BENTHIC MIDWATER INTERACTIONS ON THE MADEIRA ABYSSAL-PLAIN - EVIDENCE FOR BIOLOGICAL TRANSPORT PATHWAYS

An investigation of biological transport processes which may link the deep ocean floor to shallow depths was carried out at a site on the Madeira Abyssal Plain, depth 5440m, position 31°17′N 25°24′W. Benthic and midwater sampling was carried out concurrently; time lapse photography provided an estimate of biological activity on the bottom. Biomass was measured throughout the water column; overall biomass was low and no evidence was found for mass upward transport resulting from biological activity. The potential for transport via individual species does exist since a number of species were distributed from the sea bed to thousands of metres above the bottom. However, theres is no direct evidence for vertical migrations through these vast depth ranges and the numbers of individuals concerned is very small. The arrival and possible predation of a large food parcel on the deep sea floor was observed. © 1990.