Phytoplankton primary productivity: A dual-incubation approach for direct comparison of photosystem II photosynthetic flux (JVPII) and 14C-fixation experiments
Nina Schuback, Kevin Oxborough, Mary Burkitt-Gray, Patricia López-García, Matthew D. Patey, Emily Hammermeister, Alan Wright, C. Mark Moore
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引用次数: 0
Abstract
Singe-turnover active chlorophyll a fluorometry (STAF) can be used to assess phytoplankton photosynthetic rates in terms of the photosystem II photochemical flux (JVPII, μmol e− m−3 s−1) instantaneously, autonomously, and at high resolution. While JVPII provides an upper limit to rates of phytoplankton primary productivity in units of carbon fixation, the conversion between these two rates is variable, limiting our ability to utilize high-resolution JVPII data to monitor phytoplankton primary productivity. Simultaneous measurements of JVPII and 14C-fixation help in understanding the factors controlling the variable ratio between the two rates. However, to date, methodological inconsistencies, including differences in incubation lengths and light quality, have greatly inhibited practical assessment of such electron to carbon ratios (Φe,C, mol e− mol C−1). We here present data from a range of dual-incubation experiments in northeast Atlantic waters during which JVPII and 14C-fixation were measured simultaneously on the same sample. Time-course experiments show how Φe,C increases with incubation length, likely reflecting the transition from gross to net 14C-fixation. Dual-incubation experiments conducted under different light levels show a tendency for increased Φe,C under (super-)saturating light. Finally, data from a diurnal experiment demonstrate how Φe,C increases over the course of a day, due to downregulation of 14C-fixation. We provide a detailed description of our methodological approach, including a critical discussion of improvements to the calculation of JVPII implemented in the LabSTAF instrument used for active fluorescence measurements and the limitations of the well-established 14C-fixation approach.
期刊介绍:
Limnology and Oceanography: Methods (ISSN 1541-5856) is a companion to ASLO''s top-rated journal Limnology and Oceanography, and articles are held to the same high standards. In order to provide the most rapid publication consistent with high standards, Limnology and Oceanography: Methods appears in electronic format only, and the entire submission and review system is online. Articles are posted as soon as they are accepted and formatted for publication.
Limnology and Oceanography: Methods will consider manuscripts whose primary focus is methodological, and that deal with problems in the aquatic sciences. Manuscripts may present new measurement equipment, techniques for analyzing observations or samples, methods for understanding and interpreting information, analyses of metadata to examine the effectiveness of approaches, invited and contributed reviews and syntheses, and techniques for communicating and teaching in the aquatic sciences.