Effects of iron and light availability on phytoplankton photosynthetic properties in the Ross Sea

Marine ecology progress series

Gert L. van Dijken^1¹  Willem van de Poll^3²  Anne-Carlijn Alderkamp^1,2³  Hannah L. Joy-Warren^1⁴  Kate E. Lowry^1⁵  Patrick Laan^4⁶  Kate M. Lewis^1⁷ 

[1] Biology Department, Foothill College, Los Altos Hills, CA 94022, USA^2;Department of Cell and Molecular Biology and Graduate School of Oceanography, University of Rhode Island, Kingston, RI 02881, USA^6;Department of Earth System Science, Stanford University, Stanford, CA 94305, USA^1;Department of Medicine, University of Chicago, Chicago, IL 60637, USA^5;Department of Ocean Ecosystems, University of Groningen, PO Box 11103, 9700 CC, Groningen, The Netherlands^3;Present address: Génomique Métabolique, Genoscope, Institut François Jacob, CEA, CNRS, 91000 Evry, France^7;Royal Netherlands Institute for Sea Research, OCS, University of Utrecht, PO Box 59, 1790 AB, Den Burg, The Netherlands^4

关键词: Phytoplankton;    Photophysiology;    Iron limitation;    Ross Sea;   

DOI  :  10.3354/meps13000

学科分类：海洋学与技术

来源: Inter-Research

【 摘 要 】

Waters of the Southern Ocean are characterized by high macronutrient concentrations but limited availability of trace metals and light, often making it difficult for phytoplankton to achieve maximum growth rates. One strategy employed by Southern Ocean phytoplankton in culture to cope with low light and low dissolved iron (DFe) is to enhance light absorption by increasing their antenna size rather than the number of reaction centers, thereby reducing their Fe demand. Here we provide physiological evidence that natural populations of Southern Ocean phytoplankton employ a similar photoacclimation strategy to cope with low ambient DFe concentrations. During a research cruise to the Ross Sea in 2013-2014, we conducted 4 bioassay experiments in which we manipulated light and DFe concentrations and measured changes in phytoplankton biomass, growth rate, photosynthetic parameters, fluorescence parameters, and pigment composition. Phytoplankton responded strongly to DFe additions, exhibiting significantly higher biomass, growth rates, and photosynthetic competency. At low light, the maximum photosynthetic rate (P*max) was significantly reduced and the photosynthetic efficiency (α*) was unchanged compared to the high light treatment, regardless of phytoplankton species composition or DFe concentration. Our data suggest that Southern Ocean phytoplankton have evolved an Fe-saving strategy whereby they photoacclimate to low light by increasing their photosynthetic unit size, rather than photosynthetic unit number, even when DFe is available. It appears this Fe-saving strategy is characteristic of both Phaeocystis antarctica and diatoms, suggesting that it is a common adaptation among phytoplankton taxa that grow under Fe limitation in the Southern Ocean.

【 授权许可】

Unknown