Plankton Ingests Different Carbon Dioxide And Nitrogen Ratios Than Estimated

Researchers conducted observations on oceanic plankton that puts solid data behind a phenomenon that is very important for our planets biogeochemical cycles but not well understood until now. The Scientists from UC Irvine demonstrated that the ratio of carbon, nitrogen and phosphorous ingested by plankton isn't constant, but varies widely. Currently, researchers use the Redfield ratio to understand the biogeochemistry of the oceans. The ratio of 106:16:1, defined by Alfred C. Redfield, gives researchers an estimate of the amount of carbon, nitrogen and phosphorus fixed by phytoplankton.

The variation was shown to be mostly dependent on the geographic latitude. According to the study, plankton in ocean areas near the equator which have relatively low nutrient levels contain a greater share carbon (195:28:1) than plankton in oceans near the polar regions that ingest higher amounts of nitrogen but less carbon (78:13:1).

Plankton is defined as all organisms in the ocean that cannot propel themselves and float in the currents, which includes diverse species from bacteria, algae, fish larvae to jellyfish. These ecosystems, aside from representing the bottom few levels of a food chain that supports commercially important fisheries, play a role in the biogeochemical cycles of many important chemical elements, including the ocean's carbon cycle.

The major constituent in this is phytoplankton, a large variety of microscopic oceanic plants that account for half of all photosynthetic activity on Earth. Thus phytoplankton are responsible for much of the oxygen present in the Earth's atmosphere - half of the total amount produced by all plant life. Their cumulative energy fixation in carbon compounds (primary production) is the basis for the vast majority of oceanic and also many freshwater food webs. The effects of anthropogenic warming on the global population of phytoplankton is an area of active research.

"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 scientists undertook several expeditions to collect water samples from regions including the Bering Sea, the North Atlantic near Denmark and mild Caribbean waters. They used a sophisticated cell sorter 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.