Interacting effects of light and iron availability on the coupling of photosynthetic electron transport and CO 2 -assimilation in marine phytoplankton

Iron availability directly affects photosynthesis and limits phytoplankton growth over vast oceanic regions. For this reason, the availability of iron is a crucial variable to consider in the development of active chlorophyll a fluorescence based estimates of phytoplankton primary productivity. Thes...

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Bibliographic Details
Published in:PLOS ONE
Main Authors: Schuback, N, Schallenberg, C, Duckham, C, Maldonado, MT, Tortell, PD
Format: Article in Journal/Newspaper
Language:English
Published: Public Library of Science 2015
Subjects:
Earth Sciences
Oceanography
Biological Oceanography
Pacific
Subarctic
Online Access:https://doi.org/10.1371/journal.pone.0133235
http://www.ncbi.nlm.nih.gov/pubmed/26171963
http://ecite.utas.edu.au/108992
Description
Summary:Iron availability directly affects photosynthesis and limits phytoplankton growth over vast oceanic regions. For this reason, the availability of iron is a crucial variable to consider in the development of active chlorophyll a fluorescence based estimates of phytoplankton primary productivity. These bio-optical approaches require a conversion factor to derive ecologically-relevant rates of CO 2 -assimilation from estimates of electron transport in photosystem II. The required conversion factor varies significantly across phytoplankton taxa and environmental conditions, but little information is available on its response to iron limitation. In this study, we examine the role of iron limitation, and the interacting effects of iron and light availability, on the coupling of photosynthetic electron transport and CO 2 -assimilation in marine phytoplankton. Our results show that excess irradiance causes increased decoupling of carbon fixation and electron transport, particularly under iron limiting conditions. We observed that reaction center II specific rates of electron transport (ETR RCII , mol e- mol RCII -1 s -1 ) increased under iron limitation, and we propose a simple conceptual model for this observation. We also observed a strong correlation between the derived conversion factor and the expression of non-photochemical quenching. Utilizing a dataset from in situ phytoplankton assemblages across a coastal oceanic transect in the Northeast subarctic Pacific, this relationship was used to predict ETR RCII : CO 2 -assimilation conversion factors and carbon-based primary productivity from FRRF data, without the need for any additional measurements.

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