期刊
DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY
卷 54, 期 18-20, 页码 2045-2065出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.dsr2.2007.06.011
关键词
phytoplankton; iron limitation; light; Southern Ocean
类别
资金
- NERC [NE/C518114/2, soc010008] Funding Source: UKRI
- Natural Environment Research Council [NE/C518114/2, soc010008] Funding Source: researchfish
The CROZet natural iron bloom and EXport experiment (CROZEX) investigated phytoplankton blooms in the vicinity of the Crozet Plateau in the polar frontal zone (PFZ) of the Southern Ocean. Peak chlorophyll concentrations reached during an intense bloom within naturally iron (Fe)-fertilised regions north of the plateau were an order of magnitude higher than those observed in deeper mixed layers and low-Fe waters to the south. To establish the factors influencing phytoplankton dynamics, a suite of in situ phytoplankton physiological measurements and shipboard Fe-light perturbation experiments was performed. Addition of Fe in experiments performed during bloom decline north of the plateau resulted in increased accumulation of phytoplankton biomass and changes in a number of phytoplankton physiological characteristics. In particular photosystern II (PSII) photochemical efficiencies (F-v/F-m) measured by fast repetition rate fluorometry increased above in situ values within 24 h of Fe amendment, suggesting that Fe stress had contributed to bloom termination. In contrast, responses to Fe amendment were minor within an experiment initiated in low-silicic acid, post-bloom waters south of the Plateau. Within the intense bloom in the north, light limitation due to self-shading may have constrained the peak phytoplankton standing stock. However, in the absence of Fe amendment, incubation at higher than in situ irradiance levels had little influence on phytoplankton biomass accumulation for declining bloom populations. Instead reduced F-v/F-m, reflecting increased photoinhibitory damage to PSII, was observed in highlight incubations and was also apparent in situ. Interactions between Fe and light availability thus influenced phytoplankton physiology and growth and potentially contributed to bloom longevity during CROZEX. (C) 2007 Elsevier Ltd. All rights reserved.
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