Charles G. Trick et al., PNAS, 2010, Iron enrichment stimulates toxic diatom production in high-nitrate, low-chlorophyll areas

Proceedings of the National Academy of Sciences, published online before print March 15, 2010; doi: 10.1073/pnas.0910579107

Iron enrichment stimulates toxic diatom production in high-nitrate, low-chlorophyll areas

Charles G. Trick* (Departments of Biology, and Microbiology and Immunology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON N6A5B7, Canada), Brian D. Bill (Romberg Tiburon Center for Environmental Studies, San Francisco State University, Tiburon, CA 94920, and Marine Biotoxin Program, National Oceanic and Atmospheric Administration, Northwest Fisheries Science Center, Seattle, WA 98112, U.S.A.), William P. Cochlan (Romberg Tiburon Center for Environmental Studies, San Francisco State University, Tiburon, CA 94920, U.S.A.), Mark L. Wells (School of Marine Science, University of Maine, Orono, ME 04469, U.S.A.), Vera L. Trainer (Marine Biotoxin Program, National Oceanic and Atmospheric Administration, Northwest Fisheries Science Center, Seattle, WA 98112, U.S.A.) and Lisa D. Pickell (School of Marine Science, University of Maine, Orono, ME 04469, U.S.A.)

Edited by Penny W. Chisholm, Massachusetts Institute of Technology, Cambridge, MA, and approved February 1, 2010 (received for review September 23, 2009)

Abstract

Oceanic high-nitrate, low-chlorophyll environments have been highlighted for potential large-scale iron fertilizations to help mitigate global climate change. Controversy surrounds these initiatives, both in the degree of carbon removal and magnitude of ecosystem impacts. Previous open ocean enrichment experiments have shown that iron additions stimulate growth of the toxigenic diatom genus Pseudonitzschia. Most Pseudonitzschia species in coastal waters produce the neurotoxin domoic acid (DA), with their blooms causing detrimental marine ecosystem impacts, but oceanic Pseudonitzschia species are considered nontoxic. Here we demonstrate that the sparse oceanic Pseudonitzschia community at the high-nitrate, low-chlorophyll Ocean Station PAPA (50° N, 145° W) produces approximately 200 pg DA L⁻¹ in response to iron addition, that DA alters phytoplankton community structure to benefit Pseudonitzschia, and that oceanic cell isolates are toxic. Given the negative effects of DA in coastal food webs, these findings raise serious concern over the net benefit and sustainability of large-scale iron fertilizations. 

*Ccorrespondence e-mail: trick@uwo.ca.

Link to abstract:  http://www.pnas.org/content/early/2010/02/24/0910579107.abstract

Link to complete, open-access paper:  http://www.pnas.org/content/early/2010/02/24/0910579107.full.pdf+html