October 26, 2021

I, Science

The science magazine of Imperial College

Dr Brian Bett was interviewed for our Exploring the Deep feature. This is the full transcript of that interview.

JC: What is like exploring the deep sea from a personal perspective?

BB: In many ways I am a traditional field ecologist, it just happens that my field lies under 3-miles of water. So this means I need a ship and specialist equipment to make my observations, and I certainly enjoy the engineering and technology challenges of my science. Being stuck on a ship for 4-6 weeks at a time also has its benefits, the camaraderie is good, everyone has to pitch in to get things done, and when things breakdown it has to be a DIY fix – the AA don’t do call outs to the middle of the Atlantic Ocean.

What sort of specialist equipment have you used?

I think I have probably used all of the available types of technology useful in deep-sea biology. I continue to use the trawls and dredges that were used by pioneering deep-sea biologists in the 1860s, I have been lucky enough to dive in a submersible, I have used remotely operated vehicles (ROVs), and I have used cutting edge autonomous underwater vehicles (AUVs). All of these technologies remain useful today.

Will humans ever set foot on the bottom of the ocean?

Much of my work is focussed on abyssal plains – typically 5,000m deep – the deepest human dive (by diving suit) is 600m – a dozen men have walked on the moon, no one has (or is likely to) walked on the deep-ocean floor. A visit is possible by submersible, but with only three suitable vehicles in the world, your chances are pretty slim. “Tele-presence” using a ROV is a more realistic possibility, with around a dozen capable vehicles in the world (split between academic and commercial spheres).

What do you see the future of deep-sea exploration being in terms of the tools we use?

Today, and in to the future, the key technologies are AUVs, they will revolutionise the detailed mapping of the deep-sea floor. AUVs are unmanned and untethered systems that carry out pre-programmed diving missions, but have sufficient ‘intelligence’ to avoid and navigate around obstructions. For exploratory science they are more effective, more efficient, and most definitely much cheaper than ROVs or submersibles.

Does exploring the deep sea feel like exploring an alien world?

Two thirds of the surface of our planet is deep-ocean floor – it is the dominant habitat, we are the aliens. The exploration aspect can certainly be exciting and intriguing – many of the places I visit, the landscapes I map, and the animals I encounter are previously unknown.

What’s the atmosphere like in the control rooms when you operate the ROV’s?

It can be excruciatingly boring – hours and hours of descent and ascent through a more-or-less empty water column, or miles of transit across featureless, near-lifeless flat mud. It can be extremely tense – when the vehicle is at risk – umbilical snagged, vehicle caught on fishing gear, trying to park the ROV in its ‘garage’ in a heavy swell – the neutrally buoyant vehicle facing a heavy metal cage that is crashing up and down very quickly. It can be unbelievably frustrating – glimpsing an unknown exotic animal that disappears off in to the darkness never to be seen again; being unable to collect a sample that is right in front of you – operating remote manipulator arms requires great skill and even greater patience, but even then an apparently simple task can prove impossible. And it can be very rewarding – unexpectedly encountering the unknown / exotic; and conversely, finally tracking down a particular target – finding a needle in a very big haystack.

How reliant do you think deep-sea biologists are on unmanned vehicles?

That rather depends on what type of science you are planning on doing – if you want to carry out an in situ manipulative experiment a ROV may be essential, though a lot can be done with free-fall landers (as per Moon / Mars landers). On the other hand there are many aspects of deep-sea science for which a ROV is completely useless, say long-term observations. For example, we are currently building an AUV that should be capable of staying out on the abyssal plain for a year – each month it could carry out a photographic survey of the seafloor, then park itself on the seabed and go to sleep to conserve power.

Generally speaking, why do you think deep-sea biology is important?

Generally, deep-sea biology is as important as any branch of science. It contributes generally to the understanding of ecology and the development of ecological theory. Water depth is said to be one of the top three environmental gradients on our planet, deep-water fauna are exposed to very different evolutionary pressures than organisms elsewhere.

Apart from the sense of wonder and adventure, how can we benefit from the findings of deep-sea biology?

Dwindling resources onshore, and in shallow waters have caused a very rapid expansion of human exploitation of deep-water areas. Deep-water fishing has progressed quickly to c. 2000m and has already had devastating impacts on target fish populations (e.g. the Orange Roughy) and on fragile habitats (cold-water coral reefs). Deep-water oil exploration has now exceeded 3000m water depth, with over 500 wells worldwide. Although far from being an ‘ecological disaster’, the Deep-water Horizon blow out in the Gulf of Mexico has highlighted the need for ecological caution. Deep-water mineral exploitation (e.g. manganese nodules) has long been expected, but has only recently started in earnest (metaliferous muds and crusts). Much of this deep-water exploitation takes place in international waters – the high seas – beyond national jurisdiction. United Nations agencies / laws / policies may take some time to catch up with these developments.

Are there signs that climate change is having an impact on deep-sea ecosystems?

In a word, yes. There are only two long-term deep-ocean monitoring sites in the world. One operated by my group in the NE Atlantic, the other by US colleagues in the NE Pacific. At both of these locations, seafloor biological communities have dramatically changed over our 20-year observation period. This change appears to be driven by changes in the biochemical composition of the incoming food supply. This is in turn caused by changes in the surface ocean phytoplankton community structure, and that appears to be driven by change in regional climatology (e.g. stormier winters, deeper mixing of the ocean water column, greater nutrient resupply to the surface ocean, later onset of the phytoplankton ‘spring bloom’, promoting a change in the dominant plant types, changing the composition of the dead plankton detritus that falls to the deep-ocean floor and fuels all life there).

How diverse is the deep sea?

Well people have published estimates of total species, and total deep-sea species – all rather pointless and meaningless really. It is undoubtedly an unknowable and changing number. And indeed any answer you get is entirely dependant on how diversity is measured and which taxa you include in the analysis. I think it would be better to say that the deep sea is as diverse as anywhere else. By many conventional diversity measures deep-sea samples have high values. Though you should note, for example, that in many areas species density is very low (it is a food poor environment that may not support many individual per unit area). It is also worth bearing in mind that in any given sample 50+% of the specimens may belong to species that are currently undescribed (i.e. new species) – in the more remote oceans that number may be more like 90%. As has been the case for several decades now, the UK and the World is desperately short of taxonomists. Despite being the foundation stone of all biology, and critical to ecology and biodiversity – taxonomy remains extremely difficult to fund. So for now, and for a long, long time into the future the deep sea will contain more unknown than known species.

Do you have a favourite ‘deep-sea creature? And what is the strangest adaptation that you’ve encountered?

In my first week as a deep-sea biologist I came across an animal I could not even identify to major group, I had neither seen nor read of anything like it (in a previous nine-years of studying marine biology). It turned out to be a sorberacean tunicate, no common name, a type of predatory sea squirt only found in the deep sea. Shallow-water sea squirts live a quiet life filtering food particles from the water they pump through their bodies. Presumably as a response to the scarcity of such food particles in the deep sea, sorberaceans have evolved into predators. That first specimen I encountered was a ‘Venus Flytrap’ type, it lays six ‘leaves’ out on the seafloor and waits for some small worm or shrimp to come crawling by – the leaves curl up, and the prey meets its end.

Images: © MBARI