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 and nonrenewable 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 polychaetes are pm meiofauna rotifers harpacticoid copepods nematodes are between and pm while microfauna ciliates are pm then there are the benthic microalgae or microphytobenthos cyanobacteria benthic 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 these are more correctly considered as benthopelagic 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 nonplanktonic foraminifera either living or dead with carbonate tests which are typically mm in diameter