Modeling 415 



Xi =time- dependent rate of change of algal biomass, 



Jf 602^ = rate of photosynthesis, 



■^1 = rate of burial of surface algal cells, 



xi = rate of loss of algal cells due to ciliates, 



X201 ° 



■x^ 1 = rate of loss of algal cells due to micrometazoans, 



a: 202 ° ' 



X 1 = rate of loss of algal cells to detritus due to death, 



A401 



^ ' X501 ^ ^^^^ ^^ '^^^ °^ ^'S^' '^^"^ ^^ U-DOC due to excretion, 



•^1-^ = rate of algal respiration, and 



•A602 



Xi to Afi = rates of loss of algal cells due to chironomids 



(tour cohorts). 



The state variables, rate processes, and constants of the two 

 submodels are identified by two types of algebraic symbols. This notation 

 avoids confusion and ensures easy identification of algae, bacteria, 

 detritus, U-DOC and R-DOC (refractory DOC) which are all state 

 variables of both benthic and planktonic systems. This dual notation 

 system was also helpful in developing these two identical but separate 

 computer programs for simulation studies. 



The state variables and constants of benthic submodels are denoted 

 by subscripted x and k, respectively (Tables 10-1 and 10-4). The 

 mathematical equations for the processes of this system are numbered 

 with the prefix RB (Table 10-3). The state variables of the planktonic 

 system are indicated by subscripted y and the constants bye. The process 

 equations of this submodel are numbered with the prefix RP (Tables 10-5 

 to 10-8). 



Abiotic Input Variables 



Light and temperature are the two abiotic input variables which are 

 driving the aquatic system. Based on the data of the past 4 years an 

 empirical periodic function of the following form was developed to 

 simulate the approximate light available for epipelic algal photosynthesis: 



/. = /oexp(-£'z) (8) 



where 



'' =irradianceat the depth z (cal cm"^ hr~^), 

 /o =water surface-incident irradiance (cal cm "^ hr~'), 

 E = vertical extinction coefficient as a function of organic color 

 in the water 

 = 2.4xl0-V502 



