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Opinion: Projecting the effects of environmental change on Antarctic seals

Published online by Cambridge University Press:  16 May 2008

Donald B. Siniff ,
Robert A. Garrott ,
Jay J. Rotella ,
William R. Fraser  and
David G. Ainley
Donald B. Siniff*
Affiliation:
Department of Ecology, Evolution and Behavioral Biology, University of Minnesota, 100 Ecology Building, St Paul, MN 55108, USA
Robert A. Garrott
Affiliation:
Ecology Department, Montana State University, 310 Lewis Hall, Bozeman, MT 59717, USA
Jay J. Rotella
Affiliation:
Ecology Department, Montana State University, 310 Lewis Hall, Bozeman, MT 59717, USA
William R. Fraser
Affiliation:
Polar Oceans Research Group, PO Box 368, Sheridan, MT 59749, USA
David G. Ainley
Affiliation:
H.T. Harvey & Associates, 983 University Avenue, Los Gatos, CA 95032, USA
*
*[email protected]
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Abstract

We consider how Antarctic seals may respond to changes in climate, realizing that anthropogenic alteration of food webs will influence these responses. The species considered include the ice-obligate - crabeater (Lobodon carcinophaga), Weddell (Leptonychotes weddellii), Ross (Ommataphoca rossii) and leopard (Hydrurga leptonyx) seal - and the ice-tolerant Antarctic fur seal (Arctocephalus gazella) and southern elephant seal (Mirounga leonina). The data analysed are from long-term censuses of Weddell seals in McMurdo Sound (1997–2006), and of Weddell, fur and elephant seals at Arthur Harbour, Antarctic Peninsula (1974–2005). After considering their responses to recent changes in environmental features, as well as projected and current changes to their habitat our conclusions are that the distribution and abundance of 1) crabeater and Weddell seals will be negatively affected by changes in the extent, persistence and type of annual sea ice, 2) Ross and leopard seal will be the least negatively influenced by changes in pack ice characteristics, although, as may be the case for crabeater and Weddell, population size and distribution may be altered through changes in food web dynamics, and 3) southern elephant and fur seals will respond in ways opposite to the pack ice species, but could also be influenced most immediately by changes in their food resources due to factors other than climate.

Keywords

climate changecrabeater sealfur sealleopard sealRoss sealsouthern elephant sealWeddell seal
Type
Opinion
Information
Antarctic Science , Volume 20 , Issue 5 , October 2008 , pp. 425 - 435
Copyright
Copyright © Antarctic Science Ltd 2008

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References

Ackley, S.F., Bengtson, J.L., Boveng, P., Castellini, M., Daly, K.L., Jacobs, S., Kooyman, G.L., Laake, J., Quetin, L., Ross, R., Siniff, D.B., Stewart, B.S., Stirling, I., Torres, J. & Yochem, P.K. 2003. A top-down, multidisciplinary study of the structure and function of the pack ice ecosystem in the eastern Ross Sea, Antarctica. Polar Record, 39, 219–230.Google Scholar
Ainley, D.G., Ballard, G., Karl, B.J. & Dugger, K.T. 2005a. Leopard seal predation rates at penguin colonies of different size. Antarctic Science, 17, 335–340.CrossRefGoogle Scholar
Ainley, D.G., Clarke, E.D., Arrigo, K., Fraser, W.R., Kato, A., Barton, K.J. & Wilson, P.R. 2005b. Decadal-scale changes in the climate and biota of the Pacific sector of the Southern Ocean, 1950s to the 1990s. Antarctic Science, 17, 171–182.CrossRefGoogle Scholar
Ainley, D.G., Toniolo, V., Ballard, G., Barton, K., Eastman, J., Karl, B., Focardi, S., Kooyman, G., Lyver, P., Olmastroni, S., Stewart, B.W., Testa, W.P. & Wilson, P. 2006. Managing ecosystem uncertainty: critical habitat and dietary overlap of top-predators in the Ross Sea. CCAMLR WG-EMM-06/29, Hobart, Australia.Google Scholar
Ainley, D.G., Ballard, G., Blight, L., Eastman, J.T., Lescröel, A., Olmastroni, S., Townsend, S.E., Wilson, P.R. & Woehler, E. 2007. Paradigm lost, or is top-down forcing no longer an element of the Antarctic marine ecosystem? Antarctic Science, 19, 283–290.CrossRefGoogle Scholar
Arrigo, K.R. & Van Dijken, G.L. 2004. Annual changes in sea ice, chlorophyll a, and primary production in the Ross Sea, Antarctica. Deep Sea Research II, 51, 117–138.Google Scholar
Arrigo, K.R., Van Dijken, G.L., Ainley, D.G., Fahnestock, M.A. & Markus, T. 2002. The impact of the B-15 iceberg on productivity and penguin breeding success in the Ross Sea, Antarctica. Geophysical Research Letters, 29 (7), 10.1029/2001GL014160.Google Scholar
Atkinson, A., Siegel, V., Pakhomov, E. & Rothery, P. 2005. Long-term decline in krill stock and increase in salps within the Southern Ocean. Nature, 432, 100–103.Google Scholar
Barbraud, C. & Weimerskirch, H. 2001. Emperor penguins and climate change. Nature, 411, 183–186.CrossRefGoogle ScholarPubMed
Bester, M. & Hofmeyr, G. 2007. Seals. In Riffenburgh, B. , ed. Encyclopedia of the Antarctic. New York: Taylor & Francis, 877–880.Google Scholar
Bester, M.N. & Odendaal, P.N. 2000. Abundance and distribution of Antarctic pack ice seals in the Weddell Sea. In Davison, W., Howard-Williams, C. & Broady, P., eds. Antarctic ecosystems: models for wider ecological understanding Christchurch: Caxton Press, 51–55.Google Scholar
Bester, M.N., Hofmeyr, G.J.G., Kirkman, S.P., Chauke, L.F., De Bruyn, P.J.N., Ferreira, S.M., Makhado, A.B., Maswime, T.A.M., McIntyre, K.T., Mulaudzi, T.W., Munyai, F.M., Pistorius, P.A., Radzilani, P.M., Ramunasi, A.J., Tshithabane, N.H. & Wilkinson, I.S. 2006. The leopard seal at Marion Island, vagrant or seasonal transient? South African Journal of Wildlife Research, 36, 195–198.Google Scholar
Blix, A.S. & Nordoy, E.S. 2007. Ross seal (Ommatophoca rossii) annual distribution, diving behavior, breeding and moulting, off Queen Maud Land, Antarctica. Polar Biology, 30, 1449–1458.Google Scholar
Bonner, W.N. 1985. Impact of fur seals on the terrestrial environment at South Georgia. In Siegfried, W.R., Condy, P.R. & Laws, R.M., eds. Antarctic nutrient cycles and food webs Berlin: Springer, 641–646.CrossRefGoogle Scholar
Bonner, W.N. 1990. The natural history of seals New York: Facts on File Press, 196 pp.Google Scholar
Bornemann, H., Kreyscher, M., Ramdohr, S., Martin, T., Carlini, A.R., Sellmann, L. & Plötz, J. 2000. Southern elephant seal movements and Antarctic sea ice. Antarctic Science, 12, 3–15CrossRefGoogle Scholar
Burns, J.M., Castellini, M.A. & Testa, J.W. 1999. Movements and diving behavior of weaned Weddell seal (Leptonychotes weddellii) pups. Polar Biology, 21, 23–36.CrossRefGoogle Scholar
Burns, J.M., Trumble, S.J., Castellini, M.A. & Testa, J.W. 1998. The diet of Weddell seals in McMurdo Sound, Antarctica as determined from scat collections and stable isotope analysis. Polar Biology, 19, 272–282.CrossRefGoogle Scholar
Boyd, I.L. 1993. Pup production and distribution of breeding Antarctic fur seals (Arctocephalus gazella) at South Georgia. Antarctic Science, 5, 17–24.CrossRefGoogle Scholar
Cameron, M.F. & Siniff, D.B. 2004. Age-specific survival, abundance, and immigration rates of a Weddell seal (Leptonychotes weddellii) population in McMurdo Sound, Antarctica. Canadian Journal of Zoology, 82, 601–615.Google Scholar
Condy, P.R. 1978a. The distribution and abundance of southern elephant seals, Mirounga leonina, on the Prince Edward Islands. South African Journal of Antarctic Research, 8, 42–48.Google Scholar
Condy, P.R. 1978b. The distribution, abundance and annual cycle of fur seals Arctocephalus spp. on the Prince Edward Islands. South African Journal of Wildlife Research, 8, 159–168.Google Scholar
Condy, P.R. 1979. Annual cycle of the southern elephant seal Mirounga leonina (Linn.), at Marion Island. South African Journal of Zoology, 14, 95–102.CrossRefGoogle Scholar
Costa, D.P., Croxall, J.P. & Duck, D. 1989. Foraging energetics of Antarctic fur seals in relation to changes in prey availability. Ecology, 70, 596–606.CrossRefGoogle Scholar
Croxall, J.P. 1992. Southern ocean environmental changes: effects on seabird, seal and whale populations. Philosophical Transactions of the Royal Society of London, B338, 319–328.Google Scholar
Croxall, J.P., Trathan, P.N. & Murphy, E.J. 2002. Environmental change and Antarctic seabird populations. Science, 297, 1510–1514.CrossRefGoogle ScholarPubMed
Danieri, G.A. & Coria, N.R. 1992. The diet of Antarctic fur seals, Arctocephalus gazella, during the summer-autumn period at Mossman Peninsula, Laurie Island (South Orkneys). Polar Biology, 11, 565–566.Google Scholar
Dayton, P.K. 1989. Interdecadal variation in an Antarctic sponge and its predators from oceanographic climate shifts. Nature, 245, 1484–1486.Google Scholar
Ducklow, H.W., Baker, K., Martinson, D.G., Quetin, L.B., Ross, R.M., Smith, R.C., Stammerjohn, S.E., Vernet, M. & Fraser, W. 2007. Marine pelagic ecosystems: the West Antarctic Peninsula. Philosophical Transactions of the Royal Society of London, B362, 67–94.CrossRefGoogle Scholar
Emslie, S.D. & McDaniel, J.D. 2002. Adélie penguin diet and climate change during the middle to late Holocene in northern Marguerite Bay, Antarctic Peninsula. Polar Biology, 25, 222–229.CrossRefGoogle Scholar
Erickson, A.W., Siniff, D.B., Cline, D.R. & Hofman, R. 1971. Distributional ecology of Antarctic seals. In Deacon, G. , ed. Symposium on Antarctic ice and watermasses. Cambridge: SCAR, 55–75.Google Scholar
Forcada, J., Trathan, P.N., Reid, K. & Murphy, E.J. 2005. The effects of global climate variability in pup production of Antarctic fur seals. Ecology, 86, 2408–2417.CrossRefGoogle Scholar
Fraser, W.R. & Hofmann, E.E. 2003. A predator's perspective on causal links between climate change, physical forcing and ecosystem response. Marine Ecology Progress Series, 265, 1–15.CrossRefGoogle Scholar
Fraser, W.R. & Trivelpiece, W.Z. 1996. Factors controlling the distribution of seabirds: winter-summer heterogeneity in the distribution of Adélie penguin populations. Antarctic Research Series, 70, 257–272.CrossRefGoogle Scholar
Gian-Reto, W., Post, E., Convey, P., Menzel, A., Parmesan, C., Beebee, T.J.C., Fromentin, J.-M., Hoegh-Guldberg, O. & Bairlein, F. 2002. Ecological responses to recent climate change. Nature, 416, 389–395Google Scholar
Gilbert, J.R. & Erickson, A.W. 1977. Distribution and abundance of seals in the pack ice of the Pacific sector of the Southern Ocean. In Llano, G.A. , eds. Adaptations within Antarctic ecosystems. Washington, DC: Smithsonian Institution, 703–740.Google Scholar
Goldsworthy, S.D., Hindell, M.A. & Crowley, H.M. 1997. Diet and diving behaviour of sympatric fur seals Arctocephalus gazella and A. tropicalis at Macquarie Island. In Hindell, M.A. & Kemper, C., eds. Marine mammal research in the Southern Hemisphere. Vol. 1. Status, ecology and medicine. Chipping Norton: Surrey Beatty, 151–163.Google Scholar
Gon, O. & Heemstra, P.C. 1990. Fishes of the Southern Ocean Grahamstown, South Africa: J.L.B. Smith Institute of Ichthyology, 462 pp.CrossRefGoogle Scholar
Green, K., Burton, H.R. & Williams, R. 1989. The diet of Antarctic fur seals Arctocephalus gazella (Peters) during the breeding season at Heard Island. Antarctic Science, 1, 317–324CrossRefGoogle Scholar
Green, K., Williams, R. & Burton, H. 1991. The diet of the Antarctic fur seals Arctocephalus gazella during the late autumn and early winter around Heard Island. Antarctic Science, 3, 359–361.CrossRefGoogle Scholar
Hadley, G.L. 2006. Recruitment probabilities and reproductive costs for Weddell seals in Erebus Bay, Antarctica PhD thesis, Montana State University, Bozeman, 128 pp. [Unpublished].Google Scholar
Hadley, G.L., Rotella, J.J. & Garrott, R.A. 2007a. Evaluation of reproductive costs for Weddell Seals in Erebus Bay, Antarctica. Journal of Animal Ecology, 76, 448–458.Google Scholar
Hadley, G.L., Rotella, J.J. & Garrott, R.A. 2007b. Influence of maternal characteristics and oceanographic conditions on survival and recruitment probabilities of Weddell seals. Oikos 116, 601–613.Google Scholar
Hall, B.L., Hoelzel, A.R., Baroni, C., Denton, G.H., Le Boeuf, B.J., Overturf, B. & Töpf, A.L. 2006. Holocene elephant seal distribution implies warmer-than-present climate in the Ross Sea. Proceedings of the National Academy of Sciences of the United States, 103, 10213–10217.CrossRefGoogle ScholarPubMed
Hindell, M.A., Bradshaw, C.J.A., Sumner, M.D., Michael, K.J. & Burton, H.R. 2003. Dispersal of female elephant seals and their prey consumption during austral summer: relevance to management and oceanographic zones. Journal of Animal Ecology, 40, 703–715.Google Scholar
Hiruki, L.M., Schwartz, M.K. & Boveng, P.L. 1999. Hunting and social behaviour of leopard seals (Hydrurga leptonyx) at Seal Island, South Shetland Islands, Antarctica. Journal of Zoology London, 249, 97–109.Google Scholar
Ingolfsson, O., Hjort, C., Berkman, P.A., Bjorck, S., Colhoun, E., Goodwin, I.D., Hall, B., Hirakawa, K., Melles, M., Moller, P. & Prentice, M.L. 1998. Antarctic glacial history since the last glacial maximum: an overview of the record on land. Antarctic Science, 10, 326–344.CrossRefGoogle Scholar
IPCC . 2007. Climate Change 2007 - the physical science basis. Ch. 4. Observations: snow, ice and frozen ground. Cambridge: Cambridge University Press, 337–385.Google Scholar
Jacobs, S. 2006. Observations of change in the Southern Ocean. Philosophical Transactions of the Royal Society, A364, 1657–1681.Google Scholar
Jacobs, S.S. & Comiso, J.C. 1989. Sea ice and oceanic processes on the Ross Sea continental shelf. Journal of Geophysical Research, 94, 18195–18211.Google Scholar
Jacobs, S.S. & Giulivi, C.F. 1998. Interannual ocean and sea ice variability in the Ross Sea. Antarctic Research Series, 75, 135–150.Google Scholar
Jonker, F.C. & Bester, M.N. 1994. The diving behaviour of adult southern elephant seal, Mirounga leonina, cows from Marion Island. South African Journal of Antarctic Research, 24, 75–93.Google Scholar
Keith, M., Bester, M.N., Bartlett, P.A. & Baker, D. 2001. Killer whales (Orcinus orca) at Marion Island, Southern Ocean. African Zoology, 36, 163–175.CrossRefGoogle Scholar
Kim, S.L., Conlan, K., Malone, D.P. & Lewis, C.V. 2005. Possible food caching and defense in the Weddell seal: observations from McMurdo Sound, Antarctica. Antarctic Science, 17, 71–72.CrossRefGoogle Scholar
Kirkman, S.P., Bester, M.N., Pistorius, P.A., Hofmeyr, G.J.G., Jonker, F.C., Owen, R. & Stryydom, N. 2003a. Variation in the timing of moult in southern elephant seals at Marion Island. South African Journal of Wildlife Research, 33, 79–84.Google Scholar
Kirkman, S.P., Bester, M.N., Makhado, A.B. & Pistorius, P.A. 2003b. Female attendance patterns of Antarctic fur seals at Marion Island. African Zoology, 38, 402–405.Google Scholar
Kirkman, S.P., Bester, M.N., Hofmeyr, G.J.G., Jonker, F.C., Pistorius, P.A., Owen, R. & Stryydom, N. 2004. Variation in the timing of the breeding haulout of female southern elephant seals at Marion Island. Australian Journal of Zoology, 52, 379–388CrossRefGoogle Scholar
Klages, N.T.W. & Bester, M.N. 1998. The fish prey of fur seals Arctocephalus spp. at subantarctic Marion Island. Marine Biology, 131, 559–566.CrossRefGoogle Scholar
Kock, K.-H. 1992. Antarctic fish and fisheries Cambridge: Cambridge University Press, 359 pp.Google Scholar
Kooyman, G.L. 1965. Leopard seals of Cape Crozier. Animals, 6, 59–63.Google Scholar
Laidre, K.L., Stirling, I., Lowry, L.F., Wiig, Ø., Heide-Jørgensen, M.-P. & Ferguson, S.H. In press. Quantifying the sensitivity of Arctic marine mammals to climate-induced habitat change. Ecological ApplicationsGoogle Scholar
La Mesa, M., Eastman, J.T. & Vacchi, M. 2004. The role of notothenioid fish in the food web of the Ross Sea shelf waters: a review. Polar Biology, 27, 321–338.CrossRefGoogle Scholar
Laws, R.M. 1956. The elephant seal (Mirounga leonina Linn.). II. General, social and reproductive behaviour. Falkland Islands Dependencies Survey, Scientific Reports, No. 13, 1–88.Google Scholar
Laws, R.M. 1977. The significance of vertebrates in the Antarctic marine ecosystem. In Llano, G.A. , ed. Adaptations within Antarctic ecosystems Washington, DC: Smithsonian Institution, 411–438.Google Scholar
Learmonth, J.A., Macleod, C.D., Santos, G.L., Pierce, M.B., Crick, H.Q.P. & Robinson, R.A. 2006. Potential effects of climate change on marine mammals. Oceanography and Marine Biology, 44, 431–464.Google Scholar
LeBoeuf, B.J., Ainley, D.G. & Lewis, T.J. 1974. Elephant seals on the Farallones: population structure of an incipient breeding colony. Journal of Mammology, 55, 370–385.CrossRefGoogle Scholar
Ledley, T.S. 1997. A possible ENSO signal in the Ross Sea. Geophysical Research Letters, 24, 3253–3256.Google Scholar
Lescroël, A. & Bost, C.-A. 2006. Recent decrease in gentoo penguin populations at Iles Kerguelen. Antarctic Science, 18, 171–174.Google Scholar
Matthews, L.H. 1977. Penguins, whalers and sealers: a voyage of discovery New York: Universe Books, 165 pp.Google Scholar
McMahon, C.R. & Burton, H.R. 2005. Climate change and seal survival: evidence for environmentally mediated changes in elephant seal, Mirounga leonina, pup survival. Proceedings of the Royal Society of London, B272, 923–928.Google Scholar
Murphy, E.J., Watkins, J.L., Trathan, P.N., Reid, K., Meredith, M.P., Thorpe, S.E., Johnston, N.M., Clarke, A., Tarling, G.A., Collins, M.A., Forcada, J., Shreeve, R.S., Atkinson, A., Korb, R., Whitehouse, M.J., Ward, P., Rodhouse, P.G., Enderlein, P., Hirst, A.G., Martin, A.R., Hill, S.L., Staniland, I.J., Pond, D.W., Briggs, D.R., Cunningham, N.J. & Fleming, A.H. 2007. Spatial and temporal operation of the Scotia Sea ecosystem: a review of large-scale links in a krill centered food web. Philosophical Transactions of the Royal Society, B362, 113–148.Google Scholar
Nordøy, E.S. & Blix, A.S. 2001. The previously pagophilic Ross seal is now rather pelagic. Proceeding VIII International Biology Symposium, Amsterdam, the Netherlands, August 27–September 1, S5014.Google Scholar
Pakhomov, E.A. & Perissinotto, R. 1996. Antarctic neritic krill Euphausia crystallorophias: spatio-temporal distribution, growth and grazing rates. Deep-Sea Research I, 43, 59–87.Google Scholar
Parkinson, C.L. 2002. Trends in the length of the Southern Ocean sea ice season, 1979–99. Annals of Glaciology, 34, 435–440.Google Scholar
Pauly, D., Christensen, V., Dalsgaard, J., Froese, R. & Torres, F. Jr 1998. Fishing down marine food webs. Science, 279, 860–863.Google Scholar
Pauly, D., Watson, R. & Alder, J. 2005. Global trends in world fisheries: impacts on marine ecosystems and food security. Philosophical Transaction of the Royal Society of London, B360, 5–12.Google Scholar
Pitman, R.L. & Ensor, P. 2003. Three forms of killer whales (Orcinus orca) in Antarctic waters. Journal of Cetacean Research and Management, 5, 1–9.Google Scholar
Ponganis, P.J. & Stockard, T.K. 2007. The Antarctic toothfish: How common a prey for Weddell Seals? Antarctic Science, 19, 441–442.Google Scholar
Proffitt, K.M., Garrott, R.A., Rotella, J.J., Siniff, D.B. & Testa, J.W. 2007. Exploring linkages between abiotic oceanographic processes and a top-trophic predator in an Antarctic ecosystem. Ecosystems, 10, 119–126.CrossRefGoogle Scholar
Reid, K. & Croxall, J.P. 2001. Environmental response of upper trophic level predators reveals a system change in an Antarctic marine ecosystem. Proceedings of the Royal Society of London, B268, 377–384.CrossRefGoogle Scholar
Reid, K., Davis, D. & Staniland, I.J. 2006. Spatial and temporal variability in the fish diet of the Antarctic fur seal (Arctocephalus gazella) in the Atlantic sector of the Southern Ocean. Canadian Journal of Zoology, 84, 1025–1037.Google Scholar
Reid, K., Hill, S.L., Diniz, T.C.D. & Collins, M.A. 2005. Mackerel ice fish Champsocephalus gunnari in the diet of upper trophic level predators at South Georgia: implications for fisheries management. Marine Ecology Progress Series, 305, 153–161.Google Scholar
Ribic, C.A., Fraser, W.R. & Ainley, D.G. 1991. Habitat selection by marine mammals in the marginal ice zone. Antarctic Science, 3, 181–186.Google Scholar
Riedman, M. 1990. The pinnipeds, seals, sea lion, and walruses Berkeley, CA: University of California Press, 439 pp.CrossRefGoogle Scholar
Robinson, S.A., Goldsworthy, S.G., Van Den Hoff, J. & Hindell, M.A. 2002. The foraging ecology of two sympatric fur seal species, Arctocephalus gazella and Arctocephalus tropicalis, at Macquarie Island during the austral summer. Marine and Freshwater Research, 53, 1071–1082.CrossRefGoogle Scholar
Rogers, T., Hogg, C. & Irvine, A. 2005. Spatial movement of adult leopard seals (Hydrurga leptonyx) in Prydz Bay, eastern Antarctica. Polar Biology, 28, 456–463.CrossRefGoogle Scholar
Ross, P.S. 2002. The role of immunotoxic environmental contaminants in facilitating the emergence of infectious diseases in marine mammals. Human and Ecological Risk Assessment, 8, 277–292Google Scholar
Russell, J.L., Dixon, K.W., Gnanadesikan, A., Stouffer, R.J. & Toggweiler, J.R. 2006. The Southern Hemisphere westerlies in a warming world: propping open the door to the deep ocean. Journal of Climate, 19, 6382–6390.CrossRefGoogle Scholar
Siniff, D.B. & Bengtson, J.L. 1977. Observations and hypotheses concerning the interactions among crabeater seals and leopard seals and killer whales. Journal of Mammalogy, 58, 414–416.CrossRefGoogle Scholar
Siniff, D.B., Stirling, I., Bengtson, J.L. & Reichle, R.A. 1979. Social and reproductive behaviour of crabeater seals (Lobodon carcinophagus) during the austral spring. Canadian Journal of Zoology, 57, 2243–2255.CrossRefGoogle Scholar
Siniff, D.B. & Stone, S. 1985. The role of the leopard seal in the trophodynamics of the Antarctic marine ecosystem. In Siegfried, W.R., Condy, P.R. & Laws, R.M., eds. Antarctic nutrient cycles and food webs Berlin: Springer, 498–515.Google Scholar
Smith, R.C., Ainley, D., Baker, K., Domack, E., Emslie, S., Fraser, B., Kennett, J., Leventer, A., Mosley-Thompson, E., Stammerjohn, S. & Vernet, M. 1999. Marine ecosystem sensitivity to climate change. BioScience, 49, 393–404.CrossRefGoogle Scholar
Smith, T.G., Siniff, D.B., Reichle, R. & Stone, S. 1981. Coordinated behavior of killer whales (Orcinus orca) hunting a crabeater seal, Lobodon carcinophagus. Canadian Journal of Zoology, 59, 1185–1189.CrossRefGoogle Scholar
Stammerjohn, S.E., Martinson, D.G., Smith, R.C., Yuan, X. & Rind, D. 2008. Trends in Antarctic annual sea ice retreat and advance and their relation to ENSO and Southern Annular Mode variability. Journal of Geophysical Research, 113, 10.1029/2007JC004239.CrossRefGoogle Scholar
Stirling, I. & Parkinson, C.L. 2006. Possible effects of climate warming on selected populations of polar bears (Ursus maritimus) in the Canadian Arctic. Arctic, 59, 261–275.Google Scholar
Testa, J.W., Oehlert, G., Ainley, D.J., Bengston, J.L., Siniff, D.B., Laws, R.M. & Rounsevell, D. 1991. Temporal variability in Antarctic marine ecosystems: periodic fluctuations in the phocid seals. Canadian Journal of Fisheries and Aquatic Sciences, 48, 631–639.CrossRefGoogle Scholar
Testa, J.W., Siniff, D.B., Croxall, J.P. & Burton, H.R. 1990. A comparison of reproductive parameters among three populations of Weddell seals (Leptonychotes weddellii). Journal of Animal Ecology, 59, 1165–1175.CrossRefGoogle Scholar
Thomas, J., Demaster, D., Stone, S. & Andriashek, D. 1980. Observations of a newborn Ross seal pup (Ommatophoca rossi) near the Antarctic Penninsula. Canadian Journal of Zoology, 58, 2156–2158.Google Scholar
Van Den Hoff, J. & Morrice, M.G. 2008. Sleeper shark (Somniosus antarcticus) and other bite wounds observed on southern elephant seals (Mirounga leonina) at Macquarie Island. Marine Mammal Science, 24, 239–247.Google Scholar
Visser, I.N., Smith, T.G., Bullock, I.D., Green, G.D., Carlsson, O.G.L. & Imberti, S. 2008. Antarctic peninsula killer whales (Orcinus orca) hunt seals and a penguin on floating ice. Marine Mammal Science, 24, 225–234.Google Scholar
Ward, J.R. & Lafferty, K.D. 2004. The elusive baseline of marine disease: are diseases in ocean ecosystems increasing? PLoS Biology, 2, e120.Google Scholar
Weimerskirch, H., Inchausti, P., Guinet, C. & Barbraud, C. 2003. Trends in bird and seal populations as indicators of a system shift in the Southern Ocean. Antarctic Science, 15, 1–8.Google Scholar
Worm, B. & Meyers, R.A. 2003. Meta-analysis of cod-shrimp interactions reveals top-down control in oceanic food webs. Ecology, 84, 162–173.Google Scholar
Zwally, H.J., Comiso, J.C., Parkinson, C.L., Cavalieri, D.J. & Gloersen, P. 2002. Variability of Antarctic sea ice 1979–1998. Journal of Geophysical Research, 107, 10.1029/2000JC000733.Google Scholar