HR: 0800h
AN: OS11B-0504    [Abstracts]
TI: Diel Cycle of Photosynthetic Electron Transport and Fluorescence Characteristics in Natural Phytoplankton Communities.
AU: * Kolber, Z
EM: zkolber@mbari.org
AF: Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, CA 95039,
AU: Klimov, D
EM: klimov@mbari.org
AF: Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, CA 95039,
AB: Phytoplankton photosynthetic performance is strongly controlled by the daily irradiance cycle. The most pronounced effects are the photoinhibition of photosynthetic activity in the morning and noon hours, and the development of non-photochemical quenching throughout the day. These two effects are extensively investigated as they significantly diminish the daily production rates. Less obvious, but equally important are the daily changes in the kinetics of rate-limiting electron transport within Photosystem II and Photosystem I of the photosynthetic apparatus. Using a fast repetition rate (FRR) fluorometer operating in the continuous flow-through mode in the Eastern Tropical Pacific, we observed theses rates to decelerate by a factor of five during the night, but recovering to a full speed just before the dawn. We characterized the effects of these changes on the photosynthetic performance of phytoplankton by continuously recording the fast light curves (variable fluorescence versus irradiance relationship). Besides controlling photochemistry, these changes strongly affect the chlorophyll fluorescence yield, especially when measured with a multiple turnover excitation. We will discuss how the knowledge of these rate-limiting steps may improve the fluorescence-based estimates of photosynthesis and chlorophyll biomass.
DE: 4294 Instruments and techniques
DE: 4852 Photochemistry
DE: 4853 Photosynthesis
DE: 4855 Phytoplankton
DE: 4894 Instruments, sensors, and techniques
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting