Primary Producers 189 



obtained from these experiments were converted into hourly 

 photosynthesis rates from measurements of pH and alkahnity and 

 appropriate calculations (e.g., Vollenweider 1968). Duplicates of each 

 light bottle were run and the uptake values for a single dark bottle were 

 subtracted from the average of the light bottles. 



The seasonal course of the primary productivity closely followed the 

 chlorophyll and biomass curves (Figure 5-5). In some cases, for example 

 the increase in phytoplankton seen at the very end of August, the increase 

 in primary productivity appeared to precede the increase in chlorophyll 

 and in algal biomass. In general, the pattern was similar in all the ponds. 



At least three different patterns of photosynthesis rates over 24 hours 

 were seen in the ponds. These will be discussed in detail later when 

 photosynthesis-light relationships are taken up. Two of these patterns, one 

 with early morning and late evening peaks and one with a noon-time peak, 

 are clearly related to optimum and inhibiting light levels. One other 

 pattern (Figure 5-6), however, may also be related to the biomass of the 

 algae. Here, the low photosynthesis in the morning (1 130) may have been 

 caused by the low biomass at the same time (Figure 5-3). 



The algae from the detailed diurnal study (Figures 5-3 and 5-6) were 

 studied with track autoradiography. First, the algae were preserved with 

 acid Lugol's solution, settled, and a permanent slide made (Coulon and 

 Alexander 1972). Next, the slides were coated with photographic emulsion 

 (Rogers 1969); exposure lasted from 3.5 to 13 hours at 5°C. Development 



FIGURE 5-5. Rates of planktonic primary produc- 

 tivity in Ponds B and C, 1971. 



