When was the last time you thought about the deep sea, that mysterious place we know less about than the surface of the moon? Despite being surrounded by it on all sides, many of us take little time to think about the destruction being wrought on this often overlooked ecosystem. Personally, it was only upon coming across a paper entitled “The impact of climate change on deep-sea benthic ecosystems” led by Andrew Sweetman, that it became clear to me how much human interference is affecting marine life.
Everyone knows about the endangered rhino and the silverback gorilla, but few are aware of the extent of the havoc humanity is wreaking in the other world hidden beneath the waves. Luckily for students at the University of Edinburgh, investigations are being carried out on these little known ecosystems by researchers at our very own institution. One man conducting such research is Prof. Murray Roberts, who contributed to Sweetman’s paper. Roberts, a marine biologist and a Professor of Applied Marine Biology and Ecology in the School of Geosciences, agreed to speak to The Student and answer some questions about the work he and his team are conducting.
The Student: Many Edinburgh students seem unaware that the university has an ocean science research group. Was it always like this?
Roberts: Well this is one of the funny things from my perspective as well. Edinburgh University is large. It’s really successful and there’s actually lots of marine science going on, but it’s all separated out into different research groups, in different parts of the university. But if you look back at the history of Edinburgh University, this is the institution that essentially invented oceanography – invented deep sea biology.
In the 1860s a professor at Edinburgh University, Charles Wyville Thomson, persuaded the British Government to lend him the naval ships HMS Porcupine and HMS Lightning to explore the deep waters of the northeast Atlantic. The expedition, named Challenger, is now renowned in scientific circles. (sic) Using these ships, along with pioneering new deep seabed dredging technology, Wyville Thomson sampled what was on the deep-sea floor. The work was fundamental in shifting the paradigm that the deep sea was devoid of life, laying the foundations for a subsequent global voyage of HMS Challenger. This expedition practically invented the science of deep-sea oceanography and marine biology.
Edinburgh was there at the start of deep sea exploration and now, 100 years later, we can see just how important it is that their research is continued. We still desperately need to understand the biggest biome on earth not just for pure scientific curiosity but because human activities are moving ever deeper right around the globe and the deep ocean is feeling the effects of global climate change. (sic)
The Student: Many people do not think of the effects of climate change on the deep sea before because it is seldom referenced in the general news. Why do you think that might be? And why should people be more aware about it?
Roberts: You’re quite right. We are creatures of where we come from; we are clearly terrestrial creatures. We see the surface of the sea. We can’t see beyond it and we don’t realize that most of the global oceans are many thousands of meters deep and we don’t pay attention to the fact that 70 per cent of the earth’s surface is water. So it’s planet ocean – it’s not planet earth.
93 per cent of all the heat that has been produced as a result of global warming has been absorbed by the oceans. (sic) We burn oil and gas. We release carbon dioxide into the atmosphere which dissolves in the oceans, driving down pH. People don’t anticipate that this will affect such a large system – but it has.
One of the implications that our paper addresses is how it’s going to affect food chains in the deep seas. Some truly deep sea organisms may only get the equivalent of half a sugar cube of carbon per meter square, per year. It is an extremely slow pace of life dictated by the gradual rain of food particles from the surface which is already at a bare minimum. Now thanks to us, they’re anticipated to go down by half in the next century.
The Student: There are several coral reef sanctuaries in shallower waters – is there anything like that for cold water corals?
Roberts: Yes, there is. I am currently coordinating a European Union project called ATLAS. It’s all about the Atlantic and looking at its deep sea ecosystems, looking at how they’re functioning now and how they may change in the future. Currently the conservation areas are mostly put in place to limit the damage of deep-water fishing, a process that not only removes fish biomass but uses trawls to do so, which degrade and basically smash down and clear cut huge areas of complicated structural habitats.
The Student: So how much of the coral reefs have disappeared because of trawling?
Roberts: We can’t say for sure. But when you look at the older literature, with descriptions of the deep sea holding diverse and abundant life, and then look at it today, you start to get an idea. In Wyville Thomson’s book The Depths of the Sea he introduces what he found near the Faroe Islands. He refers to the sea bed being covered by stony copses of coral covering many miles. I remember when I was doing my post-doctoral work in the 1990s, we didn’t find these copses – they just weren’t there. We can’t say for sure, but we do know these areas have been trawled for over 30 years.
The Student: The paper also mentioned that squid and jellyfish populations are going to expand because they are more hypoxia tolerant. Is that perhaps responsible, at least in part, for the recent jellyfish blooms?
Roberts: That’s what people are wondering. Some blooms are probably related to site specific causes, but the overall trend that we see of greater mass jellyfish gatherings is likely due to that. We’re moving to an ocean that’s going to favour those sorts of animals that can deal with conditions that are going to start predominating.
The Student: Has there been any evidence of change in cold water coral habitats?
Roberts: One of the frustrations is that we don’t have a good baseline of what species are associated with these areas and the ‘native’ state of them. So one of our objectives in the ATLAS project is to create a biogeography right across the Atlantic in all these key habitats. We’re also working hard to assess what ‘Good Environmental Status’ means for deep-water Atlantic ecosystems. Sounds easy doesn’t it? The reality is keeping us all awake at night!
We are also looking at the physical properties of these coral skeletons and how they change over time, how resilient they are to more corrosive waters and attack by other organisms that bore into their skeleton which are both predicted to become more prolific in future ocean conditions. We need to understand these changes because it’s the physical structure of the coral skeletons that allows reefs, be they shallow or deep waters, to support so many other species.
Talking with Roberts over this relatively unexplored issue was hugely enlightening. Essentially, says Roberts, life will persist in spite of our wrongdoings, but to use this as an excuse to do nothing only means leaving the work to future generation to clean up our mess.
Image: JM Roberts, Changing Oceans Expedition 2012