368 J.E. Hobbieetal. 



value for a biologically mediated process (Table 8-12). The measurements 

 in 1973, when the incubations were made in the field with a minimum of 

 disturbance, resulted in an average value of 1.6. While the average is 

 believable, the amount of variability in the measurements (Table 8-12) is 

 large and unexplained. As noted earlier, the Qio estimated in this way 

 measured not only the respiration but also any increases due to changes in 

 the diffusion of CO 2 from below the surface layers and from the sediment 

 to the water. 



In the pond, as well as in the experiments, the respiration rate was 

 correlated with temperature. However, over a whole season the effective 

 temperature was altered by effects of different amount of photosynthesis, 

 etc. As a result, the correlation of respiration rate with average daily water 

 temperatures was only significant at the 5% level (r = 0.368, n = 40). 



Other workers have also noted a correlation between temperature and 

 sediment respiration. This correlation was noted over a 24-hour cycle by 



TABLE 8- 1 2 Experimental Qio's for Sediment CO 2 - C Flux 1972, 1973 



Date 



29-30 June 1972 



21 - 22 August 1972 



25 June 1973 



26 June 1973 



2 July 1973 



3 July 1973 

 20 August 1973 



26 August 1973 



Average 1972 

 Average 1973 



Average of four different determinations made over a 24-hour period. 



