Researchers Discover New Information Regarding Atmospheric Dust Nourishing Oceans
Research led by Oregon State University (OSU) scientists has identified new information on the role that dust plays in nourishing global ocean ecosystems while helping regulate atmospheric carbon dioxide levels.
OSU oceanographer Toby Westberry said this is the first time it has been shown that nutrients carried by dust being deposited on the ocean are creating a response in the surface ocean biology.
Westberry, the lead author of the study, collaborated with other scientists from OSU, the University of Maryland, Baltimore Country (UMBC) and NASA Goddard Space Flight Center on the research published in the journal Science.
Study results released in mid-May revealed the extent and magnitude of the impact of the dust, particles from sources such as soil that are lifted by the wind and then impact the Earth’s climate, information that had been previously difficult to estimate.
The ocean plays an important role in the carbon cycle. 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.
Until now, 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.
Previous research by Westberry and others examined ecosystem responses in the wake of the 2008 eruption on Kasatochi Island in Southwest Alaska. The new paper built on previous research to look at phytoplankton response worldwide, using satellite data to examine changes in ocean color following dust inputs.
It showed, for example, that greener water generally corresponds to abundant and healthy phytoplankton populations, while bluer waters represent regions where phytoplankton are scarce and often undernourished.
Researchers at UMBC and NASA meanwhile focused on modeling dust transport and deposition to the ocean surface.
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.
Researchers noted that lower latitude environments tend to be more stable, leading to a tight balance between phytoplankton growth and predation. Therefore, 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. So when dust stimulates phytoplankton growth, the predators are a step behind and phytoplankton populations exhibit both better health and increased abundance, researchers said.
The research group is continuing its studies, preparing for more advanced satellite data from NASA’s upcoming Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) satellite mission.
Westberry said that the current analysis demonstrates measurable ocean biological responses to an enormous dynamic range in atmospheric inputs, and that researchers anticipate that as the planet continues to warm, the link between the atmosphere and oceans will change.
