The initial period begins with "mobile scavengers" such as hagfish and sleeper sharks actively consuming soft tissue from the carcass. Consumption can be at a rate of 40–60 kilograms (88–132 lb) per day over a two-year period.
The second stage introduces the "enrichment opportunists". These are animals which colonize the bones and surrounding sediments that have been contaminated with organic matter from the carcass and any other tissue left by the scavengers. This process can take up to two years.
A chemoautotrophic whale-fall community, including bacteria mats, vesicomyid clams in the sediments, galatheid crabs, polynoids, and a variety of other invertebrates.
Finally "sulfophilic bacteria" anaerobically 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 H
2S, only resistant chemosynthetic bacteria survive. The bacterial mats provide nourishment for mussels, clams, limpets and sea snails. As whale bones are rich in lipids, representing 4–6% of its body weight, the final digestion stage can last between 50 and possibly 100 years.
A process called methanogenesis can also occur around whale falls. Archaea that produce methane can be abundant in anoxic sediment, but is typically not found in co-occurrence with the sulfur reducing bacteria found at whale falls. Whale falls do however support both sulfur reducing bacteria and methane producing archaea, leading to the conclusion that the area is not electron donor limited, and/or there is minimal or no competition for suitable substrate. Concentration gradients of both sulfide and methane can be found around whale falls, with the highest concentration coming within one meter of the carcass, which is several orders of magnitude higher than the surrounding sediment concentrations. Methanogenesis appears to only occur in sediments as opposed to sulfur reduction, which occurs both in sediments and on the bones of the carcass. The addition of sulfur reduction in both sediments and high lipid whale bones is a key factor for why whale falls are able to sustain deep-sea communities for extended periods of time.