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Coupling between Photosystem II electron transport and carbon fixation in microphytobenthos

Morris, E.P. and Forster, R. and Peene, J. and Kromkamp, J.C. (2008) Coupling between Photosystem II electron transport and carbon fixation in microphytobenthos. Aquatic Microbial Ecology, 50, 301-311. ISSN 0948-3055.

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Official URL: http://dx.doi.org/10.3354/ame01175

Abstract

Photosynthetic parameters of a microphytobenthic (MPB) biofilm grown in a tidal mesocosm were measured on undisturbed sediment using variable fluorescence-based measurements of electron transport rate (ETR), as well as by ETR and 14C assimilation measurements in optically thin suspensions of algal cells. Absorption cross-sections of the MPB suspensions were quantified using the quantitative filter technique and by reconstruction using HPLC-derived pigment concentrations. Photosynthetic parameters derived by the 3 methods were compared on 3 days, representing different biofilm growth/[chl a] conditions, at the start, middle and end of the daytime tidal emersion. Comparisons of ETR and radioisotope-derived photosynthetic parameters measured on optically thin suspensions were not significantly different, confirming that with an appropriate estimation of the irradiance absorbed by Photosystem II (PSII), under optically well-defined conditions, variable fluorescence is a reliable measure of MPB photosynthetic rates. In contrast, significant differences of up to 60% were observed between the maximum photosynthetic capacity (PBmax) measured on undisturbed sediment and in suspensions. These differences were observed at high [chl a] (coinciding with low growth rates) towards the end of emersion periods. Comparison of the effective quantum efficiency (ΔF/Fm’) at the highest light steps of photosynthetic-irradiance (P-E) curves suggested that the overestimation was due to the poor definition of the complex sediment optics, which interacted presumably with photo-taxis and/or single species migrations. Definition of the optics within undisturbed sediments, particularly considering the complex effects of migration, is a serious challenge, limiting the application of variable fluorescence techniques in situ on undisturbed sediments.

Item Type:Article
Institutes:Nederlands Instituut voor Ecologie (NIOO)
ID Code:4906
Deposited On:30 Sep 2009 02:00
Last Modified:26 Mar 2012 04:00

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