Iceland’s Shallow Hydrothermal VentsLatest update December 2, 2018 Started on December 2, 2018
We are planning an expedition to explore the marine animals living near Iceland’s shallow hydrothermal vents, and the adaptations they may be making to these seemingly hostile yet very productive environments.
This week, we were able to take our trident ROV on its first ever dives, to test it and get used to handling it ahead of our visit to Iceland.
We deployed it within the docks at the National Oceanography Centre, Southampton (NOCS), from the R.V. Callista. This ship is skippered by Bill, and both him his awesome pet labrador Thomas have been on many exploration adventures with us so far, so we decided to name our trident ROV Thomas in honour of Thomas the dog.
Testing went very well, and we were very impressed with the quick and easy set up of ROV Thomas, as well as the video quality. We definitely need to get better at handling it, but despite this ROV Thomas was able to reveal to us the nature of the NOCS dock seafloor, as well as the many marine invertebrates living on the dock wall.
What lives on Iceland's vent chimneys?
Time is drawing closer to our adventure, with only a month and a half to go before we visit Iceland’s shallow vent chimneys! At this stage I thought it might be good to explore what creatures we might expect to find living on them.
In Icelandic marine waters in general the fauna is made up of arctic-boreal and boreal species which can also occur in western European waters, and there are also some American species. Around 3.6 million years ago when the isthmus of Panama formed and closed the Central American Seaway, the flow of Pacific water from the Bering Strait and Arctic Ocean into the Atlantic brought a range of Pacific marine invertebrates to Iceland, including the blue mussel (Mytilus edulis) and the common whelk (Buccinum undatum).
There has been little work to document in detail specifically the animals living on Iceland’s shallow vent chimneys, but the many divers that have explored the site have provided valuable indications in the form of pictures and videos of what lives there. The chimneys appear to be dominated by algae and benthic invertebrates that occur on the sides of the chimney cones, sometimes living very close to the conduits from which the vent fluid escapes. Anemones, bryzoans and sponges appear to be abundant encrusting fauna on the vent chimney walls, with molluscs such as mussels and gastropods occurring around these. Sea urchins and seastars are also often observed on the vent chimneys.
The microbial life of Iceland’s vent chimneys has been researched in relatively more detail, with studies of shallow vent chimneys spewing alkaline fluids typically having microbial communities dominated by heterotrophic and mixotrophic Gammaproteobacteria and/or members of the Firmicutes phylum. The community of microbes found at Strytan appears to include over 50 strains of thermophilic microbes, with bacteria mainly from the Aquificales group and Archaea mainly from the Korarchaeota. These microbes appear to reflect the freshwater inputs into the Icelandic vent chimney habitat.
More on Iceland’s vent chimneys
In the deep ocean, the chemistry of hydrothermal vent environments can have a big influence on the communities of life that form at these sites. A lot of vent chimneys in the deep sea are comprised of iron sulphide minerals such as pyrite, and spew a fluid that is rich in hydrogen sulphide. This gas is used by certain types of microbes (sulphide oxidisers) to convert carbon dioxide into food. In the absence of light, these microbes can dominate deep sea vent communities and would feed the range of highly specialised animals that have made their homes there.
Iceland’s vent chimneys are somewhat different to those commonly found in the deep sea along mid-ocean ridges. Rather than iron sulphides, the Icelandic vent chimneys are comprised of saponite, a clay-like mineral which is rich in magnesium, silicon and aluminium, and the fluid that emanates from the Icelandic vent chimneys is also unlike that which flows from deep sea vents, because it is derived from rainwater, whereas the fluid flowing out of deep sea vents is modified seawater. Iceland vent chimney fluid is also alkaline, has a low mineral content, and has a temperature of around 80°C. It is thought that the chimneys have been around since the last ice age, and are 11,000 years old, while the fluid flowing from them is over 1,000 years old!
The organisms that are found on the Icelandic chimneys are also somewhat different to those at deep-sea vents - because Strýtur and Arnarnesstrýtur occur within shallow waters easily reached by light from the sun, the communities are more typical of shallow-water arctic marine environments, which are typically supported by photosynthesis rather than the chemicals coming out of the vents.
The Trident ROV is here!
We are absolutely thrilled to have received support for our project from the S.E.E. Initiative, and very grateful for their donation of a Trident ROV to help us explore!
The Trident ROV arrived safely this week in our lab at the Natural History Museum in London, and I have been attempting set up as well as trying to figure out the controls, so far it all seems fairly straightforward.
For now the Trident has been having a quick explore of our shelves of intriguing specimens brought back from various ocean expeditions, but very soon we are planning to take it on its maiden voyage. Suggestions of nearby waterbodies for this include the Serpentine lake in nearby Hyde Park and the Regents Canal, the labteam and I are very excited to put it in the water!
Iceland and its hydrothermal vents
I often hear from people who have been to Iceland that is a very odd and interesting place, with an arctic landscape that you might expect from another world altogether. This is probably due to its fairly unusual geological situation - Iceland formed around 60 million years ago as Greenland was drifting away from Scotland, due to the presence of a hotspot in the middle of the expanding Atlantic Ocean. Essentially the Mid-Atlantic Ridge runs right through Iceland, and this is responsible for making Iceland a very volcanically active place - volcano eruptions are fairly frequent on the island, as are geysers and land-based hot springs. Iceland itself is growing at a rate of 20 km per million years, and its geothermal potential is also harnessed for energy as well as food production. I was intrigued to find out that on Iceland, tomatoes are grown in large geothermally-heated greenhouses!
As Iceland is essentially a surface expression of the Mid-Atlantic Ridge, this creates the possibility for hydrothermal vents to exist at much shallower depths than they are normally found. The story goes that hundreds of years ago fishermen measuring the depth of Iceland’s northern fjord Eyjafjörður discovered hydrothermal vent chimneys there, that rise from depths of 65 m to only 15 m from the sea surface. These vents, known as the Strýtur vent chimneys, were more recently rediscovered by divers, and similar vent chimneys were also found at another nearby site in Eyjafjörður, known as Arnarnesstrýtur. As the tops of these chimneys reach depths of 15-20 m, they can readily be explored through SCUBA diving, and therefore much more easily than vents in the deep sea.
What is a hydrothermal vent?
Our ocean contains many amazing and distinct habitats, and hydrothermal vents are amongst the most remarkable.
Hydrothermal vents are essentially hot springs, but ones that occur within the ocean and most commonly in the deep sea, typically at depths of around 2500 m and in environments such as mid-ocean ridges. They form wherever there is sufficient heat and porosity to drive the convective flow of seawater. At mid-ocean ridges, stretching of the oceanic crust causes it to crack, allowing seawater to penetrate deep into the Earth's crust. On its journey towards the mantle, this water is heated, picks up dissolved minerals and gases, and is circulated back to the seabed where it erupts as a hydrothermal vent.
The water that emanates from hydrothermal vents can be over 400 °C! But it mixes quite readily with surrounding cooler seawater to create more ambient conditions in which animals can thrive.
Animals are also drawn to hydrothermal vents in the deep sea because they are incredibly productive environments compared to much of the deep ocean. The gases entrained in vent fluid can be used by microbes to fix carbon dioxide, thereby converting it to food in a process similar to photosynthesis but that occurs completely in the dark.
Because of their high productivity, animals (typically marine invertebrates) are often found at vents in incredible abundances. And the animals that thrive there are often different to those found within other deep sea habitats as they have novel adaptations to survive at vents, such as very close-knit associations with microbes that ensures a regular supply of food, and ways to cope with the heat and toxicity of the vents.
Deep-sea hydrothermal vents (or marine hot springs) are home to extraordinary, highly-specialised marine animals, adapted in a variety of ways to obtaining their energy from the chemicals emanating from these vents. While the sharp temperature gradients, unstable, and toxic conditions typical of hydrothermal vents can make them challenging habitats for marine life, the ready food supply provides a strong incentive for adapting to vents. Over Earth’s history, a wide variety of animal types have colonised hydrothermal vents, and vent environments therefore appear to be important for driving the development of novel adaptations in animals in the deep sea, but the mechanisms through which vent adaptation happens are largely unknown. Uncovering how animals adapt to vent conditions can give us crucial clues for predicting how marine life may respond to major environmental challenges such as climate change and pollution. The majority of Earth’s hydrothermal vents are fairly difficult to access as they are found at over 2 km water depth, however, off the northern coast of Iceland hydrothermal vents occur at a depth of just 15-70 metres. In this project we are planning fieldwork to explore what animals living near Iceland’s shallow vents, and the adaptations they may have made to the vents using genetic tools.
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