## Global Change and Marine Ecosystems

Evidence continues to accumulate that the environment of our planet is changing (e.g., Mitchell, 1989). Many of the changes are thought to be the consequences of human intervention into natural processes (such as the ozone depletion over the Antarctic, increased concentrations of greenhouse gases, the enhanced acidity of rainfall downwind of industrialized areas, etc.), but paleoclimatic records reveal that the earth has experienced at least some similar changes in the past. We possess little knowledge of the spatial or temporal scales of these changes. Some occur on relatively short time scales (El Nino-Southern Oscillation Events), whereas others may be operating over very long periods of time (the incorporation of carbon into the deep sea: Broecker and Peng, 1982). Even for processes that operate at a global scale, the climatic shifts are not uniformly distributed across the face of the globe. This characteristic not only complicates detection but also demands mechanistic models to permit prediction of future change. Many scientists are now deeply involved in verifying the existence and magnitude of these shifts in the environment, as well as in modeling the likelihood of various alternative scenarios for future change. These studies of the shifts in the physical and geochemical environment of our planet are of critical importance, but equally urgent is the challenge of assessing the biological consequences and the sustainability of biological life-support systems in the face of such global change.

GLOBEC (GLOBal ocean ECosystems dynamics) is a research initiative proposed by the oceanographic and fisheries communities to address the question of how changes in global environment are expected to affect the abundance and production of animals in the sea. Our approach to this problem is to develop a fundamental understanding of the mechanisms that determine both the abundance of key marine animal populations and their variances in space and time. We assume that the physical environment is a major contributor to pattems of abundance and production of marine animals, in large part because the planktonic life stages typical of most marine animals are intrinsically at the mercy of the fluid motions of the medium in which they live. Consequently, we reason that a logical approach to predicting the potential impact of a globally changing environment is to understand how the physical environment, both directly and indirectly, contributes to animal abundance and its variability in marine ecosystems.