Conclusion and Synthesis

Abstract

Figure 16-1 shows the biomass and production pyramids for the Lake Lanao plankton system plus the transfer efficiencies between trophic levels. Transfer efficiency between the solar source and the phytoplankton community is relatively high in view of the low nutrient base in Lake Lanao. The summary of IBP data given by Brylinsky and Mann (1973) shows an average value of 0.4% for transfer of photosynthetically available solar energy (PAR, ca. 350–700 nm) to gross production. In terms of net production, which is of more interest here, this would be 0.2 to 0.3% based on PAR or about 0.1 to 0.15 based on total solar radiation. The percentage reported in Figure 9-1, which is based on total radiation, is obviously quite high. Efficient nutrient cycling by the mechanisms described in Chapter 3 is in large part responsible for minimization of severe nutrient depletion and consequent maintenance of high transfer efficiency at the first trophic level (Lewis, 1974).