Mike Castellini in Antarctica

Official NSF Report
Antarctic Pack Ice Seals (APIS) Site Report

February 7-10, 2000

1. General: The APIS 2000 cruise ended on the morning of 10 February, when we arrived at McMurdo Station. Since we departed Lyttleton, NZ, on 20 December, we have had a terrific cruise that has accomplished a tremendous amount of work. A quick look at some summary numbers provides a hint of the intensity with which the APIS cruise was conducted: 45 science days, 647 separate science events, ship track sampling of approximately 800 km along the Ross Sea polynya marginal ice zone, nearly 1000 km along the coastal fast ice, 2 "short" transects across the ice-covered shelf slope zone, four "long" transects from the coast to the northern marginal ice zone (each about 600 km long), and 175 hours of helicopter flights (which yielded well over 18,000 km of aerial survey transects for seals). In addition to our work in the pack ice, during our transit from the pack ice to McMurdo over the past 4 days, we were able to squeeze in two more productive science stops along the Antarctic coastline: Cape Colbeck (77 07.0'S, 157 36.2'W) and the Bay of Whales (78 28.4'S, 163 57.7'W).
   
   The entire APIS 2000 science party is delighted with the results of the remarkable cruise that we have just completed, and we wish to extend our thanks for the great support provided by personnel from the ship (Edison Chouest Offshore) and ASA. The lion's share of the credit for our successful cruise goes to Capt. Joe, who set a very positive "can do" standard for the whole cruise. His enthusiasm, energetic determination, and skillful and creative use of ship's resources made this ambitious cruise a reality. In addition, Capt. Joe's highly capable crew not only helped to make the pursuit of our science goals a success, but also made sailing on the N.B. Palmer a real pleasure. It is difficult to imagine a better Capt. crew, and research platform than the combination that supported the APIS 2000 cruise. We also wish to recognize the excellent work done by the ASA team that sailed with us on this cruise. The ASA staff assisted with a diverse set of science tasks, maintaining their good humor and patience throughout a complicated and event-intensive cruise.
   
   
2. Seals: One of the big surprises at the Bay of Whales, in the cruise's final hours of science activities, was the number of leopard seals that had hauled out on the peripheral fast ice around the bay. We observed nine leopard seals there, whereas previously on the cruise we had seen very few (we only saw 33 leopard seals during all aerial surveys). Encountering leopard seals on the final day of the cruise allowed us to round out our deployment of satellite tags on all four species of Antarctic pack ice seals; in addition to the satellite tags already deployed on crabeater (22), Ross (4), and Weddell (3) seals, we deployed satellite tags on two adult male leopard seals at the Bay of Whales. From the perspective of the abundance and distribution component of the APIS cruise, we couldn't have ended the cruise on a higher note than that! We are also very pleased with the results of our aerial surveys conducted by the two helicopters staged from the ship. In total, we surveyed 18,576 km of pack ice habitat by air, and observed 11,414 seals (4,817 crabeater, 2,852 Weddell, 79 Ross, 33 leopard, and 3,633 unidentified seals) and 11,066 emperor penguins. Analyses of those counts will be enhanced by a superb set of sea ice data obtained from the belly-mounted digital video cameras used on all flights.
   
   Samples to evaluate seal condition and nutrition were taken from 154 seals for blood analysis (53 Weddell, 58 crabeaters, 40 Ross and 3 leopard seals) and 157 animals for detailed morphometric measurements. Almost half of these samples were collected through the use of helicopter support. More than 1,000 samples have been prepared for shipping back to the U.S. for analysis, in addition to the analyses conducted on board the Palmer. Our preliminary data indicate that only about 10% of the seals had fed within 6 hours of capture, but only 1 of the 40 Ross seals met this criteria. This fits with the theory that Ross seals come to the ice pack for molting, a time period where most seals limit their feeding activity. Accordingly, our measurements of body fat levels are similar to values seen in other species of seals during the molting period and are on the lean side. Our ability to predict seal mass from length and girth measurements was quite strong, with a better than 0.99 correlation between predicted and actual. These data indicate that most of the Weddell seals seen in the pack were young animals or generally smaller than those seen near McMurdo. Similarly, most of the crabeaters captured appear to have been subadults. Taken together, these nutritional and body morphometric data will be combined with analysis of lipid types in both the seals and their prey items to construct a model of predator-prey relationships. Finally, when combined with the extensive distribution data for seals and trawling data for prey, we expect to be able to better model how nutritional status relates to seal distribution in the pack ice of the Ross sea.
   
   Biomedical samples were collected from over 130 seals. Our most complete data set is for crabeater seals, and we performed complete medical work-ups on 7-10 crabeaters in each of the zones sampled on the cruise (pack ice transects, the northern ice edge, and the southern polynya/coastal area). We performed 85 microbiological cultures on over 70 animals, including Salmonella screens, gastrointestinal tract flora examinations, and skin and wound cultures. Detailed anesthetic records were maintained on all seals immobilized during our handling events, and sera for drug level determinations will be submitted on a subset of animals. These data will allow us to recommend refinements to chemical immobilization protocols for Antarctic phocids.
   
   A total of 432 samples was collected for population genetics and immunogenetics analyses, comprising 181 crabeater seals, 202 Weddell seals, 42 Ross seals, and 7 leopard seals. Few leopard seals were seen, as is reflected in the paucity of specimens from them, while we encountered Ross seals in much larger numbers than anticipated. Besides collecting skin samples for genetic analysis, our observations throughout the cruise gave us new ideas, perspectives, and insights into some of the ties between genetic heterozygosity and life history patterns. For example, crabeater seals are typically referred to as preferring pack ice and Weddell seals as preferring the fast ice. While we found this characterization to be generally true in the Ross Sea, we found large numbers of newly weaned pup and subadult crabeater seals in fast ice areas, in groupings similar to those we observed in the spring in the Antarctic Peninsula in the late 1970s, suggesting this phenomenon may be characteristic of young animals through more of the year than was previously thought. Older crabeater seals and fewer pups were found in the in the interior pack ice zone. From our preliminary genetic analyses, crabeater seals appeared to have little or no development of genetic population structure, i.e., suggesting they move extensively around the continent and breed in a panmictic fashion. Thus, it was particularly interesting to observe that, despite the paucity of leopard seals, the scarring rates on crabeater seals was very high, suggesting the animals had received their wounds elsewhere than in the Ross Sea area. The tendency for these young seals to be so abundant in the fast ice could be related to food availability or to reducing their vulnerability to predators.
   
   Conversely, we found larger numbers of Weddell seals than we expected in the interior pack ice zone, especially subadults and adults that appeared to have not yet entered the breeding population. The greatest number of these animals were found on large floes several km across and the seals themselves tended to be most common away from the edges, and in the middle of the floes, in habitat with considerable similarity to landfast ice. However, we are still puzzled by the predominance of younger, but apparently non-breeding, adult Weddell seals in the land fast ice that was sampled to the east of Cape Colbeck. Only when we sampled Weddell seals in the rift cracks approximately 10 km south into the Ross Ice Shelf from the Bay of Whales did we find large breeding adult males and females, suggesting this is a fully established breeding colony. It is possible that the Weddell seals we sampled in the pack ice region originated from regions other that the eastern Ross sea coastal area. Our genetic analyses will facilitate addressing this question since our analyses to date have shown significant genetic differences among populations of Weddell seals from different regions of the Antarctic.
   
   Throughout the interior pack ice zone in the Ross Sea, we encountered an unusually large number of Ross seals, usually molting as single individuals on large floes. It is likely that the reason we saw so many Ross seals was that the seals were molting at the time we were in the pack ice as it has been hypothesized that they normally pelagic for much of the year and thus not usually seen. The molt of several individuals was characterized by shedding of large amounts of hair and sloughing of skin, in a fashion reminiscent of elephant seals. This observation emphasizes the evolutionary aspects of the phylogenetic relationships between the Antarctic ice breeding seals and the elephant seals and monk seals which we hope to be able to examine. Our sample of 42 will allow us to make a statistically significant evaluation of genetic heterozygosity in this species and to compare the Ross seals of the eastern Ross Sea with those near the South African station, from which we also have a sample, albeit a smaller one.
   
   Throughout the cruise we were struck by the paucity of observations of both leopard seals and killer whales as both these top predators seem much more common in other areas of the Antarctic from which data exist. The virtual absence of leopard seals in the observations, and thus the samples as well, continues to be a puzzle. The sample size for Ross seals is now large enough to facilitate a meaningful first evaluation of the degree of population structure in this species.
   
   Finally, from observations made by other programs on the ship, it appeared that the benthic community of the shelf region along the coast had a high biomass of fish and invertebrates. Although the pathways are not clear, it seems likely this high biomass and possibly the particular assemblage of species there may be partly responsible for the patterns of distribution of adult and subadult Weddell and crabeater seals we observed.
   
   
3. Seabirds: The APIS cruise made possible the closing of the circle in the description of the natural history of the emperor penguin's annual cycle. We were able to learn the physical nature of the ice pack on which they molt, how it declines in area over the minimum ice month of the year, and the character of the floes on which they spend the month of molting. We also learned that one of the preferred areas for molt is on the fast ice in the shadow of Mt. Siple on the Marie Byrd Land coast. We now know what the preferred food is for those that choose to feed offshore in the pack before and after the molt, and what the diet is for those that feed and molt over the shelf. We were also able to determine body mass of the birds before and after the molt, a critical factor in their survival during this vulnerable period. Finally, we were also able to gain a better appreciation of who the emperor penguins neighbors and possible competitors are during this time in the eastern Ross sea.
   
   
4. Fish, squid, and zooplankton: A total of 19 4 m2 MOCNESS tows , 22 9 m2 Tucker trawls, 5 15 m midwater trawl samples, and 6 15 m bottom tows were taken during the course of the APIS cruise, encompassing ice edge, deep pack ice, and shelf-slope environments. Midwater fauna were sampled in two basic depth strata: 0-500 m and 500 to 1000 m. Bottom tows were executed on the shelf only, in depths ranging from 250 to 500 m.
   
   Preliminary results from the study area, based on the general physiognomy of the trawls, suggest a few trends. First, the upper 500 m of the water column is nearly devoid of fishes, except over the shelf. The typical inhabitants of the midwater, the lanternfishes, are restricted to depths below 500 m and are very sparse there as well. Euphausiids, when present, dominate in the upper 200 m. The major predators captured by our midwater tows were large jellies such as Periphylla and Stygiomedusa. Relative to other systems the PI has sampled extensively with similar gear, e.g. the Scotia-Weddell Sea, the California Current, and the Gulf of Mexico, the Ross Sea is a biological desert with respect to both biomass and diversity.
   
   The bottom fauna on the shelf, in contrast to the midwater, was astoundingly rich in both fish and invertebrate species. Ten minute tows produced hundreds of kilos of invertebrate biomass, and greater than twenty five species of fishes. Clearly, most of the marine life on the Ross Sea shelf is on the bottom.
   
   Our preliminary results indicate that acoustic targets were most prevalent on the shelf in the coastal polynya, where dense layers and swarms were detected. Net tows suggested that these layers were composed primarily of the euphausiids, Euphausia crystallorophias and E. superba, and a juvenile fish, Pleuragramma antarcticum. Layers of euphausiids and juvenile Pleuragramma also were detected at a few stations along the ice edge of the Ross Sea Polynya north of the shelf slope. Swarms were less frequent at stations in the interior and at the northern edge of the pack ice. In all regions, acoustic targets occurred primarily in the upper 100 m of the water column.
   
   Assessments of krill and zooplankton using divers and net tows went very smoothly throughout the APIS cruise. We completed more than 58 dives 49 net tows in a variety of coastal and offshore habitats. We saw a similar pattern as for all four long transects, catching adult and one year old Euphausia superba at the northern edge of the APIS area and Euphausia crystallorophias at the southern edge. The water column in the middle area of transect 4 was dominated by copepods and krill biomass was at a low for the transect. Diving observations correlated well with the net catches with the exception that the underside of the pack ice seems the provence of one year old and not adult Euphausia superba. Gravid adults Euphausia superba have dominated the net catches of krill along the northern ice edge, making this one of the richest areas surveyed in terms of energy available to seals.
   
   
5. Hydrography and sea ice: For the hydrography, CTD casts were accomplished throughout the study area on a spacing of 60 nm or less, along with open water stations north and south of the ice edges on the ends of the transects. Regular near surface sampling was done by the divers using a SeaCat CTD and underice sampling of water for isotopes during most of the daily dives. An additional seven ice cores were obtained on the last two transects at the once daily stops and gives a roughly regular grid of sea ice cores across the study area. On the stop at Bartlett Inlet near Cape Colbeck, small chunks of green iceberg were observed, and we sampled three of these pieces from the zodiac. Analyses are underway on ice structure, particulate content, chemical composition and subsampling for oxygen isotopes.
   
   
6. Education/outreach activities: In addition to its science activities, the APIS cruise offered many opportunities for education and outreach into the broader community. Several APIS projects were involved in such activities, and the following paragraphs provide some examples associated with the APIS Program. Michael Castellini was working with the Alaska Sea Grant Office on an outreach program. He did two radio interviews for PBS radio based in Fairbanks, and sent journal entries from the ship describing cruise activities to ENN. These articles may be found at ENN's features page, and the journal entries, as well as the NSF reports and the audio interview are on the SFOS home page. These interviews and journal entries dealt mainly with the general public and described why we were here, who funded us, what projects were on board, and personal descriptions of various highlights of the trip.
   
   Kendra Daly corresponded with students in an adult education class at Linn-Benton Community College, Albany, Oregon. The instructor, Susan Cowles, used the daily sitreps and Daly's reports to increase the students level of scientific literacy and to engage them to think about science issues beyond the world they know. The APIS science objectives and cruise activities were used to teach basic skills in computer technology (learning how to e-mail, search the web for information on Antarctica), and to provide a background in geography, basic math skills and science. In addition Daly answered e-mail sent by some of the students who were very curious about the more personal aspects of life on a ship in the Antarctic, in addition to specific questions about scientific research in Antarctica.
   
   Tamara Mau wrote reports once or twice a week to a relative, Bobbie Hansen, who incorporated them into her lesson plans at Frank Intermediate School in Oxnard, California to encourage remedial readers. The report also were used by science teachers at Frank. The teacher estimated that at least 300 students had heard about Mau adventures.
   
   Chris Simoniello started by fielding questions from children of friends. Within two weeks she had formal requests from six schools in Florida, New York and Idaho, ranging from elementary to high school. Simoniello answered e-mail, suggested related study materials, and sent digital photos taken during the expedition for class projects. She also was in contact with participants in the Oceanography Camp for Girls and a related Oceanography Workshop for teachers sponsored by the University of South Florida. She plans to give talks at many of the schools when she returns.
   
   Brent Stewart and Pam Yochem responded to questions from San Diego City School students (K-12) via e-mail. Questions were generated in response to information on Antarctic wildlife in general and seal research in particular, posted by Stewart and Yochem and by the SeaWorld Education Department on SeaWorld's educational web page.
   
   Marilyn Koski was corresponding via e-mail with elementary school students in Sacramento. Students responded to messages from Koski re: science activities, life aboard the R/V Palmer, etc. Koski also was corresponding with graduate students, faculty and staff in the microbiology and immunology departments at U.C. Davis, providing regular updates on microbiological sample collections, species encountered and laboratory work conducted about the R/V Palmer.
   
   Jose Torres wrote eight articles describing the cruise activities and APIS science objectives and preliminary results for the St. Petersburg Times. These articles were accompanied by digital photos, one which made the front page. The special section of the paper containing his articles likely has a readership of several thousand.

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And so ends the final site report from the APIS 2000 cruise. We had a great time, and we all learned a lot. We hope that you have enjoyed reading our weekly site reports and that they have given you some sense of the scientific excitement and energy that we all experienced during the cruise.

From all of the APIS 2000 Principal Investigators,

Chief Scientist: Bengtson

Seal abundance and distribution: Bengtson, Boveng, Laake

Seal condition and nutrition: Castellini

Seal health: Yochem, Stewart

Seal immunogenetics: Stewart, Lehman

Seal population genetics: Siniff, Stirling

Seabirds: Kooyman

Fish, squid, and zooplankton: Torres, Daly

Krill and zooplankton: Quetin, Ross

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