Case Study - Corals of the Gulf of Mexico

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Authigenic Carbonate

Much of the seafloor in the Gulf of Mexico is mud, this limits the distribution of many benthic species such as cold-water corals because they cannot form a solid base. The GoM is different to many cold-water coral habitats in the North East Atlantic where most hard substrate is in the form of 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.

Formed in the past, these blocks are thought to result from the precipitation of carbonate minerals. Authigenic means “formed in situ”, these carbonates in the GoM were most likely formed by bacteria that utilised hydrocarbons seeping from reserves beneath the seafloor. Now, the amount of seepage in many areas has decreased, these blocks are colonised by a diverse set of epifauna that includes thickets of cold-water corals including the reef formers Lophelia pertusa and Madrepora oculata.