Title: The Impact of African Dust Transport on Biogeochemical Cycles in the Amazon Basin and Tropical Atlantic Ocean
Abstract: African dust is transported to the Amazon Basin and the Tropical Atlantic Ocean in the winter and spring where it can deposit vital nutrients that stimulate primary productivity and help facilitate the drawdown of atmospheric carbon dioxide. Despite interest in this topic and its potential importance for Earth’s climate, few measurements exist to document this phenomenon and quantify its impacts on biogeochemical cycles. Here I will discuss aerosol measurements collected at a site in Cayenne, French Guiana located on the coast of the Tropical Atlantic Ocean that also sits at the gateway to the Amazon Basin. This site only receives long-range transported and sea spray aerosol and is ideal for determining the impact of long-range transported African dust on the Amazon Basin. In this presentation, I will discuss seasonal variations in nutrient loadings, nutrient solubility, and aerosol sources derived from bulk and single particle measurements of both iron (Fe) and phosphorus (P) containing particles. Our measurements reveal the vital importance of African dust as a supply of P and Fe to the Amazon Basin and Tropical Atlantic Ocean during peak dust transport season, and that this dust contains bioavailable forms of Fe and soluble forms of P. However, our measurements also reveal that in addition to mineral dust, other particle sources are also important for supplying nutrients to these ecosystems. In particular, I will show that freshwater diatoms that are frequently transported from African paleolakes to South America are also an important source of Fe. I will also show the underappreciated role of African biomass burning as an important driver of P solubility even during peak dust transport season. Overall, our results yield a more complete view of how African dust transport contributes nutrients to both the Amazon Basin and the Tropical Atlantic Ocean.