Photosystem II Electron Transport Rates and Oxygen Production in Natural Waterblooms of Freshwater Cyanobacteria During a Diel Cycle

• Published in: Journal of plankton research 2001-01, Vol.23 (1), p.57-66
• Main Authors: Masojídek, JiŘí, Grobbelaar, Johan U., Pechar, Libor, KoblíŽek, Michal
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Autoecology; Biological and medical sciences; Chlorophyll; Chlorophylls; Cyanophyta; Electron transfer; Electron transport; Evolution; Fish; Fish culture; Fish ponds; Fluorescence; Fluorescence in situ hybridization; Fresh water; Freshwater; Fundamental and applied biological sciences. Psychology; Inland water environment; Light effects; Oxygen; Photosynthesis; Photosystem; Photosystem II; Plants and fungi; Transport
• ISSN: 0142-7873; 1464-3774; 1464-3774
• DOI: 10.1093/plankt/23.1.57

The relationship between electron transport rate through PSII and photosynthetic oxygen evolution in cyanobacterial surface waterblooms was followed over a diel cycle. Chlorophyll fluorescence and photosynthetic oxygen evolution (PSOE) measurements were performed in a small-volume incubatin chamber on samples taken from a fish pond. Measurement of light-response curves showed a close to linear relationship between electron transport rates (ETR) and PSOE up to irradiancies of 800 quanta–2 s–1, except during mid-morning conditions. At higher irradiances, the relationship was non-linear. The regression coefficient κ (= PSOE/ETR) exhibited wide variation during the day (3.8–9.2), indicating that the use of ETR as a measure of PSOE in cyanobacterial waterblooms should be approached with caution. The involvement of alternate oxygen-consuming electron transfer pathways is discussed as a possible explanation for this discrepancy.