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   PID: hpt/lnx 1.9.0-cur 2019-01-08   
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    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   
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   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.   
      
      
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   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   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/05/230504155628.htm   
      
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