Deep-sea ecosystems of the Indian Ocean

Abstract

The deep Indian Ocean is composed of a variety of habitat types, including abyssal plains, oxygenated slopes and basins, seamounts, and trenches. The geomorphological features of the Indian Ocean include mid-ocean ridges, abyssal plains and few deep-sea trenches. Although the Indian Ocean has relatively few seamounts and islands, it contains numerous submarine plateaus and rises. We review what is known of deep-sea benthic habitats studied with modern techniques in the Indian Ocean. Recent biological studies conducted in the Central Indian Ocean Basin (CIOB) suggested remarkably rich and diverse micro-, meio-, macro-and megabenthic communities on the abyssal sea floor. The megafaunal assemblage of the CIOB has high biomass but low diversity. While macrofaunal biomass decreased away from the shore, the meiofaunal biomass increased with distance. The discovery of ‘Kairei’ and Edmond hydrothermal field near the Rodriguez Triple Junction suggests that mid-ocean ridge systems in the Indian Ocean are potential sites for hydrothermal mineralization and contain active vent fields. There are no available estimates for the numbers of seamounts in the Indian Ocean based on echo sounder recordings. Satellite altimetry data indicate that the Indian Ocean has an intermediate number of generally small to moderate-sized seamounts, mostly associated with its ridge systems. The fauna of Indian Ocean seamounts remains virtually unexplored.