When whales die and sink, they create an active community of deep-sea scavengers that come to feed in stages as the carcass decays. The First to arrive to the whale fall: Hagfish, crabs, and sharks, like the sleeper sharks seen in this clip of a grey whale from episode 2 of Blue Planet, narrated by Sir David Attenborough, can feed up to two years. More from ocean.si.edu:
In the second phase (the enrichment opportunist phase), worms, crustaceans and mollusks feed on leftover blubber, often burrowing into the nutrient-enriched sediment beneath the whale for around two years. The final stage, called the sulfophilic stage, can last decades. With only the skeleton remaining, bacteria begin breaking down lipids trapped inside the bones, generating sulfur, which attracts more bacteria and a larger community of diverse and rare species including mussels, worms, snails, and others. This diversity of species found in this last stage is larger than any known community on the deep seafloor.
And from A Whale’s Afterlife in The New Yorker:
Whale falls may occur as frequently as every ten miles on the seafloor; at any given time, there are likely hundreds of thousands of them around the world. A 2015 review paper by the deep-sea ecologist Craig Smith, at the University of Hawaii at Manoa, and a number of collaborators proposed that decaying whale carcasses may serve “as a sort of biodiversity generator,” allowing organisms from different energy-rich seafloor oases, such as thermal vents or methane seeps, to mingle. The importance of these deep-sea ecosystems makes whale falls especially fascinating. Seafloor microbes consume methane, which is a greenhouse gas, and provide biomass that ultimately sustains fish populations.