IRA FLATOW: This is Science Friday. I’m Ira Flatow. We’re coming to you a the Mondavi Center in Davis, California. And as we all know, California is bordered on the west by the Pacific Ocean. And as the globe is warming, sea water is becoming more acidic, as it sucks in increasing levels of carbon dioxide in the air.

Acidification can have a dramatic impact on ocean life, from majestic coral reefs to the humble oyster. And as a result, oyster farmers have been facing tough times and falling production. Does this mean you may no longer get to enjoy your oysters? Will it be our appetite that you have to adjust?

My first guest is studying ways to turn tide in favor of oysters and other shellfish. Tessa Hill is an associate professor of earth and planetary science at the Bodega Marine lab for the University of California, Davis in Bodega Bay. Welcome to Science Friday. We won’t be taking calls today. But if you’d like to join the conversation, you can tweet us @scifi or leave us a comment at sciencefriday.com. We can talk about ocean acidification until we’re blue in the face, but why is this happening? Is it global warming that–

TESSA HILL: Well, it’s a related problem. So as we put carbon dioxide into the atmosphere through driving our cars or industrial activities, the ocean is a tremendous sponge for that carbon dioxide. About 25% to 30% of it goes straight into the ocean. And it fundamentally changes the chemistry of the ocean. It makes the ocean more acidic.

IRA FLATOW: And what does that do for the shellfish? Why does that affect them?

TESSA HILL: Yeah. Excellent question. So as the shellfish, or corals, or sea urchins, anything with sort of hard parts or shells, as they’re trying to build their shell, they’re pulling building blocks of their shell out of the seawater. And as the seawater becomes more acidic, there are less of those building blocks available. So they have a harder time making their shells.

IRA FLATOW: And so how fast is this all unfolding?

TESSA HILL: It’s tremendously fast, actually. The ocean is in direct contact or communication with the atmosphere. And so as we put things into the atmosphere, it essentially instantaneously changes the chemistry of the ocean.

IRA FLATOW: Now I know you that you have a little demo–

TESSA HILL: That’s right.

IRA FLATOW: –for quickly this process can happen. And apparently, I’m going to be a lab rat.

TESSA HILL: You are.

IRA FLATOW: OK. Let’s go do it.

TESSA HILL: You ready?

IRA FLATOW: Yeah. Let’s go.

TESSA HILL: I find that, oftentimes, people find it hard to believe how quickly water can take up carbon dioxide and change chemistry. But it turns out as we’re all sitting here in this room and we’re breathing, we’re exhaling carbon dioxide.

IRA FLATOW: You filling up a beaker. Now first, you’re putting– oh, it looks like wine. But I’m feeling it’s not wine.

TESSA HILL: So this is a pH sensitive dye. And so the color of the dye ties with the acidity of the water. And so we have two of these.

We’re going to leave this one alone. It’s this lovely dark red, almost purple in color. I’m going to have you bubble your own breath into this one. And we’ll see what happens.

IRA FLATOW: So I’m doing a breathalyzer test?

TESSA HILL: To reiterate, please exhale.

IRA FLATOW: Exhale. OK.

TESSA HILL: A little bit longer.

IRA FLATOW: Easy for you to say.

TESSA HILL: You’re welcome to stop, if you would like.

IRA FLATOW: OK. I’m going to pass out now. Color change, they went from with dark red to a cherry red.

TESSA HILL: And we conveniently left an oyster shell here so we could talk about that.

IRA FLATOW: OK. Tell us the significance.

TESSA HILL: Yeah. So this is essentially what’s happening in the ocean on a regular basis. Just as this color change showed, so this might be an ocean before humans had an influence. And this is our current ocean. The current ocean is making it more challenging for things like oysters to make their shells.

IRA FLATOW: Does it affect young, older oysters differently?

TESSA HILL: Well, we think it probably affects all of them, but we actually have a lot of reason to believe that larval oysters or baby oysters are particularly affected by this phenomenon.

IRA FLATOW: And what about affecting the taste of the oysters?

TESSA HILL: Good question. That I know of, it does not affect the taste. But what it’s affecting for oyster farmers, what it’s affecting is their ability to successfully raise, you know, healthy oysters up to market size and actually be able to sell them.

IRA FLATOW: So you go out and actually do research on the oysters. You go into the oyster beds. What’s that like?

TESSA HILL: Yes. So we do research into Tomales Bay at Hog Island Oyster Company. And we actually are– there are some fans here of the Oyster company. We partner with them so that we measure what is happening right here. The process of ocean acidification, we measure right at the oyster farm.

IRA FLATOW: What kind of water is it that you’re working with? Is it fresh water, salt water?

TESSA HILL: No. This is salt water. It’s in an estuary in a bay. So oysters are a species that likes to live in estuaries. So sort of where the land and the sea meet, where there might be a little bit of freshwater and a little bit of ocean water.

IRA FLATOW: How does the oyster farming work, in general? How do you get an oyster like that?

TESSA HILL: So you start with a larval oyster, which is what is on the left here. And these are actual images from a shell fish hatchery in Washington. That baby oyster floats around in the water for about a week. And then it settles on to a rock or in the case at the oyster farm, it actually settles onto another piece of shell.

And then they will raise it for up to a year or maybe even two years before they can sell it to you to eat. And what you’re seeing up on the screen is the difference between a healthy normally shaped baby oyster versus one on the right that has experienced these ocean acidification conditions. It’s smaller and a little bit misshapen.

IRA FLATOW: If the oceans to continue to acidify, at this pace, what does this mean for your oyster industry? Are they on the way out, or it’s a tougher to buy oysters? What’s going to happen?

TESSA HILL: It’s a great question. I mean, I don’t think they’re on the way out. But I think that’s because the oyster industry or the sustainable aquaculture industry, as a whole, has been very proactive in trying to address this problem. And so they’re really starting to take this problem into consideration in the way that they raise the oysters and the conditions where they raise the oysters.

So they’re building a lot of resilience to this issue. But I do think it has big implications for our relationship with the ocean, what we associate with the ocean in terms of our own recreation. Our ability to eat seafood and enjoy the ocean is definitely going to be affected by this process.

IRA FLATOW: So what does a farmer like Hog Island Oyster Company going to do with it? Do they have to adjust?

TESSA HILL: Yeah.

IRA FLATOW: Like how?

TESSA HILL: Well, so I can give you two examples. One is that with the information that we’ve been learning from Tomales Bay, they can make decisions about times that might be more stressful to put oysters into the bay. So maybe they would avoid time periods of the year that were particularly acidic worse than normal.

The other thing is they’re actually building a brand new hatchery. And that hatchery is really taking this problem into account. And so they will have a state of the art, you know, water chemistry lab in their hatchery to really think about how to monitor water chemistry and plan for the inevitability of this problem.

IRA FLATOW: All right. We have someone at the mic out there with the question. Yes, sir.

SPEAKER 1: Yes. With the baby oyster being so small in size to I guess the normal size, thinking about human development and how much occurs at the beginning of life, are the oysters able to regain that, what they’ve lost? Does it just take twice as long, or will we just have smaller or less tasty oysters forever?

TESSA HILL: You know, that is a really great question. And that’s actually something we addressed directly with our research. So what we found is that if the baby oysters are exposed to these acidic conditions, even in that very narrow window of the beginning of their life, in the first week of their life, when they then settle on a rock and begin to grow, even months later, four or five months later, they have not caught up with the counterparts that were in the control group. So it looks as though that early life stage is particularly important for determining the health of the oyster.

IRA FLATOW: Thank you. We have a picture up there.

TESSA HILL: Yes. And actually you can see in this picture. Towards the bottom of the picture, there’s a particularly rounded part of the shell. It’s a little bit darker than the rest of the shell. That’s actually the larval or the baby part of the shell.

And then you can see that the shell sort of expanded outward. And that’s when the oyster was basically a teenager. And we were raising them for months to watch as that shell accumulated in the later stages.

IRA FLATOW: We know how difficult it is raising teenagers. So we won’t talk to you about that.

TESSA HILL: That’s right.

IRA FLATOW: Now you know the plants are good at pulling carbon dioxide out of the atmosphere. Can you do that in the ocean to pull the CO2 out of the water?

TESSA HILL: Yes. So I think there are some points of optimism in this story. And this is one of them, which is that there are some special places in the ocean that might actually help us fight this problem. One of them is in sea grass beds. Another example would be kelp forests.

So these are much like the forests on land, that through using photosynthesis, they’re actually taking carbon out of the atmosphere and storing it. Sea grasses and kelp forests very likely to the same. And our research group, right now, is trying to actually fix some hard numbers on that, how much carbon do they take up and for how long.

IRA FLATOW: That’s interesting. Let’s go back to the question in the audience. We have a young man out here with the microphone. Yes.

SPEAKER 2: Does this effect abalone, as well?

TESSA HILL: Wonderful. Yes, it does. We’re actually– in addition to working with oyster farming partners, we also work with groups working to culture the red abalone. And they are very concerned about the future of the red abalone, because of these conditions. And again, a point of optimism is that one of the things we’d like to do in that research is find maybe strains of red abalone or places along the coast, where you can find red abalone that are really resistant to these conditions. And so we’re going to try to help the abalone farms actually find the abalone of the future.

IRA FLATOW: Wow. That’s great. Yes, sir, step up to the mic.

SPEAKER 3: I was wondering how much CO2 is actually needed to cause the acidification the ocean, and what does that mean for other habitat in the ocean who are also experiencing this change?

TESSA HILL: Great question. So in terms of how much CO2, essentially, the ocean stays in equilibrium with the atmosphere. So any amount that we put into the atmosphere, a fraction of it ends up in the ocean. And we’re already seeing the effects of that.

The effects are projected to get worse. And it will affect many habitats that you’re used to hearing about, coral reefs, kelp forests, the mussels along the California coast. And it affects fish, as well as invertebrate.

So it’s a pretty pervasive problem. It’s also happening at the same time as several other issues in the ocean, like temperature warming and oxygenation change. So there’s a lot of things changing all at the same time.

IRA FLATOW: Well, Tessa Hill, thank you very much for taking the time to be with us today, associate professor of earth and planetary sciences, UC Davis, Bodega Bay Marine Lab, Bodega Bay California. Next up, lasers planes and a beetle invasion and no, not the latest sci-fi thriller. It’s a story of the California drought.

Let me introduce our musical entertainment this evening, Joe [INAUDIBLE]. And he’s accompanied by Sacramento percussionist Brian Chris Rogers.

[MUSIC PLAYING]

This is Science Friday from PRI.

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