CHAPTER 6. SALT MARSH VALUES AND INTERACTIONS 



6.1 VALUES 



For some decades, salt marshes have 

 been considered or known to be valuable 

 for a number of reasons. They are 

 aesthetically pleasing for their open 

 coastal spaces and attractive expanses of 

 grasses. They are also valuable as 

 habitat for shore birds and waterfowl, and 

 as refuges and nursery areas for many 

 kinds of small and young fishes; these 

 values are associated with the 

 exceptionally high productivity of the 

 regularly flooded intertidal wetlands. 



Marshes are valuable to the public as 

 a whole, to those who harvest fish and 

 shellfish, and, of course, to those who 

 own the marshes. To some owners, the 

 principal value of a marsh is as a piece 

 of real estate, which often means they 

 either fill in the marsh for building or 

 dredge it for boating. But, aesthetic 

 values can also be important for the owner 

 directly. For example, in 1965 people in 

 New England were willing to buy salt 

 marshes for from $100 to $1,000 an acre 

 (as much or more than they would have had 

 to pay for poor farmland) just to acquire 

 the view, access to the water, or "a place 

 to fly a kite," with the knowledge that 

 the buyers could make no other appreciable 

 use of the "land" (Mass. Reporter 1976). 

 With these facts in mind, we can look at 

 the present situation with regard to those 

 general values of wetlands. 



6.2 MARSH EXPORTS 



There is still considerable interest 

 in the question of outwelling of detritus. 

 In the 1962 description of energy flow in 

 a Georgia salt marsh, Teal estimated 

 export from the marsh surface of 

 approximately 40% of the marsh pro- 

 ductivity. While export estimates were 



extrapolated to the estuary, the author's 

 data actually referred only to export from 

 the grassy portions of the marsh to the 

 marsh creeks. 



Odum (1980) summarized evidence that 

 the export does go further than the marsh 

 creeks and that there actually is an 

 outwelling to coastal waters. Hopkinson 

 and Wetzel (1982) showed that the nutrient 

 and oxygen fluxes in a Georgia coastal 

 benthic ecosystem supported Odum's 

 conclusion. Direct measurement has shown 

 the same general level of export from 

 Great Sippewissett Salt Marsh as the 1962 

 estimate from the Georgia marsh. 

 Particulate carbon (detritus) equivalent 

 to 40% of the aboveground production is 

 exported from Great Sippewissett Salt 

 Marsh to Buzzards Bay (Valiela and Teal 

 1979). Prouse et al . (1983) indicated a 

 sizable export of plant material to 

 estuarine waters from marshes in the Bay 

 of Fundy. Schwinghamer et al. (1983) 

 demonstrated that salt marsh detritus is 

 widely distributed in the upper parts of 

 the Bay of Fundy. Nixon (1980) concluded 

 that available data indicate that the 

 total flux of organic carbon from salt 

 marshes is between 100 and 200 g C/m 2 /yr. 



The structure of a marsh system 

 affects its export-import role. Odum et 

 al. (1979b) have classified marshes into 

 three types according to their flow and 

 tidal exchange characteristics. The first 

 are those in which there is a restricted 

 tidal flow. The flow may be restricted by 

 a long and narrow exchange channel, by 

 natural sills with a depositional basin on 

 the marshward side of them, or by man-made 

 restrictions such as dikes with culverts 

 or bridges with a constricted channel for 

 the passage of tidal flow. The second 

 type includes marshes where the flow is 

 more open and unrestricted. The third has 

 completely free flow. All three types of 



44 



