Mike Castellini in Antarctica

Official NSF Report
Antarctic Pack Ice Seals (APIS) Site Report No. 1

December 20,1999 to January 2, 2000

1. General (Bengtson): The R/V N.B. Palmer departed Lyttleton, New Zealand, on 20 December 99 as scheduled. Favorable weather enabled us to reach the edge of the pack ice on 26 December. Because the pack ice front was well to the north of where we had expected it to be in a normal year (it was north of 65 degrees S vs. at about 70 degrees S), we modified our provisional cruise track, proceeding south into the Ross Sea polynya. This modification will allow us to reach our study area sooner and to sample seals and the ecosystems associated with frontal features near the continental shelf without having to push our way through several hundred kilometers of ice; our new plan is to sample the northern ice edge several weeks into the cruise when presumably, the ice edge will have receded southward. In our first week of science activities, we sampled the northeast ice edge of this polynya, cruising southeast to the continental coastline at Cape Colbeck (158.5 degrees W). Science activities are progressing very well, with the various projects integrating their work effectively. Over the next week, we plan to cruise easterly along the continental margin, sampling biota and the physical environment along the fast ice and ice shelf fronts.
   
   
2. Seal abundance and distribution (Bengtson, Boveng, Laake): Since entering the pack ice zone, we have been surveying the abundance of seals and penguins from the ship and helicopters. The two helicopters deployed aboard the Palmer are working out very well and they have allowed us to greatly extend the geographic coverage of our surveys. To date, ten survey flights have been undertaken (each about 90 minutes in duration). Surveys along the eastern ice edge of the Ross Sea polynya identified a sharp gradient in the abundance of seals running perpendicular to this physical front: for example, crabeater seals were more abundant (by almost a factor of 10) about 30 km inside the ice edge compared to 150 km inside the ice edge. We also have encountered Ross seals at higher densities than expected. To investigate haulout behavior, feeding ecology, and habitat selection, we have begun to deploy satellite transmitters on seals; crabeater seal adults are just beginning to enter their molt period, so no transmitters have been deployed on crabeater seals to date. However, we have tagged two molted crabeater seal pups (about three months old) and three Ross seals with satellite transmitters. The pups' movements and behavior, in light of the heavy predation pressure exerted on that age class by leopard seals, will be most interesting to follow over the coming months.
   
   
3. Seal condition and nutrition (Castellini): Our APIS project goal is to collect physiological and biochemical data on the pack ice seals in order to better understand how prey availability and geographic location impact their health and nutritional status. To do this, we collect blood samples, measure blubber depth, assess whole body water, collect blubber biopsies and measure seal length, girth and mass. In collaboration with other APIS projects (Yochem- which is assessing the medical health), Stewart (which is measuring immune genetics) and Siniff (population genetics) we have successfully worked with 21 seals in our first week in the pack ice. This includes data from five Ross seals, which are considered very rare, 14 crabeater seals and two Weddells. A great deal of laboratory work is conducted on the NBP, while remaining samples have been prepared for shipment back to our home laboratories for analysis later in the year. One of our most interesting findings to date is that most of the seals appear to have been fasting and do not show signs of recent feeding in these locations.
   
   
4. Seal health (Yochem): Our project seeks to evaluate the influence of physical (e.g., ice conditions) and biotic (e.g., prey availability) factors on pack ice seal health. We are conducting physical exams and collecting biomedical samples (e.g., blood, urine, feces, microbiological samples) from pack ice seals encountered along transects through the pack ice and across gradients such as the shelf slope. Some analyses (e.g., microbiological cultures, some preliminary blood work) are conducted on board the R/V Palmer. Other assays (e.g., reproductive endocrinology, disease serology) will be completed when we return to our home institutions. We are collaborating closely with three other APIS projects: Mike Castellini's program to evaluate pack ice seal body condition and nutritional status; Brent Stewart and Niles Lehman's project on seal immunogenetics; Don Siniff's project on pack ice seal population genetics. In our first week, we have obtained samples from 5 Ross seals (an exciting result, as we had expected to find very few of these elusive seals), 14 crabeater seals, and 2 Weddell seals.
   
   
5. Immunogenetics (Stewart): Our project objectives 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 of this genetic variability and biotic and abiotic explanatory variables (e.g., individual physical health, prey ecology, oceanographic variability, physical environmental parameters) to determine the potential for rapid population responses to new and re-emergent pathogens in the Antarctic. Project status through 3 January 2000: Skin samples have been collected from 30 seals; 7 Ross seals, 2 Weddell seals, and 21 Crabeater seals during collaborative field efforts among projects supervised by Stewart, Siniff, Yochem, Castellini, and Bengtson. A smaller number of blood samples was collected from which white blood cells were isolated. Laboratory analyses to be conducted later in the U.S. will include DNA extraction, amplification, and sequencing.
   
   
6. Seal genetics (Siniff and Stirling): Our project under the overall umbrella of USAP APIS program explores two ecological and evolutionary themes: a) the relationship between life history strategies and the degree of development of genetic variability within each of the four species of Antarctic pack ice seals, and b) a molecular investigation of the evolutionary history and origin of the pack ice seals. An additional component of our project involves soliciting genetic samples from all the pack ice seal species that have been collected by other national APIS programs into an integrated circumpolar program of research and analysis. We will also serve as the repository for storage of these samples. The USAP APIS cruise provides an important opportunity for non-lethal collection of tissue samples for genetic analysis from all four species of seals in the eastern Ross Sea, an area where little sampling has been conducted in the past. To date, we have collected genetic samples from 20 crabeater, 2 Weddell, and 7 Ross seals. The Ross seal samples are of particular interest because the species is infrequently sighted so that few samples have been collected to date from anywhere in the Antarctic and there are none previously available from the Ross Sea. However, because we have specimens from 11 Ross seals sampled by the South African program in the eastern Weddell Sea, we will be able to undertake comparative analyses of population discreteness for that species under the first hypothesis noted above.
   
   
7. Seabirds (Kooyman): Over the course of the week we have sailed from the ice edge at about 67 degrees to 75 degrees south. There has been a gradient in the emperor penguin observations from mostly year old juveniles to adult emperor penguins. Abundance appears to have increased as well in the southward track. Upon encountering very large ice floes the juveniles declined and among the adults molting individuals are seen. By the end of the week large numbers of molting emperor penguins were counted.
   
   
8. Fish, squid, and zooplankton (Torres and Daly): We have completed a total of 7 trawls, 6 in the upper 500 m, and 1 over the upper 1000 m. Unequivocally, our results suggest that the region we've sampled in the eastern Ross Sea is very low in fish biomass, so much so, that it is nearly a desert with respect to fish fauna. We have captured a total of 7 fish (!) altogether in the three types of nets, one of which is a 15 m wide midwater trawl. The system shows a vertical structure composed mainly of euphausiids in the upper 200 m with large jellies below that. The picture may change with increasing sampling effort, but for now, the system looks so depauperate with respect to fish that it is seriously big news. Our acoustic sampling effort strongly supports our trawl results. We have collected acoustic data at every station and acoustic targets are entirely in the upper 100m, corresponding to the large populations of euphausiids that have been observed by the Ross/Quetin program as well as in our shallow nets. What we are seeing so far is a "wafer thin" ecosystem: virtually all biomass is restricted to the upper 100m. We are eager to continue our sampling to see if the currently observed trends continue throughout the study area.
   
   
9. Krill and zooplankton (Quetin (in field) and Ross): Since reaching the pack ice south of Scott Island and proceeding south, our group, consisting of T. Newberger, J. White, J. Flaherty J. Schneider, and L. Quetin has completed 9 SCUBA dives and 11 net tows. Observations during dives and comparisons between dives and net tows have allowed us to reach some tentative general conclusions regarding E. superba and zooplankton in the pack ice. Most of the biomass in the upper 300 m of the water column, dominated by E. superba, is found strongly associated with the underside of the pack ice and not in the water column. E. superba was found at each of the 4 dive locations almost exclusively feeding directly on or within .5 m of the pack ice. Zooplankton in general and specifically E. superba were not evenly distributed between stations in terms of both the dominance and size of E. superba. In one location copepods dominated in biomass rather than E. superba, and the biomass and size of E. superba varied between stations. We completed 8 net tows on a transect starting from latitude 75 degrees 47 minutes south and proceeding toward the coast along 158 degrees west longitude. The transect was only partially covered with pack ice over deep water in the pelagic zone. Both E. superba, in spawning condition, and E. crystallorophias were found at stations along the transect; both species were most abundant in the marginal ice zone over deep water. The abundance of both euphausiid species and zooplankton in general dropped abruptly between two stations 2.5 nm apart and between 1759 m and 1300 m of depth. The continued low zooplankton biomass over the shelf region indicates there is a very abrupt change between these two faunal regions.
   
   
10. Sea ice and hydrography (Ackley): We established a continuous ice watch with the first sighting of icebergs north of the ice edge on 25 December, crossing the northern sea ice edge on 26 Dec. Since then we have maintained a 24 hour recording of ice conditions and meteorological observations on an hourly to three hourly interval, (depending on stops). Sea ice conditions have been characterized by high variability with admixtures of older first year ice and new ice typical of highly dynamic conditions, also reflected in varying zones of highly deformed ice, where in excess of 50% of the ice area is ridged. New ice formation appears often despite the season, at the peak period of incident solar radiation. In the northern area, flooding of floes by sea water was widespread, with intermittent flooding seen in the now colder areas in the south. The thicker and ridged ice is highly colored with sea ice algae, mostly in the near surface layers and ridges,and appears to be actively fed on by krill from observations by the seal parties in zodiacs and by the divers. Four ice cores have been taken, two in conjunction with diving operations (which have been useful in characterizing sub ice topography, which is generally even rougher than seen on the surface). The ice cores look colored and will be analyzed for physical and biological properties. A consistent method of characterizing the ice cover in association with seal habitat has been established in collaboration with the seal observers, and is providing information to determine any correlations of the seal locations with specific ice conditions. The airborne profilometer is operating well, providing useful altimetric data to the seal census groups. Some of the digital airborne video taken during the seal census flights has been screened, and is of excellent quality to provide detailed quantitative characterization of ice types, concentration and ridged area in our postcruise analysis. To this date (4 Jan) we have completed 11 CTD stations,with 6 XBT's taken. Water samples drawn for O-18 and salinities. A lowered ADCP was attached and is working well.

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