What’s going on with the oceans and what can we do?

As carbon dioxide (CO₂) rises in our atmosphere, the oceans absorb roughly a quarter of the amount. This lowers the pH level in the seawater, making the oceans more acidic. How this affects life in and out of the sea is continually studied.

This week, ocean acidification is the topic of several scientific papers. We thought we’d highlight a few of them here.

Nature Climate Change has two papers—one about the affect of acidification on several different species, and the other on how ocean acidification causes even more global warming.

For the first paper, German researchers surveyed previous studies that dealt with the consequences of ocean acidification for marine species from five animal taxa: corals, crustaceans, mollusks, fish, and echinoderms. By the end, they had compiled a total of 167 studies with the data from more than 150 different species.

Their findings? Different species are affected in different ways and to different extents, but all species are negatively affected by ocean acidification. “Our study showed that all animal groups we considered are affected negatively by higher carbon dioxide concentrations. Corals, echinoderms, and mollusks above all react very sensitively to a decline in the pH value,” says lead author Astrid Wittmann, of the Alfred Wegener Institute.

The second study demonstrates that the negative effects of ocean acidification aren’t just limited to marine life. The authors discovered that rising ocean acidity has the potential to amplify climate warming in general, through the decreased production of a biogenic sulfur compound.

Phytoplankton in the ocean produce dimethyl sulfid (DMS). As DMS is released into the air, it creates atmospheric sulfur—which increases the reflectivity of the atmosphere to incoming radiation, reducing surface temperatures. Warming acidic oceans means the phytoplankton produce less DMS, causing an even warmer planet.

In addition to the Nature papers, Philosophical Transactions of the Royal Society B has an ocean acidification-themed issue this week, with nine papers studying its effects. The papers describe three distinct effects on marine life due to ocean acidification: species interactions, decreased ecosystem functions, and adaptations. Andrew Revkin has a great summary of them on his Dot Earth blog in the New York Times.

“It’s great that some of these papers are looking at entire ecosystems,” says Aaron Pope, the Academy’s sustainability manager who works tirelessly to communicate ocean acidification issues. “There’s been lots of research in the past on individual species impacts, but data on entire natural systems was missing. Now we can start to talk about what will really happen in marine ecosystems as ocean acidification gets worse.”

One paper of the group (from local researchers at San Francisco State University) looks at tiny coccolithophores. These single-celled algae are able to sequester oceanic carbon by incorporating it into their shells, providing ballast to speed the sinking of carbon to the deep sea. The little organisms are central to the global carbon cycle, a role that could be disrupted if rising levels of atmospheric carbon dioxide and warming temperatures interfere with their ability to grow their calcified shells.

This paper might provide a bit of hope among the rest: “At least in this experiment with one coccolithophore strain, when we combined higher levels of CO₂ with higher temperatures, they actually did better in terms of calcification,” says co-author Jonathon Stillman, of SF State.

Here’s to hoping that all of these papers findings will create more awareness of ocean acidification that will lead to more solutions.

Coccolithophore image: Alison R. Taylor/PLoS Biology

“Urchins are good model systems for studying all kinds of evolutionary phenomena,” Rich explains, noting all of these recent stories about these amazing creatures. “Not only are they hardy and easy to raise in the lab, they have a wonderfully diverse and informative fossil record that allows us to talk about evolutionary events in real time.

“Besides, sea urchins are amazingly interesting animals, occupying a critical position in many ecosystems, including kelp forests off our Californian coasts and coral reefs around the world.  With more than a thousand species of sea urchins, there is much to be learned.”

Urchin Sperm Navigation

Like how their sperm travel. I’m serious. Urchins don’t mate. Rich describes them as “broadcasters.”

“Males and females are separate, but each releases sperm and eggs (respectively) into the seawater.  It is becoming apparent that certain species will aggregate so increase the chances that a sperm will meet up with an egg, but it is still a pretty iffy business.  Eggs are small, and sperm even smaller, and they have to meet while they are still vigorous.  It’s a big ocean…”

A recent study finds that these urchins have a tool to combat the vastness of the ocean—egg radar—or at least that’s how Rich explains it.  “Essentially the sperm are detecting the eggs by sensing specific chemicals in the water and sampling the chemical trace often enough (like the frequent sweeps of a radar beam say, or perhaps even more like the constant sniffing of a bloodhound searching along the ground).  The sperm sense gradients of the chemical traces and swim towards the highest concentrations.”

With any luck, finding a target within!

The next three items in today’s urchin buffet all have to do with the unusual structure and materials that make up these echinoderms.

Ocean Acidification

Last month, a group of scientists met in Monterey to discuss ocean acidification. It wasn’t all bad news—or at least not for sea urchins. Rich explains, “Unlike the shells of snails and clams, the skeleton of urchins (no one should call it a shell — the technical term is “test” to distinguish it from a shell) is internal:  a product of pretty much the same internal growth mechanisms that produce vertebrate skeletons.  We do not expect vertebrates to have problems with ocean acidification due to the rise in pH, so I don’t expect the internal skeletons of echinoderms to have difficulties.  The real problem? How easy will it be to get the calcium carbonate they use to make their skeleton from the sea water?”

Urchin Spine Strength

A new study in PLoS ONE finds the materials of an urchin’s spines to be incredibly strong but also very flexible. This odd combination of both elasticity and brittleness results from the spines’ unique chemical composition, which allows them to absorb impacts and stress under some conditions—and to snap off under others.

“Each species has its own characteristic set of spines,” says Rich. “It is hard to imagine a hard substance like limestone to be flexible, but this is pretty much what happens when it is produced in the way that echinoderms can make it.  I have been working on the distribution and systematics of a curious member of the same group discussed in the article, the ‘hair-spined urchin.’  Their whisker-thin spines are so flexible, they bend without breaking when you touch them, almost like hair.”

Urchin Elasticity of Collagen

Do urchins hold the key to the fountain of youth? No, but another study in PLoS ONE discusses the mutable collagenous tissues (MCT) in echinoderms. One headline about this study states, “What echinoderms can tell us about looking young.”

It’s not a new finding that echinoderms have this variable elasticity of collagen in their bodies, but the recent study highlights the “detection of the genes and proteins that are involved,” Rich says. “This is a long stretch from developing a skin cream!”

You can read more about MCT in these fascinating animals in Rich’s blog from last year’s Philippine Biodiversity Expedition.

Seconds, please

While you’re enjoying the banquet, Rich is busy with more urchin research. “There is the story of brooding Antarctic sea urchins, the new discoveries of deep-sea forms, and the stupendous urchin diversity in the Philippines… hard to know where to stop, or to imagine how I will manage to publish it all.”

Look for more urchin stories to come!

Image: catatronic/Flickr