Does the deposition of aeolian dust on the sea favor primary productivity?

Abstract

In the coast of the Patagonia, Argentina, strong winds from the western sector carry large amounts of dust into the sea. In previous studies it was observed that dust contains nutrients that, on certain occasions, could favor the development of primary producers. However, so far there are no direct measurements that allow corroborating the effect of dust on organisms in the marine environment. Within the framework of the Pampa Azul Initiative, during November 2017, a series of experiments were carried out on board the Oceanographic Vessel Puerto Deseado to address the effect of dust on primary productivity in situ. The goal was to study the effect of the deposition of aeolian dust in the sea on the uptake of nitrogen sources carried out by the primary producers. Through a series of Niskin bottles, 20 liters of surface seawater (5 m-deep) was collected and then filtered through a 200 μm net and divided in two parts. To one of these parts 0.05 mg L-1 of dust was added, while the other part was left as a control. These two parts were kept in incubation after the addition of 15NH4Cl and Na15NO3. Samples were taken to measure the concentration of nitrate and ammonium, and the uptake of nitrate and ammonium at three intervals of time: 0 h, 24 h and 48 h. Dust used in the experiments was collected weeks ago by means of passive collectors located on the ground. Although the addition of dust increases the concentration of nitrate and ammonium in seawater; it reduced the uptake of nitrogen sources and therefore, the primary productivity. Some possible causes of these results will be discussed in the presentation.