Application of fast repetition rate fluorometry to phytoplankton photosynthetic parameters in freshwaters

Abstract

Fast repetition rate fluorometry (FRRF) was successfully applied to various studies in modern oceanography. In this study, for the first time, the seasonality of phytoplankton photosynthetic parameters in a deep alpine lake was observed using FRRF in combination with the traditional (14)C incubation technique. Special attention was given to the differences in photosynthetic behaviour during mixed and stratified conditions, characterised especially during summer by a deep chlorophyll maximum (DCM) dominated by the filamentous cyanobacterial species Planktothrix rubescens. Maximum light-utilisation efficiency (alpha*(14C)) was in the range of 0.01-0.03 mgC (mg Chl-a)(-1) h(-1 )(mumol phot. m(-2) s(-1))(-1), while maximum quantum yields for carbon fixation (Phi(C,max)) varied from 0.01-0.07 molC (mol phot.)(-1). Higher values occurred during thermal stratification indicating acclimation of the phytoplankton assemblage. These findings were supported by FRRF-based estimates, although cyanobacterial blooms could not be characterised by FRRF-excitation due to methodological deficiencies. In general, however, instantaneous photosynthetic rates measured by FRRF-excitation correlate well at sub-saturating light-intensities with conventional (14)C-uptake rates, although they operate on different time-scales.

Influence of Nutrient Stress on the Relationships between PAM Measurements and Carbon Incorporation in Four Phytoplankton Species

“…Our slopes of the linear relationship between P Chl and ETR Chl (Φ C.e ) are in the same range as those found by Kaiblinger and Dokulil [54] but they are lower than those frequently reported in the literature [15], [17]. However, it is usually assumed that 50% of quanta are absorbed by PSI and 50% by PSII [45], [55], [56], whereas in the present study, we assumed that 74% of quanta were absorbed by PSII for diatoms and 68% for dinoflagellates [33], which leads to lower estimation of Φ C.e .…”

Diurnal variation in the coupling of photosynthetic electron transport and carbon fixation in iron-limited phytoplankton in the NE subarctic Pacific

“…For example, energy (ATP) and reducing power (NADPH) from the photosynthetic light reaction can be used directly for the reduction or assimilation of limiting nutrients, rather than for carbon fixation (e.g., Laws, 1991;Myers, 1980), resulting in an increased conversion factor K c /n PSII . Furthermore, K c /n PSII has been shown to increase under excess light conditions (Cheah et al, 2011;Corno et al, 2006;Fujiki et al, 2007;Goto et al, 2008;Kaiblinger and Dokulil, 2006;Raateoja, 2004), when the rate of charge separation in RCII can outpace the rate of electron transport along the photosynthetic electron transport chain (ETC). In order to alleviate the ensuing "back pressure", which can lead to, e.g., singlet oxygen formation and photoinhibition, photosynthetic organisms evolved a number of "safety valves" along the ETC (e.g., Niyogi, 2000).…”

Performance of Fast Repetition Rate fluorometry based estimates of primary productivity in coastal waters

“…Primary production is a fundamental measure of an ecosystem"s capacity to convert carbon dioxide into particulate organic carbon needed to fuel the foodweb, and thus underpins regulation of trophic dynamics and carbon cycling (Falkowski 2012). For decades, rates of marine primary productivity have been commonly measured using methods involving uptake of isotopically enriched inorganic carbon sources (Steeman-Nielsen 1952;Marra 2002;Kaiblinger & Dokulil 2006;Prieto et al 2008;Lawrenz et al 2013). Such methods have remained popular for a number of reasons, including their comparability with historic data.…”