Megafaunal biomass in the deep sea

Abstract

THE conventional notion of the deep-sea ecosystem has been one where a rain of fine organic particles from above provides food for a great diversity of small creatures living in and on the sediments^1–3. These, the meiofauna and macrofauna, live as deposit feeders, suspension feeders, and, in lesser proportion, as carnivores preying on other members of the fauna. The macrofauna in turn are thought to provide food for the generally more carnivorous megafauna, the echinoderms, decapods, and fishes. Although no data have been published concerning the abundance of the deep-sea megafauna in terms of biomass, the assumed trophic relationship and the Eltonian concept has led to the common feeling that the biomass of this component must be small in comparison to the meiofaunal and macrofaunal biomass⁴. Our data show that, on the contrary, the mega-faunal biomass approaches that measured in the macro-fauna. This observation re-focuses attention on the question of food supply to the deep sea, and implies that previously suggested falls of large dead animals from the pelagial^5,6 may be important.