Hydrothermal vents are veritable deep-sea geysers, located where the ocean crust is so thin that seawater percolates through it, eventually reaching the depths of the magma chamber. There, it heats up and takes up reduced compounds — such as methane, hydrogen or sulphide — and heavy metals, but is devoid of oxygen. When the hydrothermal fluid rises to the surface, it forms black smokers that expulse the transformed seawater, which can reach temperatures of up to 400°C.
Hydrothermal vents were discovered in 1977 and were a revelation for biology. Not only did they reveal the existence of hitherto unknown biodiversity and lead to the description of hundreds of new species, but they also revealed a hitherto unknown biological process: chemosynthesis.
Until then, it was commonly believed that all life depended on photosynthesis, a process based on solar energy. During photosynthesis, plants and green algae use photons from the light energy to synthesise organic matter from water and carbon dioxide. Due to this dependence on light, the deep sea was long considered to be devoid of life… but the hydrothermal vents have their own energy source: bacteria can use reduced compounds dissolved in the fluids to synthesise organic matter, thereby supporting luxurious animal communities!
Hydrothermal species depend on their environment for their survival (we call them endemic species) and live in conditions otherwise considered toxic for most living organisms. Their ability to adapt is a fascinating scientific topic.
Our knowledge on hydrothermal fauna is still very limited because it is so difficult to access these ecosystems that are often located at ocean depths greater than 1000 m. However, these ecosystems are increasingly coveted by the mining industry for their resources! It is thus important to enhance our knowledge of this environment quickly to estimate the potential impact of any future mining activities.