A.     Atkinson                                                                         


British Antarctic Survey,

High Cross,

Madingley Rd,

Cambridge CB3 OET


                                                version 13.9.01 uksoglobec1



In order to achieve an understanding of ecosystems sufficient to predict how they might respond to change, their major interactions need to be identified and examined. To make this objective tractable, GLOBEC has selected “keystone” species for study. Within the Southern Ocean, Antarctic krill (Euphausia superba) is an obvious target species. It has an enormous biomass, which not only supports commercial fisheries and a wide range of other higher predators, but also has impacts on planktonic components of the system. Krill have a broad Southern Ocean distribution, encompassing areas of seasonal sea ice cover and permanently open water regions. Climate driven changes in ocean circulation or winter sea ice will affect the dynamics and distributions of krill populations. Thus it is important to gain a mechanistic understanding of these interactions in order to predict the responses of krill-based food webs to variation and secular change in the environment. SO GLOBEC focuses on the study of key, but poorly known processes dictating krill survival. Such processes include the role of sea ice in their over-wintering success, or their growth and development during dispersal in the Antarctic Circumpolar Current.

Within the Antarctic Circumpolar Current are oceanic fronts, which may dictate the survival during dispersal of krill. These fronts are rapid current jets, which can disperse populations far from their source regions, enhance gene flow across large areas and help repopulate depleted regions. Some fronts are also zones of enhanced primary productivity; rich feeding grounds for krill. However, a major question, as yet unresolved, is the importance of these fronts in providing the phytoplankton blooms essential for krill survival and reproduction in the ice-free months. A front of major potential importance to krill is the Southern Antarctic Circumpolar Current Front (SACCF), as it forms an approximate northern boundary of their distribution. However, its relationship with the seasonal sea ice zone and its role in krill dispersal are presently unclear. The proximity of this front to the Antarctic Peninsula and South Georgia, and a possible concordance of the krill populations in each region, suggest that the SACCF may indeed transport krill between these two main fishing grounds in the Southern Ocean.

Although krill are a central focus of SO GLOBEC, it recognises the need for a multidisciplinary approach to understand the biological and physical processes governing their survival (SO GLOBEC objectives). The interactions between krill and their food, competitors and predators dictate growth and mortality. They also dictate behaviour, for example schooling and diel vertical migration, which in turn link with the 3D flow field to determine larger scale distribution. As part of its DYNAMOE programme, the British Antarctic Survey is conducting a major interdisciplinary study of the role of oceanic fronts in dictating krill growth and survival in the Scotia Sea region. A dedicated GLOBEC cruise of the James Clark Ross will be conducted in January/February 2003, crossing the Scotia Sea in a series of transects (provisional track) The information from this frontal cruise will build on a series of recent BAS and international cruises to the Scotia Sea and South Georgia, providing a context with data collected over both larger and smaller scales. It will also provide information for understanding dispersal and survival processes in the SO GLOBEC study region of the Antarctic Peninsula.



Key questions, hypotheses or issues

The UK cruise, as contribution to SO GLOBEC, will address all the general points except number 5 of the SO GLOBEC Objectives page (weblink). In addition it will address questions about ocean-basin scale transport, growth and survival of krill. This GLOBEC cruise will address the questions:


1)      How important are oceanic fronts in controlling the growth and development of krill?

2)       How important are oceanic fronts in determining the dispersal and survival of krill?


Main contributors

British Antarctic Survey

International Whaling Commission


Main source of funding

Natural Environment Research Council