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

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 AcknowledgementsWe thank the captains, crews, and participating scientists onboard the vessels John P Tully, El Puma, and Kaiyo Maru during this study. We also thank Bill Crawford, Sheila Tows, and Frank Whitney (Institute of Ocean Sciences, Sidney, Canada) for shore-side logistical support. We acknowledge the support of Maurice Levasseur (University of Laval, Quebec, Canada) in providing unpublished data for this manuscript. We thank NASA and Orbimage for the provision of SeaWiFS satellite images presented in Figs.

Phytoplankton community dynamics during late spring coccolithophore blooms at the continental margin of the Celtic Sea (North East Atlantic, 2006–2008)

“…This is most probably due to complex interplay between the dynamics of internal tidal mixing, mixed layer shoaling (higher on the shelf than the slope, Tables 3 and SP4), and meteorological conditions. Moreover, loss factors such as grazing (Holligan et al, 1993;Fileman et al, 2002;Painter et al, 2010b), viral lysis (Bratbak et al, 1996;Wilson et al, 2002) and enhanced export through aggregation (Boyd et al, 2005; Schmidt et al, in press) would further influence the distribution of phytoplankton biomass Fig. 4.…”

Ocean Iron Fertilization Experiments: Past–Present–Future with Introduction to Korean Iron Fertilization Experiment in the Southern Ocean (KIFES) Project

“…To investigate initial environmental conditions (~1-7 days before iron addition), physical and biogeochemical properties were determined at the sites of the OIF experiments (Steinberg et al, 1998;Coale et al, 1998;Bakker et al, 2001;20 Boyd and Law, 2001;Gervais et al, 2002;Coale et al, 2004;Boyd et al, 2005;Takeda and Tsuda, 2005;Tsuda et al, 2007;Cisewski et al, 2008;Harvey et al, 2010;Cavagna et al, 2011) (Fig. 6, Table 2 and 3).…”

“…However, there was little information about differences in phytoplankton biomass and communities along the longitudinal dust gradient (Duce and Tindale, 1991;Moore et al, 2002). To investigate the relationship between phytoplankton biomass/community and this dust 5 gradient, the Subarctic Pacific iron Experiment for Ecosystem Dynamics Study-1 (SEEDS-1) was conducted in July-August 2001 (13 days) in the western subarctic gyre using the RV Kaiyo-Maru (Tsuda et al, 2003, and the Subarctic Ecosystem Response to Iron Enrichment Study (SERIES) was performed in July-August 2002 (25 days) in the in the Gulf of Alaska using the RV John P. Tully, El Puma, and Kaiyo-Maru (Boyd et al, 2004(Boyd et al, , 2005. The main objective of SERIES was to investigate the duration of phytoplankton blooming (i.e., start to finish) after iron addition.…”

“…As previously mentioned, the Fv/Fm ratio, a measure of the photosynthetic efficiency of phytoplankton, is widely used to determine the degree to which iron is the limiting nutrient for phytoplankton growth (Fv/Fm ranges from 0 to 1 where conditions are less iron limited condition as Fv/Fm approaches 1) (Boyd et al, 2005). Initial Fv/Fm ratios were less than ~0.3 ( Fig.…”

“…The average initial OIF chlorophyll-a concentration was 0.43 ± 0.27 mg m -3 . Prior to the OIF experiments, except in SEEDS-1, SOFeX-S, and EIFEX where the diatoms were dominated by micro-plankton (20-200 µm), phytoplankton communities were dominated by pico-plankton (0.2-2.0 µm) and nano-plankton (2.0-20 µm) (Coale et al, 1998;Landry et al, 2000;35 Boyd and Law, 2001;Gervais et al, 2002;Coale et al, 2004;Boyd et al, 2005;Hoffmann et al, 2006;Harvey et al, 2010;Tsuda et al, 2007;Martin et al, 2013).…”