A whale fall is the carcass of a whale that has fallen deeper than 1,000 m, on the ocean floor. They create ecosystems that supply sustenance to deep-sea organisms. In shallower waters, a whale carcass will be consumed in a short period of time.
The earliest indication that whale carcasses could host specialized animal communities occurred in 1854 a new mussel species was extracted from a piece of floating whale blubber. By the 1960s, a new species was unintentionally recovered attached to whale bones.
The first whale fall was discovered on 19 February 1977. The skeleton of the carcass remained intact on the seafloor. A team of marine biologists discovered another whale fall in 1987. Other whale falls have been found by more researchers and naval submarines. The increase in detection is due to the use of sonar, which can examine the ocean floor for large objects.
A group of organisms inhabits whale falls in all oceans. Organisms that have been observed include giant isopods, bristlewoms, shrimp, crabs, sea cucumbers, and sleeper sharks Whale falls are able to occur due to cold temperatures and high hydrostatic pressures. 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 are at least three stages of decomposition. The initial period begins with “mobile scavengers”, consuming soft tissue from the carcass. Consumption can be at a rate of 88–132 lb per day over a two-year period
The second stage introduces the “enrichment opportunists”. These are animals that colonize the bones and surrounding sediments This process can take up to two years.
Finally “sulfophilic bacteria” break down the lipids embedded in the bones. Instead of oxygen they reduce dissolved sulfate SO2−4 and excrete hydrogen sulfide. Due to the toxicity of H2S, only resistant chemosynthetic bacteria survive. The bacterial mats provide nourishment for mussels, clams, and sea snails. As whalebones are rich in lipids, the final digestion stage can last between 50 and possibly 100 years.
Similar ecosystems exist when other large volumes
of nutrient-rich material fall to the sea floor.
Sunken beds of kelp create kelp falls,
and large trees can sink to create wood falls.
In more recent years, shipwrecks have also
provided bases for deep water communities.
