Components of GLOBEC's Approach

## Components of GLOBEC's Approach - Based on Understanding of Mechanisms that Influence Individual Organisms

1. GLOBEC intends to vastly increase our understanding of the fundamental mechanistic processes that dictate:

   - the abundance of marine animals,
   - the fluctuations in their abundance, and
   - the secondary production of ocean ecosystems in the context of a changing global climate.

   Our philosophical approach to predicting the possible impacts of global change on animal abundance, variation in abundance, and production in the oceans is to develop a basic understanding of how physical and biological processes at the level of the individual organism determine population change. From this fundamental understanding, we intend to assess the potential impact of global change by linking global change to change in those physical processes that affect the individual organisms and populations of organisms.

2. GLOBEC'S "first-principles" population dynamics approach to population ecology requires evaluation of fundamental biological processes:

   - feeding and growth,
   - survivorship, and
   - reproduction and fecundity.

   The rates of feeding and growth, survivorship, and reproduction and fecundity may depend upon:

   - population density,
   - passive and active movements of individuals,
   - effects of predators, competitors, and commensals,
   - key aspects of the physical environment, and
   - how physics modify biological interactions.

   We maintain that the process by which change in the physical environment influences abundance and production of animals in the sea is through modification of the success of individual organisms, which then alters parameters of population growth and thereby triggers ecosystem change. Consequently, appreciation of the role of changing physics in the ecosystems dynamics of the oceans requires a "first-principles" approach at the level of the individual organism. Such studies lie at the cutting edge of population ecology in that they demand evaluation not only of the direct effects of key physical variables, features, and processes on individual performance but also of the indirect effects of how changing physics modify the important biological interactions. For example, enhanced turbulence may alter the feeding rate of a zooplankter, positively by renewing food supplies that might otherwise become depleted in its local vicinity and by increasing encounter rates between the zooplankter and its prey, or negatively by interfering with effective deployment of its feeding appendages.

3. Only by understanding mechanism can we extrapolate, generalize, and predict from site-specific results. The standard means of justifying extrapolation of a set of results to systems outside of specific study sites is to replicate studies in each of several strata, where stratification is done along each of the variables deemed most likely to influence the outcome of whatever is being measured. Replication in this fashion is probably impossible for studies of marine ecosystems because of the high costs involved and because of the intrinsic variation in biological systems that renders true replication difficult to achieve. The alternative to this sort of inductive approach to generalization is to focus on mechanistic processes and to practice deduction as a means of extending the results to additional systems. This represents one of our major motivations in choosing a reductionist, process-oriented approach to the problem of predicting the influences of global change on marine ecosystems.

4. The understanding of the processes that determine abundance, fluctuation in abundance, and production of marine animals must necessarily involve coupled physical-biological models, linking performance of the individual organism to local physical processes and linking both the biology and local physics to basin-scale changes in global climate.

   We expect modeling to play a significant role in GLOBEC studies at several levels. The explicit incorporation of physical variables and processes into biological population models holds promise for great originality and progress. Appropriately constructed models of both physical and biological processes should guide the choice of field experiments and observations, while results of those field exercises should feed back interactively into the models. We envision use of nested models to bring the implications of global change down to the scale of events that influence the individual organism. Regional models may be nested within global models, such as general circulation model's (GCMs), and within region several submodels may reduce processes to the levels at which biological impacts occur.

5. Our optimistic prognosis for the success of GLOBEC is based in large measure on the potential for novelty and fundamental scientific breakthroughs that will come from integrating the physical and biological processes. The development of new technologies that will allow the coverage of biological sampling to approach that now possible in ocean physics promises giant steps forward.

   The oceans are notoriously undersampled. GLOBEC plans to help fill this void by developing and utilizing new technologies to sample synoptically certain targeted ocean physics and biology. Physical instrumentation such as the Acoustic Doppler Current Profiler (ADCP) can be much more widely applied to describe water movements of significance to marine plankton. Biological sampling needs to be automated by catalyzing the evolution of new instrumentation for assessing the abundance and distribution of planktonic animals. GLOBEC plans to evaluate the potential for application of acoustics, optics, biotechnology, and other tools to provide these measurements. A major thrust of GLOBEC will then be the development of the most promising of these potential technological solutions to the need to automate biological sampling.