Ninety per cent of the two-thirds of the surface of the Earth covered by the sea lies beyond the shallow margins of the continents; and most lies under 2 km or more of water. We may therefore, with some justification, speak of the deep-sea bottom as constituting the most typical environment, and its inhabitants as the typical lifeforms, of the solid face of our planet. Yet, because of the remoteness of this habitat and the difficulties in observing and sampling these organisms, they are known to only few scientists; and as living rather than pickled specimens, to less than a handful. Yet the possibility of life existing at these great depths, and a curiosity about the nature of these life forms in what appears to be one of the most ‘difficult’ of environments has fascinated Man since the early days of oceanic exploration.

This book is intended as an introduction to our present knowledge of the biology of this environment. This is the realm of the mostly sediment-covered deep ocean floor and the immediately overlying water layer, termed the Benthic Boundary Layer (BBL). Animal life has been found burrowing within, and moving on the surface of, this sedimentary ooze, and occasionally carried along by deep currents. We now know that animals survive, sometimes in spectacular numbers, at the greatest depths of the deepest ocean trench, apparently unaffected by an ambient pressure of more than 1000 atm, by the complete absence of solar radiation and a temperature of one or two degrees above freezing.