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Hydrothermal Vent Communities

At hydrothermal vents, chemosynthetic bacteria have evolved to convert dissolved chemicals into the energy needed in order for life to flourish. Thus, these vents represent one of the only places on the planet where life relies not on sunlight for energy, but on the Earth itself.

 

The deep ocean floor is a place that appears entirely devoid of life. With minimal resources, no sunlight, and only a slow trickle of nutrients making its way down here as 'marine snow', life must find unique ways to exist in the depths. Food is scarce, and with very little energy, survival in the depths is a challenge for any creature. There are some locations in the deep that life has clung to for millions of years, and where food and energy is ever abundant.

the unique life of deep sea vents

Pompeii Worm

Alvinella pompejana

This deep sea species of polychaete worm is an extremophile. It is found only at hydrothermal vents in the Pacific Ocean, and was discovered as recently as 1980 near the Galápagos islands. These worms have evolved some incredible adaptations to survive here. The white fuzz on its back is actually a colony of bacteria, which acts as insulation from the extreme heat of the vents, and the cold beyond. At 13cm long, they are able to have their tail sit in the hot vent fluid, while its head enjoys a more moderate temperature.

In the dark oceanic depths, at 6,500 feet (2000 metres) or more, life is concentrated around hydrothermal vent structures in great numbers. Hot, mineral-rich fluids supply chemicals and nutrients, forming the basis of a a diverse community of specialised organisms. 

Over 300 different species have been identified living around hydrothermal vents. 95% of these are were new discoveries, being unique to these communities. Most of them do not resemble any other creature of the planet. Instead, they belong to a divergent evolutionary path which may have splintered off in the distant past.

 

Unlike whale-fall ecosystems which last for only a few decades, these vent communities are ancient and have had far longer. Many scientists believe that life first began around 3.7 billion years ago in deep-sea hydrothermal vents. This would mean that the organisms here have had billions of years to specialise to these environments. Indeed, this is the case. Take a look below at some of the life that is found at hydrothermal vents.

Deepsea Skate

Bathyraja abyssicola

This close relative of sharks and rays is a frequent visitor to hydrothermal vents. The Nautilus research vessel made a surprising observation at the towering hydrothermal vents near the Galápagos, when the seafloor around them was covered with skate eggs. Normally, the incubation period for deep-sea skates is 4 years. But here, they were using the vents to speed up the process. Even just increasing the eggs' temperature by half a degree will rapidly decrease the incubation period. 

Yeti Crab

Kiwa hirsuta

This peculiar crab was first discovered in March 2005, living on the hydrothermal vents along the Pacific-Antarctic ridge just south of Easter Island. Its name comes from the hair that covers the crab's legs. These hairs support vast colonies of filamentous bacteria, which the yeti crab supposedly farms as a source of food.

primary producers at the vents

The chemicals expelled within the superheated vent fluid would be toxic to us humans. But to the life here, they are vital, containing nutrients that bacteria are able to convert to energy in a process that mirrors the conversion of sunlight during photosynthesis. Down here, photosynthesis is impossible and plants cannot survive. Instead, chemosynthesis is the primary source of energy as the bacteria convert hydrogen sulphide into glucose.

The discovery of chemosynthetic organisms at the vents redefined how we understand life on Earth. Before this, it was believed that life simply could not survive without the presence of sunlight to provide energy.

Like plants in the shallows and on land, the bacteria are the primary producers. They are eaten by larger animals, such as yeti crabs and bottom feeders like limpets that graze on the microbial mats.

how hydrothermal vents form

The process begins when water seeps down through cracks into the Earth's crust, usually in volcanically active regions of the sea floor like the mid-ocean ridge. The magma within the Earth's layers cause the water to become superheated, at which point the water rises up out of the ocean floor. On the way, it picks up dissolved minerals, and deposits these upon mixing with the cooler seawater above. The towering chimney structures form as a result of these minerals solidifying.

There are a number of varieties of hydrothermal vents, each one characterised by its specific mineral content. Black smokers emit hotter, darker plumes, building chimneys over 180 feet tall (50 metres). They have high levels of sulphides that precipitate out of the vent fluid to form the black smoke. 

 

Another vent variety is the white smoker, which has a mineral content of barium, calcium and silicon.

To conclude, deep sea vents are able to support a unique ecosystem and a community of highly-specialised and unique organisms in the deep. The islands of diversity and productivity that they form in the otherwise lifeless depths are sites of outstanding scientific interest, providing a relatively new insight into how life evolves, forms and adapts to a harsh environment. But with these vents only having been discovered in the 1970s, there remains a wealth of secrets in the deep sea, yet to be discovered.

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