Decomposers, Bacteria, and Microbenthos 361 



that the amount of moisture is a primary controlling factor. Indeed, at 

 Barrow Carex aquatilis litter (yellow leaves) lost around 15% of their 

 weight per year when incubated in the air (Flanagan and Bunnell 1980). 



Other experiments carried out in 1970 confirmed that about half of 

 the first year decomposition of green leaves was abiotic leaching. These 

 experiments were made with fresh green Carex, dried at 65°C and placed 

 both in nylon mesh bags (1.5-mm openings) and in plastic Whirl-Pak bags 

 with pond water plus 100 ppm HgCh. After 33 days the leaves in the six 

 mesh bags had lost 46% of their original weight while those in the plastic 

 bags had lost only 24.1%. Since the HgCli treatment prevents microbial 

 growth, the plastic bag treatment is taken as the abiotic loss. Therefore, we 

 can say that 24% of the total weight loss in the mesh bags was caused by 

 abiotic factors such as leaching and mechanical breakdown and 22% was 

 caused by biological activity. Similar results were obtained in 1972. 



Timecourse of Decomposition 



A decomposition budget may be calculated in terms of loss over time 

 from a single year's production of Carex litter in Pond J (Table 8-9). It 

 was assumed that the detritus that entered the water at the beginning of the 



TABLE 8-9 Annual Input, Decomposition, Loss by Leaching, Hydrol- 

 ysis, and Trituration o/ Carex aquatilis Detritus in Pond J^ 



1 —2—1 



Values in g C m yr , % of total for age-class in parenthesis. 



Estimated macrophyte detrital input (based on 1971 macrophyte input in Pond J). 



20 iJxn mesh litterbag dry weight loss during ice-free period. 



Whirl-Pak dry weight loss. 



Whirl-Pak dry weight loss not recovered as DOC 2 weeks after thaw. 



Whirl-Pak dry weight loss recovered as DOC 2 weeks after thaw. 



20 iJm mesh litterbag dry weight minus total DOC loss. 



Loss due to trituration from 20 jUm mesh litterbag over the winter period. 



Estimated from sediment leach in center of pond. 



