Known sources of sulfide available to L. luymesi aggregations are sulfide transported with seeping fluids [10] and sulfide generated via reduction of seawater sulfate [39,40]. The majority of the sulfide present at ULS sites is believed to be related to sulfate reduction coupled to anaerobic hydrocarbon oxidation [14,39]. Other potential sources of sulfide associated with seepage include anaerobic oxidation of deeply buried organic material [10], “sour” hydrocarbons containing a proportion of sulfur [41], and hydrocarbon interactions with sulfur-bearing minerals such as gypsum and anhydrite found in the salt dome cap rocks of the ULS [8,42,43].