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
d. Synopsis of process station 4
Process station 4 is located in the southeastern corner of Marguerite Bay and includes the entire George VI Sound. It is bounded roughly by the tip of Alexander Island vic 68.8°S 70.6°W on the NW, 68.8°S 70.0°W on the NE and the southern end of George VI sound on the south. It includes the southeastern end of the large cross-shelf canyon that runs SSE through Marguerite Bay. The canyon runs right down the middle of George VI sound. The LMG arrived at station 4 at about 1000 13 May in the vicinity of the Bugge Island group but wind and visibility prevented close inspection of the island. A trackline was developed for towing and two MOC 10's and two MOC 1's were executed on our first day of sampling. Each day thereafter the LMG spent the daylight hours surveying for seals and penguins and the night hours towing either MOC 1's , MOC 10's, or executing an ADCP/CTD survey down the length of the canyon to map current patterns. Nets were fished at two points along the length of the canyon. The southern end of the canyon was well sampled; depths were about 1000 m all the way to the perennial ice at the southern end of the canyon. There was little or no new ice in George VI sound and the coasts contained much brash and many grounded bergs More specific information is available in the individual group reports.
A few seals and numerous penguins were spotted but were inaccessible
to our predator teams due to the character of the ice, which was largely
unconsolidated glacial rubble. Station 4 was departed 17 May for station
2, which is located in the mouth of the bay on the canyon axis.
e. Individual group reports
1. BG 232-0 Burns/Costa
This week we did not have much success at sighting seals, and were
unable to conduct any research. The few seals we sighted were deep in the
pack ice and inaccessible by zodiac (n = 4) or sighted late in the day
on floes too small to support the seal and us (n = 2). The oceanography
has shown that the prey availability in this area is lower than that of
the previous station. In addition, there has not been much suitable ice
for seals in the area, as most of the ice we have seen has been either
large icebergs or very small brash. We conducted a thorough search of lower
George VI sound and the western coastline, and do not think that the seal
abundance in the area is high. It is possible that there are seals in the
area, but the low light and low suitable prey and haulout substrate makes
it unlikely that we could capture any, even if more time for searching
were available. We were able to obtain a few krill from this station for
our fatty acid and stable isotope work on seal diets, but there were few
fish caught in the trawls, and so we do not have any fish samples from
this area of the Bay. In contrast to the (lack of) work in this area, we
have been receiving data from the three seals we tagged last week by Wyatt
Island. All three are now at the NE tip of Day Island and foraging in the
same locations and to similar depths. The two seals we tagged on 5/11 both
headed to Day Island on the evening of 5/11, which coincides with the clearing
of the bay by wind (see 5/12 report). The seals are diving routinely to
~ 200m, which is just above the bottom (as determined from ETOPO 2) but
are also spending time foraging at about 50 m. The area they are frequenting
is characterized by a variable bathymetry and several deep holes. We are
very interested in returning to that area to deploy the remaining 5 tags
and to obtain some more detailed information about the prey field in the
area. The area to the south has high prey abundance and did contain some
suitable ice. Detailed Report: May 12th: We remained at Wyatt Island overnight,
following our success on 5/11. However, it blew hard in the night, and
in the morning as we rounded the North tip of the island, it became clear
that the wind had blown the bay free of ice. The ship then circumnavigated
the island, and headed to George VI Sound. May 13th: Arrived near George
IV Sound in snow and fog, no possibility of seal work as we were in open
water. May 14th: Heard from the Palmer that they had seen a large concentration
of seals at the tip of Alexander Island, and a smaller concentration 2/3
of the way up the coast (west side of the Sound). So, during the day we
searched for seals along the western coast of Alexander Island (from Damocles
Point to Cape Brown in the north). Snow and low visibility hampered our
search range, but we did not see any sea ice or any old ice of the sort
seals seem to prefer. Daylight is low, so search hours were limited to
10am 3 pm. We saw no seals of any species, no whales, and only a few birds.
The weather forecast suggested a large storm was on its way into the Bay
and so instead of continuing north to the tip of Alexander Island (which
would be exposed) the decision was made to head back down into the Sound.
As daylight was waning, we crossed through a strip of brash ice that had
crabeater seals hauled out. The floes were too small to work and the light
was fading fast (3pm). We were encouraged to see seals in the area, and
had high hopes for the search the next day. May 15th: The LMG conducted
at CTD grid all day; no seal research or sightings carried out. May 16th:
Searched the bottom of George VI Sound for seals from 10:30 am onward.
Started at the Southeastern side near Niznik Island, and followed ice edge
along bottom to west until it petered out at Marr Bluff. The ice was glacial
in nature, and packed tightly against the ice shelf and coastline. The
few seals we saw (1 leopard, 1 weddell, 2 fur seals, 3 crabeaters) were
deep within the ice, and inaccessible by zodiac or the LMG. However, we
did see a large number of Adélie penguins. The search track crossed
several CTD stations, so we stopped our search activities twice to conduct
CTD stations for Meng and Frank. This reduced our search time from 5 hours
to 3 hours. May 17th: The ship repeated the cruise track from yesterday,
this time looking for penguins. We looked for seals during the daylight,
but again did not see any that were accessible (total count 2 fur seals,
3 Weddell seals, 1 crabeater seals, no whales). May 18th: In open water
conducting trawls and CTD stations. No sea ice, no seals. Science work
completed to date: Three SRDL tags deployed on crabeater seals. Krill and
mysid samples collected for dietary analyses. Remaining science to be conducted:
Deploy 5 SRDL tags on crabeater seals Obtain samples of fish species collected
in trawls (Currently we have 3 Electrona and 4 Pleuragramma).
2. BG 234-0 Fraser
The GLOBEC seabird component aboard the Lawrence M. Gould had a mixed
week. Generally poor to dismal weather conditions, combined with poor visibility
due to decreasing daylengths, greatly limited all attempts to locate penguins
in areas where our remaining instruments could be deployed and more diet
samples obtained. These failures have nevertheless been quite instructive
in that the search for these predators has revealed some previously unknown
patterns related to movements and migration and autumn habitat choices.
On a more positive note, our previously deployed instruments are providing
an excellent and informative database on Adélie Penguin feeding
and haul-out locations, thus providing our first glimpses of how these
predators respond to circulation and bathymetry in their search for prey.
3. BG 235-5 Stewart and Marschall (for Fritsen)
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 at PS #5 on 05/12, at PS #4 on 05/13-05/17, and at PS #2 on 05/18-05/19.
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 30 m only). Not all parameters were
sampled/measured on each cast. Bacterial production rates and PE curves
for PS #5 were obtained the week prior, and were consequently not obtained
from 05/12 samples. Chlorophyll a concentrations at PS #1 and PS #5 stations
averaged between 0.20 and 0.25 ug chla l-1 while chla concentrations
in two new ice samples collected from Dog Leg Fjord at PS #5 were 3.7 and
4.95 ug chla l-1 . Rates of both bacterial and primary production
at PS #4 were approximately 50-60% of those measured at PS #1 and PS #5.
Bacterial production at PS #4 remains consistent throughout the euphotic
zone but declines below 75 m. Production and chla data from PS #2 are not
yet available. Strong winds and warm temperatures (above freezing) continued
to inhibit large-scale new ice formation at PS #4. Newly-formed grease
and pancake ice was observed only on 05/12; no ice was sampled. Perennial
land-fast ice may be present in King George Sound (PS #4). Unfortunately,
a persistent northerly wind led to the accumulation of large fields of
brash ice that hindered observations of ice conditions along the southern
and western shores of the sound. Process site #2 is free of ice.
4. BG 234-0 Daly
Euphausia superba at Process Station # 4 in King George VI Sound
appeared to have shifted to an overwintering mode. Analyses for most experiments
will not be completed until after we get back to our laboratories at our
home institutions. A preliminary assessment, however, suggests that both
larval and adult krill in this southern region have shifted to a lower
metabolism possibly in response to the diminishing day length. During this
past week, our group completed molting/growth, ingestion, and egestion
rate experiments, and an assimilation efficiency experiment for larval
and adult krill. Acoustic transects were curtailed to some extent due to
high winds and many large ice bergs in the region. Acoustic data were collected
with one 1-m2 MOCNESS tow and one 10-m MOCNESS tow. Two layers,
about 55 m and 90 125 m, were detected by the 120 kHz system. Some individual
targets were detected by the 38 kHz system at depths > 300 m.
5. BG 245-0 Torres
Five MOC 10 tows and four live net tows were executed during the occupation
of station 4. Two MOC 10's were located a third of the way down the sound
vic 69 15°S, two were located about halfway down vic. 69 25°S,
one was at the southern end vic 69 47°S. Krill were captured in moderate
abundance in the 0-50, 50-100, and 100-200 depth strata. Adults were mainly
found in the 100-200 stratum, smaller size classes and Euphausia crystallorophias
in the 50-100 and some larvae in the 0-50. Gross estimates of krill abundance
at station 4 were about 10% of those at station 5. In the deeper tows executed
at this station (200-500, 500-800 m) an oceanic fauna was present, including
the lanternfish Gymnoscopelus, the bathylagid Bathylagus
and the pasiphaeid shrimp, Pasiphaea scotiae . At the southernmost
trawling site, a new eelpout was captured, Seleniolychus , as was
the icefish Cryodraco . Pleuragramma larvae were common in
the upper 50 m, but Pleuragramma adults were not captured. Overall,
our trawls in the canyon here showed a decidedly oceanic flavor with moderate
krill abundance in the upper 200 m. In addition to the work on distribution
and abundance we completed 100 individual determinations of respiration
and excretion on krill adults and larvae.
6. BG 248-0 Zhou
George VI Sound and its vicinity
1. Bottom topography
The bottom topography was surveyed during the whole study period in
George VI Sound. The measurements indicate:
1) The canyon in George VI Sound is deeper than 800 m. It extends from
the shelf of Alexander Island, west of Marguerite Bay, into the ice edge
whose current location is at 69 54.00°S, far beyond the ice edge in
1973.
2) In the east side of the deep basin west of Bugge Islands, the topography
varies dramatically. Sea mounts rises from 1000 m to 400 m or from 450
m to 50 m in less than a quarter mile.
2. Temperature and salinity fields
The temperature and salinity fields were surveyed by 23 CTD stations
in the Sound and its vicinity. The deep water below 400 m in George VI
Sound shows similar T-S feature of the deep water below 400 m on the shelf.
CTD measurements show the permanent stratification between 150 and 400
m. The water within this layer is relative cooler and less salty than the
water on the shelf, which indicates local influence. The winter water lies
between 75-90m, however in some stations, the surface mixed layer water
is even cooler than this layer. The salinity in the surface water is relatively
low keeping the water column gravitational stable. In most of stations,
the winter water layer formed last year has been eroded, which gives an
indication of the arrival of the winter season.
The shelf water follows the deep channel into George VI Sound. At the center of the basin, the water is relatively saltier than surrounding water. Because the temperature variation is small throughout in the region, the density field is primarily determined by the salinity field. Associated with this feature of the denser water at the center, a clockwise circulation is measured by the ADCP. Oppositely, the water is less salty at the mouth of the Sound forming a low-density center, which leads to an anti-clockwise gyre.
3. Circulation
The circulation in George VI Sound is featured by these two gyres associated
with two high- and low-density centers from CTD and ADCP measurements.
Further north, the flow field is dominated by the clockwise circulation
in Marguerite Bay. ADCP measurements show the westward flow between 69
10°S and 69 15°S. This flow bifurcates between 69 30°W and
69 40°W. One branch follows Alexander Island northward, and exits on
the shelf slope. Another branch turns southward and then southeastward
as a part of the gyre at the mouth of George VI Sound. A part of the flow
intrudes into the Sound following the eastern shelf.
4. Meteorological conditions
The wind direction sensors were down on days 134 and 135. We thank
Bruce Felix for spotting the problem, and then making ceaseless efforts
to fix the problem.
| Mean | STD | Min | Max | |
| Ta(C) | -0.07 | 0.64 | -1.70 | 2.41 |
| Ts(C) | -1.41 | 0.31 | -1.76 | 0 |
| R-humidity | 95.14 | 4.76 | 73.69 | 99.62 |
| Bar | 997.3 | 3.3 | 987.9 | 1005.1 |
| Surface Fl (volt) | 0.78 | 0.10 | 0.65 | 5.86 |
| LW Radiation (W/m2) | 283.2 | 28.4 | 184.1 | 309.0 |
5. Zooplankton
Four MOC1 tows were conducted around Station 4 region. Samples show
a significant difference in species composition between Stations 4 and
5. There were no adult E. superba adults caught in this area. Overall,
samples show this is a biological active area. Large amounts of copepods
and krill larvae and moderate amount adult krill were caught in every net
tows.