Contrasting Effects of Aeolian Dust From Patagonia on Seawater Biogeochemistry According to Source Region

Abstract

Dust storms transport continental material to the sea, where its deposition can modify seawater chemical composition and influ-ence biological productivity. The aim of this study was to determine the effect of dust on seawater by analysing changes in mac-ronutrient concentration, salinity, pH, and particulate silica. For this purpose, dust samples were collected using passive collectorsat four sites in eastern Patagonia. Samples differed in grain size and mineralogical composition depending on their source. Twoseparate experiments were conducted under controlled conditions and using filtered seawater: the first assessed changes in phys-icochemical parameters (pH, salinity, and temperature) and macronutrients (dissolved silica, and nitrate) over 72 h; the secondmeasured particulate silica (biogenic and lithogenic) at a single time point after dust addition. The short-term effects of dustdeposition on seawater chemistry were greatest during the first 48 h, after which new conditions stabilised. Furthermore, allsamples contributed abundant lithogenic silica, whereas biogenic silica concentrations varied according to the dust sample.The results confirm that dust is an important regulator of seawater chemistry, with its impact dependent on compositionand grain size. Understanding the effects of dust on marine ecosystems is essential for evaluating ocean fertilisation and itsimplications for biogeochemical cycles.