164 R. T. Prentki et al. 



TABLE 4-27 Particulate Organic Carbon during Runoff, 1973* 



Date # of samples Weir #1 Weir #6 



mean SD mean SD 



*Data are expressed as jUg C liter . 



Thus, the particulate material is composed of particles of all sizes and the 

 border between the DOC and POC is an arbitrary one that is defined by 

 the retention characteristics of the filter. The 984 H filter retains all 

 particles above 0.8 ^lm in diameter. For analysis, the filtered material was 

 oxidized in a chromic acid-sulfuric acid solution and the resulting color 

 change calibrated against glucose in a spectrophotometer (Strickland and 

 Parsons 1968). The POC was measured in two or three ponds twice weekly 

 from 1971 to 1973. 



Both the snowmelt and the runoff water were high in POC, especially 

 at the start of the thaw. Snow contained 1 124 Mg C liter"' at the beginning 

 of the melt. The runoff water (Table 4-27) from Weir no. 6 (see Figure 3-1 

 for location) had an average of 1187 /xg C liter"' in the first 5 days of the 

 melt season but this dropped to 436 during the next 4 days. A similar 

 pattern, though with lower concentrations, was measured for Weir no. 1 

 (the weir that passed large quantities of water). The same high 

 concentrations early in the year were also measured in Pond B during 1971 

 (Table 4-28). The yearly means, 769, 266, and 391 ^g C liter"' for 1971, 

 1972, and 1973 (Table 4-29), reflect the great differences from year to 

 year; these differences are unexplained. 



The POC is composed mostly of non-living material. Assuming that 

 algae are 5% carbon (of wet weight) and that bacteria contain 1 .2x 10 "* ^g 

 C cell " ', then only 5.3% of the POC was made up of algae and bacteria in 

 1971, 13.4% in 1972, and 9.9% in 1973 (see Chapter 5 for biomass data). 

 We have observed that the biomass of the organisms was about equal 

 during these 3 years and so the concentration of non-living organic matter 

 changed. 



The environmental or biological factors that control the 

 concentration of POC are not obvious in these ponds. As already noted, 

 there was no correlation between the POC and algal or bacterial biomass. 

 In addition, when a series of ponds was studied in 1971 (Table 4-29), there 

 was no correlation between the productivity and the POC. Attempts to 



