Biologist studies how the increasing acidity that has come with climate change is affecting ocean life

April 14, 2015 by Gail Bambrick, Tufts University
“We have produced so much extra carbon dioxide in the atmosphere in the past 250 years or so that we have actually managed to make the world’s oceans more acidic,” says Jan Pechenik. “That is a lot of water.” Credit: Ingimages

The increasing acidity of the world's oceans is having some pretty dire effects, including damaging coral reefs and weakening the shells of clams, oysters and mussels. Acidification is also harming sea creatures at the bottom of the oceanic food chain, such as plankton and fish larvae, posing a threat to many species of marine life.

Delving more deeply into the decrease in the pH of the world's oceans, Jan Pechenik, a professor of biology in the School of Arts and Sciences, is tracking its ramifications for a common marine snail, Crepidula fornicata, also known as the slipper snail, a species that's found along both U.S. coasts and has now invaded the coastlines of Europe.

Working for the next three summers at the Friday Harbor Laboratories at the University of Washington on Puget Sound, he will also investigate other stressors that could affect the snails' development, such as rising seawater temperatures and the availability of food. His work is being supported by a three-year, $315,000 National Science Foundation grant.

Pechenik talked with Tufts Now about the causes and consequences of , what this portends for the future of the oceans and how a common snail may help provide some of the answers.

Tufts Now: What is ocean acidification?

Jan Pechenik: Basically, the concentration of hydrogen ions in seawater is increasing. Since the start of the Industrial Revolution about 250 years ago, the hydrogen ion concentration in seawater has increased by something like 30 percent. There is no controversy about that—chemists have been making those sorts of measurements for a very long time. And the ocean is now projected to keep becoming more acidic for at least the next 100 years.

Do we know what is causing acidification?

The only explanation anyone has proposed is that the ocean has been absorbing more from the air. If you dissolve carbon dioxide in water, you get carbonic acid, just like in Coke and Pepsi. The carbonic acid breaks apart in the seawater and releases hydrogen ions, which cause higher acidity.

Trucks, cars, power plants and the cement we use in construction—all that releases a lot of CO2 into the air. Scientists have estimated the ocean has absorbed about one third of that excess carbon dioxide.

There are a lot of data showing that the carbon dioxide levels in the atmosphere are higher now than they have been in the last 150,000 years.

Where is this occurring?

The marine snail Crepidula fornicata. Credit: Jan Pechenik

We are talking about all the world's oceans—all of them—becoming more acidic. We have produced so much extra carbon dioxide in the atmosphere in the past 250 years or so that we have actually managed to make the world's oceans more acidic. That is a lot of water. This is one of the most fantastic things I've heard in my life.

What is the effect of ocean acidification?

That's the big question, and we need to do more studies to find out. But we do know that animals that make shells and other calcium carbonate homes, like corals, oysters, clams and mussels, are probably going to suffer, because calcium carbonate dissolves in more acidic conditions. Studies show that lower pH often causes these organisms to calcify much less than they would normally—that is, they build weaker shells, or they build them more slowly, or both.

Clams, mussels, oysters and other marine mollusks are microscopic in their developmental stages, typically hatching at less than 100 microns as , less than the width of a human hair, and they have very thin shells. Under more , they are likely to be even more vulnerable to predators, like krill and jellyfish, and suspension feeders like bivalves and even adult Crepidula fornicata.

Other bivalves react to increased acidity by putting more energy into making strong shells, but that means they have less energy for other things like overall development, so they grow much more slowly. So either way, they will be more vulnerable to predators, and may mature at smaller sizes and produce fewer eggs.

What other effects from ocean acidity have been observed?

Some are really surprising, things I would never have expected to see. A study from a few years ago on the larvae of a coral reef fish showed that when you increase the acidity of the seawater, the larvae lose the ability to detect the scent of predators, and in fact, a lot of them swim toward the predator. That is probably due to a change in the functioning of their sensory receptors, but no one yet knows how that mechanism works.

Some of the consequences can be really subtle. Recent studies show that causes a shift in the chemical composition of single-celled algae called phytoplankton, making them less nutritious for the species that eat them. Those single-cell algae are major food sources for the larvae of clams, mussels and oysters and a whole variety of other organisms, including my snails.

Why does that matter?

I recently did laboratory research feeding three different algal species with different nutritional values to the larvae of the I am working with for this NSF study. I found that the larvae raised on the poorer algal diets all grew more slowly as juveniles, their next stage of development, even though they were given the best diet once they entered the juvenile stage.

If we find that also happening in the ocean, it means the snails are going to be more vulnerable to predators for a longer time—both as larvae and juveniles. Fewer snails mean fewer larvae that many marine animals depend on for food, and fewer larvae to make the next generation of adults.

But the ocean is not just getting more acidic, it is also getting warmer. This will change species' ranges so organisms are going to be coming into contact with animals and plants they've never encountered before; we don't know the consequences of these altered interactions. There are also the consequences of pollution to consider, and changes in ocean salinity due to altered rainfall patterns resulting from climate change. That's what I mean when I say the consequences are going to be really hard to predict, including what sea animals will be affected.

Why is the marine snail Crepidula fornicata such an ideal research subject?

It is native to the East Coast, from Nova Scotia to maybe as far south as Florida. But it is also a major invasive species—it is also on the West Coast, where I will be working, and it is spreading around the world. In the future it may be useful for monitoring the effects of global climate change and ocean acidification. The snails are easy to collect—they just sit in stacks in rocky shore areas. I wait for low tide. I go out and pick them up, put them in my bucket and take them to the lab.

Each time an individual reproduces, thousands of larvae are released, making it easy to achieve good sample sizes. They are also very easy to keep in the lab: I can raise the animals with essentially no mortality, from larvae all the way to adulthood. Also, many developmental and physiological studies have already been conducted with this species, so we're working with an animal about which quite a bit is already known.

What happens in the lab?

I have previously shown that the juveniles of this species grow more slowly if they have experienced certain environmental stresses earlier in development, as embryos or larvae, but no one has yet looked at how this is being caused: how does being stressed as an embryo or larva end up changing how fast they grow, whether they survive after metamorphosis, or how many offspring they have later?

My graduate student Robert Burns and I hope to understand the molecular basis for how these effects are caused by the combination of acidity, heat and nutritional stress. Crepidula may eventually become a model for understanding the "latent" effects of stress during fetal development of other species, including humans, in a changing climate.

Explore further: Climate change threat to mussels' shells

Related Stories

How will ocean acidification impact marine life?

February 3, 2015

Many marine organisms—such as coral, clams, mussels, sea urchins, barnacles, and certain microscopic plankton—rely on equilibrated chemical conditions and pH levels in the ocean to build their calcium-based shells and ...

Evolving to cope with climate change

March 6, 2015

Over the next two centuries, climate change is likely to impact everything from industrial agriculture to the shape of our coastlines. The changing climate will certainly cause huge changes around the world, and the challenge ...

Recommended for you

Evidence of earliest life on Earth disputed

October 17, 2018

When Australian scientists presented evidence in 2016 of life on Earth 3.7 billon years ago—pushing the record back 220 million years—it was a big deal, influencing even the search for life on Mars.

Arctic greening thaws permafrost, boosts runoff

October 17, 2018

A new collaborative study has investigated Arctic shrub-snow interactions to obtain a better understanding of the far north's tundra and vast permafrost system. Incorporating extensive in situ observations, Los Alamos National ...

Arctic ice sets speed limit for major ocean current

October 17, 2018

The Beaufort Gyre is an enormous, 600-mile-wide pool of swirling cold, fresh water in the Arctic Ocean, just north of Alaska and Canada. In the winter, this current is covered by a thick cap of ice. Each summer, as the ice ...

4 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

gkam
3.4 / 5 (5) Apr 14, 2015
These can be no question of man changing the Earth now. The question is how soon we overcome the Deniers owned and operated by Filthy Fuels.

Most Deniers are not aware we get half of our food and half of our Oxygen from the seas. If we continue to kill the bottom of the food chain, everything above will die, like in Soylent Green, where corporations took over the government and ruined the Earth.
philip_haddad_37
1 / 5 (3) Apr 14, 2015
Present acidification of the oceans (and perhaps past) may be caused by sulfurous compounds being emitted by volcanoes in the past and by the burning of coal in the present. Annual consumption is 2000 million tons of coal which contains, on average, 1% sulfur. This is equivalent to 60 million tons a year of sulfuric acid (carried as acid-rain). Because the increase in the amount of sulfate necessary to balance the increase in hydrogen ion is so small as compared to the normal sulfate concentration it is nearly impossible to confirm nor refute this possibility.
holoman
5 / 5 (4) Apr 14, 2015
You might want to study the chemistry.

http://www.iaea.o...age=2181

http://www.huffin...443.html
classicplastic
5 / 5 (1) Apr 15, 2015
Sounds like someone needs to remake Soylent Green. That way, the truth can be explained slowly, with pictures and small words.

Not that it would make any difference. If you can't change your mind, are you sure that you still have one?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.