CONICET | Buscador de Institutos y Recursos Humanos

Patagonia is recognized as a major dust source in the Southern Hemisphere originated from rivers basins, glacial activity, salt lakes or natural events such as volcanic eruptions. Additionally, dust associated with anthropogenic sources (e.g., agriculture, livestock or mining industry) was detected over this region using satellite data or in situ measurements. The aim of this project was to study the effect of dust on the microbial food web in Nuevo Gulf (Patagonia, Argentina). The experiment was carried out during the austral spring 2018, using nine outdoor microcosms incubated in situ close to the coast. Microcosms were filled with one of three treatments: Control contained seawater without dust addition, Dust 1 received low concentrations of dust (0.05 mg L-1) and Dust 2 were enriched with high concentrations of dust (1 mg L-1). The experiment lasted six days. Initial seawater was characterized by low inorganic nutrient concentrations suggesting an oligotrophic condition. Dust 2 treatment led to an increase in nitrate + nitrite and ammonium concentrations in the microcosms. In general, nitrate + nitrite concentrations decreased steadily over time in all treatments indicating nutrient uptake by phytoplankton and bacteria. The concentration of ammonium gradually decreased in all microcosms until Day 3 and then increased towards the end of the experiment. Significantly higher ammonium concentration was observed in Dust 2 which was on average two times higher than in Control and Dust 1 treatments. Silicic acid concentration peaked in all mesocosms on Day 1 and then declined reaching the lowest values on Day 5. Phosphate concentration showed a decreasing trend in all microcosms, constituting ~30-40% of the initial values at the end of the experiment. DIN:DIP ratios

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