Newsletter of the SCAR Global Change Programme, No. 4, February 1999

Southern Ocean Global Ocean Ecosystem Dynamics Program

Submitted by The SO GLOBEC Planning Group*

The Global Ocean Ecosystem Dynamics (GLOBEC) program has as a primary objective understanding marine population variability in response to environmental variability. The International GLOBEC program has identified the Southern Ocean as a region where the objectives of GLOBEC can be met. To foster the development of SO GLOBEC, the International GLOBEC Science Steering Committee appointed a Planning Group in 1996 to oversee the development of the program. However, planning for SO GLOBEC has been ongoing for some time and was initially developed as focused efforts within national GLOBEC programs.

The unique characteristics of the Antarctic marine food web make this system ideal for addressing the main objectives of GLOBEC. A single key species, Antarctic krill (Euphausia superba), provides the mechanism for linking environmental variability and primary production processes with top predator species, such a penguins and seals. Moreover, the linkage with the environment is strong through the dependence of many of the components of this food web on sea ice during some or all of their life history. These unique characteristics make the Antarctic marine ecosystem vulnerable to changes in environmental conditions, or to resource exploitation. However, predictions of how this system will respond to environmental variability and climate change first require understanding of the cycles of natural population variability, especially in those that occur in response to physical variability.

Within the SO GLOBEC program the role of sea ice and winter processes in determining krill recruitment and subsequent survival and/or breeding success of krill-dependent top predator species has been recognized to be of paramount importance. While the inclusion of winter processes has been part of SO GLOBEC planning since the outset, recent studies have indicated that coverage of this part of the year is critical to understanding the physical-biological coupling of the Antarctic ecosystem. These current ideas and hypothesis about workings of the Antarctic marine ecosystem have been incorporated into the SO GLOBEC Implementation Plan.

The SO GLOBEC program will focus on Antarctic krill as the target species; however, this focus includes krill habitat, prey, predators and competitors, such as salps. The SO GLOBEC program will be a year-round study, with emphasis on winter processes. The key science questions for SO GLOBEC for krill are: 1) What key factors affect the successful reproduction of krill between seasons?; 2) What key physical processes influence krill larval survival and subsequent recruitment to the adult population between seasons?; 3) What are krill's seasonal food requirements in respect to energetic needs and distribution and type of food?; and 4) What are the geographical variations in krill distribution in relation to the between- and within-season variability in the physical environment? Those for top predators are how does: 1) winter distribution/foraging ecology relate to characteristics of the physical environment and prey; 2) breeding season foraging ecology relate to abundance/dispersion and characteristics of krill; and 3) year-to-year variation in population size and breeding success relate to distribution, extent, and nature of sea ice and krill availability and cohort strength.

Field activities related to SO GLOBEC will begin during the 1999/2000 Antarctic field season and will consist of focused studies in limited regions that will provide information related to the SO GLOBEC science questions. Potential studies within this time frame are a March-May 1999 German cruise and three Australian cruises in 1999 (July-August, September-October, December) that will focus on demographic features of krill population. The Australian cruises will provide a limited time series that will document winter to summer changes in part of the Antarctic marine ecosystem. The British Antarctic Survey core program at South Georgia in 1999/2000 will be focused on various aspects of krill-predator interactions. The results of these field efforts will be incorporated into planning for the larger SO GLOBEC field effort. The primary field activities for SO GLOBEC will be concentrated in the Antarctic Peninsula area and the 70 E region, encompass the summer and winter seasons, and will take place in 2000/2001. It has been determined that sufficient ship resources will be available within this time frame to provide year-round coverage in the Antarctic Peninsula region and seasonal coverage, especially in the winter, in the 70 E region. The next effort for SO GLOBEC will consist of focused regional planning meetings that will design the field study efforts. These meetings will take place within the latter part of 1998 or early 1999.

The SO GLOBEC field effort will provide an opportunity to obtain distribution and abundance estimates of marine mammals in the Antarctic Peninsula and 70 E regions that are concurrent with other environmental and biological data sets. Thus, the SO GLOBEC program is currently undertaking discussions with the International Whaling Commission (IWC), concerning IWC participation in SO GLOBEC field activities. Participation by IWC would benefit the science objectives of SO GLOBEC and coordination with SO GLOBEC by IWC would further the IWC interests in determining potential effects of climate change on cetaceans and foraging ecology of baleen whales.

Information and updates on the SO GLOBEC program can be obtained by accessing or

(*J.Croxall, M. Fukuchi, E.Hofmann, M.Huntley, S.Kim, V.Marin, S.Nicol, D.Miller, V.Smetacek, J.Stromberg)