Scientists begin to unravel global role of atmospheric dust in
nourishing oceans

Date:
May 4, 2023
Source:
Oregon State University
Summary:
New research begins to unravel the role dust plays in nourishing
global ocean ecosystems while helping regulate atmospheric carbon
dioxide levels.


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FULL STORY ==========================================================================
New research led by an Oregon State University scientist begins to unravel
the role dust plays in nourishing global ocean ecosystems while helping regulate atmospheric carbon dioxide levels.

Researchers have long known that phytoplankton -- plantlike organisms
that live in the upper part of the ocean and are the foundation of
the marine food web - - rely on dust from land-based sources for key
nutrients. But the extent and magnitude of the impact of the dust --
particles from sources such as soil that are lifted by the wind and
impact the Earth's climate -- have been difficult to estimate globally.

"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 Toby Westberry, an oceanographer at Oregon
State and lead author of the just-published paper in Science.

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.

In the new paper, Westberry and other scientists from Oregon State;
University of Maryland, Baltimore County; and NASA Goddard Space Flight
Center estimate deposition of dust supports 4.5% of the global annual
export production, or sink, of carbon. Regional variation in this
contribution can be much higher, approaching 20% to 40%, they found.

"That's important because it's a pathway to get carbon out of the
atmosphere and down into the deep ocean," Westberry 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, 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. But some nutrients
are also provided through atmospheric dust.

To date, 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. In fact, previous research by Westberry and others examined ecosystem responses following the 2008 eruption on Kasatochi Island in southwestern Alaska.

In the new paper, Westberry and Michael Behrenfeld, an Oregon State
professor in the Department of Botany and Plant Pathology, along with scientists from UMBC and NASA built on this past research to look at phytoplankton response worldwide.

Westberry and Behrenfeld 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. For example,
greener water generally corresponds to abundant and healthy phytoplankton populations, while bluer waters represent regions where phytoplankton
are scarce and often undernourished.

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, research professor at the Goddard Earth Sciences Technology and Research Center
II, a consortium led by UMBC. The UMBC team used observations to confirm
a NASA global model before incorporating its results into the study.

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
predominately 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.

The research team is continuing this research, bringing in improved
modeling tools and preparing for more advanced satellite data from NASA's upcoming Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) satellite
mission, some of which will be collected by the UMBC-designed and -built
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."
* RELATED_TOPICS
o Earth_&_Climate
# Global_Warming # Oceanography # Climate # Geography
# Ecology # Ecosystems # Environmental_Awareness #
Severe_Weather
* RELATED_TERMS
o Forest o Ocean_acidification o Carbon_dioxide_sink o
Global_climate_model o Carbon_dioxide o Fossil_fuel o Acid_rain
o Climate_change_mitigation

========================================================================== Story Source: Materials provided by Oregon_State_University. Original
written by Sean Nealon.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. T. K. Westberry, M. J. Behrenfeld, Y. R. Shi, H. Yu, L. A. Remer, H.

Bian. Atmospheric nourishment of global ocean ecosystems. Science,
2023; 380 (6644): 515 DOI: 10.1126/science.abq5252 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/05/230504155628.htm

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