434 J. L. Tiwari et al. 



chironomids (RB830-RB833) and is also hydrolyzed by bacteria (RB103). 

 Some detrital carbon is lost by leaching of U-DOC and R-DOC (RB404 

 and RB405). A fraction of benthic detritus is also lost to refractory 

 particulate detrital carbon (RB403), which is one of the food sources for 

 bacteria (RB107). 



U-DOC leaks from algal cells and is secreted by chironomids in the 

 form of mucus. However, not all of the biomass removed by the death of 

 living organisms is transferred to the detrital pool. A constant fraction of 

 this dead material, the value depending upon the species, is also leached 

 into the U-DOC pool. This U-DOC is the major food source for the 

 bacterial population of the sediment. 



R-DOC is the second major food source for the bacteria. Leaching 

 from the detrital material and exchange from the planktonic system are 

 two inputs to this pool. 



Respiration of all living organisms contributes towards the total CO 2 

 concentration. (For further details of the processes and their equations see 

 Tables 10-2 and 10-3.) 



PLANKTONIC CARBON FLOW MODEL 



One of the important features of the Barrow ponds is the existence of 

 a shallow water column (average depth of 20 cm or less) that is well mixed 

 by the wind. This characteristic allows us to simplify the mathematical 

 models of the planktonic system. Thus, the vertical distribution of 

 organisms and nutrients in the water column can be disregarded and the 

 dynamics of the system can be adequately represented by ordinary 

 differential equations. The low number of species in the ponds enables us 

 to model the total ecosystem with fewer equations than a temperate pond 

 model would require. The computer simulation of these equations and the 

 estimation of their parameters are also made easier by the fact that there 

 are fewer species. 



A diagrammatic representation of the plankton system is given in 

 Figure 10-2. A list of all the processes associated with the planktonic 

 system is given in Table 10-7. The c's in the equations are the parameters 

 of the rate processes and are defined in Table 10-8. 



Primary Producers 



Algae and two species of vascular plants are the primary producers in 

 these ponds (see Chapter 5). Although there are a number of species in the 

 algal population, all are grouped together and considered as a single state 

 variable. Other models (e.g. Lehman et al. 1975) have broken up the algal 



