These findings, based on analysis of the nearly a half-century of data collected by the long-running Sir Alister Hardy Foundation (SAHFOS) Continuous Plankton Recorder sampling program, are reported in a paper in the journal Science.

The results show both the power of long-term time-series of ocean observations for deciphering how marine microbial communities are responding to climate change and offer evidence that the ocean garden is changing. We never expected to see the relative abundance of coccolithophores to increase 10 times in the North Atlantic over barely half a century. If anything, we expected that these sensitive calcifying algae would have decreased in the face of increasing ocean acidification (associated with increasing carbon dioxide entering the ocean from the burning of fossil-fuels). Instead, we see how these carbon-limited organisms appear to be using the extra carbon from CO₂ to increase their relative abundance by an order of magnitude.

—Dr. William Balch, senior research scientist at Bigelow Laboratory for Ocean Sciences and co-author

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 noted that the Science report is good news for creatures that eat coccolithophores—but it’s not clear what those are.

What is worrisome is that our result points out how little we know about how complex ecosystems function.

—Anand Gnanadesikan

Some of the key coccolithophore species can outcompete other classes of phytoplankton in warmer, more stratified and nutrient-poor waters (such as one might see in a warming ocean). Until this data proved otherwise, scientists thought that they would have more difficulties forming their calcite plates in a more acidic ocean. These results show that coccolithophores are able to use the higher concentration of carbon derived from CO₂, combined with warmer temperatures, to increase their growth rate.

When the percentage of coccolithophores in the community goes up, the relative abundance of other groups will go down. The authors found that at local scales, the relative abundance of another important algal class, diatoms, had decreased over the 45 years of sampling.

The team’s analysis was of data taken from the North Atlantic Ocean and North Sea since the mid-1960s compiled by the Continuous Plankton Recorder survey. The CPR survey was launched by British marine biologist Sir Alister Hardy in the early 1930s. Today it is carried on by the Sir Alister Hardy Foundation for Ocean Sciences and is conducted by commercial ships trailing mechanical plankton-gathering gear through the water as they sail their regular routes. Dr. Willie Wilson, formerly a senior research scientist at Bigelow Laboratory, is now director of SAHFOS.

The lead author of the paper was Sara Rivero-Calle, a PhD candidate at John Hopkins University. In addition to Balch, her co-authors were Anand Gnanadesikan of John Hopkins, Carlos E. Del Castillo of NASA, and Seth D. Guikema of the University of Michigan.

Resources

• Sara Rivero-Calle, Anand Gnanadesikan, Carlos E. Del Castillo, William Balch, and Seth D. Guikema (2015) “Multidecadal increase in North Atlantic coccolithophores and the potential role of rising CO₂” Science doi: 10.1126/science.aaa8026