Volcanic Ash and Dust Induce Differing Responses in Marine Phosphorus Cycling Depending on the Deposition Amount

CASSANDRA GASTON, Hope Elliott, Kimberly Popendorf, Amanda Oehlert, Arash Sharifi, Edmund Blades, Haley Royer, Clement Pollier, Ali Pourmand, Andrew Ault, Swarup China, Nurun Nahar Lata, Zezhen Cheng, Ravi Kukkadapu, Mark Bowden, Mark Engelhard, Adrian Hornby, Esteban Gazel, University of Miami

     Abstract Number: 239
     Working Group: Aerosol-Ecosystem Interactions

Abstract
Aerosols deposit both nutrients as well as toxins that stimulate (or inhibit) the productivity of marine biota, impacting carbon sequestration in the ocean. African dust is traditionally thought to be the most important, continuous supply of nutrients to the open North Atlantic Ocean, and this supply is well documented by an over 50-year dust time series from the Ragged Point measurement facility in Barbados. However, the impact of other aerosol sources as well as extreme events such as major dust storms on marine biogeochemical cycles remains underexplored. Therefore, we investigated the impact of the 2020 Godzilla dust storm and 2021 volcanic eruption of La Soufriere on the island of St Vincent on marine phosphorus cycling and productivity. P is limiting in parts of the North Atlantic and can stimulate nitrogen fixation in tandem with increased iron (Fe) inputs, especially in the low latitude N. Atlantic Ocean. Incubations were conducted at low and high deposition of dust and volcanic ash. Despite much lower P solubility in volcanic ash compared to Godzilla dust, the addition of both aerosol types stimulates P cycling and increased P uptake rates. However, high ash deposition induces reduced P uptake rates and slowed P cycling times, highlighting that not all aerosol deposition events are beneficial for marine biota. Bulk elemental and single particle analysis combined with elemental mapping reveals the presence of surficial Fe hot spots on volcanic ash particles not present on dust in addition to a wider suite of trace elements (Mn, Co) important for biological function. Our results highlight that both the source and amount of aerosol deposited determines the biological outcome of deposition events.