Sinking

Whale falls are generally located in areas where there is a high level of whale migration and upwellings. Locations where these two aspects are combined have the most whale fall occurrences. Natural whale mortality usually occurs in whales which are already in a poor nutritional state which causes the carcasses to sink (figure 1) towards the sea floor because they are negatively buoyant (Smith, 2006). Hydrostatic pressure causes the lungs to deflate which causes sinking to be rapid. This means that little scavenging takes place in the mid waters (Britton and Morton, 1994).

High pressure, as a result of increasing depth, inhibits the decomposition rate of the carcass from gut microbes as microbial respiration will be reduced (Allison et al., 1991). At pressure in excess of 200 atmospheres (approximately 2000m), gut microbe respiration is completely halted. Therefore, provided that the carcass sinks deep enough, it is impossible for it to be refloated as a result of decomposition gases. This marks the beginning of a whale fall ecosystem and leads into the stages of successional decomposition.

The carcass of a juvenile grey whale beginning it's journey to the sea floor. ©Doug Allan/Getty Images.

Figure 1. The carcass of a juvenile grey whale beginning it’s journey to                        the sea floor. ©Doug Allan/Getty Images.

 

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