Perspective: Continental inputs of matter into planktonic ecosystems of the Argentinean continental shelf- the case of atmospheric dust

Abstract

Land-derived dissolved and particulate matter (allochthonous matter) affect pelagic ecosystems by changing factors which include light penetration, nutrient availability, substrate concentration, and in general, biogeochemical cycles in the ocean. In a context of growing anthropogenic impact, this material may not only increase its load but also carry toxic substances. Riverine runoff is the most studied mechanism of particulate matter input from the continent to the sea in the southern region of South America where the continental shelf is widest (e.g., Atlantic Patagonia). However, there are other sources of particulate matter which are not affected by rivers in this semiarid region: aeolian material. Winds in this region (notably the Southern Hemisphere westerlies) are the only way continental aeolian material (atmospheric aerosols or "dust") can reach not only the shelf but even further onto oceanic HNLC (high nutrient-low chlorophyll) regions of the Atlantic Southern Ocean. This potential impact of Patagonian dust beyond the continental shelf attracts the attention of the global climate community, and at the same time, it opens questions about the potential effects of dust in coastal waters. According to previous work and ongoing studies, deposited particles can have significant impacts in the chemical and biological components in the euphotic zone. However the effects of this airborne material in plankton communities of South America are largely unknown, mostly due to the lack of in situ studies and observations. Since the events of dust mobilization, transport, and deposition are expected to increase (due to climate change) and interact with other global change factors such as warming and more intensive land use, the influence of dust input may become more prominent for coastal and oceanic regions of southern South America in the next decades.