Does Patagonian Aeolian Dust Deposition Enhance Marine Primary Productivity?

Strong westerly winds over Patagonia deliver substantial aeolian dust to the South Atlantic Ocean. While previous research indicates potential nutrient enrichment for primary producers, direct evidence of its impacts on the microbial food web remains scarce. Here, an in situ experiment was conducted aboard the R/V Puerto Deseado in November 2017 to investigate the effects of aeolian dust deposition on nitrogen uptake by primary producers and the microbial food web. Seawater was collected, pre‐filtered (200 µm) and divided into treatments with and without dust addition and incubated for 3 days. Macronutrient availability, humic substances (HS), chromophoric dissolved organic matter (CDOM) (0, 48 h) and microbial cell counts (0, 48, 72 h) were analysed. Nitrogen uptake was assessed over 0–24 h and 48–72 h periods. Dust addition doubled nitrate and ammonium concentrations. Surprisingly, a 50% reduction in primary productivity was observed. Microbial biomass exhibited an initial negative response during the first 48 h, followed by a slight recovery. This study provides the first direct measurements of the impacts of aeolian dust on nitrogen uptake and microbial communities in the Southwest Atlantic Ocean. The observed inhibitory effects on primary producers highlight the need for future studies to identify the underlying mechanisms, including toxic metal effects, reduced iron bioavailability due to adsorption or stimulation of specific prokaryotic or viral pathogens.