Weekly Science Report 4: LMG01-04 Southern Ocean GLOBEC

(Jose Torres, Chief Scientist)

Science days 18 May to 25 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
d. Synopsis of process stations 2 and 3.
Process station 2 was located in the mouth of Marguerite Bay along the axis of the main cross-shelf canyon that runs roughly from the shelf break to the southern end of George VI Sound. Station 2 was a large box bounded roughly in the northwest by 67o 40' S, 72o W , in the northeast by 67o 40' S, 69o 30' W, in the southwest by the northern tip of Alexander Island vic 68o 40' S 71o 30' W and in the southeast by 69oS 69oW. It was sited to cover the mid canyon region and because of its location was amenable only to open water water sampling. We completed 2 CTD's, 2 Tucker trawls for live specimens, 5 MOC 10 tows, and 3 MOC 1 tows. All tows were accompanied by 120/38 kHz acoustic sampling when weather permitted. In addition to the net sampling a partial ADCP survey was also completed before sampling was curtailed by severe weather. The science party elected to move south to Lazarev Bay during the time that would have otherwise been lost to weather.
We arrived in Lazarev Bay during first light 21 May. It was decided by the science party that the bay would replace the original process site 3 that was sited southwest of the bay in a mid-shelf location. It was in Lazarev that we encountered the first new ice of the cruise. Moreover, the character of the ice in the bay included some older, larger floes that were reasonable platforms for predator handling. Our sampling strategy in the bay focused on daylight operations, making every effort to capitalize on the very limited daylight available. It consisted of visual predator surveys from the bridge for targeting seals and penguins. Zodiac operations followed on for seal and penguin handling. Our predator teams were very successful in the bay; all remaining satellite tags were deployed.
We inspected the underside of the new ice in the bay with the first dives of the cruise and found krill furcilia already in residence under the mix of new pancake and glacial rubble. Individuals were collected for physiological work and a rough visual census was taken. Ice specimens were collected by our SIMCO team for evaluation of microbial production and biomass.
Night operations consisted of ADCP surveys for mapping the circulation and plankton biomass in the bay, live tows with the Tucker trawl to supply specimens for our ongoing physiological experiments, and one MOC 1 for quantitative assessment of the krill populations within the bay. Our sojourn in Lazarev was highly productive. It filled a primary goal of the cruise which was to examine the biological and physical characteristics of a newly forming ice regime.
e. Individual group reports
1. BG 232-0 Burns/Costa
This week has been one of remarkable, if somewhat unexpected success. At the start of the week we had yet to deploy 5 of our 8 PTTs, and were becoming concerned over the success (or lack thereof) of our project. Some of the anxiety was relieved at the science meeting on May 19th, where we all agreed to set aside several days at the end of the cruise for dedicated predator work. However, the best luck of this cruise came from our diversion to Lazarev Bay on May 20th, when we left the mouth of George VI Sound due to bad weather. Lazarev Bay was selected due to its protected location, proximity to the Wilkins Ice Shelf, and the potential for penguins, seals, and sea ice. For once everything worked as planned, and we arrived in Lazarev Bay on the 21st to find new forming sea ice, many large remnants of second year sea ice, and many ice bergs and fragments. One of the more interesting discoveries during the transit and once we began to work in the Bay was that the charts and maps of this area are remarkably poor. Rothschild Island is actually 11 miles to the south of its charted position, and we have found and named (at least for the duration of this cruise) two new small islands. This will make interpretation of the seal movement data a little complicated, as we have no faith that the charts are correct. Resolving some of the charting issues is critical because over the course of this past week, we were able to deploy our remaining 5 PTTs on 3 adult female and 2 adult male seals. All the seals we handled were captured on remnant second year sea ice, and floe size ranged from approximately 50m2 to 100m2. The floes were not covered with snow, but rather with consolidated bergie bits, and so were slick and difficult to maneuver on. In any given area, we found that the seals seemed to prefer the largest floes, but to select only remnant sea ice, and not any of the abundant small ice bergs. During the evening transit on May 21st from Bill's Island to the eastern side of the Bay towards Umber Island we noticed several crabeater seals hauled out on large floes late at night. This was encouraging, and we were hopeful that we could deploy tags in the bay.Indeed, on May 22nd, we deployed satellite tags on two seals. In the morning, we captured and tagged a large adult male on a rugged piece of very slick ice. There was a bit of wind, and the ice was moving around in the bay, so that by the time we had finished, we could not find any other seals in the area. However, we continued to observe from the bridge of the LMG, and at around 3pm, just as it was getting dark we started to see more seals hauling out. Since time was getting short (only 2 weeks left in the cruise) we decided to see what it was like to work in the dark,, and left the LMG to attempt a capture of an adult female in the twilight. The female seal we handled was deeply asleep during our approach to the floe and remained asleep through all the procedures. The waning twilight was sufficient to administer the initial drug dose, and the bridge lights from the LMG provided much of the illumination we needed to work at night. With an extremely successful evening deployment, we felt confident that if the weather held we could work at night. In fact, we repeated this pattern of searching for seals in the morning and late afternoon on the next two days. On May 23rd we deployed two PTTs on animals in the late afternoon and evening, after failing to capture animals in the morning. On May 24th, we deployed our last tag on an adult female that was captured in the dark, after failing to sight any seals during daylight hours. Night work has proven less difficult than expected. With excellent help from Skip Owens and the bridge, and optimal weather conditions, we have had good success with this technique. Over the course of our time in Lazarev bay we confirmed that the seals were showing a remarkable diel pattern of activity. We have seen very few seals hauled out in the daylight hours, but have seen many animals active in the water in the late afternoon, and animals seem to haul out just as the light fails after 15:30. This pattern of hauling out at around 4pm until just after midnight that we are seeing is similar to that being recorded by the tags deployed on instrumented animals. We are not sure why the animals are hauling out in the late afternoon, but the pattern seems widespread. As a result, we believe that the ability to work in the dark has been crucial to our success this cruise. All 8 tags are on animals and transmitting. Of the three animals that were tagged during week three, two are still in the area around Day and Hansen Islands, and the third has moved north past Liard Island, and is now more than 300km from where it was initially tagged. As yet, we have only recovered a small amount of data from the seals tagged in Lazarev Bay, but the data that we do have shows a high degree of individual variation. Two animals moved deeper into the Bay before one moved out to the North and the other moved northewest along the eastern coast of Rothschild Island before heading south along the outer (west) coast. A third animal moved directly out of the bay to the north, while the fourth moved west into the open ocean. We do not have sufficient data from the fifth animal yet to determine its movements. All have shown extensive movements in the few days since tagging (50km or more). At this point it is clear that crabeater seals do not move passively with the drifting sea ice, but instead are capable of long distance directed movements. What drives these movements, and how the animals are selecting foraging locations is the overall goal of our research project. In the few remaining days of the cruise we hope to handle a few more animals to trouble shoot procedures for the winter cruise and to bolster our sample size. The colder nights in Lazarev Bay highlighted some of the difficulties we will face in July, and the better experienced we are now, the more successful that cruise will be.
2. BG 234-0 Fraser
The GLOBEC seabird component spent much of the week searching for Adélie Penguins at our most southern station in Lazarev Bay. Our objectives were to obtain diet samples and deploy our last five remaining PTTs. Although we were unable to locate penguins in conditions suitable for diet sampling work to proceed in the field, we succeeded in our efforts to deploy the PTTs. As a result, we now have a tagged population of penguins at both the northern and southern ends of the GLOBEC grid, and a nice experiment in progress to examine aspects of the foraging ecology of this species in relation to sea ice development and bathymetry as winter conditions advance in this region.

3. BG 235-0 Stewart and Marschall (for Fritsen)

The efforts of BG-235 during week #4 have been divided between water column and new sea ice sampling for the first time during the cruise. Water column samples were taken concurrent with CTD/Rosette deployment at or around local noon from depths of 0, 5, 10, 15, 20, 30, 50, and 100 m on 05/19 at process site #2 and on 05/21 and 05/23 in Lasarev Bay. A CTD cast scheduled for 05/20 at PS #2 was cancelled due to rough seas. Sub-samples were preserved for later determination of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), particulate organic carbon (POC), bacterial and viral abundance, and spectral-absorption by phytoplankton, filtered for on-ship determination of chlorophyll a (chla) concentration, and assayed for estimates of bacterial production and photosynthesis-irradiance relationships (PE curves, at 5 and 30m only). Sea ice was not observed at PS #2 but was present in varying stages of early formation on all sampling days in Lasarev Bay. The newly-developed ice field consisted primarily of unconsolidated grease or brash ice interspersed with small (< 50 cm dia.) to large (>5 m dia.) pancakes. Sea ice coverage (by all ice types) over the water surface ranged from ~5% in wind swept areas (i.e. near "Bill's Island" on 05/25) to ~90% in fields of densely-packed pancakes (e.g. evening, 05/24). Cohesive pack ice was not yet present in any region sampled in Lasarev Bay. Samples of newly-formed ice were collected on 05/21-05/23 and 05/25 in concert with zodiak-supported seal and penguin surveys. Ice types collected ranged from grease ice and unconsolidated pancake ice (05/22 and 05/25) to brash ice chunks and consolidated pancakes (pancake holds form when handled; 05/21-23). A single sample of ice algae was scraped from the under surface of a floe by J. Torres on 05/23 during diving operations beneath ice where krill were observed to be feeding. Sea ice samples were melted in the dark and processed according to protocol for measurement of the same parameters measured for water column samples. Early observations indicate that microbial biomass is elevated in newly-formed ice of all stages (grease to consolidated pancake ice) relative to the water column while production rates (primary and bacterial) of organisms aggregated in newly-formed ice are approximately equivalent to or slightly diminished from (i.e., bacterial production) rates determined for planktonic microorganisms.
4. BG 236-0 Daly
We completed investigations at Process Stations 2 and 3. Station 2 was located over a deep canyon in Marquerite Bay. Acoustic surveys were made with two 10 m MOCNESS tows. The highest concentrations were detected near surface, consistent with the relatively abundant larval Euphausia superba collected in surface layer nets. Growth, molting, ingestion, and egestion rates were measured for late stage furciliae (Furcilia 4-6). Growth and molting rates also were determined for early stage larvae (Calyptopis 3 to Furcilia 4).
Station 3 located in Lazarev Bay provided access to early forming sea ice. Our first net tow for live animals collected large numbers of larvae and some adult E. superba, E. crystallorophias, and many Pleuragamma larvae. Few adult krill were collected in subsequent tows, possibly because towing was restricted to certain regions of the bay due to the large numbers of ice bergs. Growth, molting, ingestion, and egestion rates were measured for late stage furcilia. Clouds of furciliae were observed near the undersurface of sea ice by divers. A planned under ice experiment was aborted with the radio call that a leopard seal was seen heading our way. Furciliae collected by divers were measured for gut fluorescence. In addition, egestion rates and assimilation efficiency were determined for these larvae. No acoustic surveys could be conducted in this bay due to the ice conditions.
5. BG 245-0 Torres
Process site 2. Five MOC 10 tows were completed at two different locations in the mid-canyon region of site 2. Both sites exhibited high fish biomass relative to tows executed in other regions of the Marguerite Bay study area. The faunal composition at site 2 was decidedly oceanic, with strong representation by the lanternfishes Electrona, Gymnoscopelus, and Protomyctophum and the bathlagid, Bathylagus. Krill were in low abundance in all five tows. No Pleuragramma were collected at process site 2.
Process site 3. Lazarev Bay saw a change in our sampling scheme as we switched from net tows to diving as our major sampling tool. We completed 3 dives in the five days on site and observed krill under the new ice in all three dives. Our highest numbers were in a glacial rubble/ new ice mix at the eastern edge of the bay. The eastern side of the bay has a narrow, but very deep canyon that runs along part of its eastern margin and our most productive dive was located very close to it. Our Tucker tows for live specimens revealed a robust krill population in the bay with both adults and furcilia well represented. The high ice concentrations in the bay precluded MOC 10 tows. About 125 individual determinations of respiration and excretion were made on krill at site 3.
BG 248-0 Zhou
Station 2: The entrance into Marguerite Bay
1. Bottom topography
The bottom topography was surveyed during the whole study period. Our soundings match etopo3 map well in most of area except near the coast of Alexander Island. There are several unmarked shallows and deep canyons near the northern tip of the island.
2. Temperature and salinity fields
A CTD transect of 9 stations were made crossing the exit current region approximately from 6830S/70 00W to the northern tip of Alexander Island. Measurements indicate the water near the island is significantly less salty that produces a horizontal density gradient and a baroclinic component in the exit current.
A 20x20 nm CTD and ADCP survey grid was designed covering mooring stations B1, B2 and B3 after we established the site of Station 2 at the middle of the entrance into Marguerite Bay. One of the purposes is to compare shipboard and mooring physical data for a better understanding spatial and temporal variability. The survey started when a northward wind increased to 30 knots. CTD stations were eliminated and replaced by xctd launching from 02 deck. After 4 successful launches, wind increased to 40 knots. The survey was called off.
3. Circulation
ADCP measurements consistently show an exit current along the shelf of Alexander Island. The current measurements on the east side of the deep canyon show a southward intruding current.
We finished 4 ADCP transects at Station 4 crossing mooring B1 once and B2 twice. Though CTD stations were nearly abandoned, ADCP measurements were reasonably good from the percentage good index. The ADCP measurements show a southwestward current even at 30m while wind was northward. The survey was longer than 13 hours, the semidiurnal tidal period. The current was always southwestward and varied from 5 to 40 cm/s.
4. Meteorological conditions
SurfaceFl (volt)
LWRadiation (W/m2)
5. Zooplankton
Three MOC1 net tows were conducted in Station 2 area. Net samples show relatively small amount of krill larvae, few krill adults, and small amount of copepods. ADCP echo intensity measurements show relatively weaker backscattering in this area which agree with the net tow samples.
Station 3: Lazarev Bay
1. Bottom topography
The bottom topography down to the ice edge in the bay was surveyed first time. The Rothschild Island is approximately 11 mile due south, and the west coast of Alexander Island is approximately 5 miles due west. Survey shows the water depth in most of the area in the bay varies between 100 and 300 m except some uncharted islands and rocks. A narrow deep canyon of 800-1000 m extends into the bay along the coast of Alexander Island. Because it is so close to the island, and there are many icebergs, we could not survey most of the deep canyon area so that we do not know the width and how far it extends into the bay. The canyon is nearly a 200-600 m straight drop.
2. Temperature and salinity fields
The water below 400 m in the canyon shows similar T-S characteristics of deep shelf water, which indicates the connection of this deep canyon to the shelf region. The water above 400 m is modified which is much fresher and cooler.
3. Circulation
The ADCP current measurements at the mouth of the bay show a southwest shelf current as an extension of the current along Alexander Island. A small branch turns into the bay at the deep canyon. In the western shallow region, the flow is northwestward forming a clockwise circulation, and then joins the southwest shelf current.
4. Meteorological conditions
SurfaceFl (volt)
LWRadiation (W/m2)
5. Zooplankton
One MOC1 net tow to 300m was conducted at the deep canyon near the entrance. A MOC1 net tow in the bay was precluded by icebergs. Net samples show moderate amount of krill larvae, total 2 adults, and large amount of copepods between 150-300 m. OPC measurements show the similar pattern as the net tow samples.