Delayed fluorescence (DF) excitation spectrometry was examined as a proxy for phytoplankton activity in comparison to pulse-amplitude-modulated (PAM) fluorometry and dissolved oxygen (DO) evolution. During several day-night cycles, the three target variables were monitored simultaneously, together with pH, temperature and photosynthetically active irradiance in an exponentially growing Chlorella population exposed to natural light conditions. It was found that during a diel cycle prompt and DF signals corresponded to each other and were negatively correlated to the light intensity, with maximum values during night and vice versa. The DF signal showed a strong linear relationship with the quantum yield of photosystem II. Our findings thus suggest that, in addition to the continuous monitoring of active chlorophyll of different taxonomical groups, DF excitation spectrometry also carries the potential to continuously monitor the quantum yields and relative electron transport rates in natural phytoplankton assemblages.
Bibliographical noteFunding Information:
Acknowledgements E. K. thanks the ‘‘Yochai Ben Nun Scholarship’’ from the Israel Oceanographic and Limnological Research Ltd. for support during this work. Fruitful discussions and technical assistance by V. Gerhardt and U. Bodemer are gratefully acknowledged. We wish to thank A. Sukenik and Y.Z. Yacobi as well as two anonymous reviewers for their critical comments of the manuscript. This study was presented as a contributed paper at the Bat Sheva de Rothschild seminar on Phytoplankton in the Physical Environment—the 15th workshop of the International Association of Phytoplankton Taxonomy and Ecology (IAP).
- Delayed fluorescence
- PAM fluorometer
- Prompt fluorescence
- Quantum yield
ASJC Scopus subject areas
- Aquatic Science