mangrove peat has a 6 13 value of minus 

 22. Because these values are dramatically 

 different from the values for sea grasses 

 and many algae, the possibilities for 

 using this tool in mangrove ecosystems is 

 excellent. Macko (1981) also suggested 

 the utility of using stable nitrogen ra- 

 tios for future mangrove food web investi- 

 gations; he reported 6 15 values of plus 

 6.0 to plus 6.5 for mangrove tissue and 

 plus 5 for mangrove peat. 



In reviewing contemporary knowledge 

 of energy flow in mangrove ecosystems, 

 three conclusions emerge. 



(1) We have a hypothetical framework 

 of mangrove energy flow of a qualitative 



nature. This framework appears to be 

 reasonably accurate although subsequent 

 developments, such as elucidation of the 

 reduced sulfur hypothesis, may require 

 some modification. 



(2) Measurements of the relative 

 importance of various carbon sources are 

 generally lacking. 



(3) Detailed measurements of energy 

 flow including the relative inputs of 

 different carbon sources are critically 

 needed. Technological difficulties, high 

 costs, and difficulties inherent in 

 transferring findings from one estuary to 

 the next present a major challenge to 

 estuarine ecologists of the future. 



39 



