Chemosynthetic ecosystems including hot vents, cold seeps, mud volcanoes and sulphidic brine pools are highly fractured and diverse deep-water habitats shaped by dynamic, small- and large-scale geological processes, which vary substantially in time and space. The discovery of hydrothermal vents, cold seeps and gas hydrates in subsurface sediments and rocks showed that significant ecosystems on Earth are fuelled by reduced chemical substances (H2S, H2, Fe) and hydrocarbons (e.g. CH4). These ecosystems show the highest biomasses and productivity of all those found in the deep sea. Only a tiny fraction of the microbiota at vents and seeps has been identified, and a huge diversity of more than 99% remains to be discovered. Larger animals inhabiting chemosynthetic ecosystems display intriguing symbiotic associations, physiological adaptations, life cycles, reproduction and dispersal strategies.
Organisms in chemosynthetic habitats require distinct features and cues, such as temperature, presence of sulphide and methane, hard ground or particle flux, to maintain their populations. Life histories and dispersal of organisms restricted to these isolated and highly fractured ecosystems remains a major question for understanding the interconnectivity and resilience of these dynamic ecosystems.
Microbial chemosynthetic communities have been found to play a role in controlling greenhouse gases. However, our understanding of the geodynamic and biological controls and feedback mechanisms remain limited. The connection between seafloor structure and dynamics, episodic release of chemical energy, temperature changes or catastrophic destruction and the formation, distribution and longevity of chemosynthetic ecosystems is still to be explored.
HERMIONE investigated the distribution and interconnectivity of chemosynthetic ecosystems. Climate-driven effects on methane production and gas hydrates and their associated communities as indicators of changes in methane flux were investigated. Research was also undertaken into human impacts from litter. The capacities of chemosynthetic organisms to fix carbon dioxide, to produce or consume methane, cycle sulphur, oxidize hydrogen and hydrocarbon and adaptations to extreme physiochemical and energetic conditions were also explored. Links between specific genomic and physiological capacities and diversity supporting ecosystem function and services were examined as was the conservation and management of these potential services in relation to biotechnological exploration.