of Adelaide Island for an ADCP survey during the hours of darkness and then moved up Laubeuf Fjord (station 5) to the vicinity of Day Island for a seal survey, arriving there at first light on the 28th. We found a very changed environment there, with much of the glacial rubble and small floes gone, presumably blown out by the prolonged high winds that plagued us all during the first three weeks of May. The fjord was ice- and seal-free so the LMG moved further north into Hanusse Bay, vic Laird Island, for the last science day. We completed an ADCP survey of the bay during darkness, surveyed for seals and penguins at first light on the 29th, completed an HTI drift station, and finished the science ops with a successful MOC 10 and MOC 1. Hanusse Bay was dubbed process station 7.

f. Individual Group Reports

1. BG 232-0 Burns/Costa

This week we headed north from Lazarev Bay with the hope of capturing a few additional crabeater seals to increase sample sizes and refine procedures before the cruise ended. However, weather and ice conditions were not optimal and we did not spot any seals in George VI Sound (lots of thin, new ice, May 26th) or in Neny Bay (no ice, May 27th). On May 28th we returned to Wyatt and Day Islands, where two of our tagged seals were still diving. However, the weather pattern had shifted to snow with high winds from the NE, and conditions were far from optimal for sighting or working on seals. We sailed up Lawrence Channel to the head of Wyatt Island and from there up Hinks Channel to the head of Day Island without sighting any ice or seals. At the head of each channel we mapped the coastline with the ships radar. This was to confirm that the glaciers had receded from their charted positions and that the many locations we were receiving from seals ""on land"" were really due to errors in the charts themselves. Following the mapping exercise, we continued north through the Gullett and into Crystal Bay. While technically outside the study area, one of our animals (PTT 23100) had moved on a direct track through Crystal Bay between the 24th and 26th, and we were interested in surveying the area. We did not see any seals until late in the afternoon, when several were sighted hauling out in the glacial rubble that was windpacked against the western coastline of the channel. This pattern of hauling out late in the afternoon fit with the behavior of our tagged animals and was a repeat of the pattern we saw in Lazarev Bay. May 30th we searched for seals in the fjords and bays in the southeastern corner of Crystal Bay, but again were unsuccessful at spotting any animals, despite the fact that we knew at least one seal had moved past this area just a few days before. The minimal amount of ice suitable for a seal to haul out upon likely contributed to our poor sighting success, for on May 31st during our transit to Palmer Station, we passed through extensive areas with good sea ice and second year pans, and saw many crabeater, leopard, and Weddell seals hauled out, suggesting that sighting success is dependent on both ice and weather conditions. As we leave the study area, all 8 of our tags are still transmitting. Two of the seals remain in the area around Day Island, one has continued to track north and is now about 200km south of Anvers Island, and the 5 that we tagged in Lazarev are using the open ocean habitat to the west of Lazarev Bay. While these 5 seals are all using slightly different areas at any given time, there are remarkable overlaps in their foraging locations, which suggests some persistent oceanographic features that may be concentrating prey in certain areas. We look forward to integrating the seal data with that obtained by the NBP during its survey of the area. This cruise has been successful, and we are looking forward to the next one in July. Then we hope to deploy another 8 tags and discover more about what drives seal behavior in the wintertime.

2. BG 234-0 Fraser
The GLOBEC seabird component aboard the LMG had a most successful last week, thus achieving most of its planned objectives for this cruise. Earlier gaps in our spatial coverage of Adélie Penguin diets were in part filled by Dr. Chris Ribic and her group aboard the NBP,  who were able to find birds in a few key locations not investigated by the LMG. Analyses of these diet samples suggest striking differences in the types of prey being taken by penguins in the Marguerite Bay region when compared, for example, with the diets of penguins north of this region. We have also obtained the first evidence that Adélie Penguin diets in the Marguerite Bay region may be sex-specific, suggesting that males and females engage in different foraging strategies during the autumn/early winter period. And finally, the PTT data are suggesting that Adélie Penguins are highly localized foragers in autumn, and tend to focus their search efforts around areas where circulation and bathymetry provide a retentive environment for prey. These findings have arisen in part through on-board collaborations with Dr. Meng Zhou and his group, who provided valuable ADCP data. This collaboration is expected to continue as the analyses of respective data are completed n the US. We conclude this brief report by thanking Captain Warren and his crew and the Raytheon staff aboard the LMG for their excellent support of our program.

3. BG 235-0 Stewart and Marschall (for Fritsen)
Substantial concentrations of newly-forming sea ice were encountered for the last time during LMG 01-04 at the southern end of King George VI Sound on 05/26. The ice field was contained primarily within a belt paralleling the coast/ice sheet and consisted of patches of newly-consolidated clear pack ice (without snow cover; gray in appearance) interspersed within patches of open water, mixed-age pancake ice, new grease ice, and small (<5 m) to large (>100 m) icebergs. New pack ice was sampled from the deck by using a net to collect chunks broken from the pack by the hull of the ship. The new pack ice was 12.5 cm in thickness. Pack ice samples were diluted with filtered seawater and melted in the dark prior to sub-sampling for chla concentration, bacterial biomass, dissolved organic carbon, nutrients, and dominant algal taxa. Chlorophyll concentrations in King George VI Sound and Lasarev Bay ice samples were variable (~0.1-1.0 mg l-1) but, in general, elevated relative to water column concentrations, reflecting the tendency for plankton cells to be "scavenged" by newly-formed ice crystals rising through the water column and coalescing at the surface. Vertical profiles of in vivo fluorescence, irradiance (PAR), salinity, and temperature were obtained from CTD casts conducted at or around local noon on 05/26 in King George VI Sound, on 05/27 en route to Neny Island, on 05/28 in Lawrence Channel (near process site 5), and on 05/29 in the northern part of Lallemand Fjord (north of process site 5). An assay designed to measure bacterial production over time within new ice and surface seawater from Lasarev Bay was terminated on 05/30. Production over an eight day time period was best fit by an exponential equation (R2 = 0.7323). Days 05/31 and 06/01 were devoted to waste disposal and lab cleaning.

4. BG 236-0 Daly

This past week we completed experiments on krill rate measurements from Process Station #3. We spent one day exploring Neny Fjord, as a potential location for new ice formation and predators. This region turned out to be much warmer than at the southern end of the Marguerite Bay, with air temperatures about 1.8°C and surface sea water at - 0.99°C. There was no sea ice and few seals or penguins. We ran three acoustic surveys, two with the Tucker Trawl and one with the 1m MOCNESS. The 38 kHz frequency indicated fish targets throughout the water column and the 120 kHz frequency detected a small near-surface layer at about 15 m and a relatively dense layer between 50 and 300 m. Net catches included Pleuragramma, larval and adult Euphausia superba, E. crystallorophias, many copepods (such as Paraeuchaeta) and siphonophores. By the time we reached the Avian Island later in the evening, the winds had increased preventing us from collecting acoustic data during the ADCP survey of that region.
On our last science day, we did a standard target sphere calibration in Lillemand Fjord and then collected acoustic data in Hanusse Bay during 10 m and 1 m MOCNESS tows. This region is upstream from Marguerite Bay and, therefore, may act as a source population for krill and fish. Relatively dense layers were detected near surface, in the upper 30-40 m, and between 100-200 m depth. Net catches included Electrona and a large number of larval and adult E.superba.
Several preliminary observations for this cruise are noteworthy, with the caveat that many samples have yet to be analyzed.
(1) Larval E. superba were exceptionally abundant throughout the study area and included individuals in many stages of development, from Calyptopis 3 to Furcilia 6. These observations suggest that the past summer was a strong year for krill reproduction, that reproduction extended over a relatively long period, and that circulation was favorable for advecting and/or retaining larvae on the shelf.
(2) There was a general absence of juvenile krill throughout Marguerite Bay and immediately to the north in Hanesse Bay. This indicates that there has been little recruitment to the juvenile year class for the past couple of years. The krill population in this region could be at a critical juncture and dependent on successful reproduction of adults, as well as the overwintering survival of larvae and recruitment to the juvenile year class in spring during the next two years. Southern Ocean GLOBEC is uniquely situated to investigate the processes that influence krill population dynamics during this key period.
(3) Large adult krill were very abundant in the coastal fjords and embayments in Marguerite Bay. Few adults were collected in nets in the open waters of Marguerite Bay. All adults had regressed to an immature stage. Penguins and seals were relatively abundant in the coastal areas, co-occurring with adult krill, except in those fjords (e.g., Bourgeoise and Neny Fjords) with low currents where siphonophores were abundant. Larvae appeared to be less abundant in these fjords, possibly owing to predation by siphonophores.(4) Larval krill molted about every 18-20 days, whereas adults molted about every 30-37 days. Growth rates were measurable, but require further analyses. Gut fluorescence, a relative measure of feeding on phytoplankton or ice algae, and the production of fecal pellets indicated that both larvae and adults were feeding during the study period. The much smaller larvae, however, had gut fluorescence levels similar to that in adults. Gut fluorescence in larvae collected by divers under sea ice was about two-fold higher at one site and similar at another site, relative to that found in larvae collected from the water column in net tows. These combined observations suggest that larval krill were actively feeding and growing during autumn in Marguerite Bay in preparation for winter.
5. BG 245-0 Torres
Three Tucker trawls (live tows) were completed during our last 4 d, two in the vicinity of Neny Fjord and one in Hanusse Bay. In addition, we had one successful MOC 10 within Hanusse Bay. Catches were quite different in the two regions. In Neny Fjord, we observed a fairly typical shelf fauna including Pleuragramma larvae and adults, E. superba larvae and adults, E. crystallorophias, the bathydraconid Psilodraco, many Pareuchaeta and Calanoides acutus, and a surfeit of siphonophore bracts. In Hanusse Bay, the krill populations were very much higher. Our very rough MOC 10 break down was as follows:
    0-50 m: a few E. superba adults and larvae were present, as were the amphipods Themisto and Eusirus
    50-100: nine liters of E. superba adults, Eusirus
    100-200: four liters of E. superba adults, Eusirus
    200-300:a few E. superba adults, 2 specimens of Paraliparus terraenovae, Thysanoessa macrura, many Eusirus of different sizes
    300-400: a few E. superba adults, Pareuchaeta in abundance, many Eusirus of different sizes.
Note also that our 0 net oblique haul captured 2 specimens of the lanternfish, Electrona antarctica.
Our krill catches in Hanusse Bay were about equal to those in Laubeuf fjord, the highest of the cruise. We made 100 individual determinations of metabolism and excretion in krill and other species in the last four days of science.
6. BG 248-0 Zhou
Bill raised a question to Jose, Kendra and me one day: taking the record of 30,000 pairs of Adelaide penguins on Avian Island, how much food do they need in a day? We found there were a lot adult krill in Laubeuf Fjord from our intensive mesoscale surveys and process studies in the 2nd week (See our 2nd report). Though we found a fair amount of adult krill in George VI and Lazarev Bay, the catches cannot be compared to those in Laubeuf Fjord. Questions we raised: Is there another place like Laubeuf Fjord, and where are the sources of those adult krill? We examined the records of penguin sites, circulation patterns we just learnt, and topographic features. The plan was: 1) to conduct an exploratory survey of krill, penguins and seals in the vicinity of Neny Fjord, 2) to conduct an ADCP survey in the vicinity of Avian Island for krill population and circulation patterns for a better understanding of krill spatial distribution and circulation pattern utilizing the night time in the transit from Neny Fjord, and 3) to explore Hanusse Bay north of Laubeuf Fjord for the potential physical and biological linkage between these two if there was time available after the seal searching operation. The vicinity of Neny Fjord (68 37.2°S, 67 38.0°W) We have learnt in our first two weeks that adult E. superba were concentrated approximately between 50 and 120 m and larvae at the surface. It was quite easy to identify the layer of adult E. superba on the ADCP. The difficulties are they usually stay near the sides of deep canyons with unpredictable shallows, and their horizontal scale is relative small varying between 100s m and 2-4 km except the largest patch in the deep canyon at Laubeuf Fjord. A typical MOCNESS tow lasts 1.5-2 hours and approximately 3-4 nm. It is hard to predict that the nets would be in the adult krill swarm. We frequently missed this E. superba layer. One MOC1 tow and one CTD were conducted utilizing the available time during the night transit between George VI Sound and Neny Fjord, and the period during zodiac operation for seal and penguin searching. The net tow samples show: a large amount of copepods, salps, fish larvae, and anpheapots, some krill larvae and several krill adults between 300 and 150 m, a large amount of krill larvae between 150 and 25 m, and few krill larvae between 25-0 m. We missed the adults. A CTD cast was conducted at the entrance of Neny Fjord, which is relatively shallow approximately 300m. Because the water depth is shallower than the depth of intruding deep water, the vertical temperature and salinity structure represents local and regional effects. Comparing with those at the similar depth, the water in the upper 300 m is relatively saltier, warm and heavier than the water near the entrance of George VI Sound. Though the water is saltier in Neny Fjord than that of Laubeuf Fjord, the temperature is similar, approximately -1°C. The ADCP measurements on May 26 and 27, 2001 do not show the clockwise circulation in the east part of Marguerite Bay. Along the tracks from George VI to Neny and from Neny to Laubeuf, there are several mesoscale eddies in a spatial scale of 20-30 km. Vicinity of Avian Island The objective of this ADCP survey is to further investigate the prey and predator relation. Data from tagged penguins show that penguins had been feeding in the vicinity of Avian Island. To have a better complete survey of adult krill fields may bring us some insight into the penguin behavior. In the second week of our cruise, we had very detailed ADCP-MOCNESS survey covering Laubeuf Fjord, Lawrence Channel, Bourgeois Fjord, and the opening area below Pourquoi Pas Island. We missed the vicinity of Avian Island because of the time limit and the complicated topography consisting of many shallows. The survey started from the west slope of the deep canyon at the entrance of Laubeuf Fjord in order to understand the entering flow pattern along the Adelaide Island and the adult krill distribution. We found a lot adult krill on the slope. We passed the Elliott Passage into the deep basin south of C. Alexandra. We again found a lot of adult krill. We crossed a shallow ridge, and surveyed the deep basin from the Avian Isalnd along the Woodfield Channel. To our surprise, there is no adult krill aggregation in the Woodfield Channel. Finally, we took a straight run from woodfield Channel, through Laubeuf Fjord to Lawrence Channel. The measurements show again a large amount of adult krill. The coastal current turns into Marguerite May around the south tip of Adelaide Island. It joins the southward at the deep canyon. A branch turns to the south along the western slope of the deep basin south of C. Alexandra, and flows around the Consul Reef forming a clockwise circulation. The shallow is too shallow for adult krill. But it can induce a topographically induced eddy which may provides the retention mechanism at nearby deep basins in Laubeuf Bjord. An acoustic survey in such an area consisting of many shallows and reefs is doable after a careful planning and a good communication with the bridge which is to work out a plan with the captain together. Of course a forward looking sonar will be very valuable to the safety and time-efficiency. Hanusse Bay It is not to our surprise that Hanusse Bay is a very productive area. We had the biggest adult krill catches in the entire cruise. The most abundant area is south of Liard Island. Similar to Laubeuf Bay, adult krill concentrated between 50 and 120m behind seamounts and deep canynon. The ADCP measurements shows a anticlockwise circulation. The water is saltier here comparing to other side of Barlas Channel at the upper 100 m so. If there is a density driven current cross the narrow between Laubeuf and Hanusse, the top layer should have a southward mean flow which is in favor for krill advected into Laubeuf Fjord. We should have shot CTD and XBT when we crossed the narrow channel.