PARENT SESSION

Symposium S5D Emerging techniques and systems
Wednesday September 1st, 2004 10:20 AM-12:20 PM Room 510A
Chair: Conrad Mullineaux
Co-Chair: Barry Osmond

Photoacoustics as a tool for probing environmental effects on photosynthetic energy storage in phytoplankton. Yulia Pinchasov¹, David Kotliarevsky², Zvy Dubinsky^*,1, David Mauzerall³, Osnat Chomsky¹, Jehuda Feitelson², ¹ Faculty of Life Sciences, Ramat Gan, Israel² Department of Physical Chemistry, Jerusalem, Israel³

ABSTRACT- In Nature conditions for the growth of phytoplankton rarely support their maximal potential doubling rates. The main rate-limiting factor determining the doubling rates of phytoplankters is photosynthesis. This key process is in turn controlled, and frequently limited, by the available light, by lack of essential nutrients, or by the presence of noxious pollutants. Any decrease in the rates of photosynthesis is associated with reduction in the efficiency of light utilization in that process. We present here the effects of photoacclimation, depletion of nitrogen, phosphorus and iron on the photosynthetic energy storage efficiency of phytoplankton, as measured by photoacoustics. Such effects have been documented extensively by other methods such as fluorescence yield, growth rate, carbon assimilation and oxygen evolution. However photoacoustics uniquely directly measures the energy storage efficiency of the photosynthetic process. We determined that efficiency, by this method, in phytoplankton species belonging to different taxa. Our results illustrate the power of photoacoustics as a tool in aquatic ecology and in the physiological research of phytoplankton. We also discuss the separate energy storage efficiency of the two photosystems under different conditions.

KEY WORDS: photoacoustics, photosystems, energy-storage-efficiency, phytoplankton