With immense pressures, and temperatures higher than 350°C, deep-sea hydrothermal vents are one of the most extreme environments on Earth. Discovered in 1977 along the Galapagos Rift, vents are complex and dynamic habitats where chemically reduced hydrothermal fluid mixes with cold, aerobic seawater. Minerals precipitate from vent fluids, forming complex chimney structures characterized by steep thermal and chemical gradients and a diverse array of reduced compounds that are potential metabolic energy sources for microbes.
These unique physico-chemical gradients provide diverse niches for prokaryotic communities as well as megafauna-microbial symbioses. The abundance of reductants and oxidants for chemosynthesis enable tremendous microbial productivity, and result in communities whose biomass can be comparable to that of rainforests. Moreover, the diversity microbial physiologies, their substantial biomass, and the timescale on which water circulates through the vents suggest that these microbes could contribute significantly to global biogeochemical cycles. As such, much of our vent research is focused on understanding the physiological capacities and activities of endolithic microbes to better constrain their activities. Together with our research on vent animal-microbial symbioses, these studies are aimed at identifying and understanding the physiological and biochemical adaptations that govern life in chemically reducing ecosystems.
Figure 1. Vents in the South Pacific host different megafaunal assemblages than those characteristic at other sites. Moreover, they can have very different geochemical compositions that other sites, resulting in wildly colorful sulfides. Courtesy of C. Fisher and WHOI.
Figure 2. Vents in the Pacific Northwest are vigorous, and many host brightly colored vent tubeworms called Ridgeia piscesae. These worms are related to the well known vent tubeworm Riftia pachyptila, and also host chemosynthetic bacterial symbionts. Courtesy of PMEL.