Scholarship at UWindsor

Title

The evolution and termination of an iron-induced mesoscale bloom in the northeast subarctic Pacific

Authors

Philip W. Boyd, University of Otago
Robert Strzepek, University of Otago
Shigenobu Takeda, The University of Tokyo
George Jackson, Texas A&M University
C. S. Wong, Institute of Ocean Sciences, Fisheries and Oceans Canada
R. Mike McKay, Bowling Green State University
Cliff Law, National Institute of Water and Atmospheric Research
Hiroshi Kiyosawa, Marine Biological Research Institute of Japan
Hiroaki Saito, Tohoku National Fisheries Research Institute, FRA
Nelson Sherry, The University of British Columbia
Keith Johnson, Texas A&M University
Jim Gower, Texas A&M University
Neelam Ramaiah, The University of Tokyo

Document Type

Article

Publication Date

1-1-2005

Publication Title

Limnology and Oceanography

Volume

50

Issue

6

First Page

1872

Last Page

1886

Abstract

We initiated and mapped a diatom bloom in the northeast subarctic Pacific by concurrently adding dissolved iron and the tracer sulfur hexafluoride to a mesoscale patch of high-nitrate, low-chlorophyll waters. The bloom was dominated by pennate diatoms and was monitored for 25 d, which was sufficiently long to observe the evolution and termination of the bloom and most of the decline phase. Fast repetition-rate fluorometry indicated that the diatoms were iron-replete until day 12, followed by a 4-5-d transition to iron limitation. This transition period was characterized by relatively high rates of algal growth and nutrient uptake, which pointed to diatoms using intracellularly stored iron. By days 16-17, the bloom was probably limited simultaneously by both iron and silicic acid supply, because low silicic acid concentrations were evident. Modeling simulations, using data from our study, provided an estimate of the critical threshold for algal aggregation. Observed diatom abundances during the bloom exceeded this threshold between days 13 and 17. Mass sedimentation of diatoms and diatom aggregates was recorded in surface-tethered free-drifting sediment traps at 50 m in depth on day 21. Although the termination of the bloom was probably controlled by the availability of both iron and silicic acid, we cannot rule out the role of algal aggregation. The bloom decline was likely triggered by the onset of mass sedimentation. During our study, evidence of both diatom species succession and species-specific aggregation point to important links between algal nutrient stress and the initiation of algal aggregation. © 2005, by the American Society of Limnology and Oceanography, Inc.

DOI

10.4319/lo.2005.50.6.1872

ISSN

00243590

Recommended Citation

Boyd, Philip W.; Strzepek, Robert; Takeda, Shigenobu; Jackson, George; Wong, C. S.; McKay, R. Mike; Law, Cliff; Kiyosawa, Hiroshi; Saito, Hiroaki; Sherry, Nelson; Johnson, Keith; Gower, Jim; and Ramaiah, Neelam. (2005). The evolution and termination of an iron-induced mesoscale bloom in the northeast subarctic Pacific. Limnology and Oceanography, 50 (6), 1872-1886.
https://scholar.uwindsor.ca/glierpub/609