For the better part of four decades, Craig Smith, a biological oceanographer with the University of Hawai‘i’s School of Ocean and Earth Sciences and Technology, has been studying the deep sea floor. Most recently, he has been investigating life in what might be the planet’s most pristine, untouched environments: the abyssal plains of the eastern Clarion-Clipperton zone, an ocean region stretching from southeast of Hawai‘i to nearly the coast of Mexico. That area has a high abundance of polymetallic nodules (also called manganese nodules) resting on the sea floor, which has caused it to be targeted for mining.
Smith, who will be the featured speaker at Environment Hawai‘i’s dinner on January 18, spoke about his discoveries recently with editor Patricia Tummons.
Could you talk about what led you to investigate the deep ocean environment?
Well, I’ve long been interested in deep sea biology. In 1983, as a Ph.D. candidate at Scripps, I started studying sources of food for the deep sea – what is getting down from the surface ocean to feed the deep-sea animals.
But even then, there was interest in mining the deep sea, particularly nodules on the abyssal plain. It was natural for me to study that. In the 1980s, I did some work with NOAA [the National Oceanic and Atmospheric Administration] to look at the nature of abyssal impacts from mining.
Didn’t you also pioneer research on whale falls?
When I was a grad at Scripps, I actually tried to sink a whale. We weren’t able to sink one. Not enough ballast. But in 1987, we happened upon a 20-meter-long blue whale fall. That’s what got me started. There was a giant whale skeleton with a rich community of animals similar to those found on hydrothermal vents. I still work in this area, whale falls, wood falls in the deep sea. But now there are hundreds of papers on whale falls and many groups of scientists around the world studying them.
The abyssal plain was long thought to be pretty much devoid of life. But you seem to have found plenty – although not, perhaps, in forms that many of us would recognize.
Yes. Interestingly, if you go back to Challenger reports from the late 1800s, they got a high diversity of animals from their abyssal samples. A lot of that was ignored. [The H.M.S. Challenger explored the oceans from 1872-1876, identifying nearly 5,000 new species.]
It was long thought that the abundance of life and biomass is low. And this is true. Food is attenuated as it comes down from the surface ocean. But even though the availability of food is low, biodiversity is quite high. We’re finding in the eastern Clarion-Clipperton Zone some of the highest diversities ever found in the deep sea, from megafauna (large animals) to microbes.
There’s high diversity of animals that are found only on the nodules – an obligate nodule fauna. We have found about 100 spe- cies that live only on nodules in the eastern CCZ. And there are probably many more that have not been identified. We have seen them in photographs but have not collected them for identification.
Could you describe some of the creatures you have found in the Clarion-Clipperton Zone?
Some of them are huge. A new order of cnidarians lives on glass sponge stalks, with tentacles up to 15 feet long trailing in the weak currents. There are lots of sea cucumbers. One of them – the gummy squirrel, we call it – is a fluorescent yellow sea cucumber about three feet long with a tail that sticks up in the water. We think the tail might be used as a sail to navigate to food sources. Other sea cucumbers are purple, red, yellow, green.
There are corals that can grow a meter or more high. All kinds of worms – hundreds and hundreds of species of bristle worms, all kinds and sizes, including a squid worm. It’s about a foot long and swims in the water column, looking like a squid. No one had ever seen these below 2,000 meters, but we found one at nearly 5,000 meters.
Lots of interesting fish. Rattail fish. Eels. Giant amphipods. Big crustaceans. Shrimp 30 centimeters – a foot – long.
Xenophyophores, kind of like monster amoebas from sci-fi films of the 1960s. They’re giant, one-celled animals, 20-30 centimeters across that live inside houses made of sediments. There’s a huge variety of them. We found more than 30 species of these in one small area. They seem to particularly like the abyssal Clarion-Clipperton Zone. One-third of the total known global diversity of these animals is found there.
Of course, this may be because we have looked for them there more than anywhere else. Their tissue is soft and amorphous. But the shell they form from sediments, their ‘house,’ is kind of rigid.
They’re amazing. Lots of different kinds of xenophyophores, each with a different shape. They can look like big, black baseballs or golf balls. Some have ruffled patterns, like a ruffled skirt. Some are fan shaped.
You also came upon metal-plated fossilized whale skulls That’s an amazing find.
My post-doc Diva Amon and I discovered that together. We found quite a few whale bones out there and recovered some initially. Diva has been working up photo surveys we’ve done from the area and has also obtained photographs from other scientists. She is counting the number of whale fossils. Most of the recognizable bones we see are jawbones and skulls.
They’re incredibly abundant, especially for beaked whales. I’m not sure if this is just because this area is more studied than anywhere else, but beaked whales are known to feed in the eastern Clarion-Clipperton Zone.
This is also potentially interesting from a paleontological perspective. More fossils, especially of beaked whales, are available here than anywhere else. Many thousands of them.
Do you see evidence of 21st century life at these depths? When the Mariana Trench was explored a few years ago, a Budweiser can was found on the ocean floor. Have you seen anything like that here?
We do find trash occasionally. But this area is probably the most pristine ecosystem in the ocean – probably on the whole planet. Even the South Pole has lots of evidence of human occupation.
Here we do occasionally see trash, but it’s very rare. We can go for hundreds of kilometers but see no evidence of human activity. There are some tracks created from test mining decades ago. They look fresh, like they could have been created yesterday. But in general, it’s a very pristine environment.
And this is an important thing for people to recognize. Some of those who have promoted ocean mining argue that deep sea ecosystems have already been impacted by humans. But these are the most intact ecosystems on the planet. They’re thousands of miles away from human activity on land, and thousands of meters below shipping activity.
In all the photo surveys we’ve made of the area, over three cruises, we’ve taken tens of thousands of images of the sea floor – and have seen just two or three pieces of trash. And some of that probably came from re- search vessels exploring for minerals.
Could other regions be equally biodiverse?
We think the eastern Clarion-Clipperton Zone may be particularly diverse for a number of reasons. There’s greater habitat heterogeneity because there are hard substrates, with the nodules, and also soft sediments. Also, there is more food coming down in the eastern zone than in the west or north, or even north of Hawai‘i, where there are nodules but the food sources are extremely poor. The eastern Clarion-Clipperton Zone conditions combine to create higher biodiversity. Also, it’s close to the equator, where there’s a high diversity of sediment-dwelling animals. So there may be some influence from equatorial high productivity areas.
I think the eastern Clarion-Clipperton Zone may hold up as one of the most diverse ecosystems in the ocean – but there are still lots of places we haven’t studied.
The effects of ocean mining would clearly be devastating to the animals in the areas directly disturbed. But would there be other consequences?
On a local scale, where direct mining occurs, it will be very destructive. Everything in the path of mining will be killed. But mining will also inevitably create a sediment plume that will disperse some distance. The best modeling suggests the plumes will disperse at least 10 kilometers, creating higher sedi- ment and turbidity levels.
In the Clarion-Clipperton Zone, there are the clearest bottom waters – clearer than the clearest surface waters, actually, with very few particles suspended in the water column. Currents are slow. The mining plume will have major impacts on the animals living there.
This is a controversial topic. Some min- ing contractors argue that the impacts will be much smaller, but my best guess is that a single mining operation will impact directly 500 square kilometers per year, while the plume will impact five times that, or a total of 2,500 square kilometers per year. A mining operation that lasts 30 years could therefore impact 75,000 square kilometers, a large area.
The Clarion-Clipperton Zone is also a large area, about the same size as the 48 continental states of the U.S. And a lot of animals are probably widely distributed. So my gut feeling – not based on data, but a gut feeling – is that one mining operation, even carried out for 30 years, isn’t going to cause any species extinction. But many more mining operations, and you’ll begin to pose the risk of altered ecosystem functions and extinctions.
We’re not really going to know about the scale of impacts until real mining occurs. My feeling is, it ought to be allowed to occur incrementally. Have one mining operation that’s studied over a long time. Look at how it’s impacting things and then see whether we can allow more.
One reason it’s important to proceed incrementally is that the removal of nodules is permanent. They’re gone for millions of years. No area that’s impacted by nodule removal can possibly recover ecologically before the last area is mined.
The nodules grow at a rate of a couple of millimeters per million years. So one nodule can be 10 million years old.
Is this area insulated from the impacts of climate change, or do you suspect that changes in ocean chemistry will sooner or later affect this environment as well?
Climate change and ocean warming is now penetrating into the abyssal ocean. It’s probably not an ecological impact yet at these depths, but you can see a warming signal in the ocean already, at depths of 2,000 meters or more. I do think, in terms of anywhere in the ocean, these may be the areas most insulated from climate change effects. But they are very stable places, so even small changes may affect the ecosystem.
One thing that is expected to change is the pattern of primary production in the overlying water column. Fewer nutrients will be upwelled and less food will sink to these abyssal areas. It’s quite likely that the flux of food to these areas will stress these communities. Mining on top of that will only add to the stress.
Why are these organisms important? What would we stand to lose if they were wiped off the face of the Earth?
Biodiversity is the raw material for evolution. If we cause species extinctions, we are changing the course of life on earth from this point onward.
I think causing species extinctions is im- moral and is not what we should be doing to this planet.
We don’t know what many of these consequences will be, because we don’t know what these species are doing. Some may be really important in the future, in terms of biotechnology. Deep-sea organism physiology is quite different from that of shallow-water organisms. There’s a great potential for new discoveries in biotechnology.
Also, we need to be careful we don’t alter ecosystem functions. One of the potential consequences of mining that we need to be aware of also will be midwater sediment plumes. A lot of the fish species that we har- vest in the open ocean feed on vertical migrators that migrate to depths of 1,000 meters or greater. If we create sediment plumes that cause problems at this depth, it could affect the food supply of commercially fished species that feed on these vertical migrators.
The deep sea is also an important repository for organic carbon. It’s part of the biological carbon pump, with carbon being buried in sediments. Deep-sea sediments help buffer the pH of the ocean.
We would have to mine an awful lot of the sea floor to affect the carbon cycle, but we should be aware of the scale.
I find it interesting that people have no trouble understanding why destroying biodiversity in the Amazon rain forest is a bad thing. But it’s equally bad to do it in deep-sea systems, where there are such unusual suites of organisms.
Dr. Smith will be speaking in Hilo on January 18 at the annual dinner of Environment Hawai‘i. Reservations are $70 (which includes a $35 donation). To make a reservation, call (808) 934-0115.
A video about the work of Smith and his colleagues is at: https://oceanexplorer.noaa. gov/explorations/18ccz/logs/logs.html
Environment Hawai‘i reported on Smith’s work on whale falls in April 2002. See “Contact – at 700 Fathoms,” available at www.environment-hawaii.org.
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