## Working Group II - Integration Across Scales and Linking of Scales

Botsford (chair), Klinck, Paffenhöfer, Prestidge, Smith

The working group focused on the many and often wide ranging scales that are involved in measuring and modeling secondary production. The overarching theme that emerged was a concern for how to measure secondary production processes so that observed distributions of secondary production could be understood and modeled. The measurement of secondary production was felt to be straightforward, but understanding the underlying processes responsible for the temporal and spatial patterns is difficult. It is the latter part of the problem that is most relevant to the goals and objectives of U.S. GLOBEC.

Secondary production in marine environments is usually measured on groups of similar (patches or aggregations) or dissimilar (communities, ecosystems) organisms. However, processes that occur at the scale of the individual organism may determine secondary production patterns observed at the larger scales. In order to understand secondary production at larger scales, processes at the scale of the individual need to be understood. Thus, for example, efforts might be directed toward obtaining a better understanding of the full range of ingestion responses by the individual. The working group recommended that modeling over a range from individuals to populations to metapopulations to communities might be done with nested models, each of which considers processes over a limited range of space and time scales. Also, this may be an area in which Individual Based Models (IBMs) might be an appropriate modelling framework as opposed to the more traditional stage, size and age structured models.

Development of models that treat a wide range of spatial and temporal scales will require concurrent development of techniques to transfer information between scales. The working group recommends the development of approaches (i.e., parameterizations) for transferring information from smaller to larger scales (scale-up). Additionally, it was recognized that models constructed for one scale (e.g., turbulent, regional) must be able to include forcing (e.g., climate) from larger scales (scale-down) and consider larger-scale boundary conditions. For modelers to successfully address this "scale-transfer" issue will require coordination with experimental and empirical scientists. Moreover, it is necessary for those doing the experimental studies to work at scale interfaces as well as at particular scales, which will require coordination among empiricists who work at different scales.

The complexity of integrated processes in models of secondary production should not be beyond what can be justified by experimental data. Not all the complexity at one particular level has to be transferred to the next higher level. Modeling can occur on different levels simultaneously. Empirical information presently available at two or more scales provide starting points for initiating cross-scale modeling efforts. This collaboration is encouraged.

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