H-10 



RESEARCH PROGRAMMES 



of the light regime which alternates between complete perpetual darkness in winter to 

 continuous daylight during summer; (c) the nearly uniform sea temperature which varies little 

 with depth or season; (d) the extensive cloud cover; and (e) the circumpolarity of the surface 

 waters and the dominant influence of the circumpolar fronts (El-Sayed and Green, 1974). It is 

 in response to the physical/chemical environments that the Antarctic organisms have developed 

 their characteristic features. For example, the marked seasonal variations in incoming solar 

 radiation have a pronounced effect on plant and animal life: the rise and fall of primary produc- 

 tion in the circum-Antarctic waters appears to be a direct response to the amount of energy 

 received (El-Sayed, 1971). 



More is known about large scale surface discontinuities such as the polar front (or 

 Antarctic Convergence) and Antarctic Divergence than about small scale discontinuities. The 

 fact that most species appear to have a circumpolar distribution and that those south of the 

 polar front are distinct from those to the north suggests that the biogeography of the Southern 

 Ocean is governed largely by the dynamics of ocean circulation. 



The general pattern of ice cover, arrangement of water masses, distribution of currents, 

 water column structure and nutrient salts regime are known, and it is clear from recent work 

 that there is great variability in these parameters, both seasonally and from year to year, thaYi 

 had previously been thought. The extent of ice cover in the Southern Ocean varies with the 

 season and is influenced by wind; the production of cold dense bottom water may be sporadic; 

 there is considerable variation in currents and mass transport within the West Wind Drift; a 

 well defined clockwise eddy exists in the Weddell Sea; primary production and krill abundance 

 vary considerably from region to region, and so on. 



This newly appreciated variability is currently the focus of great interest by the physical 

 oceanographers and meteorologists participating in the ISOS programme (International 

 Southern Ocean Studies). In the BIOMASS programme there is a need for independent research 

 programmes in physical/chemical oceanography, and for conducting a systematic series of 

 environmental studies on the physics, chemistry and biology of the Southern Ocean that is 

 oriented primarily towards an understanding of the Antarctic marine ecosystem. These 

 environmental studies will need to be closely coupled to studies of the living resources and 

 closely co-ordinated from one ship to another and from ship to shore to satellite. 



Measurements by current profilers and moored current meters, as well as frequent STD 

 casts, should provide information on vertical transport and stability and on advection. A 

 knowledge, from sampling, of the spatial distribution and density of krill swarms in relation to 

 the abundance and size spectra of phytoplankton, should further our understanding of the 

 reactions of a krill swarm to its food base and the effects of grazing on the phytoplankton. 

 Besides quantitative sampling for kriU within and outside swarms, biological observations should 

 include controlled, quantitative plankton sampling for analyses of phytoplankton and 

 zooplankton abundance and composition in different depth layers and at different times of day 

 and night. Recordings of vertical distribution of chlorophyll and detritus provide additional 

 information on the biotic environment of krill. These studies should be carried out at several 

 selected places, mainly in different areas of high krill concentrations at the ice edge, in the 

 neritic zone of the Antarctic Peninsula and of the Antarctic islands, as well as in the open ocean 

 of the West Wind Drift, the East Wind Drift and the upwelling zones. If possible they should be 

 repeated at different seasons. 



2.3.2 Objectives 



The objectives of this section are to provide relevant information on the physical/chemical 

 components of the marine ecosystem in the Southern Ocean as they affect the living resources 

 and, in particular, to: 



