The third step of succession is the sulphophilic stage which lasts up to ten years (Smith and Baco, 2003). In this stage decomposition is highly advanced and species richness is greatest with up to 185 macrofaunal species present- the highest of any other deep sea hard substratum community (Smith and Baco, 2003). Also, diverse assemblages of chemoautotrophic and heterotrophic bacteria are present, growing on the surface of the skeleton (figure 4).
The stage is characterised by the presence of sulphate-reducing bacterial mats which anaerobically break down the lipids of whale bones. A 40t whale may have a skeleton which contains roughly 2000kg-3000kg of lipids (Smith and Baco, 2003). Anaerobic microbial decomposition dominates the further decay of the carcass. Hydrogen sulphide is produced by bacteria which is then used by invertebrates such as bivalve molluscs and crustaceans for sustenance through their endsymbiotic chemoautotrophic sulphophilic bacteria. This stage has been compared to that of hydrothermal vent communities as a result of the chemoautotrophic component (Smith, 2006; Treude, 2009). This stage also has high abundances of the whale fall specialist annelid worms Osedax which have only ever been found boring into the bones of sunken mammals.
The sulphophilic stage also begins to see the arrival of sessile suspension feeders which have the potential to settle on the whale carcass and lead into the “reef stage” of succession.