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.

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

“…The quantum efficiency of PSII charge separation (F v /F m ) is widely used as an indicator of the nutrient stress of phytoplankton cells [36], [37], [38]. A reduction in F v /F m as a function of nutrient limitation is generally expected.…”

INFLUENCE OF PHOSPHORUS LIMITATION ON TOXICITY AND PHOTOSYNTHESIS OF ALEXANDRIUM MINUTUM (DINOPHYCEAE) MONITORED BY IN‐LINE DETECTION OF VARIABLE CHLOROPHYLL FLUORESCENCE1

“…By measuring variable chl fluorescence, the photosynthetic efficiency of cells can be assessed. Many studies have revealed that the supply of N, P, silicate, and iron have strong influences on phytoplankton fluorescence in the field and in the laboratory (Kolber et al 1988, Geider et al 1993a,b, Lippemeier et al 1999, 2001). Most of these studies showed a strong reduction in the fluorescence‐based photochemical efficiency of nutrient limited cells.…”

“…Most of these studies showed a strong reduction in the fluorescence‐based photochemical efficiency of nutrient limited cells. In‐line measurements of variable fluorescence comprise the direct detection of fluorescence with a glass fiber cable from the culture (Lippemeier et al 2001). The advantage of measuring in‐line fluorescence, in comparison with the typical fluorescence measurements taken in a cuvette, is that in‐line measurements are not influenced by changes in ambient conditions (irradiance, temperature, gas exchange) induced by sample transfer.…”

“…In contrast to field measurements, in situ detection of fluorescence with laboratory or outdoor cultures have only been used in a limited number of investigations. These studies investigated the influences of irradiance (Ibelings et al 1994, Kroon 1994, Torzillo et al 1996) or variable nutrient supply (Lippemeier et al 2001) on the photochemical efficiency. The only in‐line measurements of variable fluorescence of planktonic dinoflagellates to date have been taken by Kroon et al (1993) while studying the chromatic regulation of quantum yields in Heterocapsa pygmaea.…”

Fast Detection of Nutrient Limitation in Macroalgae and Seagrass with Nutrient-Induced Fluorescence

“…It can thus be interpreted as a measure of photosynthetic efficiency, and is widely used as an index for the physiological status of phototrophic organisms [9], [19], [22], [31], [32].…”