Chemistry 127 



TABLE 4-20 A nmial Phosphorus Budget for Pond B 



mg P m "^ yr~^ (40% of input) is retained in lake sediments and individual 

 streams entering the lake annually supply 1 to 7 mg P m " of watershed 

 (deMarch 1975, 1978). Thus pool retention of phosphorus may be 

 characteristic of arctic water bodies. 



Phosphorus Cycling 



In this section we report data on the uptake and release of phosphorus 

 by planktonic and benthic animals and plants. The next section (Control of 

 Phosphorus), deals with the movement of phosphorus between the 

 sediment and the water. 



Details of all the methods are given in Prentki (1976); isotope 

 techniques for the plankton are also reported in Barsdate et al. (1974) and 

 for the plants in McRoy and Barsdate (1970). 



The seasonal picture of DRP concentrations is a chaotic one (Figure 4- 

 16a). The reason for this is that the DRP cycles very rapidly. Some 

 indications of this come from a series of DRP measurements in a pond 

 over 32 hours (Figure 4-17). The changes were greater than 2-fold and 

 concentrations appeared to increase when photosynthesis decreased 

 (Figure 4-18). Some of the water was also incubated for 3.0 hours in 

 plastic bottles in the ponds (Figure 4-17). The changes in these bottles were 

 almost exactly the same as those in the pond; this indicates that processes 

 in the water itself, rather than some advective or benthic process, caused 

 the changes. 



