How is climate change affecting the oceans and marine life? What are the interactions between the earth, the atmosphere, and the ocean, and how does that affect human life? What measures can people take to prevent massive environmental damage? Maria Armoudian speaks with Karina Nielsen, Stephen Palumbi, and Scott Doney.
Karina Nielsen is a Professor of Biology at San Francisco State University. She is an expert in coastal ecosystems.
Scott Doney is a Professor in Environmental Change at the University of Virginia. He is an expert in oceanography and biochemistry.
This interview has been edited for clarity and length
Maria Armoudian: We have finally got the media and much of the world focused on climate change and what it means for life on earth, but there has been less attention on the intersection with the oceans. Scott Doney, could you explain a little bit about the dynamics between the climate and the oceans?
Scott Doney: We think the oceans have absorbed about a quarter to a third of all the human emissions of carbon dioxide into the atmosphere. That is a positive, but on the negative side, that is changing seawater chemistry leading to ocean acidification. The other thing the oceans are doing is actually slowing the warming of the planet. A lot of the excess heat building up in the planet is actually building up in the oceans, so if it wasn’t for the oceans there would be a lot more carbon dioxide in the atmosphere and the atmosphere would be warmer.
MA: So if it is absorbing a chunk of the carbon dioxide, is there a limit where it just cannot absorb anymore?
SD: We think it is going to slow down. It doesn’t stop but it will probably slow down. One of the concerns is what is going to happen to some of the land carbon forces. So potentially, if the climate warms up enough you will get venting of a lot of carbon out of the Arctic and then that is going to make it even harder for the ocean to buffer our climate and carbon system.
MA: And then what happens then?
SD: Well then atmospheric carbon dioxide goes up, that drives more climate change and an accelerating pace of change that society needs to deal with.
MA: What is the likelihood of that right now?
SD: I would say it is probably likely that the land also is helping to buffer some of this carbon dioxide. We think that the land is going to slow down, whether it is going to reverse and become a source we don’t know.
MA: Karina Nielsen, what would you add to that?
Karina Nielsen: We are concerned about the potential slowdown of the ocean’s capacity to absorb carbon dioxide. I am not as knowledgeable about what might happen on land but I think the things I am seeing in my world is changes that are underneath the ocean that are visible to those of us who study the ocean but are invisible to a lot of people who are not divers or who are not directly connected to underwater life.
MA: What are some of those?
KN: What is close to my research area has been what has been happening on the northern California coast with real decline in our kelp forests which seems to be associated with some of the marine heatwaves and things that are happening that are probably being accelerated or accentuated by climate change.
MA: Stephen Palumbi?
Stephen Palumbi: I agree with both Scott and Karina. The way I think about it is the ocean is warming and the land is warming because of climate change and we are seeing increased storms on land and increased storms in the ocean. But there are two other things associated with climate change that are pretty unique to the ocean. One is that there is more of it: the sea level is going up, and a combination of sea level going up and increased storms gives us things like king tides and coastal flooding. Cities are now just used to having seawater in their streets during high tides because of a combination of increased sea level and storms and waves. And then what Scott mentioned was acidification of the ocean, that is where C02 going into the ocean turns into carbonic acid and that makes it more acidic than it usually is. And then that then cascades down to the ability of a lot of marine organisms to grow and make their shells. So those categories of change in the ocean because of climate change are global, they are accelerating, they have caused all marine biologists to worry about the future of marine ecosystems and like Karina said, we are seeing those things play out right now.
MA: So all of you have mentioned ocean acidification and I don’t think people know very much about it. I know the ocean has a particular PH balance which is changing as a result of the climate change. So I wonder if Scott Doney you could walk us through exactly what ocean acidification is, its dynamics, how it interacts, and how it is manifested?
SD: So carbon dioxide is a gas. The way it gets into the ocean is it dissolves in the water, so it is much like if you have a bottle of soda, you have bubbled carbon dioxide through, the carbon dioxide gets dissolved. But as Steve mentioned, unlike other gases like oxygen and nitrogen, carbon dioxide actually reacts with the water and makes a carbonic acid. If you think of a piece of limestone that is actually made out of calcium ions and carbonate ions. And many of the plants and animals and microbes in the ocean build shells out of the same material. So corals, shellfish, clams, oysters, some types of crustaceans, many types of plankton. And when the water gets more acidic, we have shown in the lab and also in the field that it makes it harder for these organisms to build their shells, they have to use more energy and that is energy that cannot go to growth or reproduction or defense against parasites and diseases. And so we think that in addition to the climate warming, many parts of the ocean life are being threatened by ocean acidification.
MA: And to what extent is that threat happening and does it also set off some kind of a domino effect? Steve Palumbi?
SP: The effects of ocean acidification come in two kind of flavours. One is the global effect which is slowly accumulating over time as the C02 in the atmosphere goes up. But there is also these things called acidification storms. They occur in coastal areas and they happen due to a combination of global C02 in the atmosphere plus things like plankton blooms that decay and release a lot of C02 into the local environment. And those storms have already impacted things like oyster farms along the west coast of the US where the tiny little baby oysters are very sensitive to PH and those farms have had whole years where acidification storms have prevented them from being able to grow those oysters. So that is a little example of the kind of unexpected consequences of this big chemical change that is happening in the ocean.
MA: Karina Nielsen, you look at coast lines and ecosystems, what are you seeing as a result of acidification and also sea level rises?
KN: Well we are seeing both. There is kind of link between the two on the estuary here. We have been trying to restore some of our native oyster species and we are concerned about ocean acidification impacting our ability to do that. But the ironic thing in some ways is that we have been looking at nature-based ways of limiting the impact of sea level rise and one of those ways has been to promote oysteries and the development of those structures to help reduce erosion and help soften, if you will, some of the potential impacts of sea level rise. So we are not really sure if those two things are going to interact in negative ways but you can imagine as we are trying to recover these species that have benefits for us in other ways than just existing or being food for other animals, we may be actually compromising our abilities to protect some of the shore line. That is kind of the unexpected surprises that Steve was talking about. This is an area that is emerging as our understanding of how the PH of the ocean changes the way organisms can smell the water, the chemistry of the water, and I think that is a scenario we may see a lot more surprises in.
MA: In terms of things like stratification, altering ocean currents, what exactly happens? Scott Doney?
SD: So the ocean is heating up and it is heating up starting with the surfaces where you are getting the most warming. And so in a typical ocean situation the water is stratified, light water near the surface and denser water as you go down. As you warm up the water right at the surface you are actually increasing that stratification, the water gets less and less dense and that makes it harder for the ocean to mix and that has a lot of effects on ecosystems because that mixing is what brings up nutrients from below. Nutrients get stripped out of the surface of the ocean by plankton and if there is not a mechanism to recover those nutrients it may slow down biological productivity, particularly in the tropical regions around the planet.
MA: What about dead zones that I have been reading about? What exactly is causing that, is it a similar dynamic?
SD: The ocean holds oxygen and the animals need that oxygen that eventually comes from the surface of the ocean. When the water moves away from the surface, oxygen slowly gets consumed because you have a lot of organic matter, basically dead cells sinking down from above. So as you get deeper and deeper into the ocean there are regions where the oxygen declines naturally because of this biological clump of organic matter. In terms of a more stratified ocean, what we are seeing is in large parts of the global ocean oxygen is declining because there is not a circulation of slowing and the pathway of bringing that fresh oxygen into the ocean interior is being reduced. And potentially that could reach a spot where large parts of the ocean are not hospitable to marine life.
KN: One of the ways it can get exacerbated is that the coastal regions are really productive. And sometimes there is low oxygen waters, it may actually get brought up to the surface, they can sometimes have a lot of nitrogen or nutrients in them. We sometimes see this at the mouths of estuaries, so on the coast of California this particular mechanism I was describing might happen, off the coast of Oregon, it might happen there when we have die offs and things like that. So it can cause disruptions to where these organisms live, they may move away from these low-oxygen areas, they may die in place if they are not very mobile.
SP: A lot of the dead zones for example, are not that much related to climate change, they tend to form at the mouths of estuaries or the mouths of big rivers like the Mississippi. One of the famous first dead zones was described in the Gulf of Mexico near the mouth of the Mississippi River. Huge amounts of fertiliser go down the river, it causes plankton blooms which die and the bacteria eat them and produce lots of C02 and eats up all the oxygen. That is exacerbated by things being warmer because the process is happening faster. But dead zones are another way that the human impact on the ocean is particularly strong around coast lines and these very productive waters.
MA: What does this mean for us?
SP: One of the big differences is, we started out talking about the differences between the land and the ocean, but we are still using the ecosystems in the ocean to a very large extent, we don’t get much wild food off land anymore. Certainly places in Africa and South America they do, but we get a lot of wild food out of the ocean, we get a lot of direct benefits from ocean ecosystems whereas on land we have tended to push those natural ecosystems away from where we live. And as a consequence, let’s say for coral reefs which I spend a lot of time studying, those reefs support the livelihoods of literally hundreds of millions of people. There are people that get most of their animal protein from fishing around coral reefs, the reefs themselves grow enormously great storm walls, a good healthy reef can absorb up to ninety-seven percent of the wave energy that hits it. So these living, growing reefs protect communities and towns and structures all along the tropics. We use these natural communities an enormous amount and they benefit billions of people.
SD: I just want to follow up on the food supply point and fisheries. One of the really interesting things we are seeing is that as the ocean warms, fish species have basically a thermal range, a thermal tolerance, they don’t like it too warm or too cold, and each species has a different range. And what we are seeing is that the species are moving polar. For example, where I live in Virginia, the species that used to be found off Virginia are now found off New England and we are seeing a shift to species that used to living off Georgia and Florida, and that is not only changing the kind of fish there but it is making it really challenging for communities that depend upon fishing for their economy. And so fishers are having to travel further or switch the gear they are using and that is having a huge impact. The other thing that we are seeing with climate change is the expanding of marine diseases, so parasites, bacteria are moving as well with the warmer waters and we are seeing expanded outbreaks of disease up and down coastlines.
KN: The other way it affects people aside from the commercial fisheries, is recreational fishing and tourism. Also, flooding affecting coastal developments where there is housing and infrastructure up against the edge of that ecosystem and as you start losing the beach you start losing the blanket space, so to speak, and that can have a cascading effect through an entire coastal community because it can be a very important part of the economy. It happens also when people are diving or spear fishing, you know when the things that they are used to doing are not there anymore they may not come back to those communities.
MA: There have been dramatic headlines written where it says if we want to save the ocean we have to stop eating fish. What do you make of something like that?
SP: I am not sure that that is going to stop climate change and so without stopping climate change we are not saving the ocean. I really do believe we can continue to eat fish and also save the ocean. How we do that, how we eat fish and which fish we eat has to change and we have made good strides there, there is still a lot of ground to cover. Certainly the ability of people to know how to fish sustainably and to choose to buy certain fish and to choose to have certain fish in restaurants has had a big impact on the way fishing is done at least in some places. Unfortunately, there are an enormous number of people around the world who are desperate for even a small income from fishing and they don’t have the luxury of deciding not to eat a fish because it might be overfished, and those are the real problems because those people need that food, they need that protein, they need that income and the impoverishment of coastal ecosystems actually is one of the huge problems that we face in knowing how to use the ocean sustainably.
MA: What are some of the mitigation measures that we really need to be taking? Obviously reducing our emissions is a big one which is hard to do when we have got certain leadership in place that are wanting to destroy rainforests and increase the carbon industries. What do we do given all this? Karina Nielsen?
KN: I have been thinking deeply about this for a long time. I think a lot of people feel disempowered because doing the things that need to be done are somewhat out of our reach. But I really believe firmly that every action we take at the local level, every conversation you have with someone who may not be cued up on the importance of climate to their day to day lives makes an increment. You can think about death by a thousand cuts two ways, you can think about it having an impact in a negative way or you can think about the collective action of all of us pushing forward with both education and advocacy through democratic processes for the changes we want to see. So I don’t think people should walk away feeling disempowered, conversations are really important. I think pressing our elected officials in the places where we have agency is really important.
MA: Are there specific measures that you would advocate for given what you know as a scientist?
SD: I have a few. In addition to the carbon mitigation you mentioned, one of the biggest impacts in coastal regions is coastal development and destruction of these valuable wetlands, marshes, mangrove forests. So that is one area where we have learned that we cannot take those for granted, we need to actually protect those. The other particular thing for coastal areas, as Steve and Karina mentioned, these excess nutrients that are coming into the coastline – those are things that our actions on land whether it is agricultural, sceptic systems and sewage, fertiliser, we have a pretty good idea how to reduce those nutrients. But it takes community willpower to be able to do that.
KN: The wetlands and the underwater vegetation – that is something we think about a lot, and they hold an enormous amount of carbon just by existing. And so preserving what we have and trying to encourage restoration of wetlands and underwater eel grass beds and meadows and things like that can actually be things that can be done on a local level that are very helpful.
MA: I want to turn to some of the animals and the effects on animals. I thought you, Steve Palumbi could talk about what is happening to some of the animals.
SP: One of the ways biologists and conservationists can really help is by looking around and saying ‘How can I help preserve what is here so that when we solve the climate crisis and the planet starts getting better and the C02 levels start to drop there is enough left to grow back from’. And so that is what I try to dedicate what I do to, saving as much as we can now. The best climate story that I know about marine mammals is actually the lost grey whales. Grey whales migrate up through the Pacific and they go to Alaska and they feed on bottom critters in very cold water. And as that water is warmed they have started to go further north into the northern slopes of Alaska and along Canada and one of them actually appeared off the coast of Israel. And we saw this picture and thought, there is no way a grey whale is off the coast of Israel, but there it was. And the answer for that was that the whale had migrated way far north, was way up above Canada, it started getting to be winter and so they did what they do: they headed south through the nearest ocean. And then it turned left into the Mediterranean, poor thing, it was totally globally lost due to climate change and no one saw it again. That is the kind of shift where fish stocks and lobsters and all kinds of creatures are moving as a response to ocean warming. You can look at it two ways, you can look at it in terms of a strong change, but you can also say this is the resilience of these populations that can actually move and keep their environment because they can move into a new one. I tend to work on things that live and attach to the bottom like corals and they cannot move, they are like a tree they are there for one hundred years. There we have been looking at how different corals in different places can adapt and change themselves through an environmental process or an evolutionary process to become better at living in warmer water. And that process of adaptation in the future is something I am very interested in knowing how much it will help us save what we need to.
MA: Are some species really more resilient than others?
SP: There are some kinds of corals that are much more resilient to heat and even acidification than others. The really big corals that form mounds in places like the Caribbean and Pacific are pretty well known to be the most resilient to heat and acidification. But they also grow really slowly and they are not the kinds of things that can rebound quickly from, say, a hurricane. The fast growing corals can rebound quickly, those corals are pretty susceptible to heat and that is what has caused coral bleaching all over the world in the last couple of years especially, and it is a serious problem in these corals basically dying over the course of a week because the water is too warm for them.
MA: And then that would have an effect on all of the critters that rely on them, and also, aren’t the coral reefs the providers of oxygen?
SP: They photosynthesise because they have these symbiotes inside them that help them make food. They are not a huge source of oxygen and actually at night they absorb and they use oxygen so I am not even sure they produce that very much.
MA: So the aspect of corals that are considered the lungs when people refer to them as lungs, what is that referring to?
SP: I don’t remember people talking about corals so much as lungs. There are certainly lots of parts of the ocean that are producing a lot of oxygen and those are the microscopic algae that are floating through the ocean, they produce a vast amount of oxygen – something like a third of the oxygen in our atmosphere now comes from them.
SD: There has been a lot of confusion about oxygen and of all the problems facing our planet we actually have quite a bit of oxygen in the atmosphere. Even if something catastrophic were to happen on land or on the ocean it is not going to have a big dent on atmospheric oxygen. There are bigger problems to worry about and I think it goes back to all these other things whether it is recreation, or tourism, or fishing, those are the things I spend more time worrying about.
SP: The real thing about what corals do in regards to producing oxygen and photosynthesising, is they invented this trick about a quarter of a billion years ago. They grow in pretty non-productive waters and that is why tropical waters are so wonderful because it is warm and clear because it is not very productive. But coral reefs are very productive ecosystems and it is because corals have formed the home for these algae that live inside them and the coral feed the algae the nutrients they need to be productive and then the algae have a place to live in very bright sunlight and photosynthesise. This symbiosis between a coral and its algae is the reason why coral reefs can be so productive and the reason why human communities around the tropics have been able to do so well because they are living in a very productive marine environment.
MA: What about the loss of sea ice? We keep seeing headlines about a glacier melting. Is there a quantification of what is actually happening? Scott Doney you have looked at this, how should we understand this loss of sea ice?
SD: The first thing is to explain what sea ice is compared to glaciers. When we talk about sea ice we are usually talking about ice that is floating on the surface of the ocean: it may be between a few feet to maybe ten feet thick. Meanwhile, glaciers and ice sheets are based on land and they can be two kilometres thick. It is important in two ways, one is that when ice on land melts that extra water from that melt is acting to raise sea level. But if sea ice melts, it is already floating, it doesn’t have an effect on sea level. Biologically many types of polar life have adapted to the presence of sea ice and particularly in the Arctic. Around the coast of Chile and Argentina we are seeing large disappearance of sea ice and that makes it very hard for the organisms, these polar organisms, they don’t have any place else to migrate to unlike temperate species that can move north where it is a little bit cooler, if your life history depends on that sea ice for breeding or for feeding, when that disappears it makes it almost catastrophic for those species.
MA: What are some of those species that you are talking about?
SD: I work in the Antarctic. One of the penguin species in the environment we work in is called the Adelie. And the Adelie’s use the ice during the winter to feed off of and then during the summer when the ice melts, it actually stratifies the water and traps phytoplankton right near the surface where there is a lot of light and you get these giant phytoplankton blooms that are then fed on by krill and the krill are then fed on by the penguins. And so they have their breeding colonies in spots where they have big phytoplankton blooms. When that ice goes away, we don’t see the blooms as nearly as large and we think that is leading to what we see which is a very large collapse in some of these populations along the Antarctic Peninsula. Similar things are seen in the Arctic with walrus, polar bears, lots of different species which depend on the sea ice.
MA: Steven Palumbi, how are organisms adapting to these changes?
SP: What we see in coral reefs but also along the west coast of the US is that these marine species live in very heterogeneous environments and that means some of them live in warmer waters and some in cooler waters. And as a result, over time, they have evolved strategies of dealing with variation in temperature. For example, we work in Palau and you can be snorkelling across a coral reef and you realise this water is really warm and it might be thirty-five degrees centigrade, and those corals are supposed to be dead at those temperatures because they cannot survive those warm temperatures. But those corals can do it and those places have really sparked us to wonder where you find corals that are heat-resistant and to develop a way of mapping them. We find them in lots of different places and lots of different settings and it gives us hope that in fact as the oceans warm at least some populations of corals will last a little bit longer. I still think personally they are going to need help and their current level of heat-resistance is nowhere near going to be enough. But it does give us a handle, it gives us something to work on, and some way of saying ‘This is what we are going to do for the next twenty years as biologists as we encourage the financial part of our society and the political part to help us solve climate change’.
MA: Do you think that some of these resilient species will also be some of the larger fauna?
SP: I don’t know. You can think of the larger ones as the mammals, the large fish, in some cases they are not that resilient but they can move. And so those are big advantages to species like that. Our job is to make sure they are allowed to move, that when they start migrating into new places we reformulate the fisheries regulations so it protects them in new zones as well as their old zones. And those are ways of thinking forward and helping these species help themselves.
KN: There are things to do now to protect things into the future. I think there are lots of surprises in store for us and I hope they are not all bad ones. But I think these local conservation actions, the little refuges that we are going to create to hold and nurture the species that are doing well under more changed circumstances and allow them to move and thrive and do well in new places is going to be really important work.
MA: What about those penguins Scott Doney?
SD: Well we are seeing an invasion of a different penguin species. I work at one of the US bases along the peninsular and the penguin species that is declining has a very rigid life history and it is being replaced by penguin species that is more flexible, and so there will be winners and losers. This is what we are going to see, a shift in what populates the ocean. There are lots of organisms that may actually thrive under a different climate but it is how we as a society going to adapt to those changes in what is there.
MA: Final thoughts. Where are we going from here? Scott Doney?
SD: I guess I am optimistic that the oceans are more and more being included in policy discussions from the local level up to the international level. I think as a scientist my goal moving forward is to help work on solutions, solutions that work both for the natural environment but also for human communities, and how can human communities find a balance of how they interact with the ocean so that we can all benefit.
MA: Karina Nielsen?
KN: That is pretty much aligned with what I do here. My hopes for the future, I work a lot with students who are very passionate about the ocean and the natural environment and teaching them solutions is what I am working on every day.
MA: Final thoughts Steven Palumbi?
SP: I totally agree. One of the problems of the ocean is that it is so big and any problem that is significant in the ocean is by its nature a really big problem. People are naturally inclined to say it is too big, we cannot handle that, it is too much. But in fact we can begin to handle that and a lot of the efforts people are putting in are local efforts but they build up to help along the whole coastline. For example, marine protected areas are very local, if local communities agree to protect some part of the shoreline from some kind of fishing or extraction or pollution or something they see an immediate local benefit from that. So convincing people that the ocean is big and wonderful and they can do something locally that will help is part of the solution. I also totally agree about the future of students and how we get them engaged and excited about it and that I think is one of the things these kinds of conversations can really say. There is hope out there, we have a lot of work to do, let’s try and take what hope there is and then fan the flames so we get the most out of it.
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