A new paper by researchers from MBARI has revealed the true extent of the famous Endeavour Segment of hydrothermal vents in the Pacific Northwest. Their high resolution map of 572 chimneys has changed what we know about this region and hydrothermal vents in general, as well as opening up new possibilities for researchers.
Hydrothermal vents are one of the most important and least understood habitats in the deep sea. This is primarily because they can be extremely hard to locate thousands of metres beneath the surface. For years one of the best places to study hydrothermal vents has been the Endeavour Segment in the Pacific, a field of deep sea chimneys located around 350 kilometres Northwest of Washington State. However new research carried out by a group of researchers from MBARI (Monterey Bay Aquarium Research Institute) has revealed that there are far more vents there than previously realised, with a total of 572 chimneys mapped by an AUV. Not only has this changed what we know about hydrothermal vents in this area, but also in general, as well as providing researchers with a new way of finding and studying them.
What are hydrothermal vents?
In order to understand why this new research is important, it is perhaps best to first recap what a hydrothermal vent is and why they are of so much interest to marine biologists and oceanographers. Hydrothermal vents occur at places in the deep ocean where magma below the seafloor superheats the water that seeps down through the bedrock. This superheated water is then pushed back through the seafloor, absorbing metals and minerals from its surroundings as it goes. When the boiling hot water penetrates the seafloor and mixes with the freezing waters of the deep oceans, it causes the metals and minerals in the water to condense and forms underwater structures or chimneys that continue to pump out the superheated water into the ocean.
These chimneys are important for many reasons. Firstly they are key habitats for deep sea ecosystems. This is because they are surrounded by specially adapted creatures with high thermal tolerance, some of which have the ability to convert the sulphur they produce into energy. This means that vents are very important to the deep sea food web by providing a source of energy for other animals that can’t depend on sunlight or other sources of food. In addition to this, hydrothermal vents are also a major candidate for the birthplace of life on Earth billions of years ago. Today they are also financially valuable due to the accumulation of valuable metals that make up the chimneys and are targeted by destructive deep sea mining companies.
The Endeavour Segment
The new research by MBARI was focused upon the Endeavour Segment of the Juan de Fuca ridge located in the Northwest Pacific. This site has been of particular interest to those studying hydrothermal vents, because it is a site of historically high volcanic activity. The seafloor has very literally been ripped apart by this activity over the last few thousand years and provided places for multiple vents and chimneys to grow. It has been constantly surveyed by submersibles and underwater robots since 1982 and as a result researchers believed there were between 45 and 60 vents, one of which ‘Godzilla’ grew to 45m tall before toppling in 1995, all located in a long narrow valley about 14km long and 1.5km wide. However due to poor visibility, total darkness and limited technology, it was hard to determine the exact number for certain.
Mapping new chimneys
To finally determine exactly how many vents were actually located in the Endeavour Segment, researchers from MBARI decided to map the field with sonar. However most sonar maps created on research vessels on the surface lack the resolution needed to identify the smaller vents. Therefore they instead used their AUV (Autonimus Underwater Vehicle) ‘D. Allan B.’ to map the site with sonar at just 50m above the seafloor. The result was a new map with a resolution of 1.25 metres that showed not just 45-60 vents, but an incredible 572. The map and other results from the survey were recently published by the MBARI team in a new paper in the journal AGU.
A surprising discovery
Obviously these results came as a surprise to many researchers who had majorly underestimated the number of hydrothermal vents in the Endeavour Segment. However one of the more valuable discoveries to come out of the new paper was that a large proportion of these vents are actually inactive. Compared to other areas mapped by MBARI, such as the Alcon Rise in the Gulf of California, the endeavour segment has a much higher percentage of chimneys that no longer funnel superheated water. This is something that eventually happens to all hydrothermal vents over time as there is a build-up of minerals and metals that clog up the water flow. However the large proportion of them in this one location has sparked a new theory about hydrothermal vents.
In their new paper the MBARI team suggest that the reason the Endeavour segment has so many sleeping chimneys is because despite its history of high volcanic activity, it is actually starting to become much less active. They propose that the reason areas like the Alcon Rise have fewer vents but more active ones, is that they are in a different period of volcanic activity. Because of this they have also proposed a new life-cycle of hydrothermal vent fields including the following three main stages…
- A magmatic phase, lasting up to tens of thousands of years, when large amounts of magma erupt and cover the seafloor with lava.
- A tectonic phase, lasting perhaps 5,000 years, when the magma supply slows, and the seafloor cools and contracts.
- A hydrothermal phase, lasting just a few thousand years, when resurgent magma below the surface heats fluids that percolate upwards through seafloor cracks, forming large numbers of vents.
A research breakthrough
Not only has the new map of the Endeavour Segment changed what we know about hydrothermal vents in terms of their life cycles and abundance, but it is also a proof of concept for this new way of studying them. By following MBARI’s example other researchers should also be able to study other hydrothermal vent fields in much greater detail and maybe even find new sites for their research. Hopefully this means that over the next few decades we will be able to uncover more of their secrets and gain a better understanding of deep-sea habitats and ecosystems, which will enable us to better protect them.
Marine Madness 