CARBON IN ESTUARIES 



233 



200 



■100 



JUNE 



JULY 



AUG. 



SEPT. 



OCT. 



NOV. 



DEC. 



Fig. 4 The flux of dissolved organic carbon (DOC) and total C0 2 through the 

 Flax Pond channel in 1971. Losses from Flax Pond are indicated below the 

 zero line. 



Sedimentation 



Some fraction of the fixed carbon entering estuaries participates in 

 exchanges with sediments, driving segments of such important mineral cycles as 

 S and N, discussed elsewhere in this symposium. 



Accumulations of fossil fuels, peat, and shallow organic sediments leave little 

 question of the importance of sedimentation in removing carbon from 

 circulation, at least temporarily. The rate of sedimentation is measurable in part. 

 In the marsh at Barnstable, Mass., the rate of accumulation of peat was measured 

 by Redfield and Rubin, 19 as indicated in Fig. 5. A change in the rate of rise of 

 water against the land accounts for the shift in slope of the curve and emphasizes 

 the importance of this factor in determining storage of C. In the modern world 

 we have seen many examples of how rapidly eutrophication of estuaries and 

 other shallow-water bodies can build substantial accumulations of organic 

 sediments locally. Worldwide, however, it seems reasonable to assume that 

 water-level fluctuations are more important in affecting the rate of accumulation 

 of C in estuarine sediments than other factors. The maximum rate at which C can 



