Phytoplankton cells draw the energy to drive photosynthesis from the sunlight entering the sea water. The quanta of this light are selectively absorbed by the various pigments contained in these cells. PD98059 concentration However, only part of the energy activating the pigment molecules as a result of light absorption is expended during photosynthesis; the remainder is deactivated in two other processes, namely, fluorescence, and radiationless nonphotochemical quenching, which generates heat (Butler and Kitajima, 1975, Weis and Berry, 1987, Kolber and Falkowski,

1993 and Ostrowska, 2001). The objective of the present work is to investigate and model the distribution of the activation energy of phytoplankton pigment molecules among these three processes under the many and various conditions prevailing in the

marine environment. Photosynthesis itself is, of course, the most important of the three processes, its yield being governed by environmental factors determining their utilization of this energy. Our models describe the distribution of this energy by comparing the quantum yields and energy efficiencies of the three processes. These yields/efficiencies are complex functions of environmental state parameters. Our models take these relationships into account and enable the distribution of the pigment excitation energy to be calculated for the various this website typical conditions obtaining in the waters of the World Ocean. The light-absorbing pigments in phytoplankton cells can be classified into two groups. One comprises the photosynthetic pigments, PSPs (the main abbreviations and symbols used in the text are listed in Annex 1), contains chlorophyll a and a set of pigments accessory to chlorophyll a. These accessory pigments absorb light from different spectral bands, and the energy thereby acquired drives the processes contributing to the photosynthesis

of organic matter. Plant cells form PSPs in order to make optimal use of the light spectrum available in their particular living environment. The other group consists of Methane monooxygenase photoprotecting pigments (PPPs), which protect chlorophyll a at the photosynthetic reaction centres from an undesirable excess of light energy (e.g. Bartley and Scolnik, 1995, Majchrowski, 2001, Pascal et al., 2005 and Woźniak and Dera, 2007). Figure 1 shows in a simplified way how these pigments absorb this energy and how it is distributed among the various processes. Excited PPP molecules are mainly deactivated as a result of radiationless transitions, during which they release their excitation energy EAPPP to the surroundings in the form of heat EH1.