319 in eutrophic polar waters (E5) in winter. Finally, the smallest range of variation, just ca 1.3 times, is characteristic of the radiationless nonphotochemical conversion selleck screening library of pigment excitation energy into heat. Quantum yields
of heat production <ΦHze><ΦH>ze (see Figure 6c, and the data in Annex A3) vary from ca 0.678, a value typical of eutrophic waters (E5), to ca 0.887 in oligotrophic tropical waters (O1) and (O2) in summer. It is also worth having a look at the dependence of the separate aspects of the pigment excitation energy budget on (1) the surface chlorophyll a concentration Ca(0), i.e. the trophic index of the water; (2) climatic zone and season. These relationships can be briefly summarized as follows: • The trophic index is the factor most strongly differentiating the aspects of the overall energy budget recorded in nature. All the plots in Figure 6 show that this factor far outweighs any influence due to seasonal or climatic variation. This effect of the
trophic index is of course different with respect to the various aspects of this budget. Trophic differences alter the amount of pigment excitation energy expended in the euphotic zone on chlorophyll a fluorescence by nearly two orders of magnitude, on photosynthesis by about one order and on heat production by a factor of ca 1.2. The Selleck PD-166866 nature of the dependence of these aspects of the budget on surface chlorophyll a concentration Ca (0) is also different. The quantum yield of photosynthesis <Φphze><Φph>ze (see Figures 6b)
rises with increasing Ca (0) across almost the whole range of variability. Only in supereutrophic basins E6 is there a slight drop in this quantum yield, which is undoubtedly due to the very much smaller thickness of well illuminated water in the euphotic ID-8 zone in which photosynthesis takes place. The quantum yields of chlorophyll fluorescence <Φflze><Φfl>ze and heat production <ΦHze><ΦH>ze display opposite tendencies, however: <Φflze><Φfl>ze decreases exponentially with the increase in Ca (0) over the entire range of this trophic index (see Figure 6a), and likewise, the yield of heat production <ΦHze><ΦH>ze decreases with rising Ca (0) over a wide range of trophic types (see Figures 6c). The only slight divergences from this regularity occur in ultra-oligotrophic basins (O1 and O2) and in supereutrophic ones (E5 and E6), where <ΦHze><ΦH>ze shows a slight tendency to increase with rising Ca(0). Previously derived by the authors and modified for the purposes of the present work, the model descriptions of the three principal processes in which the excitation energy of marine phytoplankton pigments is deactivated, that is, the natural fluorescence of chlorophyll a, photosynthesis and heat production, were used to calculate the quantum yields and energy efficiencies of these processes in sea waters of different trophic types, in different seasons and climatic zones, and at different depths in the sea.