Our aim in this chapter is to examine whether water movement is fundamentally important in aquatic ecosystems to productivity and materials cycling in the ways briefly outlined in the next section. The testing of a suitable ecosystem level null hypothesis in which water movement is excluded is probably an unrealistic task. Yet, the idea of such a test should be kept in mind as we examine the real-world ecosystems which follow.

We note that the thrust of this chapter, ecosystems interacting with flow, is contradictory to the book's theme. This is because, in most of the book, we concentrate on suspension feeders and largely ignore the rest of the ecosystem of which they are a part. Yet, for ecosystem analysis we must be concerned with all of the biological and physical variables that are important in energy flow. Thus, for this chapter only, we have relaxed our definition to mean complete ecosystems including hydrodynamic effects on macroflora and macrofauna, inclusive of plant canopies, which are clearly not suspension feeders, but important primary producers. Our review of the contemporary benthic literature suggests that plant canopies and bivalve and coral reef ecosystems are best studied from the hydrodynamic perspective.

The examples we have chosen to include in this chapter are plant canopies, e.g. seaweed and seagrass ecosystems, and marine/estuarine environments with suspension feeding bivalve reefs.