Carbon dioxide in the air can be reserved deep underwater by biological material, much of it trapped in the feces of microscopic animals.
The process by which this occurs is known as the biological pump of global ocean carbon export. A new study by David Seigel from the University of California Santa Barbara examined this process in detail.
As fish are eaten by other animals, some of their body parts are unconsumed by predators, and sinks to the bottom of the ocean as waste. Along with this particulate matter, deceased algae and feces can also be found. Carbon dioxide can reside in that waste, laying on the ocean floor, for centuries.
Siegel and his group considered the life cycle of zooplankton and phytoplankton in their model of the cycle. The microscopic creatures, which make up the bottom of the marine food chain, were often ignored in earlier studies.
Data collected from satellites revealed the amount of organic material created from carbon dioxide by phytoplankton. This measurement includes both the tiny droppings of the animals. This process is called net primary production, or NPP.
"Quantifying this carbon flux is critical for predicting the atmosphere's response to changing climates. 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," Siegel said.
The carbon cycle regulates temperatures on Earth. Vast quantities of the material are stored in fossil fuels, atmosphere, soil and the oceans. Carbon can move between each of these reservoirs in a flux, and when the atmosphere absorbs more CO2, temperatures can rise.
The new data indicates ocean flux may remove up to 6.6 billion tons of carbon dioxide from the air every year. That represents nearly two-thirds of the nearly 10 billion tons sent into the atmosphere from fossil fuels every twelve months.
Study of the global cycle can help environmental scientists better model the effect carbon is having around the world as a greenhouse gas.
"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," Siegel said.
The team of researchers plan to conduct field tests as a follow-up to the latest study.
Analysis was funded by NASA's Ocean Biology and Biogeochemistry program. Details of the study into the role of food waste in carbon export was published in the journal Global Biogeochemical Cycles.
