In total darkness, they survived by chemosynthesis.

The sulphide in the vent fluid is the primary substance supporting the unique vent ecosystem, through chemosynthesis.

Although vent fauna in the vicinity of mining activities would undoubtedly be affected, vent communities may have the ability to re-establish at severely disturbed sites as long as there are hydrothermal emissions to support microbial chemosynthesis.

It was erroneous to assume that the vent communities demonstrated the ability to re-establish themselves at severely disturbed sites as long as there were hydrothermal emissions to support microbial chemosynthesis.

Hydrothermal vents. Hydrothermal vents are mineral-rich regions in the ocean floor, present at depths of 1,800 to 3,700 metres and characterized by the ejection of superheated water saturated with minerals from underlying magma.153 They are rich in polymetallic sulphides, the primary substance supporting the unique vent ecosystem through a process called chemosynthesis.

Biological productivity at hydrothermal vents is sustained not by photosynthetic products arriving from the sunlit surface ocean, but rather by the chemosynthesis of organic matter by vent micro-organisms which use energy from chemical oxidations to produce organic matter from CO2 and mineral nutrients.

Hydrothermal vent ecosystems functioned on the basis of a process known as chemosynthesis (as opposed to photosynthesis, which characterized most other life forms), through which hydrogen sulphide gas was transformed into energy by microbes, which in turn constituted the basis of the food chain of the ecosystem.

High animal density and the presence of unusual species are known to be common characteristics of deep-sea vents all over the globe, with the composition of the fauna varying between sites and regions.115 Massive groupings of giant worms, clams and mussels cluster around hydrothermal vents; the biomass in this area can be 500 to 1,000 times that of other deep-sea areas.116 Instead of photosynthesis, hydrothermal vent ecosystems thrive on chemosynthesis, a process that uses energy from chemical oxidations to produce organic matter from CO2 and mineral nutrients.