Benthic infaunal distributions in shallow hydrothermal vent sediments

This study examined the macrofaunal communities of two shallow hydrothermal vent areas, in Bahía Concepción (12 m depth), Mexico, and White Point (8 m depth), California. We tested whether the infaunal community compositions in these systems were different from the surrounding communities, and if the observed differences were related to pore-water and other habitat variables. A combination of temperature, hydrogen sulfide, salinity, and pH influenced the species composition within zones of venting. The vent communities, with a few exceptions, were a sub-set of the surrounding community, represented by a limited diversity of outside fauna in lower abundance. Examination of infaunal life-histories revealed that tube-dwelling and mobile species represented a relatively higher proportion of the fauna near vents than away. Tubes were proposed as a beneficial life-history strategy to inhabitants of the high temperatures of Bahía Concepción, but did not predominate in the high sulfide sediments of White Point. Furthermore, there was no evidence for chemosynthetic strategies amongst the shallow vent infauna, unlike fauna at deep-sea hydrothermal vents and cold seeps.