Mike Castellini in Antarctica

Official NSF Report
Antarctic Pack Ice Seals (APIS) Site Report No. 3

January 10-16, 2000

1. General (Bengtson): At the approximate half-way point in our schedule, it is very satisfying to report that our APIS cruise is going extremely well! In the past week we completed our transit of the fast ice along the continental coastline. We also completed two 100 nm transect lines oriented across a pack-ice covered zone ice that included the continental shelf, the shelf slope, and pelagic areas. Those transects allowed us to sample three of the four main pack ice habitats that we are targeting during this cruise. One of the two transect lines across the shelf slope formed the southern anchor for the first of our long sampling lines, which we intend to run from the continental coastline northwesterly to the northern ice edge of the pack ice. The first of these long transect lines will be approximately 440 nm in length. We continue to experience mostly favorable weather, which has allowed us to make excellent progress to date. The RVIB N.B. Palmer is proving to be an outstanding platform for conducting the APIS Program's multi-disciplinary research. The ship's enthusiastic and highly capable personnel, plus the able assistance of the ASA staff are helping us to accomplish a tremendous amount—both safely and effectively. The helicopter detail sailing with us has also been terrific, and the helicopters are a research tool that we are utilizing to the fullest extent that weather will allow. On a typical day, it is not unusual for our simultaneous science activities to include two helicopters aloft flying seal surveys, two or three zodiac boats supporting local seal work, divers, and sea ice sampling, and a CTD cast or HTI acoustic survey being conducted from the ship. Net tows are conducted in the evening when the seals go in the water to feed. Science aboard the N.B. Palmer is hopping!

2. Seal abundance and distribution (Bengtson, Boveng, Laake): To date, we have flown 30 helicopter surveys for seals, which included 7 flights over coastal fast ice and 23 flights over pack ice. We are also conducting seal surveys from the conning tower of the ship as it moves through the pack ice. Our surveys across the ice-covered shelf and shelf slope zones revealed a higher density of seals compared to the ice-covered pelagic zone north of the shelf. Crabeater and Weddell seals were abundant through the shelf slope area, but we have seen surprisingly few leopard seals. In addition to seals, our aerial surveys are yielding good information on the abundance and distribution of emperor penguins in the pack ice. The penguins are molting during this period, and by the end of the cruise we should have a much better idea of the habitats that they select at this time of year. For our studies of pack ice seal behavior, we have attached satellite transmitters to a total of 6 crabeater seal pups and 3 Ross seals. The transmitters appear to be working normally, and we are beginning to receive ARGOS data summaries of their dive behavior, haulout patterns, and location/habitat selection. We are maintaining a close watch on the progression of molt on crabeater seals, and are hoping to begin deployment of satellite transmitters on crabeater seal adults in the next week or so.

3. Seal condition and nutrition (Castellini): We are now approximately half-way through our sampling effort to collect health and nutrition data from the pack ice seals. In conjunction with the Yochem, Stewart and Siniff teams, as of January 17, we have obtained blood samples from 67 seals (31 Weddell, 27 crabeater, 7 Ross and 2 leopard). Basic hematological values for these blood samples have been conducted onboard the NBP and the blood samples are stored at -80 for ultimate shipment back to Fairbanks for further analysis. We have conducted morphological examinations on 63 of these animals and detailed blubber depth measurements on 30. The data continue to suggest that the Weddell seals in this region are either smaller or younger than the seals in the McMurdo sound vicinity. The Ross and crabeater seals are the same total mass as each other, but the crabeaters are significantly longer and the Ross seals have significantly thicker blubber. In collaboration with the Quetin and Torres projects, we continue to collect both krill and fish samples for trace lipid and stable isotope analysis to help identify the regional prey items of seals.

4. Seal health (Yochem, Stewart): In collaboration with the Seal Nutrition, Seal Immunogenetics, and Seal Population Genetics teams, we have collected biomedical samples from an additional 32 seals since 9 January, working at a previously-unreported Weddell seal colony in the fast ice at Siniff Bay, across an ice-covered shelf/slope front, and along our first major north-south transect through the pack ice. The R/V Palmer continues to be an extremely effective platform for seal operations, allowing access to the ice via personnel baskets or zodiacs. The helicopters have been especially helpful, spotting seals in advance of the cruise track and providing transport and close support on large ice floes. With 67 seals sampled to date, we are hopeful that we will be able to meet our goals for samples sizes in the various zones during the APIS cruise for at least crabeater seals and Weddell seals. Leopard seals continue to be more elusive than expected, although sightings have increased over the past week. Interestingly, we also have seen several crabeater seal pups with fresh leopard seal wounds during the past two days; we conducted complete physical exams and collected samples from two of these.

5. Immunogenetics (Stewart (in field), Lehman): Our tactical goals under the APIS project are to: a) document the molecular genetic variability at loci that direct the synthesis of key elements of the immune system response to invasion by bacterial and viral pathogens, and b) assess the relationship between this genetic variability and biotic and abiotic explanatory variables (e.g., individual physical health, prey ecology, oceanographic variability, physical environmental parameters). Based on results from those analyses our strategic objectives are to determine the potential for rapid responses of pack ice seal populations to new and re-emergent pathogens in the Antarctic. Project status: Since 9 January, skin samples have been collected from an additional 87 seals (2 Ross seals, 59 Weddell seals, 24 crabeater seals, and 2 leopard seals) in the slope front zone and the southern reach of the pelagic zone of transect 1 (eastern-most of the S-N, N-S transects). Samples are being collected collaboratively with the Seal Health (Yochem & Stewart), Seal Nutrition (Castellini) and Population Genetics (Siniff and Stirling) projects and being shared with the latter. Since the beginning of the cruise, skin samples have been collected from 177 seals (9 Ross seals, 113 Weddell seals, 52 crabeater seals, 3 leopard seals). The goal for the coming week is to collect skin samples from 3 or more seals of each species in each zone (pelagic zone, ice-edge front, slope front, shelf zone) of transects 1 and 2.

6. Seal genetics (Siniff and Stirling): Our APIS project centers on the exploration of two hypotheses: 1) the relationship between life history patterns and genetic variation among regions of the Antarctic pack ice, for the four species of Antarctic pack ice seals, and 2) a molecular investigation examining the evolutionary history and origin of the pack ice seals. In addition, our project is responsible for soliciting and organizing genetic samples collected by other national APIS programs, and serving as the depository for storage and analysis of these samples. Our sample collections total to date are: Weddell seals - 114; crabeater seals - 52; leopard seals - 3; Ross seals - 9. Since the last report, we have sampled additional Weddells in particular in the pack ice. As we move further offshore, we expect the proportion of Weddell seals to decline and of crabeaters to increase. A 24 hour watch has been maintained throughout the cruise, and is continuing, so the ship can be stopped briefly to collect a skin sample from either a Ross or leopard seal in order to maximize the sample size of these seals which, to date, we have seen less frequently. The majority of the Weddell seals sampled in the pack have been subadult animals.

7. Seabirds (Kooyman): After noting a remarkable concentration of emperor penguins along the Marie Byrd Land coast during the previous week their numbers began decline as the cruise track headed north. During this track a trend in the color of the emperor penguin guano seemed to be developing. Consequently some guano samples were taken and enough otoliths and squid beaks were found to indicate this as a useful guide to diet patterns in the regions to be traversed. Samples are collected on an opportunistic basis if specimens are in the vicinity of the hydrographic stations. The usefulness of the guano analysis is becoming apparent and the effort to collect samples is intensifying. A library of otoliths of the locally caught fish is being developed specifically for the identification of otoliths found in the stomachs and guano of emperor penguins. Torres' group is making fish available for the extraction of otoliths. Satellite transmitters were also tested, and reliable receptions received and sent by Argos via email to the ship. Everything is ready for deployment once birds that have finished molting are found. Deployments are expected to begin in about one week as the probable peak of molting is passed and many satisfactory birds become available.

8. Fish, squid, and zooplankton (Torres and Daly): The highlight of the last week was our series of four successful bottom trawls ranging in depth from 300-500 m. Invertebrate and vertebrate biomass was enormous, suggesting that much of the life in the coastal zone, as viewed from our net and acoustic surveys, is in the upper 100 m of the water column and on the bottom. We captured over 25 species of fishes in those four trawls alone. Our midwater trawling and acoustic results still suggest a very depauperate water column relative to other midwater systems, with a particularly large contribution to the total biomass by the large scyphomedusae : Periphylla and Stygiomedusa. Fish continue to be poorly represented in the midwater. Krill swarms in the upper 50 m were detected acoustically and successfully sampled using the 1 m MOCNESS by the Quetin/Ross program.

9. Krill and zooplankton (Quetin (in field) and Ross): This past week we finished dive, tow and acoustic stations in the shelf zone and along the fast ice edge before sampling at the shelf break zone as we began heading north on our eastern-most transect line. We completed 10 dives, including video transects, and 6 Mocness tows, two with simultaneous acoustics. No Euphausia superba were found during the dives, and E. crystallorophias, when present, were not strongly associated with the ice, but found at depths starting at 7 m. We have had good success using the 1-m Mocness to verify some of the acoustic targets, and in one instance, the net was at the correct depth to sample a school of krill seen acoustically. We had one catch of E. superba at the shelf break, but on the shelf we continued to find low zooplankton biomass in the water column, no E. superba and low catches of E. crystallorophias. Copepods have dominated the catches when euphausiids are absent. In the next few days we expect biomass and catches of E. superba to increase as we move further north of the shelf.

10. Sea ice and hydrography (Ackley (in field) and Jacobs): The eastern end of the coastal section was completed with a set of six CTD casts across the shelf and continental slope in conjunction with net tows and acoustics. This section at 129 west therefore parallels the 158 W section completed just prior to the transect along the coast, only over an ice-covered rather than ice-free continental shelf. An initial Sea Beam survey was used successfully to correctly position the CTD stations over a steeply dropping continental slope. Sea ice observations in the offshore showed thicker (3 meter) and heavily deformed multi-year ice probably originating in the Amundsen Sea. Two or more annual layers were seen in the snow covers of these thicker floes. On the northern transect, we have added ice algal observations in relation to ice type into the continuous observation record. Chlorophyll measurements taken from ice cores, in collaboration with L. Quetin's group, will be used to quantify the chlorophyll concentration in relation to visually observed ice types and obtain some regional estimate of the total algal biomass in the ice.

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