A new research has studied the extent and the magnitude of the role that dust, soil particles lifted by the wind and impacting the Earth's climate, played in nourishing global ocean ecosystems and helping regulate atmospheric carbon dioxide levels.
This research, led by an Oregon State University (US) scientist, is published in the journal Science.
Researchers have long known that phytoplankton rely on dust from land-based sources for key nutrients.
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The ocean plays an important role in the carbon cycle through a pathway known as biological pump. Carbon dioxide from the atmosphere dissolves in surface waters, the carbon from which gets turned into organic matter by the phytoplankton through photosynthesis. Some of this organic matter sinks from the surface ocean to the deep sea, where it gets locked away.
In the new paper, the scientists estimated dust deposition to support 4.5% of the global annual export production, or sink, or carbon. They found regional variation in this contribution to be much higher, around 20 to 40%.
"That's important because it's a pathway to get carbon out of the atmosphere and down into the deep ocean," Toby Westberry, an oceanographer at Oregon State and lead author of the study, said. "The biological pump is one of the key controls on atmospheric carbon dioxide, which is a dominant factor driving global warming and climate change."
In the ocean, a process known as mixing or upswelling brought up nutrients from deep waters up to the surface, providing vital nutrient for phytoplankton growth. But some nutrients are also provided through atmospheric dust.
In this paper, building on past research to assess phytoplankton response globally, the scientists examined ocean colour changes following dust inputs using satellite data.
For example, greener water generally corresponded to abundant and healthy phytoplankton populations, while bluer waters represented regions where phytoplankton were scarce and often undernourished.
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They modelled dust transport and deposition to the ocean surface.
The team of researchers found that the response of phytoplankton to dust deposition varied based on location.
Lower latitude environments tended to be more stable, leading to a tight balance between phytoplankton growth and predation. Thus, when dust improved phytoplankton health, or growth rate, this new production was found to be rapidly consumed and almost immediately transferred up the food chain.
At higher latitudes, constantly changing environmental conditions weakened the link between phytoplankton and their predators. Thus, with dust stimulating phytoplankton growth and the predators being a step behind, the phytoplankton populations were found to exhibit both improved health and increased abundance.
