title: Interacting Effects of Light and Iron Availability on the Coupling of Photosynthetic Electron Transport and CO2-Assimilation in Marine Phytoplankton.
abstract: 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 CO2-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 CO2-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): CO2-assimilation conversion factors and carbon-based primary productivity from FRRF data, without the need for any additional measurements.
authors.affiliation: Departement of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Nina
authors.initials: N
authors.lastname: Schuback
authors.affiliation: School of Earth and Ocean Sciences, University of Victoria, Victoria, BC, Canada.
authors.forename: Christina
authors.initials: C
authors.lastname: Schallenberg
authors.affiliation: Departement of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Carolyn
authors.initials: C
authors.lastname: Duckham
authors.affiliation: Departement of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Maria T
authors.initials: MT
authors.lastname: Maldonado
authors.affiliation: Departement of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC, Canada; Department of Botany, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Philippe D
authors.initials: PD
authors.lastname: Tortell
mesh_terms: D002244:Carbon / Q000378:metabolism; D057486:Carbon Cycle / Q000502:physiology; D002245:Carbon Dioxide / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D004579:Electron Transport / Q000502:physiology*; D004777:Environment; D007501:Iron / Q000378:metabolism*; D008027:Light; D009792:Oceans and Seas; D010788:Photosynthesis / Q000502:physiology*; D045332:Photosystem II Protein Complex / Q000378:metabolism* / Q000502:physiology*; D010839:Phytoplankton / Q000378:metabolism* / Q000502:physiology
chemical_list: D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D002245:Carbon Dioxide; D002244:Carbon; D007501:Iron; D000077194:Chlorophyll A