Whale fall

A whale fall is the carcass of a cetacean that has fallen into the bathyal or abyssal zone (i.e. deeper than 1,000 m, or 3,300 ft) on the ocean floor. They can create complex localized ecosystems that supply sustenance to deep-sea organisms for decades. This is unlike in shallower waters, where a whale carcass will be consumed by scavengers over a relatively short period of time. It was with the development of deep-sea robotic exploration that whale falls were first observed in the late 1970s.

Organisms that have been observed at deep-sea whale falls include giant isopods, squat lobsters, bristleworms, prawns, shrimp, lobsters, hagfish, Osedax, crabs, sea cucumbers, and sleeper sharks.

Whale falls are able to occur in the deep open ocean due to cold temperatures and high hydrostatic pressures. In the coastal ocean, a higher incidence of predators as well as warmer waters hasten the decomposition of whale carcasses. Carcasses may also float due to decompositional gases, keeping the carcass at the surface. In the deep-sea, cold temperatures slow decomposition rates, and high hydrostatic pressures increase gas solubility, allowing food falls to remain intact and sink to great depths.

There have also been studies based on the carcasses of other, non-mammalian marine vertebrates that have fallen to the deep sea. In particular, the chance discovery of a whale shark carcass and three mobulid ray carcasses led to observations on the communities that form surrounding large elasmobranch falls as opposed to whale falls. Whale sharks inhabit waters of roughly 1,000 meters depth regularly, which suggests it could be a regular form of food fall in areas where it is abundant. Many eelpouts (Zoarcidae) were found surrounding the whale shark with some evidence of direct feeding as boreholes were observed on the carcass. Another theory suggests that the eelpouts were waiting for their main prey, amphipods and other small benthic animals. The three rays found were at varying stages of decomposition, leading to varying assemblages found surrounding the individuals. A higher abundance of scavengers was found surrounding the more intact individuals, including scavengers typical of whale falls like hagfish. Around the least intact individual a bacterial mat was observed in the zone of enrichment, but no clams or mussels typical of this environment (i.e. whale falls) were seen.

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Wikipedia