Photosynthetic activity of natural microphytobenthos populations measured by fluorescence (PAM) and 14C-tracer methods:a comparison

Abstract

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 166:53-62 (1998) - doi:10.3354/meps166053 Photosynthetic activity of natural microphytobenthos populations measured by fluorescence (PAM) and 14C-tracer methods: a comparison Peter Hartig*, Kirsten Wolfstein**, Sebastian Lippemeier, Franciscus Colijn Research and Technology Centre Westcoast, University of Kiel, D-25761 Büsum, Germany *E-mail: [e-mail] **Present address: Sustainable Forest Management Network, G-208 Biological Science Building, University of Alberta, Edmonton, Alberta T6G 2E9, Canada PAM (pulse-amplitude-modulated) fluorescence measurements of motile microphytobenthic algae were carried out in June 1996 at Sylt, Germany. Comparisons between 14C-based and fluorescence-based production rates were made. A very high correlation between 14C- and fluorescence-based production rates was found for maximal production rates (Pmax values). 14C-based maximal production rates varied during the study period between 0.65 and 1.7 mg C mg chl a-1 h-1, comparable to variations of Pmax measured with the fluorescence-based method. For other photosynthetic parameters [α (maximum light utilization coefficient), Ek (light saturation index), Emax (light intensity at which Pmax is reached)], differences between the 2 methods were much larger. Highest carbon quantum yields (φass) (mol C mol quanta-1 absorbed) were obtained at low irradiances. Considering the whole range of investigated carbon quantum yields, we found that initially these values decreased at low to moderate irradiances without a concomitant decline of the actual photochemical efficiency (Fm' - F)/Fm' (F and Fm': minimal and maximal fluorescence signals in the light). Therefore, a high linearity between the actual photochemical efficiency and the carbon quantum yield could only be observed up to values of 0.018 mol C mol quanta-1. This is different to higher plants, for which linearity can be observed up to carbon quantum yields of 0.042 mol C mol quanta-1. It was shown that, for the calculation of the overall production rates based on the fluorescence method, it is necessary to carefully measure the mean specific absorption coefficient (a*) of the algae. Unless this is achieved, PAM measurements cannot be used to calculate absolute production rates. Photosynthetic activity · Fluorescence · PAM · Primary production · Microphytobenthos · German Wadden Sea Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 166. Publication date: May 28, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.