Climate Change > Ask a Scientist About Climate Change and Marine Life

Ask a Scientist About Climate Change and Marine Life

How is climate change affecting the oceans?

LEANNE MELBOURNE: Climate change is affecting the oceans in a number of ways. The major one that we can think of is through warming. So we know about global warming with rising carbon dioxide levels leading to warmer temperatures. But we see that warmer temperature in the ocean as well.

The other problem that we have in the oceans is that carbon dioxide dissolves in the ocean and reacts with the water to form this weak acid. Ocean acidification is what we call it. So the oceans are becoming slightly more acidic. They're lowering their pH, which makes it very difficult for certain organisms to survive.

So when we talk about the oceans becoming more acidic, we're really referring to this idea of them moving to a less basic state. The oceans on average have a pH about 8.1. And so as this increase in acidity, we're moving from more basic to less basic. But it's not actually becoming an acid.

And then there are a whole load of other problems. We have rising sea levels. We have increases in intense storms as well. And then with warmer waters, warmer waters means that it's harder to hold gas in the oceans. So we're seeing increase in areas of deoxygenation. So we're losing oxygen from the oceans.

How is climate change affecting marine life?

Leanne Melbourne: Climate change is affecting marine life in a number of ways. And it's very complicated because no two organisms are the same. So you can think about seaweeds and fleshy algae, like the green plants that we see in the ocean, would actually quite like the increase in CO2 in the ocean because it's good for photosynthesis for growing. But something like calcified organisms, like oysters and corals and coralline algae, an organism that produces calcium carbonate-- when we think of calcium carbonate, you can think of chalk. For that, that will dissolve in a more acidic ocean.

So it's harder for calcifying organisms to build their shells, their skeletons when the oceans are becoming more acidic. Through ocean warming, that really will affect maybe more their distribution. It can also affect how they grow. So there's lots of different things that can affect these organisms.

And for some of them that form these kind of habitats, the increase in storms, more frequent storms, more intense storms, those kind of things will affect their ability to maintain that habitat function. So organisms like oysters and mussels and corals, they will find it harder to calcify under a more acidic ocean, whereas fresh algae actually might do a little bit better.

Why is it important to study calcifying organisms?

Leanne Melbourne: It's important to study calcifying organisms mainly because it's just important to study all life. And to really understand how these organisms are affected by things that we are doing. I think for me, why I really like studying calcifying organisms, they have this added function as a habitat.

So by understanding how they are affected by climate change, you are also starting to have a deeper understanding of all of the other organisms that live within these habitats and call these places home.

What do you hope to find out by studying calcifying organisms?

LEANNE MELBOURNE: So what I hope to find out from studying calcifying organisms is how the environment is really affecting how they grow and their shape. And how that affects their ability to function as these habitat formers. So in finding out that information, hopefully, I can help influence policy and other aspects of government to help really protect them in the future.

How do you study calcifying organisms?

LEANNE MELBOURNE: I study calcifying organisms in a number of ways. I think for me personally, I'm really interested in the shape and how they grow. For mussels and oysters, actually, how the shell is formed, and for corals and coralline algae, how the skeleton is formed. And so really what I do is I crack them open and look at them under a variety of different instruments.

We use microscopes to look at the internal structures. So the microscope that I use is called a scanning electron microscope. We also use different instruments to look at the chemistry of the shells and skeletons, so how the elements are changing. And that, I use an electron probe micro analyzer.

And then some of the instruments I use are really cool and they press into the shell to work out how hard and how stiff it is. And that instrument is called a nanoindenter.

How did you figure out you wanted to be a scientist?

LEANNE MELBOURNE: The future of coralline algae is very complicated. These are marine plants that ultimately need CO2 for photosynthesis and growth. So you'd think that that's actually quite a good thing. But because they also calcify-- they produce calcium carbonate within their cell walls that gives them this hard, chalky-like appearance-- they are affected by increasing CO2 levels and ocean acidification, which will make it harder for them to create their skeletons.

So there are predictions that we might lose them from further north, because the waters will be more corrosive to them. But at the same time, you'd think that they might move further north to get away from those warmer temperatures. For the coralline algae that I look at that produce these important habitats and ecosystems, things like storm surges and the predictions [? with ?] increased intensity of those storm surges-- that could be very devastating to them, and make it harder for them to maintain that function as a habitat former.

Why is biodiversity of marine life important?

Leanne Melbourne: The biodiversity of marine life is really important to humans in a number of ways. If you really love your seafood, that all comes from the oceans. But also, if you're thinking more globally-- because there's so much life in the ocean with primary producers, so things like seaweeds and seagrasses that will take in CO2-- a lot of carbon is absorbed into the ocean. And if we didn't have the oceans, our levels in the atmosphere would be so much higher.

But then we also have this producer of oxygen as these primary producers release oxygen. And as humans, we need oxygen to survive. So there's this great exchange between carbon dioxide and oxygen in the oceans that help sustain life on this planet. But fundamentally, it's just important to, as humans, to look after all of this life that we do have on this planet.

What are you most hopeful about in your research?

LEANNE MELBOURNE: What am I most hopeful about in my research? I think my research kind of shows how, actually, how resilient these organisms are and how stable they are. I've been doing a lot of work using historical collections, so things that were collected about 100, 150 years ago. And more recently, I've actually been looking at fossil collections. So these things were alive 55 million years ago.

And the results that are coming out are showing that these organisms are more stable. And if the change in environment is slow enough, these organisms are able to adapt and survive and sustain their function as habitat formers. So it gives us hope that if we do reduce our carbon dioxide emissions and we slow our rates down, that it gives us hope that these organisms will survive in the future.