The Weird And Wonderful Ecosystems Of Hydrothermal Vents

Life finds a way in the deep places of the ocean

Are there volcanoes in the ocean?

Both dry land and the “land” underneath the oceans are part of large, rocky plates that are made of the Earth’s crust and upper mantle – the topmost layers of the Earth, or lithosphere. Oceanic plates, which lie under the oceans, are made of basalt and are denser than those that give rise to continents.

Plates are always moving, if slowly, which means that they come into contact with each other – sometimes coming together, moving apart, or sliding alongside each other in what are known as “boundary interactions.”

Where plates converge or diverge, magma can find paths to the surface from underground magma chambers, in events we call volcanic eruptions. The Earth’s surface is mostly water, which means that most plate boundaries are found in the ocean – and that is where most volcanoes are!

The eruptions and other activities of these volcanoes change the ocean floor, forming underwater mountain ranges and landscapes that are just as complex as the ones we see around us on land.

Can life survive around underwater volcanoes?

In areas around underwater volcanoes, such as mid-ocean ridges, ocean basins, and volcanic hotspots, seawater seeps through cracks in the ocean floor where it can get superheated to up to 867°F by molten magma underneath!

The chemical reaction between the seawater and the magma creates hydrothermal fluid, creating hydrothermal vents that release complex chemicals and provide important nutrients to the world’s oceans. Over time, these vents can look like huge underwater chimneys as minerals are released and added to the tops.

Inactive hydrothermal vents
Inactive hydrothermal vents at the Galapagos Rift, Credit: Wikimedia/ NOAA Photo Library

No light from the surface can reach these vents, which are found at a depth of 2,100 meters or 7,000 feet on average. But without light, how can life survive? At first, oceanographers thought that vent organisms would rely on “marine snow” – the organic detritus that sinks from the surface layers of the ocean.

However, we now know that the volcanoes take the place of the sun as the source of energy.

The mineral-rich waters that are released by the vents are used by microorganisms like bacteria and archaea that thrive in these harsh conditions. They take the place of plants as “primary producers” in these ecosystems – instead of photosynthesis, they perform chemosynthesis, using chemical energy instead of light energy to convert carbon dioxide into sugar, that is, food.

These microorganisms form the first level of the food chain in hydrothermal vent ecosystems, allowing a variety of other organisms to thrive.

Who lives in hydrothermal vents?

The denizens of hydrothermal vent ecosystems have adapted to the acidic water, high temperatures, lack of sunlight, and extreme water pressure. Fascinatingly, habitats in these areas exist both above and below the seafloor!

Swimming shrimp
Swimming shrimp, squat lobsters, and vent mussels on a hydrothermal vent, Credit: Wikimedia/ NOAA Photo Library

The primary producers, chemosynthetic bacteria, grow in thick mats – they provide food for copepods and amphipods that graze on them. These are then preyed on by larger organisms like shrimp, crabs, and octopuses. Eels and other fish are also found in these systems, though they are outnumbered by invertebrates.

Some inhabitants of hydrothermal vents have not been found living anywhere else, including yeti crabs and scaly-foot gastropods. Tube worms and vent mussels form large colonies, while the Pompeii worm lives on the sides of vent chimneys and is one of the most heat-resistant multicellular animals known to science.

Under the vents, scientists have found tube worm larvae – this suggests that, like the animals that live in cavities underground, another kind of ecosystem lurks below the one living around the vents! Species above and below the surface depend on oxygen in the seawater above and the vent fluid from below.

Hydrothermal vents have probably existed since our planet was very young – in fact, they might have been where life on Earth first began. Scientists have found animal fossils from hydrothermal vents that are about 440 million years old, while microbial remains from hydrothermal vents go back 3.5 billion years ago.

How were hydrothermal vents discovered?

Unlike coral reefs or other ecosystems found in shallower waters, human divers cannot explore hydrothermal vents. The rocky, uneven terrain also makes trawling difficult. Instead, scientists are learning about these fascinating ecosystems using remotely operated vehicles and sometimes manned submersibles, equipped with robotic arms to collect samples, not to mention cameras and lights.

Specialized scientific equipment
Specialized scientific equipment allows researchers to study hydrothermal vent ecosystems, Credit: Wikimedia/Susan Lang, U. of SC. / NSF / ROV Jason / 2018 © Woods Hole Oceanographic Institution

Scientists first discovered hydrothermal vents along the Galapagos Rift in 1976, while the chemosynthetic ecosystems in this region were first observed in 1977. Since then, researchers from the Scripps Institution of Oceanography, Woods Hole Oceanographic Institution, and many other teams globally have been exploring these diverse and mysterious systems. More than 550 active hydrothermal vent fields are currently known.

These regions produce valuable mineral deposits like cobalt, gold, copper, and rare earth metals. Due to rising metal prices, mining in hydrothermal vents is receiving more attention, especially in countries like Japan, which depend heavily on mineral imports. Japan led the world’s first large-scale mining expedition in 2017, focusing on hydrothermal vent deposits in the Okinawa Trough.

Companies are advancing plans to extract these minerals using modified technology. However, this mining poses significant environmental risks, including disturbance to vent ecosystems, release of heavy metals, and increased sedimentation.

Efforts are underway to understand and mitigate these impacts, but research efforts are often skewed towards better-studied vent ecosystems, potentially overlooking the specific challenges of mining sites.

While mining minerals from the seafloor has been attempted before, such as for manganese nodules in the 1960s and 1970s, it presents complex challenges and potential environmental consequences. Despite past attempts, the feasibility and impact of seafloor mining remain subjects of ongoing debate and research.

On the subject of recent findings in hydrothermal ecosystems, Dr. Wendy Schmidt, co-founder and president of the Schmidt Ocean Institute, noted, “The discovery of new creatures, landscapes, and now, an entirely new ecosystem underscores just how much we have yet to discover about our Ocean – and how important it is to protect what we don’t yet know or understand.”

To us, the denizens of this world seem strange and alien, at home in the dark. Who knows what bewitching discoveries are yet to be made in the lightless depths of the ocean?

People also ask

What are examples of hydrothermal vents?

In terms of temperature, hydrothermal vents can be classified as diffuse vents that emit clear, low-temperature waters up to 30°C; white smoker vents that release milky fluids at temperatures of 200–330°C; and black smoker vents that discharge jets of water blackened by sulfide precipitates at temperatures between 300 and 400°C.

Why are hydrothermal vents important?

Hydrothermal vents act as natural “plumbing systems” that transport chemicals and heat from the Earth’s interior and thus help regulate the geochemistry of the ocean while accumulating large amounts of valuable minerals on the ocean floor.

Who discovered hydrothermal vents?

Deep-sea hydrothermal vents and their surrounding chemosynthesis-based biological communities were found in the Galapagos in 1977 by a team of researchers including oceanographer Dr. Robert Ballard and geophysicist Dr. Jean Francheteau in a submersible called Alvin.

References

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