What Mysterious Life Form Is Filling up the Oceans?

December 9, 2015 | Joanne Kennell

Scanning electron microscope image of Gephyrocapsa oceanica, a coccolithophore
Photo credit: NEON ja/Wikipedia (CC BY-SA 2.5)

The opposite of what scientists predicted is happening, and no one knows why.

Oceans, which cover 70 percent of the Earth’s surface, are important in maintaining the stability of climate — they are a reservoir for heat and carbon, as well as a home for more than one million known species.

But something very strange is happening in the oceans right now.  Phytoplankton, which are floating micro-organisms, have been thriving in the North Atlantic over the last four decades.  However, scientists had previously predicted that the opposite would be happening.  They had believed that the increase in acidity occurring in the oceans would result in a decline in phytoplankton.  So what is going on?

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The study, which was led by researchers from Johns Hopkins University, showed a staggering ten-fold increase in the number of coccolithophores — a single-celled algae with a limestone shell — between the years of 1965 and 2010.  “Something strange is happening here, and it’s happening much more quickly than we thought it should,” said Anand Gnanadesikan, associate professor at John Hopkins and one of the study’s five authors, in a press release.

The research team analyzed data from the Continuous Plankton Recorder (CPR) from the North Atlantic Ocean and North Sea, which showed that higher levels of carbon dioxide in the oceans may be leading to an increase in the population of coccolithophores.  The CPR was launched in 1931 by a British marine biologist in order to continuously study near-surface plankton, which are a vital part of the marine food chain.

“Our statistical analyses on field data from the CPR point to carbon dioxide as the best predictor of the increase in coccolithophores,” said Sara Rivero-Calle, a Johns Hopkins doctoral student and lead author of the study.  “The consequences of releasing tons of CO2 over the years are already here and this is just the tip of the iceberg.”

According to William M. Balch of the Bigelow Laboratory for Ocean Sciences in Maine, a co-author of the study, scientists expected that increasing ocean acidity due to higher amounts of carbon dioxide would suppress the formation of these limestone-shelled organisms.  The new study revealed that it doesn’t.

“Coccolithophores have been typically more abundant during the Earth’s warm interglacial and high CO2 periods,” said Balch.  “The results presented here are consistent with this and may portend, like the ‘canary in the coal mine,’ where we are headed climatologically.”

According the the researchers, the results may help clarify the effects of increasing carbon dioxide on marine species.  “These clearly represent major shifts in ecosystem type,” Gnanadesikan said.  “But unless we understand what drives coccolithophore abundance, we can’t understand what is driving such shifts.  Is it carbon dioxide?”

“What is worrisome,” said Gnanadesikan, “is that our result points out how little we know about how complex ecosystems function.”  Although an increase of coccolithophores is definitely good news for species that eat them, Gnanadesikan notes that it is not clear whether a larger abundance of this type of plankton is harmful or beneficial to the planet overall.

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