Cetacean distributions and oceanographic features near the Kerguelen Plateau



Cetacean surveys were conducted in the austral summer during World Ocean Circulation Experiment hydrolegs I8S and I9S in the southeastern Indian Ocean. The highest density of cetaceans occurred along the southern flank of the Kerguelen Plateau and northern edge of the Princess Elizabeth Trough, where the distribution of whales coincides with the mean positions of the Southern Front of the Antarctic Circumpolar Current (ACC) and southern water mass boundary (Southern Boundary) of the ACC. The topographic steerage of these features of the ACC around the southern edge of the Kerguelen Plateau brings shoaled, nutrient-rich Upper Circumpolar Deep Water (UCDW) to higher latitude than in adjacent basins. The higher concentrations of cetaceans near the Kerguelen Plateau suggests that whales benefit from a cascade of trophic dynamics associated with the poleward extent of UCDW, the marginal ice edge zone, and the proximity of several oceanographic features: the high latitude penetration and close alignment of the Southern Front and Southern Boundary of the ACC; the unique poleward extent of the Southern Boundary as it is topographically steered around the plateau; the entrainment of macronutrients into the surface mixed layer near the Southern Boundary; isopycnal shoaling in cyclonic eddies; the presence of complex bathymetry; and the advection of a tongue of ice northward along the eastern side of the plateau. The association between these concurrent oceanographic features and whales suggests that the southeastern edge of the Kerguelen Plateau is a predictably productive foraging location for cetaceans and their prey.