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Photoinhibition of benthic diatoms: a limiting factor of the productivity of estuarine intertidal flats
Coordinator - João Serôdio
Programme - Programa PESSOA 2012-2013
Execution dates - 2012-01-01 - 2013-12-31 (24 Months)
Funding Entity - FCT
Funding for CESAM - 5000 €
Total Funding - 13200 €
Proponent Institution - Universidade de Aveiro
Participating Institutions
Université de La Rochelle, França

Marine biological productivity is largely based on the photosynthetic activity of diatoms, microalgae that account for 40% of global oceanic carbon fixation. In estuaries and shallow coastal zones, up to 50% of the primary productivity is due to microphytobenthos (MPB), the diatom-dominated benthic communities that form dense biofilms on intertidal flats. The high photosynthetic performance of MPB under the extreme conditions of the intertidal habitat is considered to be due to highly efficient photoprotective processes that allow the cells to withstand direct exposure to solar irradiance during the prolonged low tides. Exposure to high light causes photoinhibition, irreversible damages to the photosynthetic apparatus. Under the nutrient-replenished conditions of estuarine sediments, photoinhibition is expected to represent a major cause of limitation of photosynthetic productivity. The success of MPB in coping with high light has long been attributed to two types of photoprotective processes: the xanthophyll cycle, a physiological mechanism through which energy-dissipating pigments are formed under high light; vertical migration, a unique mechanism amongst photoautotrophs, which enable diatoms to avoid exposure to photoinhibitory light conditions. However, studies have been centered on characterizing the operation of photoprotective processes, while little is actually known on the actual photoprotective effects on avoiding photoinhibition. Here we propose to quantify the occurrence of photoinhibition through the combined use of specific inhibitors of the main photoprotective processes and a novel use of imaging-fluorometry. This new methodological approach will enable to test simultaneously a large number of experimental treatments on undisturbed biofilms. The combination of the equipment and expertise of the different teams will contribute towards a better understanding of the processes underlying the regulation of photosynthetic processes in benthic diatoms. This will yield important information on basic knowledge on diatom photobiology and will, ultimately, help explaining the high productivity of estuarine intertidal areas.

Members on this project
João Serôdio


CESAM Funding: