previous section  |  Table of Contents  |  next section
Antarctic Pack Ice Seals  

Pack-Ice Seals
At least half of the seals in the world inhabit the pack ice around Antarctica. Six of the known 31 species are here, including about 80 percent of the world's total pinniped (carnivorous, aquatic mammals, including the walrus and all seals) mass. As a group, these seals are one of the the dominant predators in Southern Ocean ecosystems. Changes in population size, growth patterns, life histories, and behavior provide a rich source of potential information, about not only seal/pinniped biology, but also the history of their environment in time and space. The Antarctic Pack Ice Seals (APIS) program is designed to track the distribution of these creatures and provide a better understanding of their ecology. In January and February 2000, a research cruise (through the pack-ice zone of the eastern Ross and western Amundsen Seas) will enable scientists to survey and sample along six transects perpendicular to the continental shelf. Each of these transects will pass through five environmental sampling strata – continental shelf zone, antarctic slope front, pelagic zone, the ice-edge front, and the open water outside the pack ice. This plan will encompass all potential ecological zones except for the open water.

Antarctic pack ice seals (APIS): Ecological interactions with prey and the environment.
John L. Bengtson, Jeffrey L. Laake, and Peter L. Boveng, National Oceanic and Atmospheric Administration, National Marine Fisheries Service; Stanley S. Jacobs, Lamont-Doherty Earth Observatory; Joseph J. Torres, University of South Florida; Kendra Daly, University of Tennessee; Stephen Ackley, U.S. Army Cold Regions Research Laboratory; Langdon Quetin and Robin Ross, University of California, Santa Barbara.

During surveys along each transect we will gather data on the seals' environment (i.e., bathymetry, hydrography, sea-ice dynamics and characteristics), their trophic (nutritional) resources (i.e., phytoplankton and ice-algae stocks, and prey species such as fish, cephalopods and euphausiids), and on their numbers, distribution and diet. This collaborative project involves four different groups of researchers, each responsible for different aspects of the field program:

Seals: Surveys by air and ship; capture and attach instruments to track behavior; collect diet samples to better understand their food habits. (Bengtson, Boveng, and Laake)

Sea ice and hydrography: Measure near-surface temperature, salinity, and sea-floor bathymetry; record sea-ice and iceberg distribution and properties; collect ice cores; make CTD measurements from the ship and from ice floes. (Jacobs and Ackley)

Fish and cephalopods: Assess species composition, distribution, and relative abundance, using hydroacoustic techniques and net tows; compare these data with distribution and abundance data for fish prey –such as krill – and for fish predators – such as seals. (Torres and Daly)

Euphausiids and other zooplankton: Sample abundance and distribution of krill and other zooplankton, using hydroacoustic techniques, net tows and direct observations by divers; sample the demographics of krill at various depths within the study area; measure chlorophyll concentrations to evaluate the diet of krill. (Quetin and Ross)

A primary goal of this interdisciplinary research is to test a central hypothesis: Measurable physical and biological features in the Southern Ocean create an area of high biological activity by upper trophic level predators. We expect this physical/trophic approach to investigating an ecological web to develop insight into the interplay between pack-ice seals and the biological/physical features of antarctic marine ecosystems, and also to aid scientists in predicting seal population fluctuations attributable to environmental change. (BE-198-A, BE-198-B, BE-198-C and BE-198-D)

Antarctic pack ice seals (APIS): Distribution and abundance along the Oates and George V Coast.
John L. Bengtson, Jeffrey L. Laake, and Peter L. Boveng, National Oceanic and Atmospheric Administration, National Marine Fisheries Service.

The Oates and George V coasts offer one of the primary sea-ice habitats for seals during the austral summer. This component of the APIS program entails surveying the numbers and distribution of four seal species: Crabeater (Lobodon carcinophagus), leopard (Hydrurga leptonyx), Weddell (Leptonychotes weddellii), and Ross (Ommatophoca rossii) seals.

As some seals will be in the water during the line transect surveys, we will correct our estimates by attaching satellite-linked, time-depth recorders to crabeater seals and deriving estimates from published values for the other species. As part of the survey, we will also monitor sea-ice characteristics, such as ice type, floe size, and percentage of coverage. Our objective is to investigate the relationships among seal abundance, bathymetry, and sea-ice characteristics. We hope to produce new insights into the ecology of pack ice seals and to improve the precision of population estimates for these prominent (but still poorly-chronicled) members of the upper-trophic antarctic marine ecosystem. (BE-198-E)

Antarctic pack ice seals: Nutritional physiology and body condition of seals.
Michael A. Castellini, University of Alaska, Fairbanks.

This component of the APIS program examines seal nutritional physiology – health, body condition and nutritional status – using a suite of biomarkers and morphometric indices. We will make comparisons within and between species, measuring: Blood and clinical markers, nutrition indices, lipid signatures and stable isotope signatures, as well an array of protein markers. This work complements other studies on the health status of Antarctic ice seals. (BE-199-O)

Antarctic pack ice seals: Immunogenetic diversity of antarctic pack ice seals.
Brent S. Stewart and Niles E, Lehman, Hubbs-Sea World Res Institute.

Like any species, pack-ice seals display genetic variability among individuals. This component of the APIS program examines two sets of genetic loci:

the major histocompatibility complex, which is involved in immune system responses; and

the microsatellite locus, which does not code directly for a gene product.

This dual approach will enable the team to assess how much immunologically-relevant genetic variation occurs against the background of overall genetic variation. This study complements others on the health status of Antarctic ice seals. (BE-229-O)

Antarctic pack ice seals: Health, disease and pathology.
Pamela K. Yochem and Brent S. Stewart, Hubbs-Sea World Res Institute.

There has been very little clinical data developed on the health of animals residing in undisturbed populations, seals in Antarctica in particular. Thus baseline information on the incidence of disease organisms and pathology is critical. This component of the APIS program undertakes to evaluate the health, pathology, and exposure to disease of antarctic pack ice seals encountered during the cruise. These data should enable us to investigate population dynamics as a function of disease and pathology. (BE-230-O)

An examination of genetic patterns and phylogeny of Antarctic pack ice seals:
A coordinated multinational project.

Donald B Siniff , Curtis Strobeck, and Ian Stirling, University of Minnesota-Twin Cities

Antarctica represents an enormous tableau against which to examine genetic diversity, especially for the discrete species of seals. This component of the APIS program is investigating genetic relationships within and between all four species. Since the seal populations tend to be widely dispersed, studies of genetic diversity may indicate patterns of evolutionary strategies, as well as common and divergent traits.

We will employ microsatellite techniques to explore heterozygosity patterns within each species and to relate these patterns to what we know about their life histories. Mitochondrial DNA analysis should indicate the sequence of divergence among and between the four species, work that will be abetted through a collaboration with the University of Alberta, Canada. (BE-309-O)

previous section  |  Table of Contents  |  next section