Fluxes of Atmospheric Nutrients during Dust Events to the Atlantic Ocean and their Impact on Regional Ocean Productivity

Abstract

Environmental change and human activities are increasing anthropogenic particle loads in marine ecosystems, affecting phytoplankton growth and production. To understand how oligotrophic ecosystems respond to atmospheric deposition during dust episodes, 22 PM10 samples were collected at the Cabo Verde Atmospheric Observatory (CVAO) station. From these samples, the fluxes of inorganic ions and trace metals deposited and their potential impact on primary production were determined. The samples were collected using a low volume sampler on 37 mm diameter quartz fiber filters from January 27 to February 18, 2022. The investigated species included NO3−, NO2−, NH4+, PO43−, SO42−, K+, Mg2+, Ca2+, Al, Fe, Ti, P, Zn, V, Ni, and Cr. The Copernicus satellite data was used to investigate impacts of dust events on the marine ecosystem. The results showed that the PM10 concentration during the dust events (118.80 μg m−3) was seven times higher than that in the non-dust events (16.64 μg m−3). Chemical analysis showed that concentrations of trace metals and inorganic ions during the dust episodes were very different from those of non-dust days, with increases ranging from 4 to 144% for ions and 3 to 642% for trace elements. The back trajectory analysis indicated that mixing mechanisms during the transport route may affect species concentrations. Zn, NO2−, NH4+, and PO43− had low deposition rates to the ocean after dust storms, while the other nutrients such as NO3−, SO42−, K+, Mg2+, Ca2+, Al, Fe, and Ti showed faster deposition rates. Using a non-linear deposition model, we estimated dry deposition fluxes, with mean fluxes of dissolved inorganic nitrogen (DIN = NO3− + NO2− + NH4+) and PO43− of 2.6 and 0.04 μmol m−2 d−1, respectively, during dust events, and 1.8 and 0.03 μmol m−2 d−1, respectively, during non-dust events. The inorganic N/P ratios were above the Redfield ratio, indicating increased nutrient input and potential phosphorus limitations in surrounding waters. Satellite data showed an increase in chlorophyll a and phytoplankton biomass after dust episodes. We have successfully captured atmospheric nutrient input fluctuations through laboratory measurements of nutrient content in particulate matter. This has improved our knowledge of dust deposition impacts on marine planktons and highlights the need for more research to understand the species-specific response to high nutrient inputs.