PLATE 3a A simple representation of microbial loops and the changes in food web structure with decreasing rates of nutrient input from right to left. This figure, based on Azam et al. (1983) and Cushing (1989). is reprinted from Figure 1 in Steele (1998), with permission from Proceedings of the Royal Society of London.

PLATE 3b A conceptual diagram showing the current concept of the predominate food web structure in the pelagic water column. Recognition of the role of microbes has added a suite of new trophic levels to the classic "diatom-zooplankton-fish" food chain. Organisms at the lower left, whose sizes are indicated roughly by the adjacent scale bar, are responsible for the fluxes indicated by arrows. This figure was originally developed by P. Johnson for the OEUVRE workshop described in Jumars' paper in this volume.