Nova Southeastern University NSUWorks Marine & Environmental Sciences Faculty Department of Marine and Environmental Articles Sciences 8-13-2019 African biomass burning is a substantial source of phosphorus deposition to the Amazon, Tropical Atlantic Ocean, and Southern Ocean Anne E. Barkley Rosenstiel School of Marine and Atmospheric Science Joseph M. Prospero Rosenstiel School of Marine and Atmospheric Science Natalie Mahowald Cornell University Douglas S. Hamilton Cornell University Kimberly J. Popendorf Follow this and additional works at: https://nsuworks.nova.edu/occ_facarticles Rosenstiel School of Marine and Atmospheric Science Part of the Marine Biology Commons, and the Oceanography and Atmospheric Sciences and MeteorSee nextology page Commons for additional authors Find out more information about Nova Southeastern University and the Halmos College of This Article has supplementary content. View the full record on NSUWorks here: Natural Sciences and Oceanography. https://nsuworks.nova.edu/occ_facarticles/1159 NSUWorks Citation Anne E. Barkley, Joseph M. Prospero, Natalie Mahowald, Douglas S. Hamilton, Kimberly J. Popendorf, Amanda M. Oehlert, Ali Pourmand, Alexandre Gatineau, Kathy Panechou-Pulcherie, Patricia Blackwelder, and Cassandra J. Gaston. 2019. African biomass burning is a substantial source of phosphorus deposition to the Amazon, Tropical Atlantic Ocean, and Southern Ocean .Proceedings of the National Academy of Sciences of the United States of America , (33) : 16216 -16221. https://nsuworks.nova.edu/ occ_facarticles/1159. This Article is brought to you for free and open access by the Department of Marine and Environmental Sciences at NSUWorks. It has been accepted for inclusion in Marine & Environmental Sciences Faculty Articles by an authorized administrator of NSUWorks. For more information, please contact [email protected]. Authors Amanda M. Oehlert Rosenstiel School of Marine and Atmospheric Science Ali Pourmand Rosenstiel School of Marine and Atmospheric Science Alexandre Gatineau ATMO-Guyane Kathy Panechou-Pulcherie ATMO-Guyane Patricia Blackwelder Rosenstiel School of Marine and Atmospheric Science, [email protected] Cassandra J. Gaston Rosenstiel School of Marine and Atmospheric Science This article is available at NSUWorks: https://nsuworks.nova.edu/occ_facarticles/1159 African biomass burning is a substantial source of phosphorus deposition to the Amazon, Tropical Atlantic Ocean, and Southern Ocean Anne E. Barkleya, Joseph M. Prosperoa, Natalie Mahowaldb, Douglas S. Hamiltonb, Kimberly J. Popendorfa, Amanda M. Oehlerta, Ali Pourmanda, Alexandre Gatineauc, Kathy Panechou-Pulcheriec, Patricia Blackweldera,d, and Cassandra J. Gastona,1 aRosenstiel School of Marine and Atmospheric Sciences, University of Miami, Miami, FL 33149; bDepartment of Earth and Atmospheric Sciences, Cornell University, Ithaca, NY 14853; cATMO Guyane, 97343 Remire-Montjoly, Guyane (French Guiana), France; and dCenter for Advanced Microscopy, Department of Chemistry, University of Miami, Coral Gables, FL 33146 Edited by John H. Seinfeld, California Institute of Technology, Pasadena, CA, and approved June 28, 2019 (received for review April 9, 2019) The deposition of phosphorus (P) from African dust is believed to soluble and could be a more important source of SP transported to play an important role in bolstering primary productivity in the the TAO (15, 18, 23–25). Due to the buoyancy of smoke plumes, Amazon Basin and Tropical Atlantic Ocean (TAO), leading to BB aerosols can be emitted directly into the free troposphere and sequestration of carbon dioxide. However, there are few mea- the particles are typically smaller in size than dust increasing the surements of African dust in South America that can robustly test atmospheric lifetime of BB during transport (26, 27). this hypothesis and even fewer measurements of soluble P, which The source and solubility of P that impacts the Amazon and is readily available for stimulating primary production in the TAO changes due to the seasonal migration of the Intertropical ocean. To test this hypothesis, we measured total and soluble P Convergence Zone (ITCZ) and seasonality of BB in Africa (28, in long-range transported aerosols collected in Cayenne, French 29). During the boreal winter and spring (December to April), Guiana, a TAO coastal site located at the northeastern edge of the African dust is the main aerosol transported to these ecosystems Amazon. Our measurements confirm that in boreal spring when African dust transport is greatest, dust supplies the majority of P, when the ITCZ is largely south of the equator (1, 5, 8, 12, 15). of which 5% is soluble. In boreal fall, when dust transport is at an BB from the Sahel south of the Sahara can be cotransported with annual minimum, we measured unexpectedly high concentrations dust (3, 28, 30, 31) and potentially provides additional P to the of soluble P, which we show is associated with the transport of Amazon and TAO in boreal winter and spring. During the boreal biomass burning (BB) from southern Africa. Integrating our results fall (September to November), the ITCZ is located at ∼5° to 10°N, into a chemical transport model, we show that African BB supplies inhibiting African dust transport to South America (5, 32). There up to half of the P deposited annually to the Amazon from are few measurements of P over the TAO, but the measurements transported African aerosol. This observational study links P-rich that exist suggest that both total P (TP) and SP can be elevated in BB aerosols from Africa to enhanced P deposition in the Amazon. fall (22, 33). BB from southern Africa has been speculated to Contrary to current thought, we also show that African BB is a reach South America and the TAO during this season (28, 34–36); more important source of soluble P than dust to the TAO and however, the ability of African BB to supply TP and SP to the oceans in the Southern Hemisphere and may be more important Amazon and the TAO has not been investigated. for marine productivity, particularly in boreal summer and fall. Significance dust | biomass burning | phosphorus | Atlantic Ocean | Amazon Basin Phosphorus (P) deposition from aerosols can stimulate primary eposition of phosphorus (P) by aerosols to P-depleted productivity in P-depleted marine and terrestrial ecosystems. We Decosystems modulates primary productivity and can conse- tested the hypothesis that African dust fertilizes the Amazon quently impact atmospheric carbon dioxide levels on a global – Basin and Tropical Atlantic Ocean (TAO) by measuring wind- scale (1 4). Every year, African dust is transported across the borne dust, P, and soluble P in samples collected at a coastal site Tropical Atlantic Ocean (TAO) to South America in boreal on the northeastern edge of the Amazon. Using satellite data winter and spring (5, 6). Nutrients associated with dust are hy- – and models, we identified a previously underestimated source of pothesized to alleviate P limitations (1, 7 10) on a timescale soluble P: biomass burning aerosol transported from southern of days in marine environments to millions of years in tropical Africa that can supply P to the Amazon, TAO, and Southern terrestrial ecosystems (4, 9, 11). P deposition to the Amazon Ocean. Because P associated with biomass burning emissions is from African dust has been estimated using remote sensing and more soluble than P in transported dust, biomass burning models (8, 12, 13); however, P deposition associated with the aerosols immediately impact P cycling and primary production, long-range transport of nondust aerosol has not been measured. especially in marine ecosystems like the TAO. The chemical composition of aerosols affects the solubility of P, which determines its bioavailability and how readily P is uti- Author contributions: A.E.B., J.M.P., K.J.P., and C.J.G. designed research; A.E.B. performed lized by primary producers. In the ocean, soluble P (SP) is rap- research; A.E.B., J.M.P., N.M., D.S.H., K.J.P., A.M.O., A.P., A.G., K.P.-P., P.B., and C.J.G. idly used and removed by marine organisms (14). In terrestrial contributed new reagents/analytic tools; A.E.B., J.M.P., N.M., D.S.H., K.J.P., A.M.O., A.P., environments, the residence time of P in soil is longer, facili- and C.J.G. analyzed data; and A.E.B., J.M.P., and C.J.G. wrote the paper. tating the transformation of insoluble P into more bioavailable The authors declare no conflict of interest. forms (9). African dust is thought to be the largest contributor of This article is a PNAS Direct Submission. P to the Amazon and TAO (15), but its solubility is low (16–20). Published under the PNAS license. While P in dust can be transformed into more soluble forms via 1To whom correspondence may be addressed. Email: [email protected]. reactions with acids (20, 21), the importance of this process This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10. during transport is debated (19, 22, 23). In contrast, P in aerosols 1073/pnas.1906091116/-/DCSupplemental. from biomass burning (BB) and fossil fuel combustion are more Published online July 29, 2019. 16216–16221 | PNAS | August 13, 2019 | vol. 116 | no. 33 www.pnas.org/cgi/doi/10.1073/pnas.1906091116 Downloaded by guest on March 31, 2021 dust and black carbon (BC) from BB (SI Appendix,Fig.S5). This evidence indicates that African BB was cotransported with dust, which is supported by previous studies (28, 30, 38) and is the likely aerosol source that increases TP in our samples above levels previously measured in Saharan soils. Air mass back trajectory (BT) analysis (Fig. 1C) confirms that air masses passed over the Sahara and the Sahel where BB is active, providing evidence that BB contributed to our observed TP. Dust and SP were positively correlated (Fig. 1 B, Middle); how- ever, the percent of P that is soluble decreased with increasing dust (Fig.