Atmospheric dust plays surprisingly crucial role in stabilizing ocean ecosystems

Atmospheric dust is a crucial source of nutrients for the world’s oceans, according to new research led by Toby Westberry, an oceanographer at Oregon State University. Phytoplankton, which form the base of the marine food web, rely on dust from land-based sources for key nutrients. 

However, until now, the extent and magnitude of the impact of atmospheric dust on ocean ecosystems had been difficult to estimate globally. 

In the new study, Westberry and his colleagues estimate that atmospheric dust supports 4.5 percent of the global annual export production of carbon. Regional variation in this contribution can be much higher, approaching 20 to 40 percent, they found.

“The nutrients carried by dust being deposited on the ocean are creating a response in the surface ocean biology,” said Westberry.

“That’s important because it’s a pathway to get carbon out of the atmosphere and down into the deep ocean. The biological pump is one of the key controls on atmospheric carbon dioxide, which is a dominant factor driving global warming and climate change.”

The ocean and the carbon cycle

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

While vital nutrients for phytoplankton growth are largely provided through the physical movement of those nutrients from deep waters up to the surface, a process known as mixing or upwelling, some nutrients are also provided through atmospheric dust. 

The new research shows that the impact of dust on ocean ecosystems is more widespread than previously thought, with the contribution of dust to the biological pump varying by region.

In the past, the understanding of the response by natural marine ecosystems to atmospheric inputs has been limited to singularly large events, such as wildfires, volcanic eruptions and extreme dust storms. 

Comparing this study to previous studies on atmospheric dust

Westberry’s previous research examined ecosystem responses following the 2008 eruption on Kasatochi Island in southwestern Alaska. However, this new study is the first to use modern observational records to estimate the impact of atmospheric dust on the world’s oceans at a global scale.

“This is really the first time it has been shown, using the modern observational record and at the global scale, that the nutrients carried by dust being deposited on the ocean are creating a response in the surface ocean biology,” said Westberry.

Phytoplankton, which are plantlike organisms living in the upper part of the ocean and are the foundation of the marine food web, have long been known to rely on dust from land-based sources for key nutrients.

What the researchers learned

In the new paper, Westberry and other scientists from Oregon State University, University of Maryland, Baltimore County, and NASA Goddard Space Flight Center estimate that deposition of dust supports 4.5 percent of the global annual export production, or sink, of carbon. 

Phytoplankton turn carbon dioxide from the atmosphere into organic matter through photosynthesis, which sinks from the surface ocean to the deep sea where it is locked away, a pathway known as the biological pump. 

“The biological pump is one of the key controls on atmospheric carbon dioxide, which is a dominant factor driving global warming and climate change,” said Westberry.

While the ocean plays an essential role in the carbon cycle, the understanding of the response by natural marine ecosystems to atmospheric inputs has been limited to singularly large events such as wildfires, volcanic eruptions, and extreme dust storms. 

The experts built on past research to look at phytoplankton response worldwide. The team focused their efforts on using satellite data to examine changes in ocean color following dust inputs. 

Ocean color imagery is collected across the global ocean every day and reports changes in the abundance of phytoplankton and their overall health. The scientists at UMBC and NASA focused their efforts on modeling dust transport and deposition to the ocean surface.

“Determining how much dust is deposited into the ocean is hard because much of the deposition occurs during rainstorms when satellites cannot see the dust. That is why we turned to a model,” said UMBC’s Lorraine Remer, a research professor at the Goddard Earth Sciences Technology and Research Center II. The UMBC team used observations to confirm a NASA global model before incorporating its results into the study.

Different roles of phytoplankton

Working together, the research team found that the response of phytoplankton to dust deposition varies based on location. In low-latitude ocean regions, the signature of dust input is predominantly seen as an improvement in phytoplankton health, but not abundance. 

In contrast, phytoplankton in higher-latitude waters often show improved health and increased abundance when dust is provided. This contrast reflects differing relationships between phytoplankton and the animals that eat them.

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 rapidly consumed and almost immediately transferred up the food chain.

At higher latitudes, the link between phytoplankton and their predators is weaker because of constantly changing environmental conditions. Accordingly, when dust stimulates phytoplankton growth, the predators are a step behind, and the phytoplankton populations exhibit both improved health and increased abundance.

Continuing the research

The team is continuing and improving upon this research by bringing in improved modeling tools and preparing for more advanced satellite data from NASA’s upcoming Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) satellite mission and the HARP2 instrument.

“The current analysis demonstrates measurable ocean biological responses to an enormous dynamic range in atmospheric inputs,” Westberry said. “We anticipate that, as the planet continues to warm, this link between the atmosphere and oceans will change.”

The findings have important implications for our understanding of the carbon cycle and the role of the ocean in mitigating climate change. 

By showing that dust plays a key role in nourishing global ocean ecosystems while helping regulate atmospheric carbon dioxide levels, the research highlights the need for continued monitoring and study of the impact of dust on the world’s oceans.

More about atmospheric dust

Atmospheric dust, also known as aeolian dust or mineral dust, is composed of small particles of various mineral matter and organic compounds that are lifted into the air by wind and transported across continents and even oceans. 

This dust can come from both natural and human-made sources, such as desert regions, volcanic eruptions, wildfires, and human activities such as agriculture and land-use changes.

Atmospheric dust has both positive and negative impacts on the environment. On the one hand, dust plays a critical role in the formation of clouds and precipitation. These particles can act as nuclei for cloud droplets, facilitating the formation of clouds and rainfall. 

Additionally, atmospheric dust can fertilize ecosystems, providing essential nutrients such as iron and phosphorus to plants and microorganisms.

However, high levels of atmospheric dust can also have negative consequences for the environment and human health. Dust can contribute to soil erosion and land degradation, leading to loss of vegetation cover and degradation of soil quality. 

Furthermore, dust particles can have adverse effects on human health, particularly respiratory health, when inhaled. High levels of atmospheric dust can also contribute to air pollution and reduce visibility.

The impact of atmospheric dust on the global carbon cycle, as highlighted in the recent study from Oregon State University, is an important area of research as it could potentially influence climate change. 

By providing essential nutrients to phytoplankton, atmospheric dust can enhance the ocean’s ability to absorb and store carbon dioxide from the atmosphere, potentially mitigating the effects of climate change.

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