Massive Whale-Fall Necropolis Discovered in Deep Indian Ocean

A team of researchers using the deep-submersible Fendouzhe mapped a 1,200-kilometre segment of the Diamantina Fracture Zone in the southeastern Indian Ocean and documented an extensive accumulation of whale remains. Between February and March 2023 they recorded 485 sites containing either fossil cetacean bones or active whale-fall communities, with five carcasses still in the sulfophilic stage of decomposition. The deepest active fall, a beaked-whale skeleton at 6,789 m, is among the deepest whale-fall ecosystems known.

The associated fauna were highly diverse, comprising 35 macrofaunal taxa dominated by bone-eating worms (Osedax), chemosymbiotic bivalves, and brittle stars, with local densities reaching up to 2,840 individuals per square metre. Many of the organisms appear to be new to science, and molecular analysis identified only one bivalve species with confidence, suggesting a largely undescribed community.

Paleontological analysis of 43 fossils revealed five beaked-whale species and one baleen-whale species, including modern ziphiids Mesoplodon bowdoini and M. layardii and extinct genera such as Pterocetus and Izikoziphius. Isotopic dating indicates that whale falls have accumulated in the region for at least 5.3 million years, aided by the area’s ultra-low sedimentation rates and the dense, mineral-rich bones of deep-diving beaked whales.

Researchers propose that the zone’s V-shaped topography funnels carcasses onto the seafloor, creating a “whale-fall supercorridor” that may serve as a biogeographic stepping stone for chemosynthetic communities. The findings extend the known depth range of whale-fall ecosystems by more than 2,500 m and provide a valuable fossil archive for studying the evolution and ecology of deep-diving cetaceans.