WAITING FOR A WHALE: HUMAN HUNTING AND DEEP-SEA BIODIVERSITY

Organisms in the deep sea are highly food-limited, relying primarily on organic matter raining down from above. Whale carcasses may be particularly important because they are large and sink fast enough with sufficient tissue still intact for exploitation. Lipid-rich whale skeletons have further been found to support an animal community nourished largely by sulfur-reducing chemoautotrophic bacteria. Whale skeleton-associated species are similar, and in some cases identical, to organisms previously thought to be restricted to the chemosynthetic-based hydrothermal vents and other deep-sea microbial reducing habitats. Whale skeletons scattered like islands in the deep sea may thus provide some of the critical stepping stones for organisms between hydrothermal-vent communities, themselves insular and temporary habitats.

Given the potentially important role of whales to deep-sea biodiversity, these communities may have been altered by human hunting of whales. A profound effect of whaling was a vastly reduced—and in some regions, obliterated—whale skeleton supply to the deep sea due to an acute decrease in hunting-generated carcasses (after the turn of this century, whalers retained the entire animal) and to a dramatic decrease in whale populations. This decrease meant a severe spatial interruption, if not elimination, of dispersal corridors between reducing-habitat communities, with potentially marked alterations to biodiversity in hot-vent and cold-seep regions.

Unfortunately, the magnitude and consequences of changes in biodiversity resulting from this type of human activity are difficult to evaluate because of the lack of data on most whale population sizes and distributions, because the region impacted is far removed from the disturbance source, and because effects are being considered nearly a century after the fact. This example does, however, underscore the importance of ''thinking big" and "thinking remotely" in evaluating the potential impact of society's activities on nature.