Study Shows Plankton Soak up More Carbon Dioxide than Estimated

Planktons near the surface of water have more carbon than was previously believed, according to a new study. Researchers argue that the scientific models that estimate the amount of carbon dioxide in water need to be revised, as data on phytoplankton has shown that these planktons soak up double the amount of carbon dioxide than estimated.

Currently, researchers use the Redfield ratio to understand the biogeochemistry of the oceans. The ratio, defined by Alfred C. Redfield, gives researchers an estimate of the amount of carbon, nitrogen and phosphorus fixed by phytoplankton. The ratio is 106:16:1

Researchers in the present study show that the ratio of carbon, nitrogen and phosphorous isn't constant, but varies widely. And, the variation isn't based on the depths of the ocean, but on the latitudes. According to the study, oceans near the equator which have low nutrient levels have more carbon (195:28:1) than oceans near the polar regions that have high nutrient content but low carbon content (78:13:1).

"The Redfield concept remains a central tenet in ocean biology and chemistry. However, we clearly show that the nutrient content ratio in plankton is not constant and thus reject this longstanding central theory for ocean science. Instead, we show that plankton follow a strong latitudinal pattern," said lead author Adam Martiny, associate professor of Earth system science and ecology & evolutionary biology at UC Irvine.

The study team made several expeditions to collect water samples that included Bering Sea, the North Atlantic near Denmark and mild Caribbean waters. They used a cell sorter (costing about $1 million) that was aboard the research vessel to analyze the samples. The data obtained was then compared with data from 18 other such expeditions.

Researchers say that the Redfield ratio has remained part of textbooks on understanding biogeochemical cycles of the oceans although "there have been people over time putting out a flag, saying, 'Hey, wait a minute,'" Matiny said

"...a couple of models have suggested otherwise, but they were purely models. This is really the first time it's been shown with observation. That's why it's so important," Martiny said in a news release.

The study is published in the journal Nature Geoscience.