Progress 10/01/99 to 09/30/09
Outputs
The distribution of seabirds and pinnipeds and their relationship to physical and biological variables were investigated within the U.S. Southern Ocean Global Ocean Ecosystem Dynamics progream along a study grid near Marguerite Bay on the West Antarctic Peninsula during late fall (April-May) and winter (July-August) cruises conducted during 2001 and 2002. Analysis of the 2002 datawas started in 2004. During the 2002 cruises, ice concentrationsand types varied considerably throughout the area. The sourthern sector of the grid, south of Marguerite Bay and offshore of ALexander Island, was characterized by first-year, vast floes greater than 1m thick. Overall, there was very little open water in this region of the grid.In general, in the northern and central sectors, there was a gradient from large to small floes and cake ice moving offshore as ooen ocean swells were absorbed by the pack, breaking the sea-ice into smaller pieces. Offshore surveys in the northern and
central sectors brought the ship within just a few kilometers of the ice-edge. Ice wasan important habitat variable that structured the seabird assemblage in the study area. In the northern, ice-free portion of the study area species known to forage in open-water habitat,such as Cape Petrel, Southern Fulmar, Albatross spp., Wilsons Storm Petrel and Blue Petrel, were observed during sprint 2002. Within the open water there appeared to be a concentration of open water species offshore and adjacent to the northern end of Adelaide Island,perhaps in association withthe intrusion of Antarctic Circumpolar Deep Water observed by physical oceanographers during the cruise. Open water species also appeared to be concentrated near shore along the southwestern shroe of Adelaide Island. During the winter 2002, virtually all species present in the pack ice were those adapted to foraging in ice habitat.Adelie Penguin, Antarctic Petrel, and Snow Petrel abundances were greater in the northern portion
of the grid. Crabeater Seals were more abundant in the southern sector of the grid. The distribution of top predators appears to be giving a clear signal that certain areas within the grid are sites of important processes that influence the availability of preyto predators.
Impacts
Sea ice is a key to structuring the community of Antarctic seabirds. Any changes in how sea ice forms, such as due to global climate change, will affect these species. For example, delays in sea ice development may allow seabirds, and seals access to biologically important areas for longer periods of time, thereby increasing predation on zooplankton and fish.
Publications
- No publications reported this period
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Progress 01/01/04 to 12/31/04
Outputs
The distribution of seabirds and pinnipeds and their relationship to physical and biological variables were investigated within the U.S. Southern Ocean Global Ocean Ecosystem Dynamics program along a study grid near Marguerite Bay on the West Antarctic Peninsula during late fall (April-May) and winter (July-August) cruises conducted during 2001 and 2002. Analysis of the 2002 data was started in 2004. During the 2002 cruises, ice concentrations and types varied considerably throughout the area. The southern sector of the grid, south of Marguerite Bay and offshore of Alexander Island, was characterized by first-year, vast floes greater than 1m thick. Overall there was very little open water in this region of the grid. In general in the northern and central sectors, there was a gradient from large to small floes and cake ice moving offshore as open ocean swells were absorbed by the pack, breaking the sea-ice into smaller pieces. Offshore surveys in the northern and
central sectors brought the ship within just a few kilometers of the ice-edge. Ice was an important habitat variable that structured the seabird assemblage in the study area. In the northern, ice-free portion of the study area species known to forage in open-water habitat, such as Cape Petrel, Southern Fulmar, Albatross spp., Wilsons Storm Petrel and Blue Petrel, were observed during spring 2002. Within the open water there appeared to be a concentration of open water species offshore and adjacent to the northern end of Adelaide Island, perhaps in association with the intrusion of Antarctic Circumpolar Deep Water observed by physical oceanographers during this cruise. Open water species also appeared to be concentrated near shore along the southwestern shore of Adelaide Island. During the winter 2002, virtually all species present in the pack ice were those adapted to foraging in ice habitat. Adelie Penguin, Antarctic Petrel, and Snow Petrel abundances were greater in the northern
portion of the grid. Crabeater Seals were more abundant in the southern sector of the grid. The distribution of top predators appears to be giving a clear signal that certain areas within the grid are sites of important processes that influence the availability of prey to predators.
Impacts
Sea ice is a key to structuring the community of Antarctic seabirds. Any changes in how sea ice forms, such as due to global climate change, will affect these species. For example, delays in sea ice development may allow seabirds and seals access to biologically important areas for longer periods of time, thereby increasing predation on zooplankton and fish.
Publications
- Chapman, E.W., C.A. Ribic, and W. R. Fraser. 2004. The distribution of seabirds and pinnipeds in Marguerite Bay and their relationship to physical features during austral winter 2001. Deep Sea Research Part II 51: 2261-2278.
- Gauthier-Clerc, M., J.-P. Gendner, C.A. Ribic, W.R. Fraser, E.J. Woehler, S. Descamps, C. Gilly, C. Le Bohec, and Y. Le Maho. 2004. Long-term effects of flipper-bands on penguins. Proceedings of the Royal Society B (Suppl.), published online, doi:10.1098/rsbl.2004.0201.
- Ainley, D.G., C.A. Ribic, G. Ballard, S. Heath, I. Gaffney, B.J. Karl, K. Barton, P. Wilson, and S. Webb. 2004. Geographic structure of Adelie Penguin populations: overlap in colony-specific foraging areas. Ecological Monographs 74: 159-178.
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Progress 01/01/03 to 12/31/03
Outputs
We investigated the temporal and spatial variability in the diet of chick-provisioning adult Adelie Penguins breeding at all colonies within one isolated cluster in the southwestern Ross Sea, Antarctica, 1994-2000. Diet was described on the basis of both conventional means (stomach sample analysis) and stable isotope analysis of chick tissues (toenails of older chicks killed by South Polar Skuas. Penguin diet composition was very similar among the 4 study colonies. Diet composition among colonies of the study cluster varied as a function of year, time within the year, and percent of foraging area covered by sea ice, but did not vary by colony location. Size of fish eaten varied by year but not by colony; one colony consumed slightly younger krill in one year. The stable isotope analysis revealed that diet at one colony where conventional sampling was not possible was also similar in composition to the others. Our results confirm that sea ice importantly affects diet
composition of this species in neritic waters. Data analysis for this project will continue. The distribution of seabirds and pinnipeds and their relationship to physical and biological variables were investigated within the U.S. Southern Ocean Global Ocean Ecosystem Dynamics program along a study grid near Marguerite Bay on the West Antarctic Peninsula during late fall (April-May) and winter (July-August) cruises conducted during 2001 and 2002. Analysis of the 2001 data was started in 2003. During the late fall 2001, seabirds were associated with water mass structure. Most of the birds had higher densities in Inner Shelf Water, particularly where a coastal current was present. The index of zooplankton abundance was significantly higher in the Inner Shelf Water compared to the other water masses. Seabirds were also associated with variability in bottom depth, suggesting that processes associated with bathymetry may have been important in structuring bird distributions. After the
development of pack ice, seabirds were primarily associated with ice characteristics (e.g., ice concentration, ice type) rather than the water column environment, while crabeater seals continued to be associated with Inner Shelf Water. Though the zooplankton index values in the winter were low compared to the late fall values, the index of zooplankton abundance was still highest in the Inner Shelf Water. Spatial variability within a transect was apparent. On a single transect in the late fall in the Inner Shelf Water, there was concurrence of the zooplankton index and seabird and pinniped abundances. At the beginning of the transect where the zooplankton index was low, seabird and pinniped abundances were low while towards the end of the transect where the zooplankton index increased, the top predator abundances were higher. Data analysis of the 4 cruises done in 2001 and 2002 will continue.
Impacts
Sea ice has an important effect on the ecology of Antarctic seabirds. Any changes in how sea ice forms, such as due to global climate change, will affect these species. For example, delays in sea ice development may allow seabirds and seals access to biologically-important areas for longer periods of time, thereby increasing predation on zooplankton and fish.
Publications
- Woehler, E. J., M.J. Riddle, and C. A. Ribic. 2003. Long-term population trends in southern giant petrels in east Antarctica. IN Antarctic biology in a global context (A.H.L. Huiskes, W.W.C. Gieskes, J. Rozema, R.M.L. Schorno, S.M. Van der Vies, and W.J. Wolff, eds.), Backhuys Publishers, Leiden, The Netherlands, pp. 290-295.
- Ainley, D. G., G. Ballard, K.J. Barton, B. J. Karl, G. H. Rau, C. A. Ribic, and P. R. Wilson. 2003. Spatial and temporal variation of diet within a presumed metapopulation of Adelie penguins. Condor 105:95-106.
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Progress 01/01/02 to 12/31/02
Outputs
Project 1: Ross Island: Telemetry data that was collected 1997-2001 were analyzed and papers submitted for publication. Project 2: Southern Ocean surveys: Our primary hypothesis is that the winter distribution and abundance of predators is predictable, and is determined by unique habitat features that facilitate access to dependable prey resources. We further hypothesize that these habitat features are associated with 1) a cyclonic gyre on the central Antarctic Peninsula continental shelf that retains krill for extended periods of time, and 2) across-shelf canyons that act as a conduit for the transport of CDW and the intrusion of oceanic species, and results in enhanced prey diversity and biomass. To test these hypotheses and predictions we will 1) quantify the distribution and abundance of predators within the study area, and seek mechanistic explanations that account for observed variability, 2) describe the winter foraging ecology of these predators, in particular
their impacts on krill life history stages and size classes, and 3) develop food web models that estimate energy flows to each major predator group. This project has two primary tasks that capitalize on nesting small-scale process studies within large-scale surveys. The first is to assess the large- scale distribution, abundance and habitat use of seabirds within the study area. The second is to use a scaled down approach to investigate seabird distributions, diet composition and foraging behavior. The large scale distribution and abundance data will be collected using strip-transect (300 m width). Data on the distribution, movements and habitat use of a key, krill-dependent winter apex predator will be obtained by attaching ARGOS-linked satellite transmitters (PTTs) to Adelie penguins. Diet composition will be determined by scat analysis and stomach lavage. The field work for the project, four cruises, has been completed as of September 2002. Data entry and proofing have been
started.
Impacts
By understanding the causes of natural fluctuations in penguin populations, we will be able to better predict the impact of global climate change.
Publications
- Ballard, G., D.G. Ainley, C.A. Ribic, and K. Barton. 2001. Effect of instrument attachment on foraging trip duration and nesting success of Adelie penguins. Condor 103: 481-490.
- Woehler, E.J, J. Cooper, J.P. Croxall, W.R. Fraser, G.L. Kooyman, G.D. Miller, D.C. Nel, D.L. Patterson, H-U. Peter, C.A. Ribic, K. Salwicka, W.Z. Trivelpiece, and H. Weimerskirch. 2001. A statistical assessment of the status and trends of Antarctic and Subantarctic seabirds. Report to the Scientific Committee on Antarctic Research Bird Biology Subcommittee, Scientific Committee on Antarctic Research, Tasmania, Australia.
- Ainley, D. G., G. Ballard, K.J. Barton, B. J. Karl, G. H. Rau, C. A. Ribic, and P. R. Wilson. 2003.Spatial and temporal variation of diet within a presumed metapopulation of Adelie penguins. Condor 105:95-106.
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Progress 01/01/01 to 12/31/01
Outputs
We investigated the foraging ecology of Adelie Penguins nesting in three colonies that differed in size by 3 orders of magnitude: Cape Crozier (140,000 pair), Cape Bird (38,000 pair), and Cape Royds (3,600 pair). We used PIT tags and a computerized weighbridge to determine foraging trip duration; radio telemetry to determine foraging trip distance; and time-depth-recorders (TDRs) to determine foraging depth. Data are still being collected at Ross Island, Antarctica. This season, the main problem for the penguins has been the extensive fast ice in McMurdo Sound, and the extensive pack ice in the larger Ross Sea. This state of affairs resulted from a lack of katabatic winds during the winter and spring. The result of these conditions has been an almost complete reproductive failure at all the colonies. Data analysis has started of previously collected data. We founds that foraging trip duration, foraging trip distance, and foraging depth increased over time during the
chick-provisioning period and also increased with colony size. We hypothesize that the foraging of the penguins (perhaps with help from minke whales) is decreasing the availability of prey (krill, fish), both horizontally and vertically near to colonies, either by direct depletion or by interference competition. In that the penguins' maximum diving depth is limited by light level (as determined by light meters on the TDRs), the intensive foraging activity near to colonies may be forcing the prey to descend into the darker portion of the water column.
Impacts
By understanding the causes of natural fluctuations in penguin colony size and productivity, we will be able to better predict the impact of global climate change on the Antarctic ecosystem.
Publications
- Ballard, G., D.G. Ainley, C.A. Ribic, and K. Barton. 2001. Effect of instrument attachment on foraging trip duration and nesting success of Adelie penguins. Condor 103: 481-490.
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Progress 01/01/00 to 12/31/00
Outputs
Project 1: Ross Island. Telemetry data were collected 26 Dec. 2000-14 Jan. 2001 on Ross Island. Adelie Penguins from 4 colonies were equipped with standard radios and their feeding areas identified using triangulations collected from 5 listening posts. Data analysis continues. Project 2: Southern Ocean Surveys. The primary objective of our project is to evaluate the hypothesis that the winter distribution and abundance of predators is predictable, and is determined by unique habitat features that facilitate access to dependable prey resources. We further hypothesize that these habitat features are associated with 1) a cyclonic gyre on the central Antarctic Peninsula continental shelf that retains krill for extended periods of time, and 2) across-shelf canyons that act as a conduit for the transport of CDW and the intrusion of oceanic species, and results in enhanced prey diversity and biomass. To test these hypotheses we will: 1) Quantify the distribution and
abundance of predators within the study area, and seek mechanistic explanations that account for observed variability. 2) Describe the winter foraging ecology of these predators, in particular their use of various krill life history stages and size classes. 3) Develop food web models that estimate energy flows to the major predator groups. Our general approach on nesting small-scale process studies within large-scale surveys. The large-scale surveys will involve line and strip transects, acoustics and net tows. These methods will be used to obtain data on the distribution, abundance and species diversity of predators across the study area. Additional data on the distribution, movements and habitat use of key, krill-dependent winter apex predators will be obtained by attaching ARGOS-linked satellite transmitters (PTTs) to Adelie penguins. The process studies will involve collections of predator scat and stomach contents, localized apex predator censuses, and surveys based on under-ice
diving operations and through-the-ice acoustics and net tows. These methods will be used to obtain data on predator foraging ecology and behavior, and to determine their distribution, abundance and species diversity at smaller spatial and temporal scales within the process study grid. The first cruise will occur April-May 2001.
Impacts
(N/A)
Publications
- No publications reported this period
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