CHAPTER FOUR 

 THE MARSH IN THE COASTAL BASIN 



flarshes are open ecosystems; that is, 

 they are not isolated islands out of touch 

 with their surroundings. Quite the 

 contrary, the main reason that they are of 

 particular interest to environmentalists 

 and conservationists is because they are 

 strongly coupled with surrounding 

 ecosystems. In Chapter 2 we say that the 

 main physical driving forces for marshes 

 are the upstream river and the downstream 

 ocean. Both are outside the marsh, but 

 the annual variation in river flow, the 

 periodic switching of its channel and 

 thereby its nutrients and sediment, and 

 the periodic variation in the gulf water 

 level and salinity all determine the 

 character of the marsh. Similarly, 



marshes are open biotically - they 

 contribute biologically to many other 

 ecosystems. Figure 65 illustrates these 

 couplings with other ecosystems: marsh 

 zone to marsh zone; marsh to estuary; 

 marsh/estuary to gulf, river and adjacent 

 uplands; and intercontinental couplings. 



COUPLINGS AMONG ECOSYSTEMS 



Intra-Basin Couplings 



The coastal basin can be viewed as a 

 set of coupled subsystems, for indeed the 

 marshes, bays and streams in the basin are 

 tightly coupled. A typical basin is 

 organized by the internal freshwater-salt 



MARSH ZONE 

 TO MARSH ZONE 



Figure 65. Conceptual diagram illustrating the coupling of delta marshes to 

 other ecosystems. 



79 



