We now address the level of spatial structure existing within a community of deep-sea animals. We therefore concern ourselves with pattern at scales from perhaps hundreds of metres down to a few millimetres. Such pattern is, of course three-dimensional, and can be measured on both horizontal and vertical planes. Assumptions of randomness in the spatial patterns of shallow-water benthos have been shown to be grossly misleading. Frequently, what appears as ‘randomness’ is the resulting balance of a multitude of spatial variables affecting the pattern of individual organisms in the sediment fabric.

At a practical level, information on the intensity and scale of these patterns is vital in assessing the validity of estimates of standing crop obtained in quantitative samples from the deep sea. Beyond this, the description of the spatial structure displayed in the locations of individuals provides us with a powerful, if indirect, indicator of interaction between organisms on the deep-sea floor. We shall see later that such information is relevant in understanding the processes maintaining the unexpectedly high species diversity found amongst the smaller organisms of the deep-sea floor. Furthermore, a knowledge of the spatial patterns in locations of deep-sea benthic organisms becomes of increasing importance in modelling biogeochemical and stratigraphic processes: the accuracy and precision of such models, embodying parameters of the effect of benthic organisms on their environment, might be severely limited by unwarranted assumption of a random pattern in the distribution of biota.