Stressed-Out Fish and Ocean Acidification: Consequences of Climate Change

Published Nov 5, 2019

Dr. Sarah Cooley explains how changes in ocean chemistry are having a ripple effect on sea life and our economy.

In this episode
  • Colleen learns that fish can get stressed out (and how scientists measure their anxiety levels)
  • We take a look at how climate change is acidifying our oceans
  • Sarah breaks down what these changes mean for the environment and economy
Timing and cues
  • Opener (0:00-0:31)
  • Intro (0:31-2:29)
  • Interview part 1(2:29-12:17)
  • Break (12:17-13:02)
  • Interview part 2 (13:02-23:02)
  • Sidelining Science Throw (23:02-23:14)
  • Sidelining Science (23:14-27:16)
  • Outro (27:16-28:30)
Related content
Show credits

Sidelining Science: Shreya Durvasula
Editing: Omari Spears
Music: Brian Middleton
Research and writing: Jiayu Liang and Pamela Worth
Executive producer: Rich Hayes
Host: Colleen MacDonald

Full transcript

Colleen: Sarah, thanks so much for coming over and joining me on the podcast.

Sarah: Thank you for having me. It's a lot of fun to get to talk about one of my favorite subjects.

Colleen: What is ocean acidification and how is it related to global warming?

Sarah: So, ocean acidification and global warming have one of the same root causes, carbon dioxide in the atmosphere. So when we burn fossil fuels and when we change land uses and release carbon dioxide into the atmosphere, some of it stays in the atmosphere and about 25% of it goes in the ocean. And when the carbon dioxide dissolves in the ocean, it creates an acid, and that acid is fundamentally changing the chemistry of our oceans and creating ocean acidification as we know it.

Colleen: So I'm thinking of those little pH strips that, I would use them when working in a dye studio dyeing fabric and the water, we would have to test it and make sure that the pH was right before we could dump that water. So, is that more or less what's happening with the ocean? You could stick a strip in there and see what's going on?

Sarah: Yes. And there's actually been international observing efforts to survey what the ocean's chemistry is for decades now. And both those shipboard observations and observations based at time-series stations... Locations, where measurements are made repeatedly every month, are showing that there is a progressive decline in ocean pH. So, ocean pH has dropped about 0.1 pH units since the Industrial Revolution. And that doesn't sound like a lot, but it actually is quite a significant change because most of the animals and ecosystems that are in the ocean today are really accustomed to conditions that they've had for thousands of years well before the Industrial Revolution even began.

Colleen: Is it happening in the ocean equally in all areas or are there sort of hotspots?

Sarah: So the whole ocean on average is taking up carbon dioxide from the atmosphere. There are certain areas of the ocean that are more prone to take up carbon dioxide than others. For example, high latitudes near the Arctic Ocean and near Antarctica, there's cold water there, and so the carbon dioxide dissolves more easily into that water. And so that's one of the areas where the change is happening faster than other areas. There are other areas in the ocean where a lot of processes converge. So, the coastal zones are especially complicated. Not only are coastal zones taking up carbon dioxide from the atmosphere, but they're also experiencing a lot of influences from land. Some of those influences change the carbon dioxide content of coastal water, and some of those influences also change the pH of that water through other chemical processes separate from carbon dioxide to solution. So, coastal zones are an especially complicated area. And so we know that coastal zones are experiencing acidification, but right now, it's a real challenge scientifically to peel apart which processes are most responsible.

Colleen: How is ocean life going to be affected?

Sarah: Well, we first noticed the changes from ocean acidification affecting animals with hard shells, and especially the smallest of those animals in the ocean. So, little tiny sea snails were the first species that was noticed to experience problems from acidification. And what happened was there were a bunch of scientists working in Antarctica and they had these sea snails in a sealed bottle to do some observations on it. And as those sea snails spent time in the bottle and they were breathing carbon dioxide out into the water, so they were kind of doing their own little mini-cosm of ocean acidification, their shells started to kind of fray and wear away and the scientists recognized right away that, "Wow, this is profound and we've never seen anything like this before."

Initial studies really focused on animals with shells and skeletons. So, shellfish, corals, those tiny sea snails in the ocean. And the initial studies really showed that the calcification or the building of the hard parts of those animals was really affected by acidification. So, it slows down and those animals are less able to grow and survive as they become adults. And the effect is most strong on larval corals and larval shellfish. So, that was kind of where the research really began because it kind of seemed like, "Oh, we're changing the calcium carbonate balances in the ocean, therefore, things with calcium carbonate should be the most affected." But then later studies started to branch out and look at how other animals are affected. And studies have found that animals with more complex systems like finfish and marine mammals tend to be less profoundly affected or we may not have detected an effect yet on those, but there are some that have these really unusual and surprising effects. So, clownfish are one of the species that... they change their behavior because of acidification. They dart out from the reef and away from protection, and they're more likely to get eaten by predators when they do that. There are other species that actually increase their anxiety. Which cracks me up. How can you measure anxiety in a fish? But there's definitely sort of anxious responses that the biologists were able to detect. And again, it's behavioral changes.

Colleen: So, how do you detect that, though? How do you do an experiment to figure that out?

Sarah: So, a lot of the fish studies have involved putting fish into chambers where the water flows past them. And so they'll put maybe a food queue or something upstream, and then the food smell will come through the water to the fish or the predator smell. And what they were finding with some of these fish that make bad choices, because of acidification, is that they're more likely to move towards the smell of a predator than a fish in normal conditions. So, you can see that some of these things are pretty subtle and kind of hard to trace. But the ultimate process at work has been found to be a change in brain chemistry and olfaction, so smelling has been changed. So, that's kind of one of these like very quirky responses that scientists didn't really expect at first, but they seem to be really scattered among the animal kingdom. And so, identifying what overall principles are at work is still one of the frontiers of ocean acidification research on animals.

Colleen: Let's talk about coral for a minute. You hear a lot about coral bleaching. Is is that connected, or is it connected to ocean acidification?

Sarah: Coral bleaching is the response of corals to incredibly stressful conditions. And most of that bleaching is a response to intense warming periods, so heatwaves in the water or sometimes even disease that the corals are struggling with. And what happens when a coral bleaches is corals typically have little cells that live inside them of another species, and those are called symbionts. And when the coral gets too hot, the coral tissue will kick out the symbionts. And the problem with that is that the symbionts normally provide food for the coral animals. But once the coral gets all stressed out, it's not reacting properly, it's going, "Oh my gosh, get the invaders out." It kicks out those symbionts and then it loses one of its most important food sources. So, coral bleaching is actually a kind of a rare emergency response by corals and it actually can be something that's fatal. It's not always fatal. Sometimes the corals can recover and regain symbionts and get through the tough times. But what we're seeing with acidification is it works a little bit differently than heat-induced bleaching.

So, acidification tends to change the speed at which corals can grow their skeletons and it also can change the reproductive success. And so what that means is, if you have a coral that has just gone through some really tough times, maybe it's just recovering from a bleaching event, or it's gotten physically broken by a ship strike, or even a storm, it's going to be less able to regrow and spread and put out descendants because of acidification. So, acidification is kind of just tilting the survival landscape for corals and making it just that much harder for them to bounce back from other stresses they might be experiencing. Of course, it's incredibly difficult to be a coral biologist and like piece out exactly which elements of a coral's response is due to one driver or another because the rotten thing is acidification and warming rarely happen apart from each other. So, these things are happening at the same time to different degrees in different waters. Sometimes oxygen is also declining in these waters because of warming and changes in circulation. And all of those things are just really, really hard for marine life to cope with all at once.


Colleen: Are there any effects that the average individual person would feel?

Sarah: I think, fortunately, at this time, there aren't gonna be any effects that the average beachgoer is going to experience. You're not gonna go in the water and feel your eyes burning or any changes on your skin. We are much more protected than that. Our skin and our eyes and our circulatory systems do a marvelous job of protecting us from sort of environmental changes. But for things like shellfish and oysters, it's not quite so simple. They're very, very exposed to their environment. And in the mid-2000s there were a couple of years when the Pacific oyster industry had really, really significant losses of oyster larvae in their hatcheries. Now, what's important to know is the Pacific oyster industry... It's on the Pacific, but the Pacific oyster is a specific species of oyster too and that species is primarily supplied through hatchery supplies. So, it's supplied to aquaculturists from hatcheries that grow up the larvae, sell the baby larvae to growers that then put it out in nature and grow it out. So, that creates a bottleneck in that industry. And when you had a couple of hatcheries all reporting massive losses of larvae, there was a lot of worry that that would jeopardize the entire industry. And so the growers who are incredibly resourceful and scientifically-minded, right away started teaming up with local scientists to say, "What's changing in the water?" At first, the hatchery owners thought, "Aha. We've had these kinds of things before. It's some kind of a pathogen. Let's scrub everything." So, they scrubbed out all their pipelines, they cleaned everything, you know, perfectly clean as a whistle and they still had these problems.

What turned out to be the problem was that there were several years of conditions along the Pacific Northwest coast that really favored upwelling of water that was rich in carbon dioxide and a little bit more acidified than other water that they had been receiving. And these hatcheries pump water in to big tanks just on the coast where they raised the larvae. And the initial fix, once they realized that this was the connection, was that hatcheries would wait for upwelling to subside, and then they would pump in the water to refresh their tanks. But they recognized that acidification continues to advance, that's not going to be a forever solution. So, the hatcheries are now investing in experimenting with developing strains of shellfish breeding strains that are more hardy to a wider variety of conditions. They're also exploring ways to kind of protect those larvae, maybe sweeten the water with what's essentially an antacid to kind of raise up the pH of that water, kind of buffer it, just a little Calgon...

Colleen: Tums for the...

Sarah: ...or maybe Tums. Exactly. And making the water a little more pleasant for everyone. And so there's some really innovative solutions that hatcheries have been applying. But what's important to think about is these hatcheries because they supply that whole industry, that industry is a major job creator in some very rural areas along the Pacific Northwest coast. And so the economic considerations of impacts of acidification were immediately brought to the forefront. And leaders in Washington and Oregon realized that this is actually something that could threaten one of the livelihoods of many of our citizens and one of our natural industries that we're most proud of. So, really, the economic considerations here that acidification can maybe change the harvest of particular marine species in a way that makes the industry a little bit less lucrative or a little bit less secure have actually been one of the biggest motivators of action by political leaders.

Colleen: So, this was my next question because they're coming up with sort of workarounds, but we're not solving the root problem. So, is there a solution for ocean acidification?

Sarah: Yes. We need to cut atmospheric carbon dioxide. That is it. That is our thing. In the meantime, there are a number of these sort of more local scale or more industry-specific opportunities. And as I mentioned before, with coastal acidification, we can improve water quality in coastal zones to decrease the runoff of other things that might intensify that acidification signal. So, in that way, improving coastal water quality is kind of a win-win. We might do it for reasons other than acidification mitigation, but it sure does help with mitigating acidification. So, those are things that regional leaders are really looking into because they have the controls at their fingertips to improve local water quality or to sustain marine dependent industries or to help those industries change their practices when times call for it. So, I think those are a lot of the local to regional scale options that are being explored. But you're absolutely right, at the highest level cutting carbon dioxide is the final fix.

First of all, acidification is happening now to people that we know in this country. It's not a tomorrow problem. It's not a somebody else's problem. It's happening now. But we can do things about it. We can invest in research and monitoring so that when there is a period of more intense acidification due to upwelling or due to some kind of prevailing conditions, we can detect it and we can respond to it. We can invest in targeted research efforts that will close knowledge gaps. For example, the coastal acidification story is incredibly complicated. And we know a whole lot of really amazing things from 10 years of federal investment in ocean acidification science. But not all of that information has been placed end to end to understand, "Okay. We need to look into improving some methods to look at X, Y, and Z here in the coastal zone. We need to connect this with Coastal Zone Management in this and that and that way."

Colleen: How do I explain to my cousin in the Midwest that ocean acidification is an issue that she should care about?

Sarah: One of the main reasons that life on Earth exists is because we have an ocean. We're the only planet that has an ocean and it does a lot to make life livable for us. And then usually I'll talk with somebody about, what do they care about most? And someone who lives in the Midwest may care passionately about knowing that coral reefs are out there. They may never have visited them, but maybe they want to know that they're there and they watch them on Discovery Channel and they watch educational programming about it.

Colleen: Maybe their dream. It's on their bucket list.

Sarah: Exactly. It could be on a bucket list. I've got relatives in Wisconsin that are dedicated watchers of Discovery Channel type programming on ocean health. It could be because we're related, but you know.

Colleen: It doesn't hurt.

Sarah: But I think knowing that ocean systems are out there is much more important than we might give credit to on like a financial balance sheet. For folks who are more economically-minded, a lot of times, I like to point out that the benefits that we get from the ocean, the fisheries, the industries that depend on the ocean might not be quite so successful in the future. Fish prices might go up. You might see a difference in what is for sale at the fish counter. You might find that businesses that support marine-based industries, service industries, they might have a tougher time too. So, I really like to talk to people about what their primary connection to the ocean is and kind of work back from there.

Colleen: So, Sarah, what gives you hope in this situation?

Sarah: The thing that gives me the most hope is how deep the connections are between the ocean or the idea of the ocean and a healthy and wonderful ocean with pretty much everyone I ever talk to. Even people who don't go to the coast still need to know and are nourished by the fact that the ocean is out there. So, that gives me a lot of hope because there's a ready and willing piece in everyone I talk to to do right by the ocean. And I think the challenge is to really break down how do we take a big problem that we've gotten into over a long time and kind of walk it back in stepwise fashion? But I'm seeing a larger and larger cadre of experts who are willing to put their minds to this and to work across disciplinary boundaries to come up with something really fresh and new. That gives me a lot of hope and it gives us a lot of opportunity to kind of start with hope and then kind of wedge that open and come up with solutions that we can all get behind.

Colleen: That's excellent. We need some hope. That's a good note to end on.

Sarah: Thanks.

Colleen: Thank you.

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