The decline and fate of an iron-induced subarctic phytoplankton bloom

• Published in: Nature (London) Vol. 428; no. 6982; pp. 549 - 553
• Main Authors: Boyd, Philip W., Law, Cliff S., Wong, C.S., Nojiri, Yukihiro, Tsuda, Atsushi, Levasseur, Maurice, Takeda, Shigenobu, Rivkin, Richard, Harrison, Paul J., Strzepek, Robert, Gower, Jim, McKay, R. Mike, Abraham, Edward, Arychuk, Mike, Barwell-Clarke, Janet, Crawford, William, Crawford, David, Hale, Michelle, Harada, Koh, Johnson, Keith, Kiyosawa, Hiroshi, Kudo, Isao, Marchetti, Adrian, Miller, William, Needoba, Joe, Nishioka, Jun, Ogawa, Hiroshi, Page, John, Robert, Marie, Saito, Hiroaki, Sastri, Akash, Sherry, Nelson, Soutar, Tim, Sutherland, Nes, Taira, Yosuke, Whitney, Frank, Wong, Shau-King Emmy, Yoshimura, Takeshi
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.04.2004; Nature Publishing; Nature Publishing Group
• Subjects: Alaska; algal blooms; Analysis; Animal, plant and microbial ecology; Applied ecology; Bacillariophyceae; biogeochemistry; Biological and medical sciences; Carbon; Carbon - metabolism; Carbon sequestration; Cold Climate; Diatoms - growth & development; Diatoms - physiology; Ecotoxicology, biological effects of pollution; Fundamental and applied biological sciences. Psychology; Geoengineering; Humanities and Social Sciences; Iron; Iron - analysis; Iron - metabolism; letter; Marine; Marine and brackish environment; multidisciplinary; nutrient availability; Oceans; Oceans and Seas; organic compounds; Pacific Ocean; Particulate organic carbon; Phytoplankton; Phytoplankton - growth & development; Phytoplankton - physiology; Plankton; population dynamics; Science; Science (multidisciplinary); Seawater - microbiology; Silica; Silicic Acid; Silicon Dioxide; Thermocline; Time Factors; Pacific Ocean; Gulf of Alaska; North Pacific; Alaska; INE, USA, Alaska, Alaska Gulf; USA, Alaska; Nutrition; Silicic acid; Algae; Iron; Bioavailability; Particulate carbon; Marine environment; Heterokontophyta; Biogeochemistry; Bacillariophyta; Bloom; Phytoplankton; Thallophyta
• ISSN: 0028-0836; 1476-4687; 1476-4687
• DOI: 10.1038/nature02437

Iron supply has a key role in stimulating phytoplankton blooms in high-nitrate low-chlorophyll oceanic waters 1 , 2 , 3 , 4 , 5 . However, the fate of the carbon fixed by these blooms, and how efficiently it is exported into the ocean's interior, remains largely unknown 1 , 2 , 3 , 4 , 5 . Here we report on the decline and fate of an iron-stimulated diatom bloom in the Gulf of Alaska. The bloom terminated on day 18, following the depletion of iron and then silicic acid, after which mixed-layer particulate organic carbon (POC) concentrations declined over six days. Increased particulate silica export via sinking diatoms was recorded in sediment traps at depths between 50 and 125 m from day 21, yet increased POC export was not evident until day 24. Only a small proportion of the mixed-layer POC was intercepted by the traps, with more than half of the mixed-layer POC deficit attributable to bacterial remineralization and mesozooplankton grazing. The depletion of silicic acid and the inefficient transfer of iron-increased POC below the permanent thermocline have major implications both for the biogeochemical interpretation of times of greater iron supply in the geological past 6 , 7 , and also for proposed geo-engineering schemes to increase oceanic carbon sequestration 3 , 8 .