Much of the seafloor in the Gulf of Mexico is muddy, which limits the distribution of many benthic species such as cold-water corals because they cannot find a hard surface to settle onto. The GoM is different to many cold-water coral habitats where the corals settle onto bedrock, boulders or cobbles. Littered throughout the GoM are solid carbonate deposits. At first glance, these blocks look like boulders or bedrock but closer inspection reveals something different.
These blocks form from the precipitation of carbonate minerals. Authigenic means “formed in situ” and these carbonates in the GoM were probably formed by bacteria using hydrocarbons seeping from reserves beneath the seafloor. Now that the amount of seepage in many areas has decreased, these blocks are colonised by diverse communities including thickets of cold-water corals like the reef framework formers Lophelia pertusa and Madrepora oculata.