Scientists believe the unexpected rapid growth of microscopic marine algae in the North Atlantic is a result of environmental changes such as increases in carbon dioxide.

The researchers documented a tenfold increase in the abundance of single-cell coccolithophores between 1965 and 2010, with the most dramatic spikes occurring after 1990, Johns Hopkins University reported.

"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 and one of the study's five authors.

The researchers are not sure if this rapid algae growth is good or bad news for the planet. The increase in algae populations could be good for animals that feed on the tiny plants, but there could be other detrimental effects that are yet to be seen.  Survey data from the North Atlantic Ocean and North Sea taken since the mid-1960s suggests rising carbon dioxide in the ocean is linked to the rapid growth of sea algae. Recent laboratory studies also support the hypothesis.

"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."

Scientists may have suspected that ocean acidity from higher carbon concentrations would have suppressed the growth of the algae, but instead the opposite is true. The researchers noted the phenomenon does line up with historical occurrences 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," said William Balch of the Bigelow Laboratory for Ocean Sciences in Maine, a co-author of the study.

The findings were reported in a recent edition of the journal Science