Chemistry 129 



4.0 



FIGURE 4-18. Primary 

 productivity in 3-hr bottle 

 incubations, 30 June 

 through 1 July 1972. The 

 water was taken from Pond 

 B, 3.1 \jig phosphate-P 

 liter^ was added, and the 

 bottles were incubated in 

 the pond. The lines at each 

 point indicate the range of 

 duplicate samples. 



If the changes of DRP in the water are linked to photosynthesis, then 

 the ratios of uptake of C to P are extremely low. For example, between the 

 hours of 1200 and 1600, the photosynthesis was about 8 Mg C liter"' while 

 the change in DRP was 1.5 Mg P liter"' (ratio is 5.3: 1). If the phosphorus 

 is being incorporated into all structures, then a (weight) ratio of 40:1 is 

 expected. Therefore, much of the P is either being excreted or is being 

 stored (luxury uptake). 



Luxury consumption of phosphorus, however, did not account for any 

 of the phosphorus uptake. Luxury storage was monitored throughout the 

 experiment by following cellular surplus phosphorus (SP) concentrations 

 (method of Barsdate et al. 1974). The SP procedure extracts the 

 polyphosphates which constitute the luxury storage pools for P in algae 

 (Fitzgerald and Nelson 1966, Rhee 1972). Throughout the duration of the 

 experiment, SP averaged 0.7 ^g P liter"' and increased from 0.63 ng P 

 liter ~ ' at the beginning of the experiment to 0.98 /zg P liter ' at the end. 

 For the period from 1200 to 1600 on 1 July, SP decreased by 0.15 ^g P 

 liter"' so the luxury storage can not account for the loss of 1.5 ^ig DRP 

 liter"'. 



The radioisotope ^^P was used to investigate further the planktonic 

 rates of cycling. The uptake rates were calculated from the initial 

 exponential change in the concentration of ^^P04 " (Barsdate et al. 

 1974). For 17 measurements in the ponds we observed uptake rates of 13 



