It is a pleasure and a distinct honour for me to greet the participants, guests and ob servers of this Fourth International Symposium on Antarctic Biology which has adopted nutrient cycles and food webs as its central theme. On behalf of the Scientific Committee on Antarctic Research (SCAR) and other bodies of the International Council of Scientific Unions (ICSU), I bid you welcome. SCAR is pleased to acknowledge the role of the co-sponsors for this Symposium which include the Scientific Committee on Oceanic Research (SCOR), the Interna tional Association of Biological Oceanography (IABO), and the International Union of Biological Sciences (IUBS). In addition, SCAR and its co-sponsors wish to acknowledge the financial support of the Council for Scientific and Industrial Re search (CSIR) and the Department of Transport (DOT) of the South African govern ment. Nor should we forget to acknowledge also the role of the South African Scientific Committee on Antarctic Research (SASCAR) and one of its leaders and Vice President of SCAR, Mr. Jan de Wit, in arranging this charming venue for this Symposium.

Antarctic Ecosystems comprises 55 papers presented at the Fifth Symposium on Antarctic Biology held under the auspices of the Scientific Committee on Antarctic Research (SCAR) in Hobart, Australia, 29 August - 3 September, 1988. Both short- and long-term changes in ecosystems and community structures caused by natural and human factors were discussed to help understand the ecological processes taking place in a changing environment. The variability of ecological factors must be known for the development of realistic monitoring strategies and sound conservation practices.

A structured account of the full range of environments in Antarctica and of the microbial communities that live within them. The author examines the major features of the chemical and physical environment in each habitat, and the influence of these features on the population structure and dynamics of their microbiota. Each chapter considers a specific type of environment, the microbial species that dominate, their community structure and dynamics, and the microbial processes that operate and have been measured in the ecosystem. The chapters conclude with an overview of the ecosystem trophic structure and an introduction to the larger organisms that depend on the microbiota. Separate chapters examine the range of cellular strategies adopted by microorganisms within the Antarctic environment, and the increasing influence of humans on these communities.

BIOMASS (Biological Investigations of Marine Antarctic Systems and Stocks) was a unique, large-scale, long-term, international research programme established in 1977 to investigate the ecology of the Southern Ocean. Its main aim was to gain a greater understanding of the biological systems and stocks in the marine Antarctic environment, thereby providing a sound basis for the future management of the living resources within this immense ocean. The programme was drawn to a close in 1991 and its completion marked by a colloquium which brought together key researchers to summarise and review the results obtained. This volume, arising from that colloquium, provides a succinct, state-of-the-art account of the ecology of the Southern Ocean and serves as a comprehensive record of this unique and successful international project.

During the intensification of research activities in the Southern Ocean in recent years, both at national levels and through international cooperation in such projects as BIOMASS with its FIBEX and SIBEX phases, the need was felt increasingly for closer collaboration between biologists, meteorologists, and oceanographers in the study of the interaction between the atmospheric forces, the water masses, and the living resources. Better knowledge in this regard is not only of scientific interest but also of practical importance, especially for the management of the resources and the protection of the Antarctic marine ecosystem. As a follow-up on a recommendation by the IOC Program Group for the Southern Oceans made in March 1983, the Intergovernmental Oceanographic Commission organized a meeting of experts on oceanography related to the dynamics of the Antarctic ecosystems. During this meeting, held in Kiel, Federal Republic of Ger many, in May 1984, biologists and oceanographers involved in BIOMASS activities met with the oceanographers of SCOR Working Group 74 to discuss ways and means for additional physical and chemical observations in the oceanographic research within BIOMASS. It was the time when large fluctuations in the distribution of krill with subsequent detrimental effects on predator species dependent on krill had just been observed, and the question arose whether this was possibly the result of changes in the Antarctic water circulation.

Biology of Antarctic Fish presents the most recent findings on the biology of fish in the unique environment of the Antarctic ocean. At present the year-round temperature of the coastal waters is very near -1,87 ° C, the equilibrium temperature of the ice-seawater mixture. This extremely low temperature affects different levels of organization of fish life: individuals, organ systems, cells, organelles, membranes, and molecules. Exploring ecology, evolution, and life history as well as physiology, biochemistry, and molecular biology of Antarctic fish the book describes the mechanisms of cold adaptation at all these levels. It provides material for discussion also for fundamental questions in the field of adaptation to an extreme environment and therefore is of particular interest not only to specialized scientists, but also to those involved in basic and evolutionary biology.

The International Committee on Microbial Ecology (ICOME) sponsors both the Interna tional Symposium on Microbial Ecology, held in various parts of the world at three-year intervals, and the publication of Advances in Microbial Ecology. Advances was estab lished to provide a vehicle for in-depth, critical, and even provocative reviews in microbial ecology and is now recognized as a major source of information for both practicing and prospective microbial ecologists. The Editorial Board of Advances nor mally solicits contributions from established workers in particular areas of microbial ecology, but individuals are encouraged to submit outlines of unsolicited contributions to any member of the Editorial Board for consideration for pUblication in Advances. Chapters in Volume 11 of Advances in Microbial Ecology include those on micro bial transformations of chitin by G. W. Gooday, organic sulfur compounds by D. P. Kelly and N. A. Smith, and phosphorus, including its removal in waste water treatment plants, by D. F. Toerien, A. Gerber, L. H. Lotter, and T. E. Cloete. The importance of diffusion processes in microbial ecology is discussed by A. L. Koch, and 1. I. Prosser reviews the application of mathematical modeling to nitrification processes. Considera tions of particular ecosystems include the Antarctic by D. D. Wynn-Williams and Australian coastal microbial mats by G. W. Skyring and 1. Bauld. Other chapters include the regulation of N2 fixation by H. W.