The Tropical Atlantic Ocean (TAO) relies on the deposition of nutrients, such as phosphorus (P), from atmospheric aerosols to stimulate primary productivity and facilitate the sequestration of carbon dioxide. Every winter and spring, African dust is transported to South America and hypothesized to be the main supplier of P to the TAO. However, the impact of dust on marine productivity has been questioned because dust contains forms of P that are insoluble in seawater limiting their impact on marine biota. Motivated by these issues, we measured dust in addition to total and soluble P in aerosols collected year-round in Cayenne, French Guiana, a coastal site in South America. While dust is a major source of P, we found that smoke transported from Africa provided highly soluble P nearly year-round to the TAO. Using a chemical transport model, we estimate that smoke may be more important than dust for supplying soluble P to both the TAO in addition to parts of the Southern Ocean. To test how our findings impact P utilization by marine phytoplankton, we performed incubation experiments with natural plankton communities and additions of leachate from aerosol filters containing dust or smoke. We traced the incorporation of P into cells as well as different pools of the adenylate system used for metabolism and growth (e.g., ATP and AMP, respectively). P from dust was taken up by phytoplankton at a faster rate than P from smoke, which we suggest is due to the presence of organic forms of P in smoke that are slower to incorporate. Further, dust and smoke elicited different metabolic responses and growth rates as suggested by differences in ATP and AMP production rates. Our work demonstrates that aerosol source determines the impact of atmospheric deposition on marine productivity and the sequestration of carbon into the ocean.

Determining the impact of African dust and smoke on phosphorus cycling and marine biota in the tropical Atlantic Ocean

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.