Atmospheric dust plays a global role in nourishing the oceans

May 5. (EUROPE PRESS) – –

New research begins to unravel the role dust plays in nourishing global ocean ecosystems, while helping to regulate atmospheric carbon dioxide levels, as published in ‘Science’.

Researchers have long known that phytoplankton depend on dust from terrestrial sources for key nutrients. But the scope and magnitude of the impact of dust — particles from sources like the ground that are blown up by the wind and affect Earth’s climate — have been difficult to estimate on a global scale.

“This is really the first time that it has been shown, using modern observational records and on a global scale, that nutrients carried by dust deposited in the ocean drive a response in surface ocean biology,” he says. in a statement Toby Westberry, an oceanographer at Oregon State University and the paper’s lead author.

The ocean plays an important role in the carbon cycle; carbon dioxide from the atmosphere dissolves in surface waters, where phytoplankton convert carbon into organic matter through photosynthesis. Some of the newly formed organic matter sinks from the ocean surface to the deep sea, where it is retained, a pathway known as the biological pump.

In the new study, Westberry and other scientists from Oregon State University, the University of Maryland and NASA’s Goddard Space Flight Center estimate that dust deposition contributes 4.5% to annual global export production. , or sink, of carbon. The regional variation of this contribution may be much larger, approaching 20% ​​or 40%, according to their conclusions.

“It’s important because it’s a pathway to take carbon out of the atmosphere and into the deep ocean,” Westberry explains. “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, nutrients vital to phytoplankton growth come largely from the physical movement of those nutrients from deep water to the surface, a process known as mixing or upwelling. But some nutrients also come from atmospheric dust.

Until now, understanding of the response of natural marine ecosystems to atmospheric inputs has been limited to single, large-magnitude events such as wildfires, volcanic eruptions, and extreme dust storms. In fact, previous research by Westberry and other researchers examined ecosystem responses following the 2008 eruption on the island of Kasatochi in southwestern Alaska.

In the new work, Westberry and Michael Behrenfeld, a professor in the Oregon State Department of Botany and Plant Pathology, along with scientists from UMBC and NASA, build on this earlier research to analyze the response of phytoplankton around the world.

Westberry and Behrenfeld focused their efforts on using satellite data to examine changes in ocean color after dust ingress. Ocean color images are collected daily across the globe and report changes in phytoplankton abundance and general condition. For example, greener waters tend to correspond to abundant and healthy phytoplankton populations, while bluer ones represent regions where phytoplankton is scarce and is usually malnourished.

Scientists from UMBC and NASA focused their efforts on modeling the transport and deposition of dust on the ocean surface.

“Determining how much dust is deposited in the ocean is difficult, because much of the deposition occurs during rain storms, when satellites cannot see the dust. For this reason, we use a modelexplains Lorraine Remer of UMBC, a research professor at the Goddard Center for Technology and Research in Earth Sciences II, a consortium led by UMBC. The UMBC team used observations to confirm a NASA global model before incorporate their results into the study.

Working together, the research team discovered that Phytoplankton’s response to dust deposition varies depending on location.

In low-latitude ocean regions, the dust ingress signature is perceived predominantly as an improvement in phytoplankton health, but not in their abundance. In contrast, phytoplankton in higher latitude waters tend to show improved health and increased abundance when dust is added. This contrast reflects the different relationships between phytoplankton and the animals that feed on it.

Lower latitude environments tend to be more stable, leading to a tight balance between phytoplankton growth and predation. Thus, when dust improves phytoplankton health or growth rate, this new production is quickly consumed and almost immediately transferred to the food chain.

The team continues to investigate, improve modeling tools, and prepare to receive more advanced satellite data from NASA’s upcoming PACE (Plankton, Aerosols, Clouds, Ocean Ecosystems) mission, some of which will be collected by the HARP2 instrument, designed and built by UMBC.

“The current analysis demonstrates measurable ocean biological responses to a huge dynamic range of atmospheric inputs,” Westberry says. “We predict that as the planet continues to warm, this link between the atmosphere and oceans will change.”