Carbonate geologist Justin B. Ries discusses his work

Justin B. Ries talks with and answers a few questions about this month’s New Hot Papers paper in the field of Geosciences.

Why do you think your paper is highly cited?

I think that this paper has been highly cited because it was among the first to show that calcifying marine organisms can exhibit both positive and negative responses to CO2-induced ocean acidification.

Does it describe a new discovery, methodology, or synthesis of knowledge?

The novel aspect of this study is the range of calcifying marine organisms that were investigated and the variety of responses to ocean acidification that were observed. To the extent that it was expected that marine calcifiers would exhibit a universally negative response to CO2-induced ocean acidification, then, yes, our finding that a portion of the organisms began calcifying at higher rates under elevated atmospheric CO2 was a relatively novel finding.

Would you summarize the significance of your paper in layman’s terms?

It is widely expected that CO2-induced reductions in seawater pH, or “ocean acidification,” would make it harder for marine organisms to build their calcareous shells and skeletons. We investigated this hypothesis by rearing 18 different species of marine calcifiers, including clams, oysters, scallops, mussels, corals, urchins, crabs, lobsters, shrimp, snails, conchs, calcifying worms, and calcifying algae under seawater saturation states predicted for the next 500 years.

We found that 10 of the 18 species exhibited a major decline in calcification under conditions of elevated atmospheric CO2 (reduced saturation state). However, we also found that seven of the species, including the crabs, shrimp, lobsters, calcifying algae, a temperate urchin, and a limpet, actually began to calcify more rapidly under moderately-to-extremely elevated CO2 conditions. And one of the organisms, the mussel, exhibited no response.

How did you become involved in this research, and how would you describe the particular challenges, setbacks, and successes that you’ve encountered along the way?

I am trained as a carbonate geologist—which means that I study limestones. Most limestones are derived from the shells of marine organisms—such as corals, calcifying algae, mollusks, and foraminifera. Therefore, just as igneous geologists study volcanoes and magma to investigate how igneous rocks form, I study calcifying organisms in order to explore how limestones form.

I am interested in understanding not only how future anthropogenic elevations in atmospheric CO2 may impact marine calcifiers, but also how marine calcifiers would have been impacted by rapid changes in atmospheric CO2 throughout the geologic past. That is one of the reasons that we employed a CO2 level in our experiments that was higher than what we will probably encounter anytime in the near future.

The greatest challenge to doing this research is not the science—that is actually the fun part! The most challenging aspect is responding to the manipulation and distortion of our scientific results by those seeking to further a specific political, social, or economic agenda. Many individuals and groups have publicly interpreted our results as evidence that ocean acidification is not a cause for alarm.

What they overlooked is the fact that 10 of the 18 species that we investigated exhibited a very negative response to ocean acidification. In fact, the shells of six of the 10 species that responded negatively actually began to dissolve on a net basis under the highest CO2 condition. I am perplexed by how anyone could interpret the negative response of 10 of 18 key marine species as a good thing. Benthic marine ecosystems are finely tuned and well-balanced systems. The decline of even one key species can cause major problems for the ecosystem as a whole.

When explaining the issue to non-scientists, I often compare the benthic marine ecosystem to their house (oeco- is actually Latin for “house”). I pose the question: “If someone removed 10 of every 18 bricks from your house, is that still a house in which you would want to live?”

Where do you see your research leading in the future?

The next step in my research is to investigate the mechanisms by which marine calcifiers are both negatively and positively impacted by CO2-induced ocean acidification. This means that we have to get into the microfluids from which the organisms are producing their shells. We have made progress on this front with corals, and the results are very intriguing.

Apparently, organisms are able to control the speciation of inorganic carbon through ion pumping. Of course, there is no free lunch—it takes energy to drive these pumps. Indeed, research by other groups have shown that although some organisms may build bigger shells under high-CO2 conditions, this may come at the cost of other vital processes, such as tissue growth and/or reproduction.

Do you foresee any social or political implications for your research?

I think that our results underscore the urgency of addressing the world’s CO2 problem. Ten of the 18 species investigated exhibited a very negative calcification response to elevated CO2—with the shells of six species actually showing dissolution. The organisms that were investigated were selected not only because they are key members of benthic marine ecosystems, but also because many of them form the basis of the multibillion dollar global shellfish and dive-tourism industries.

This work contributes to the growing body of evidence that CO2-induced ocean acidification presents a real threat not only to marine ecosystems, but also to human economies. Hopefully, this evidence will be duly considered by the legislators and policymakers that have the power to curb CO2 emissions—before the effects become irreversible over human timescales.<

Justin B. Ries, Ph.D.
Assistant Professor of Marine Geology
Department of Marine Sciences
University of North Carolina at Chapel Hill
Chapel Hill, NC, USA

Science Watch, January 2011. Article.

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