Tuesday, 5 March 2013

20 - Bottoms up ocean sampling!

Isis  is recovered after another deep sea mission
In recent weeks I've become accustomed to live images of the deep ocean. I now realise that if we lived on the seafloor we would probably know a lot more about it. It's easier to learn about things we can see and touch – and so not surprising that we've learnt more about our close surroundings than the farther horizons of our planet and solar system.

To fill the gaps in understanding, scientists often explore parts of our world that are difficult to reach like our polar wildernesses. Oceanographic scientists inherently face a similar challenge – examining our remote oceans to learn how the planet functions. But there is a mismatch in our understanding of ocean chemistry for instance, between its surface and deep waters, which I think reflects the obscurity of deep waters from our view.

Expeditions like these, which bring cameras to the unseen ocean floor, remind me just how different our understanding of oceanography would be if we had begun ocean exploration from the bottom, up.

The seafloor, viewed from the remotely operated vehicle Isis, is an endless field of chemical interaction between minerals and seawater that is rich with life – somewhat reminiscent of the thin line between land and atmosphere that we call home.

From the bottom of the ocean, the view up is often bleak. Ascend just a few metres and all that you're likely to see is vast and empty, but there is undoubtedly more here than meets the eye, we just don't know it yet.

Seawater chemistry in the surface ocean is anything but even or empty. In fact, there is a complex ecosystem in the surface layer of the ocean nourished by dissolved nutrients, metals and gases that is responsible for pumping carbon between geologic and atmospheric realms, and is also sensitive to subtle changes in seawater composition. We know this because we've looked there many times, in many parts of the world, and made countless measurements, to build a detailed knowledge of chemical interactions in different areas.

Our understanding of bottom water chemistry however, and its impact on global ocean processes, such as carbon cycling, nutrient supply and transport, is naive compared to the surface oceans due to the scarcity of measurements near the seafloor.

A mismatch in surface and deep ocean observations is anticipated given the difficulty of sampling close to the seafloor from far above, but precision instruments like Isis  are pioneering new measurements of deep water and sediments; the Isis  piloting team has been operating 24 hours a day, diligently sampling the seafloor in a way that conventional methods never could.

It is an exciting time to be an oceanographer - a step change in understanding ocean chemistry will come from the partnership of science and technology in deep-sea research. From what I have seen in recent weeks, the Isis  team of the National Oceanography Centre has exemplified the power of this cooperation with scientists aboard the RRS James Cook. Long may this partnership continue!

By Will Homoky

Saturday, 2 March 2013

19 - Crossing the Caribbean

Pete Talling points out the island of Montserrat.  The hazy cloud is ash blowing off the flank of the volcano behind which is the slowly inflating volcanic dome and the devastated town of Plymouth.
After four days we are now just off the volcanic island of Montserrat for voyage JC083. This island is one of the Lesser Antilles island arc, a chain of volcanic islands that marks the western edge of the Caribbean.

Island arc volcanoes form where the ocean crust is consumed back into the Earth’s interior at deep-ocean trenches. The best known of these are the trenches surrounding the Pacific Ocean, and the island arcs are popularly known as the ‘Pacific Ring of Fire’.

In the Caribbean, the Lesser Antilles arc is also a fiery phenomenon. No more so than at Montserrat, which over the past 20 years has been devastated by a series of volcanic eruptions. The capital city of Plymouth is just a ruin now, barely visible below the thick carpet of ash and debris erupted from the volcano. Our task here will be to trace the trail of devastation out to sea.

Surge deposits, dumped by hot clouds of ash and gas at temperatures of hundreds of degrees Celsius and travelling at many tens of kilometres per hour scour the land over which they travel and rush out over the sea where they eventually dump millions of tonnes of debris onto the seafloor.

No one knows what these deposits look like, or what effect they have had on the seabed below. Using the ROV Isis, we will make highly detailed maps of the deposits on the seafloor. Then, with a new piece of equipment called a vibro-corer attached to the ROV, we will take cores from these deposits to examine the physical and chemical effects of these highly destructive volcanic eruptions.

Pete Talling is leading this part of the expedition and hopes to be the first to make a study of an underwater volcanic surge deposit. To get the shallow part of the deposit, Captain Peter Sarjeant has special permission from the volcano observatory to take our ship, the RRS James Cook, inside the exclusion zone and to within a kilometre and a half of the coast just off the devastated town of Plymouth.

Already, we can see and smell the ash cloud blowing off the side of the volcano.

Wednesday, 27 February 2013

18 - The final word from team biology

Sampling west shrimp gully at Beebe Vent Field
The Isis  ROV has captured the last glance of the seabed on our final dive at the Beebe Vent Field and we’ve collected our last batch of samples from the distant reaches of the deep ocean, where sunlight is a stranger and pressure exerts a tight grip. The cold, black waters revealed on the ascent unveil nothing of the marvels of life we leave behind and whose secrets we are endeavouring to unlock.

A final glimpse of the deepest vents
During the last few weeks we’ve collected hundreds of hours of video footage and thousands of stills of the creatures inhabiting the Von Damm and Beebe vent fields, and of the halo of life surrounding these island-like oases. We’ve catalogued, processed and photographed a diverse array of animal life, including abundant blind vent shrimp and elusive echindoderms, elongate tubeworms and squat lobsters, fragile sponges and corals, and exquisite anemones. One of our objectives has been to elucidate the biodiversity at the deepest vents and our final species list is still in preparation as we collate the data we’ve accumulated and begin to analyse what we’ve found. At the time of writing we don’t know if we’ve discovered any new species…but as you read this we’ll be working hard to find out!

Jon Copley using skype to show his SOES1006 class
our discoveries from the deep
The biologists have got a tremendous amount of new information and samples from this expedition and we’ll be kept very busy for the foreseeable future. I hope none of us will ever forget the wonders we’ve had the privilege to see and experience, captured by the cameras on Isis  and viewed through the eyes of awed human beings.

Jon Copley has been an inspirational principal scientist; in addition to leading on science he has made several daily Skype calls to schools across the UK and even taught his first year marine ecology practicals via Skype from the ship.

Paul Tyler
It has been a pleasure to sail with such a great team of scientists, technicians, officers and crew. And finally we raise a glass to Professor Paul Tyler, without whom none of this would be possible. His vision and commitment to deep sea biological exploration has shaped UK marine science. This is Paul’s last voyage and many of us have sailed with him on his 60+ expeditions – cheers Paul, here’s to a long and happy (semi) retirement.

By Verity Nye, Rachel Mills and Team Biology

Monday, 25 February 2013

17 - Geostrauphic wonders

A rare fish at the vent site
As our time at the deepest vents draws to a close, we reflect on what we have learned during these past nights. I say ‘nights’ as this is how it feels; immersed in the perpetual darkness of the abyssal depths, cameras for our eyes, the only light is that being reflected back as Isis picks out the colourful hues and dark shadows of the Beebe Vent Field.

The colours at the vent site are stunning
As geologists, we have wandered the furthest from the main vent site, mapping the surrounding hills and valleys. Here, we have found a landscape of volcanoes and lavas. Pelagic sediment sits like a recent snow-fall, picking out the texture and detail of the rocky surface in brilliant white filaments of chalk. Striking like dark streaks across this alpine scene are black fissures: cracks forming the plate boundary where the seafloor drops vertically away into the darkness below. Not even our most powerful lights can penetrate here, leaving the bottom a mysterious realm of shadows and gloom.

At the astonishing depth of 5080 metres, in the bottom of the deepest valley, we find a carpet of bright orange mud. Such a startling contrast in colour means only one thing: even down here, the minerals falling out from the distant vent field are having a profound impact. The orange colour is the result of iron. Spewed from the hydrothermal waters at over 400°C, the iron oxidises rapidly and falls as rust onto the seabed below. The accumulations here speak of thousands of years of fall-out.

Up slope, the seafloor shows signs of past catastrophes. Sink holes appear where earthquakes have shifted the rocks below and the rusty sediment has sunk to fill the resulting holes. A little further up the slope we are met by huge blocks of sulfide perched precariously on top of each other, teetering on the brink of the abyss. Some are as large as a bus, massive blocky lumps, with rusty scree in between, from which shimmering water seeps.

The colours here are amongst the most amazing sights: oranges and reds from the abundant iron, but also peacock hues of green, blue and purple: sure signs that copper is also in abundance. In places, green ‘stalagmites’ cling precariously to the rocky overhangs. Formed from a copper mineral called ‘atacamite’, here the copper is literally leaking out of the rock. This is an amazing sight to us as it confirms one of the hypotheses that bought us here: that the hydrothermal minerals at these depths and high temperatures will be rich in copper. Back on the ship, these rocks are indeed like peacocks: their vibrant colours attract everyone’s attentions and, for the first time, compete on an even footing with the biology for being the most photogenic.

The science party relaxing at sunset on deck after completion of dives.

Sunday, 24 February 2013

16 - This is only the beginning…

Will, Diva and Leigh in relaxed mode!
Team Chemistry have finished sampling and are wrapping up the analyses in the shipboard laboratories. We have stunk the ship out with hydrogen sulphide collected in the water samplers used by Valerie and Alain. We have measured huge amounts of this smelly gas in the hot, metal-rich vent fluids, along with other gases such as methane. We have traced this methane up through into the ocean, transported with the buoyant plume of material gushing from the vents. We have filtered over a tonne of sea water to extract the particles of different sizes to understand how the metals are dispersed in the ocean. We have probed the seafloor to measure temperature and collected mud to extract the fluids that ooze through the edges of the sulphide mounds. This is just the start of our work to understand the impact of these deepest vents on the ocean.

Detailed analysis of samples back at the National Oceanography Centre and the Geosciences Environment Toulouse laboratory will enable us to relate the chemistry in the local vent environment to discoveries made by the geology and biology team on the distribution of different rock types and organisms across the Beebe and Von Damm vent fields. This allows us to see how different species survive and tolerate different chemical environments. The micro-organisms that survive in these harsh, toxic conditions are an example of how life can survive in the most inhospitable places and may be our best model to search for life in other parts of our solar system.

On this expedition, biologists, geologists and chemists have collaborated to generate new views of the deepest known vents on the planet.

Team Chemistry: Alain Castillo, Valerie Chavagnac, Jeff Hawkes, Will Homoky, Aly Lough and Rachel Mills

Rachel on deck

Friday, 22 February 2013

15 - Vent energy and chocolate cake

We’ve just had a few birthdays on board, meaning great quantities of delicious chocolate cake for everyone. We’ve also been sampling the fantastic Beebe Vent site fluids, and so it seems a good opportunity to make some food comparisons.

The vents are furiously spewing out an estimated 300 kg of water every second, and that water contains about 12 millimoles (mM) of hydrogen sulfide, the main food for the bacteria which feed the shrimp. We’ll say 12 mM is about 1.25 Calories (kcal; after great calculations by McCollom and Shock in 1997).

Our chocolate cake, which is ginormous, is probably at least 15000 kcal – so a little maths tells us that our vents are serving up about a slice of cake every second – and more than 2,000 delicious chocolate cakes each day. Plenty of food for bacteria – if only they can get to the fluids – which (unfortunately for them) are more than 400°C. It’s probably safer for them to stay in the diffuse areas, which have less hydrogen sulfide, but much more comfortable temperatures around 50°C. Funnily enough, this is where we find the majority of the shrimp – which carry the bacteria in their gills and other convenient parts of their bodies. Personally, I prefer chocolate cake to rotten-egg smelling hydrogen sulfide – but each to their own!

By Jeff Hawkes

Jeff taking a sample from the CTD carousel to analyse methane – another great food source for bacteria

Wednesday, 20 February 2013

14 - Geo team at the Beebe Hydrothermal Vent Field

Beebe black smoker image from previous HYBIS expedition
Looking over the side of the ship into the deep blue of the Caribbean Sea, it is hard to believe that directly below us, almost 5 km (3 miles) down, lies the Beebe Hydrothermal Vent Field, the deepest of its kind yet discovered, and by a team from the National Oceanography Centre. The site is named after William Beebe, the first ecologist to observe deep-sea animals in their natural habitat. Today, we will be diving at the site for the geo team’s first sampling on JC82 with the Isis  ROV.

The extraordinarily high pressure (of 500 x atmospheres) at the Beebe site, situated at nearly double the normal depth of most known hydrothermal systems, is important due to the physical changes that seawater undergoes at extremely high pressures and temperatures. Instead of being a liquid or vapour, the vent fluid becomes supercritical. These supercritical fluids are very reactive, dissolve metals at depth in the Earth’s crust, and transport them to the seafloor where they form spectacular hydrothermal vents and mineral deposits.

The Beebe site is also fascinating because it contains a history of hydrothermal activity represented by a series of older mounds. Sampling them will give us an idea of how the deposit has changed through time. The mineral deposits oxidise (like rusting) to a bright red colour, a process that greatly increases the concentration of valuable metals: a process known as ‘supergene enrichment’.

We are studying the Beebe site because it is a natural laboratory in which to study the effects of temperature and pressure on the composition of hydrothermal mineral deposits. Studying modern day hydrothermal systems like the Beebe Field allows us better to understand the formation of land-based ore deposits from which humankind gets all its essential metals.

By Matt Hodgkinson

Verity teaches Matt a lesson