Ocean Food Web is a Major Component in Global Carbon Cycle

Researchers using satellite images examined the key role of oceans in the global carbon cycle, according to a new study.

In this study, researchers at the University of California Santa  Barbara, focused on the life cycle of phytoplankton and zooplankton, the microscopic organisms present at the bottom of the food chain. The researchers developed a new model with these micro-organisms to determine the emission of carbon from the oceans.

The food-web-based-model designed by the researchers was solely based on satellite observations. They used this data to observe how the phytoplanktons generate organic matter using carbon dioxide in the water.

"What we've done here is create the first step toward monitoring the strength and efficiency of the biological pump using satellite observations," said Siegel, who is also a professor of marine science in UCSB's Department of Geography. "The approach is unique in that previous ways have been empirical without considering the dynamics of the ocean food web."

The space/time patterns created by these empirical approaches are inconsistent with how oceanographers think the oceans should work, he noted.

They have focused on the ocean's biological pump that exports organic carbon from the upper surface by sinking the particulate matter, mostly zooplankton feces and aggregates of algae. When these particulates exit the euphotic zone (upper ocean) by sinking in the deep water of ocean, the carbon can be captured for centuries.

Carbon is present in the atmosphere and is buried in soils, oceans and Earth's crust. The movement of carbon between these reservoirs is termed as flux.  The researchers claim that oceans play a key role in global carbon cycle by storing, transporting and transforming the carbon constituents.

"Quantifying this carbon flux is critical for predicting the atmosphere's response to changing climates," Siegel said. "By analyzing the scattering signals that we got from satellite measurements of the ocean's color, we were able to develop techniques to calculate how much of the biomass occurs in very large or very small particles."

On analyzing the data the researchers predict that every year there is a mean global carbon export flux  of 6 petagrams (Pg). It is also called as gigaton. One petagram is equal to one quadrillion (1015) grams. Per year the current fossil fuel combustion represents a flux of 9 Pg.

"Understanding the biological pump is critical," Siegel concluded. "We need to understand where carbon goes, how much of it goes into the organic matter, how that affects the air-sea exchanges of CO₂ and what happens to fossil fuel we have emitted from our tailpipes."

The finding was documented in the Journal Biogeochemical Cycles.