Knowledge of these patterns is important, as they enable us to understand the habitat requirements of the biodiversity of shelf organisms, as well as having implications for exploitation of both renewable (Figure 8.3) and non-renewable resources (eg sand extraction, heavy minerals of terrigenous origin) associated with particular sedimentary facies. Further distinctions can be made on the basis of the size of the organism: macrofauna (such as amphipods, isopods, gastropods and poly-chaetes) are >1 000 pm, meiofauna (rotifers, harpacticoid copepods, nematodes) are between 45 and 1 000 pm, while microfauna (ciliates) are <45 pm. Then there are the ben-thic microalgae or microphytobenthos (cyanobacteria, ben-thic diatoms, and flagellates) which form a layer on shelf sediments in the euphoric zone and which can contribute substantially to continental shelf productivity (Gattuso and others, 2006), these are more correctly considered as ben-tho-pelagic, as they can be suspended in the water column, particularly during turbulent seas, thereby forming part of the plankton. Also included in the benthos are the non-planktonic foraminifera, either living or dead, with carbonate tests which are typically <1 000 mm in diameter.