Originally published on the Reefbites website.

For many, the word reef conjures up images of snorkeling in bath-temperature water above vibrant corals and fishes next to a sunny beach. Yet there are more species of corals that illuminate the wintery waters of the deep sea, forming habitats that rival the colors and biodiversity of shallow-water reefs. Cold-water coral and sponge reefs are found around the globe at all latitudes and depths. Anything below 200 meters is deemed “deep-sea,” out of the reach of light. Unlike their shallow-water cousins, cold-water corals don’t have symbiotic algae that provides food via photosynthesis, so they rely on food falling from the sea surface.

Reefs in the deep

Originating from the Norwegian term “rif,” a reef historically referred to corals presenting a danger to ships. However, deep-sea corals can form massive three-dimensional structures thousands of meters underwater, far out of the reach of ships. Thus, deep-sea scientists debate still today about when and if they should use the term to describe most cold-water coral and sponge ecosystems. Cold-water stony corals can settle on the dead skeletons of previous corals, forming large structures typically called reefs, mounds, and hills. The best studied deep-sea coral is Desmophylum pertusum, previously named Lophelia pertusa, because it forms large reef-structures in the northern hemisphere, while Solenosmilia variabilis forms bright orange reefs in the southern hemisphere. In addition to reefs formed by hard corals, octocorals and black corals form deep-sea coral gardens and beds. Even sponges can form large reef structures in the deep!

Species associations

Though not as familiar as the bond between clownfish and anemone, the symbiotic relationship between the coral Desmophylum pertusum and the worm Eunice norvegica is equally fascinating. The worm steals food from the coral polyps, but repays the debt by moving coral fragments together to strengthen the reef framework. In addition, commercial fishes use deep-sea coral and sponge habitats as nursery and feeding grounds, and many other suspension-feeding invertebrates settle at the tops of reefs to feed above the slow moving water nearest the seafloor. 

Threats to deep-sea reefs

Although the deep sea seems far out of the reach of humans, our actions still impact deep-sea corals and sponges. Climate change is warming the deep waters, depleting the oxygen necessary to life. Ocean acidification is dissolving coral skeletons in the deep sea more rapidly than seen in shallow-water corals. As cold-water coral and sponge ecosystems harbor commercial species, fishing activity can destroy the structure-forming species. Even trash from land can reach the deep sea and become entangled in corals and sponges. Fortunately, as the technology for ocean exploration advances, increased understanding of deep-sea coral and sponge ecosystems allows us to make educated management decisions.

References

Miller, Karen J., & Rasanthi M. Gunasekera. 2017. A comparison of genetic connectivity in two deep sea corals to examine whether seamounts are isolated islands or stepping stones for dispersal. Scientific Reports 7: 1–14.

Oppelt, Alexandra, Matthias López, Carlos Rocha. 2017. Biogeochemical analysis of the calcification patterns of cold-water corals Madrepora oculata and Lophelia pertusa along contact surfaces with calcified tubes of the symbiotic polychaete Eunice norvegica: Evaluation of a ‘mucus’ calcification hypothesis. Deep-Sea Research Part I: Oceanographic Research Papers 127: 90–104.

Roberts, J. Murray, Andrew Wheeler, Andre Friewald, Stephen Cairns. 2009. Cold-Water Corals: The Biology and Geology of Deep-Sea Habitats. Cambridge University Press, New York, United States.

Rogers, Alex D., Andrew S. Brierley, Peter L. Croot. 2015. Delving Deeper: Critical challenges for 21st century deep-sea research. European Marine Board: Technical Report

“Seafloor Ecology Spring Expedition.” n.d. Monterey Bay Aquarium Research Institute

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Oceanography and marine science mentions (counted by Google) peaked in the 1960’s at the time of intense exploration and record breaking dives to the ocean depths (and of course the Apollo missions into space). The latter part of the 20^th century was then characterised by sustained efforts to explore the ocean depths, with the discovery of deep sea hydrothermal vents near seafloor volcanoes and development of a new integrated understanding of how the oceans function, control the climate and how ecosystems operate in this vast, and largely invisible realm. This period saw the burgeoning of new science disciplines and cross-disciplinary efforts and the relative frequency of the words ‘oceanography’ and ‘marine science’ subsequently decreased systematically through to 2019 in Google search counts.

Ocean science has evolved as a specialist subject at a number of Universities in each country across most of the globe. This silo-ing of the subject has not helped its integration into the national psyche, broader society nor mainstream Sustainable Development. Marine science is only touched on in the UK National Curriculum and is taught in a relatively small number of Universities world-wide. To compound this lack of integration, policy making in the coastal, marine and deep-sea realm is distributed across a bewildering number of Government Departments, Agencies, Organisations and Bodies globally, making integrated approaches difficult.

The oceans control our weather, our future climate, supply much of our protein, hold many of our future energy and other resources and are the global highway for ships, cables and pipelines supplying the huge coastal cities across the globe. As the global population increases to well over 9 billion by 2050, our demands on the oceans will increase significantly, yet we have only limited understanding of how to do this sustainably. We know that human activity has already led to ocean-warming, acidification, sea-level rise, depletion of fish-stocks, increases in pollutants and wide-spread degradation. We also know that different combinations of environmental stressors hugely amplify these negative impacts in ways that are hard to predict or reverse.

We need an Ocean Decade to integrate ocean science into our global society, into our education systems, into broader academic research, into our policy-making at every level of Government, into our individual and collective actions.

We need an Ocean Decade to break down national barriers and to define ways to work together to identify regions of our ocean that are most at risk of irreversible damage and protect these as a priority.

We need an Ocean Decade to agree how to create the ocean we need to sustain life on this planet.

There have been 46 different United Nations Decades since the first UN Development Decade (1960-1970).  Our ambition is to make this new Decade of Ocean Science for Sustainable Development one that transforms our discipline, our society and the future of our planet.

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As an Honorary Fellow of both the Geological Society of America and the Geological Society of London, he was recognised for his achievements, not only in science but as an ambassador for geological science and its promotion to the wider public. His citation for the Geological Society of London states, ‘Maarten de Wit is one of Africa’s most distinguished earth scientists whose research interests span geodynamics, tectonics and stratigraphy, early earth processes and the evolution of the Gondwana supercontinent.  Despite his European birth, he has become an ambassador for the entire African continent. His promotion of the ‘Africa Alive Corridors’ programme is inspirational, as it embraces science, culture, landscape in a positive, educational, pan-African context and is a genuine attempt to embrace all African society.’

I met Maarten in 2016 on my first visit to South Africa to build the partnership between the University of Southampton and Nelson Mandela University. It took some time at the outset for Maarten to recognise that the Southampton collaboration was not a corporate, management-led delegation and that there was real benefit in working together on our common goals. Once we had passed this test, he was the most fabulous host, always challenging and insightful, always generous with his ideas and time.

He took us swimming at dawn in Summerstrand Bay with his group of hardy year-round swimmers.  Laughing, he did nothing to settle my nerves around Great White attacks by telling us to the stay in the middle of the group of swimmers to avoid being picked off. Discussions over breakfast on the deck while the beach came to life was as always, stimulating and challenging.

He and his group in the Africa Earth Observatory Network are pushing the boundaries of cross disciplinary thinking and challenging the way we educate the next generation, from all backgrounds and we can learn much from these new ways of thinking.

We made Maarten a visiting Professor in Southampton later in 2016 and his visit to our campus was memorable in so many ways for staff and students at the National Oceanography Centre Southampton. A particularly unfogettable day was in the field at Portland Bill, where he was still challenging our thinking about geological time, pulling disparate strands of science and society together to produce new concepts.

He hosted the University’s digital team visit to Nelson Mandela University in 2017, inducting them in the beauty and splendour of the Eastern Cape. The contributions from young researchers from the Africa Earth Observatory Network, Bastien Linol and Stephanie Plön, add a fantastic international dimension to our Exploring our Ocean course the continues to fascinate our learners and develop new conversations in each and every run.  We dedicate our current run of Exploring our Oceans to the memory of our passionate colleague and great friend, Maarten de Wit.

May his unbounded spirit live on in the next generation of learners and stewards of this planet.

Rachel Mills, April 2020.

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One of my pastimes these last days of lockdown is to do a digital sort out of my online presence and my hard drive and I’ve realised what a massive job this is that will take me weeks. Relevant to deep ocean exploration here are some things I found that brought back great memories:

Spending time in a small space, with the same people during lockdown, day in, day out is a little like being at sea. Routine provides the same measure of the passing of time and sundown in the garden marks the end of each day.

Going through my hard-drive I realise I have thousands of pictures of sunsets, most of which are only identifiable by their date – I love sunsets but do I need so many?

So come join us online, come share your passion for the ocean and join a global community of over 50,000 learners. Share your photos and ideas with us all, and together we can make a difference.

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“What does it feel like to be an octopus? To be a jellyfish? Does it feel like anything at all?”

So asks Peter Godfrey-Smith in his book, Other Minds: The Octopus, the Sea, and the Deep Origins of Consciousness. Just one of the manifold obscure influences to feed my long-standing fascination with the oceans. A somewhat bizarre philosophical inspiration perhaps, but the multitude of esoteric books I was reading on my daily commute into work were becoming something of an academic itch that I needed to scratch.

And then four months ago – the catalyst. I was listening to The Life Scientific on Radio 4; Jim Al-Khalili was interviewing Rachel Mills, the Dean of the Faculty of Environmental and Life Sciences at the University of Southampton. As a renowned Oceanographer she was talking about hydrothermal vents, the rare earth elements associated with these deposits and the ecosystems they sustain. She went on to discuss the research that was being done to study these extraordinary environments amidst growing interest from governments and corporations interested in mining them.

I was suddenly buoyed by the knowledge that there were people out there with the dedication, brains and technology to ensure that these intriguing marine environments were better understood. And ultimately, that policy around exploiting them was intelligently informed. I went straight to the University of Southampton website and applied for the MSc Oceanography course.

Thirteen years after graduating from Durham with a BSc (Hons) in Natural Sciences, I have begun my Masters in Oceanography at Southampton. Having spent the last decade and a bit doing business development for financial services firms, and latterly running my own digital marketing company, I’m having to dig deep to get my scientific brain back in the game. But how rewarding it is to be able to study something I love day in, day out. And, one day, with any luck, I’ll do my bit to get others fascinated with the oceans too.

Hannah Sharman, MSc Oceanography 2018/19.

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Our last day of science sampling and we are collecting water just above a site where we suspect there is low-temperature fluid flow at the seafloor 2.5km below the ship.   This is the site that in 1974 was named TAG after dredging hydrothermal deposits from the eastern rift-valley wall. I worked on these precious samples much later in the 1990’s and demonstrated that hydrothermal neodymium could be traced in these ferromanganese crusts demonstrating that they formed from low-temperature vent fluids rather than from seawater. We want to see what we can see in the deep water over this site and measure the input from the seafloor.

Over the last 38 days we have put our sampling rosette into the deep water 83 times and collected nearly 30,000 litres of seawater for processing, filtering, measuring and archiving. We have pumped over 45,000 litres of seawater through our deep sea cartridges to strip out natural radioactive isotopes that we use measure time in the deep sea. We have filled the container on the aft deck with over 100 crates of samples carefully wrapped for transport around the world to our labs in the UK, the US and elsewhere. Our physics team have made over 20 million measurements of turbulence through the water column and measured the plumes wafting through the deep waters in intricate detail.

We have steamed 4200 nautical miles since we left Southampton and have over 1000 to go to get to Guadaloupe. We have drunk over 7000 cups of coffee and eaten nearly a tonne of potatoes and over a 1000 rashers of bacon. We’ve hit the gym (perhaps because of the potatoes) and collectively rowed, run and cycled thousands of kilometres. We’ve played 350 games of cribbage, nearly 500 games of table football and some challenging games of darts when the ship is rolling.

All 52 people on the ship have worked (and played) really well together on this expedition – we have made new friends and close collaborations that will last a long time. On this long passage south to Guadaloupe we are drafting the ideas for the next proposals, practicing the talks for the big conferences coming up in 2018 and of course getting our fancy-dress costumes designed and made for the ‘RPC’.

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I have studied this hydrothermal site called TAG, nearly 4km below us on the seafloor, for nearly 30 years. First for my PhD, then on and off over the years. TAG is now one of the most well studied, deep-sea vent sites anywhere on the seafloor. The nations that explore the deep have mapped every square metre of the active hydrothermal mound, we have drilled deep beneath the seafloor into the stockwork that lies underneath the mineral deposit, we have mapped out the older inactive mounds littered over the rift valley floor, marking past sites of venting.

The International Seabed Authority has granted IFREMER (France) a 15-year exploration licence for a suite of 100, 10x10km blocks that include this area of the mid-ocean ridge. This remote and extremely deep mineral deposit is one of the largest in the Atlantic but I question whether mining will ever happen here despite the significant levels of copper, gold and other metals present right at the seafloor. We don’t know what the impact of extraction is on specialist vent fauna and the extreme depths and associated pressure makes operations extremely risky compared with shallower (or land-based) sites.

We are here to assess the impact of these vents on the wider ocean chemistry. To test how leaky they are – which metals, sulphide and other species are dispersed up into the water column and how far this enriched plume of essential micro-nutrients can be tracked into the deep ocean interior.

Our physics team track the hot buoyant fluid up over several hundred metres into the overlying water; zig-zagging the sampling frame through the plume to measure instabilities and mixing. We overlay the chemistry onto these physical observations to look at iron oxidation, sulphide complexation, particle exchange reactions and the fate of these elements. We repeat sample along the ridge; close to vents, far from vents to track the water as it disperses.

One of the most important elements of this work is the way we integrate our results into the global GEOTRACES programme – our measurements are made to the same rigorous protocols and carefully cross-calibrated so we can contour our data straight into the global database. We are looking forward to adding our piece of the puzzle to the global understanding of how the geology of the seafloor controls the chemistry of the ocean.

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We still ‘sail’ in rather larger science teams for much shorter periods of time. The rhythm of work on a ship and the lowering and hauling of wires is very familiar. We collect water samples in large bottles that can be closed remotely at depth and are arranged around an array of in situ sensors that give us real time data of ocean properties as we sit in the lab. The samples are recovered at awkward times of day and night – these samples need to be processed immediately to catch the helium atoms that escape out of the sample, the oxygen samples that are compromised as soon as the tap is opened, the microbial and chemical measurements of trace amounts of rare elements that we use to understand the scale and timing of ocean processes. We pump tonnes of water through cartridges to strip out radioactive isotopes that help determine the timescales in the deep ocean.

All this happens in slick sequence time and time again as we progress South along the volcanic ridge towards the subtropics. After a couple of weeks we are a great team – called on deck at odd hours to process samples under ultra-clean conditions, careful not to contaminate that water from the deep. Make decisions, move on South.

The key to effective work on the ship is of course how well this team works. You would all recognise the dynamics – the Captain is in charge of the ship – the Chief Scientist is in charge of the programme and together they make decisions every day to curtail a bit of this, cut a bit of that, move on if this isn’t working. The rest of the team are here to get the most out of this fantastic opportunity to track all the known volcanic vents in this region.

Ocean expeditions are fabulous training grounds for the next generation of scientists. We have an undergraduate student from California, a POGO funded postgraduate student from Malaysia, a whole group of PhD students from Southampton and Liverpool and the graduate students from collaborating labs in the US and France aboard. They work relentlessly round the clock and still have the energy to have fun – friendships made at sea last a lifetime.

The ship is a melting pot for people from all sorts of backgrounds, all sorts of experiences, all sorts of life stories and these are shared during the night shift over cups of Maeve’s espresso. The bridge calls down to point out those things that we can only really appreciate out here – dolphins on the starboard bow, alignment of Jupiter and Mars off the port deck.

The best part of being at sea is the freedom to focus on the task at hand and nothing more, nothing less. Time slows down, problems are solved, solutions are found, new data is stuck to the walls, new ideas forged as we each contribute to the picture emerging of plumes of metals wafted deep along the ridge. I love the rhythm of the days and nights – the sunsets and sunrises, the slow passing of time. We love the singularity of purpose.

The worst part is the severing of connections with home over the first few days and the vague feeling of institutionalisation and repetition that takes over after several weeks – all lifestyle decisions are out of your hand – what you eat, what you drink, when you sleep, when you do laundry, how you exercise, who you mix with.

The FRidge team is exceptional. I have made new friends, really cemented some work relationships and am looking forward to working with these great scientists over the next few years to get these samples measured and our new ideas out into the community and beyond.

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Jump forward to the end of 2017 and we are here again – over the last decades there have been vast improvements in our analytical capabilities, we can measure our tracers at orders of magnitude lower levels, we can sample without contaminating our water samples, we have a new framework within which to interpret our data and we can plot our data in real time onboard ship. We are here to assess the trace metal and isotope impact of the hydrothermal vents that populate the ridge from the Azores southwards.

This has made me think what we have learnt since the early 1990’s and here is my list:

1. Hydrothermal vents are almost as common along the slow spreading ridges of the Atlantic as they are along the fast spreading ridges of the Pacific and elsewhere. Contrary to early opinion, the slow spreading ridges host a wide range of vents that mine heat through deep faults on the rocky axial rift-valley. Many of the Atlantic sites are controlled by tectonic processes that cut deep into the crust rather than volcanic processes supplying hot lava to the seafloor.
2. Hydrothermal vents supply significant iron and other trace metals to the deep ocean – while a lot of metals are precipitated in the chimneys and sediments at the seafloor there is a lot of chemical complexation that happens in the water above the vents that stabilises the metals and off they go into the deep ocean to be transported around the global ocean.

   

3. The vents are all very different and we haven’t by any extent found them all – they occur in the middle of the ridge segments, they occur at the discontinuities between the segments, they occur on-axis, they occur off-axis, they are high temperature, they are low temperature – it is really hard to generalise and we are still in the discovery phase of finding new things in the deep oceans.
4. If you are careful and consistent and wrap things up carefully in clean plastic it is possible to measure 10 picomoles of reduced iron per litre of seawater on a ship made out of steel using a winch and sampling system that is greasy and grubby.

   

5. If you put a team of chemists, biologists, physicists, computational scientists, geologists and engineers on a ship for 6 weeks extraordinary things happen – the shipboard environment provides an uninterrupted space for incredible thinking, testing of new ideas and is a key part of the progress of our science from the days of the HMS Challenger Expedition to the modern ocean exploration. The key is the team you choose to take to sea and how you get them to interact once you are there.

   

   We’d love hear what your thoughts are…….

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