Anthropogenic iron alters the spring phytoplankton bloom in the North Pacific transition zone
Abstract
Industrial activities have increased the supply of iron to the ocean, but the magnitude of anthropogenic input and its ecological consequences are not well-constrained by observations. Across four expeditions to the North Pacific transition zone, we document a repeated supply of isotopically light iron from an atmospheric source in spring, reflecting an estimated 39 ± 9 % anthropogenic contribution to the surface ocean iron budget. Expression of iron-stress genes in metatranscriptomes, and evidence for colimitation of ecosystem productivity by iron and nitrogen, indicates that enhanced iron supply should spur spring phytoplankton blooms, accelerating the seasonal drawdown of nitrate delivered by winter mixing. This effect is consistent with regional trends in satellite ocean color, which show a shorter, more intense spring bloom period, followed by an earlier arrival of oligotrophic conditions in summer. Continued iron emissions may contribute to poleward shifts in transitional marine ecosystems, compounding the anticipated impacts from ocean warming and stratification.
Article Details
Journal Info
Proceedings of the National Academy of Sciences
National Academy of Sciences
Authors (21)
Nicholas J. Hawco
Department of Oceanography, University of Hawai’i at Mānoa
Tim M. Conway
College of Marine Science, University of South Florida
Sacha N. Coesel
School of Oceanography, University of Washington
Benedetto Barone
Department of Oceanography, University of Hawai’i at Mānoa
Emily A. Seelen
Department of Earth Sciences, University of Southern California
Shun-Chung Yang
Department of Earth Sciences, University of Southern California
Randelle M. Bundy
School of Oceanography, University of Washington
Paulina Pinedo-Gonzalez
Department of Earth Sciences, University of Southern California
Xiaopeng Bian
Department of Earth Sciences, University of Southern California
Matthias Sieber
College of Marine Science, University of South Florida
Nathan T. Lanning
Department of Oceanography, Texas A&M University
Jessica N. Fitzsimmons
Department of Oceanography, Texas A&M University
Rhea K. Foreman
Department of Oceanography, University of Hawai’i at Mānoa
Daniela König
Mora J. Groussman
School of Oceanography, University of Washington
James G. Allen
Department of Oceanography, University of Hawai’i at Mānoa
Lauren W. Juranek
College of Earth, Ocean, and Atmospheric Sciences, Oregon State University
Angelicque E. White
Department of Oceanography, University of Hawai’i at Mānoa
David M. Karl
Department of Oceanography, University of Hawai’i at Mānoa
E. Virginia Armbrust
School of Oceanography, University of Washington
Seth G. John
Department of Earth Sciences, University of Southern California