Because of its remoteness and inaccessibility for direct measurements, it is far easier to study the distribution of fauna on the ocean floor and to record the results of their various activities than it is to study the processes from which these patterns in space arose. In particular, data on the rates of any biological process are sparse and difficult to obtain. The traditional view of the deep sea has become one of a low-activity ecosystem where biota subsist on low levels of available food. This perception has resulted from the extremely low densities of organisms and the low levels of organic material of very poor nutritive value available for them as food. Furthermore, the low numbers of microorganisms in deep-sea sediments have suggested rates of microbial activity to be exceptionally low. This view seemed to be dramatically confirmed by the ‘Alvin’ lunches – when the food left in the flooded submersible was found to be well preserved on its recovery from the deep-sea bed one year later. The concept of exceptionally low rates of growth and turnover of the animal populations has become deeply embedded as a consequence of radiometric estimates of around 100 yr for the age of large specimens of the small deep-sea bivalve Tindaria callistiformis.

In this section we shall see that this view is being challenged by new findings from the deep sea by our most recently won data on a variety of biological processes, from respiration to reproduction, and feeding mechanisms to bioturbation of the sediment.