Bigger is Better: The Role of Whales as Detritus in Marine

0,67
MB Ecosystems

46
stron

4856
ID University of Hawaii at Manoa

2005
rok

Abstract. Dead whales are the largest, most food-rich detrital particles in the ocean, typically

containing >10^6 g of organic carbon in energy-rich lipids and proteins. Most whales suffering natural

mortality appear to sink rapidly to the deep-sea floor, with little loss of tissue during transit.

Although whale detritus constitutes a small proportion of total organic flux to the deep sea, whale

falls provide energy-rich habitat islands that are frequent on regional scales (e.g., with a mean

nearest neighbor distance of <16 km in the northeast Pacific). Experimental studies on the

California slope demonstrate that deep-sea whale falls support a succession of diverse

macrofaunal assemblages, characterized in sequence by (1) mobile scavengers, (2) enrichment

opportunists, and (3) sulfophiles (including chemoautotrophs); the entire successional process lasts

for decades on large carcasses. The enrichment-opportunist and mobile-scavenger stages harbor at

least 32 species that appear to be whale-fall specialists. Whale detritus in pelagic, continental

shelf, and intertidal ecosystems does not appear to be a significant source of energy or habitat for

novel animals, although some mobile, intertidal scavengers (e.g., polar bears), may obtain

significant energetic benefits from whale carrion. Commercial whaling drastically reduced the

occurrence of detrital whales in all marine ecosystems, and is likely to have caused substantial

species extinction in deep-sea whale-fall assemblages due to loss of 65-90% of the whale-fall

habitat. The species extinctions were likely most severe in the North Atlantic where whales were

decimated in the 1800’s, and may be ongoing in the Southern Ocean and northeast Pacific, where

intense whaling occurred into the 1960’s and 1970’s. Whaling may also have caused a decline in

highly mobile coastal scavengers, in particular the California condor, that depended on stranded-

whale carrion. Experimental implantation of lipid-rich, whale-bone packages in a variety of ocean

basins could help to determine whether whaling induced extinctions have modulated biodiversity

levels of whale-fall communities.