‘Something strange is happening here, and it’s happening much more quickly than we thought it should …’
Atmospheric carbon dioxide ending up in the world’s oceans may be fueling a population explosion of microscopic marine algae in the North Atlantic, scientists said in a new study that shows how greenhouse gases can drive dramatic ecosystem changes.
But even as they tracked the surge in the abundance of single-cell coccolithophores between 1965 and 2010, scientists couldn’t agree if it’s good news or bad news for the planet.
“Something strange is happening here, and it’s happening much more quickly than we thought it should,” said Anand Gnanadesikan, associate professor in the Morton K. Blaustein Department of Earth and Planetary Sciences at Johns Hopkins University, one of the study’s five authors.
Describing the findings, published in Science, Gnanadesikan said the study details a tenfold increase in the abundance of the pale-shelled floating phytoplankton.
“What is worrisome,” he said, “is that our result points out how little we know about how complex ecosystems function.” The result highlights the possibility of rapid ecosystem change, suggesting that prevalent models of how these systems respond to climate change may be too conservative, he said.
The study examined data from continuous plankton-recording survey data dating back to the mid-1960s. Rising carbon dioxide in the ocean is causing the coccolithophore population spike, said Sara Rivero-Calle, a Johns Hopkins doctoral student and lead author of the study.
“Our statistical analyses on field data … point to carbon dioxide as the best predictor of the increase” in coccolithophores, Rivero-Calle said. “The consequences of releasing tons of CO2 over the years are already here and this is just the tip of the iceberg.”
William M. Balch of the Bigelow Laboratory for Ocean Sciences in Maine, a co-author of the study, said scientists might have expected that ocean acidity due to higher carbon dioxide would suppress these chalk-shelled organisms. It didn’t. On the other hand, their increasing abundance is consistent with a history as a marker of environmental change.
“Coccolithophores have been typically more abundant during Earth’s warm interglacial and high CO2 periods,” said Balch, an authority on the algae. “The results presented here are consistent with this and may portend, like the ‘canary in the coal mine,’ where we are headed climatologically.”
Coccolithophores are single-cell algae that cloak themselves in a distinctive cluster of pale disks made of calcium carbonate, or chalk. They play a role in cycling calcium carbonate, a factor in atmospheric carbon dioxide levels. In the short term they make it more difficult to remove carbon dioxide from the atmosphere, but in the long term – tens and hundreds of thousands of years – they help remove carbon dioxide from the atmosphere and oceans and confine it in the deep ocean.