To the more than 1 billion people who depend on the oceans for their sustenance and livelihoods, increasing  acidification presents a worrisome question. Which sea creatures will survive in waters that have had their chemistry altered by global CO2 emissions from fossil fuels?

A study led by Melissa Pespeni, a Stanford Ph.D., and co-authored by Stephen Palumbi, a senior fellow at the Stanford Woods Institute for the Environment and director of Stanford’s Hopkins Marine Station, revealspreviously unknown adaptive variations that could help some marine species survive in future acidified seas. The study, published in Proceedings of the National Academy of Scienceson April 8, finds that purple sea urchins have the capacity for rapid evolution of skeletal development and acid-base regulation when faced with increased acidity. That capacity depends on a surprising level of genetic variation for healthy growth in high CO2 conditions.

Urchin larva grown at high CO2 levels – remarkably healthy because it has the right genes to thrive under these conditions.

“It’s like bet hedging,” Palumbi said. “Betting on multiple teams in the NCAA playoffs gives you a better chance of winning. A parent with genetic variation for survival in different conditions makes offspring that can thrive in different environments. In an uncertain world, it’s a way to have a stake in the Final Four.”

The authors including ecologist Eric Sanford and collaborators at the University of California Davis’ Bodega Marine Lab speculate that other marine species that have long dealt with environmental stresses may have similar adaptive capacity. If true, these capabilities could provide important clues about how to maintain robust marine populations amid the effects of acidification, climate change, overfishing and other human impacts.

Scientists have known for decades that high CO2 emissions from fossil fuels are increasing the levels of carbonic acid in the world’s oceans, leading to increased acidity. Hundreds of undreddhof studies have shown that acidification at levels expected by the year 2100 can harm ocean life. But little is known about marine species’ capacity to adapt evolutionarily to this condition. The delicate embryos of marine species are especially susceptible. The West Coast oyster farm industry nearly collapsed in 2007 because of oyster larvae sensitivity to increased acidification of coastal waters.

Pespeni and co-authors examined how purple sea urchins – creatures with the most well-mapped genome of any marine species – reacted to acidification levels predicted by 2100. They exposed the larvae to high CO2 ocean water in special culture facilities at the Bodega Marine Lab. Using new genome sequencing tools, the scientists found all the genetic variants in the urchin’s genome, then measured those that changed in high CO2 larvae compared to those in regular sea water. By tracing back the function of the genes that changed, Pespeni discovered which of the urchins’ physiological systems were most sensitive to acidification, and which had the gene variants to thrive under future conditions.

“The high CO2 larvae grew almost as well, and that was a surprise,” Pespeni commented. “The reason why they didn’t suffer was that among them were some with the right genes to be able to grow well in those harsh conditions.”

Purple sea urchins, like other West Coast marine species, normally live in cold water that wells up along the coast, bringing seasonally higher CO2 levels. The study’s results suggest that this long-term environmental mosaic has led to the evolution of genetic variations enabling purple sea urchins to regulate their internal pH level in the face of elevated CO2. There are important lessons to learn from this evolutionary story, “There are hundreds of west coast species that similarly evolved in these conditions. Maybe some of these have the genetic tools to resist acidification, too.” Palumbi said. “We need to learn why some species are more sensitive than others.”

The study was funded by the National Science Foundation.

Contact

– Melissa Pespeni, Indiana University: cell, 831-601-8345, office, 812-856-1783; mpespeni@indiana.edu

– Stephen Palumbi, Stanford Woods Institute for the Environment: cell, 831-601-7002; office, 831-655-6210; spalumbi@stanford.edu

– Eric Sanford, University of California, Davis: office, 707-875-2040; edsanford@ucdavis.edu

– Rob Jordan, Stanford Woods Institute for the Environment: office, 650-721-1881; rob.jordan@stanford.edu

More Information

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Ocean Science Now, 7 April 2013. Article.