In-line recording of PAM fluorescence of phytoplankton cultures as a new tool for studying effects of fluctuating nutrient supply on photosynthesis

Abstract

Turbidostat cultures of Dunaliella salina (Chlorophyceae) and Thalassiosira weissflogii (Bacillariophyceae) were grown at fluctuating concentrations of nitrate, phosphate and silicate. In-line measurements of PAM fluorescence were used to monitor the effects of fluctuating nutrient supply on the photochemical efficiency of photosystem II reaction centres of light-adapted cells (∆F\F h m ). Besides the maximal photochemical efficiency of photosystem II reaction centres of dark-adapted cells (F v \F m ), chlorophyll a, particulate organic carbon, nitrogen and phosphorus, and the cell number were measured frequently during the experiments. Following nutrient-replete growth, the cells were supplied with medium from which either nitrate, phosphate or silicate was omitted. When significant effects of nutrient starvation were indicated by the fluorescence parameters, a pulse of the deficient nutrient was added to the cultures. Our experimental set-up for in-line fluorescence measurements provided sensitive and reproducible detection of the various fluorescence signals, revealing strong influences of nutrient supply on the photochemical efficiency of photosystem II. In general the fluorescence values changed substantially within 1-30 min after re-addition of the deficient nutrient. Addition of phosphate and silicate induced an immediate characteristic decrease in fluorescence, whereas nitrate addition was characterized by a strong, delayed increase in fluorescence. Complete recovery to pre-starvation fluorescence values took about 48 h in all experiments. The physiological background of nutrient uptake is used to explain the observed tight couplings between fluorescence responses and nutrient re-addition. Our study clearly demonstrates that in-line fluorescence measurements provide a new tool for the investigation of phytoplankton reactions to fluctuating nutrients and offer the possibility to detect nutrient starvation in the field.

Photosynthetic activation of the dark-acclimated diatom <i>Thalassiosira weissflogii</i> upon light exposure

“…3). Similar levels of F v /F m were observed on both days, with a mean and standard deviation of 0.62±0.024, regardless of the dark storage length but dependent on silicate availability (Table (Lippemeier et al 2001). Therefore, T. weissflogii was able to recover to a photosynthetically active state with maximum F v /F m even after up to 14 days of storage in dark conditions under an abundant supply of macronutrients, including silicate ( Fig.…”

“…Variations in the light-saturated photosynthetic rate (assessed by either 14 C or Chl fluorescence methods) have been correlated with silicate concentrations (Malone et al 1980, Lippemeier et al 1999 and have also been correlated with the cell cycle phase (Claquin & Martin-Jézéquel 2005). Particularly, the low concentration of silicate toward the end of batch incubation may influence the photosynthetic efficiency of the PSII reaction centers under light-limited conditions (Lippemeier et al 2001).…”

Photosynthetic efficiency and rapid light curves of sediment-biofilms along a water quality gradient in the Great Barrier Reef, Australia

“…For example, Nstarved cultures of the diatom Phaeodactylum tricornutum distinctly decreased from values of around 0.6 to less then 0.2 after several days, with a similar but less pronounced trend for P starvation (Geider et al 1993). Both effective and maximum efficiency of PSII were distinctly reduced under N, P or Si starvation in 2 planktonic diatom species studied by Lippemeier et al (2001). Several other plankton species of the Chlorophyta and Bacillariophyta also showed a clear decrease in efficiency with P limitation (Graziano et al 1996, Beardall et al 2001.…”

“…Reductions in PSII efficiency under nutrient starvation were usually related to a decrease in the ratio of functional over non-functional (i.e. centres without or with damaged D1 protein) PSII centres (Lippemeier et al 2001). It is likely that nutrient starvation represents a more severe stress for the photosystem than nutrient limitation.…”

Growth- and nutrient-dependent gene expression in the toxigenic marine dinoflagellate Alexandrium minutum

“…Stationary phase: significantly up-or down-regulated in all stationary-phase samples in relation to the control culture in exponential phase; N-/P-limitation: differentially expressed and showing the same trend between stationary-phase N-or P-limited cultures and both exponentially growing and stationary-phase control samples; nutrient limitation: identified for N-and P-limitation and same trend in both; stationary phase-control: differentially expressed between stationary and exponentially growing control and stationary phase control and both stationary-phase N-and P-limited cultures; transition to stationary phase: differentially expressed and showing the same trend in all comparisons between Day 5 samples and the control cultures in exponential phase. The decrease in F v /F m measured in all stationary cultures may correspond to a higher proportion of damaged PSII reaction centers due to impaired repair mechanisms (Lippemeier et al, 2001;Takahashi and Murata, 2008) or to down-regulation of photosynthesis-associated processes in non-growing cells. The lower demand for carbon compounds, ATP and redox equivalents (see Geider et al, 1993) in combination with the reduced availability of dissolved CO 2 at higher pH values in older cultures, can lead to a diversion of photosynthetic electrons to oxygen, resulting in the production of reactive oxygen species (ROS) (Vardi et al, 1999).…”