marshes are common along the east coast. 

 The exchanges determined by these 

 morphologies would be enhanced by 

 increased tidal amplitude or increased 

 freshwater input. It seems logical that 

 the first type of salt marsh would 

 normally have restricted export of organic 

 matter, while the other two would be 

 characterized by a much greater tidal 

 export. 



The age of a marsh may have a 

 significant influence on its behavior as 

 an exporter of organic detritus. A marsh 

 eventually fills its basin to the high 

 tide level and acts as a sediment sink 

 only in relation to the rise in sea level. 

 For example, the Great Sippewissett Salt 

 Marsh exports suspended particulate 

 organic carbon through the marsh creek to 

 Buzzards Bay while the younger Flax Pond 

 Marsh shows net import of suspended 

 particulate organic carbon from Long 

 Island Sound (Table 7). Houghton and 

 Woodwell (1980) indicate that there is a 

 large export of litter in the form of dead 

 Spartina stems from Flax Pond, principally 

 at times of storms. As Dow (1982) points 

 out, "Even systems which import organic 

 carbon to marshes, based on sampling 

 of selected tidal cycles, can become 



exporters when catastrophic events are 

 considered. " 



The significance of organic carbon 

 export must be considered in the context 

 of the coastal zone it reaches. Nixon 

 (1980) emphasized this, concluding that 

 the export of organic carbon "may provide 

 a . . . significant fraction of the open 

 water primary production in many areas of 

 the South . . . but it does not appear to 

 result in any greater production of . . . 

 fish than is found in other coastal areas 

 without salt marsh organic supplements." 

 Nixon was writing about production on a 

 regional basis. On a local basis, 

 enhancement of production can be important 

 to the population of a small area. The 

 contribution to the total fish catch in 

 Massachusetts of a small port where all of 

 the fishing is inshore from small boats 

 might be almost insignificant. While the 

 most valuable portion of the State catch 

 comes from the Georges Bank, that local 

 catch may be very important to the 

 citizens of the small port and essential 

 to their economy. An inshore fishery in 

 Massachusetts may be marsh- and estuarine- 

 dependent even though the offshore fishery 

 is totally independent of these coastal 

 features. Recreational fishing is almost 



Table 7. Comparison of age and properties of two northeast United States salt marshes 

 (Valiela 1982). 



Age and properties 



Age of marsh (yr) 

 Indicators of maturity: 



Average accretion rate (mm/yr) 



Expanding part of marsh 



Established part of marsh 

 (Accretion/net production) x 100% in terms 



of carbon 

 % of area non-vegetated 



% of area covered by tall Spartina alterni flora 

 Average aboveground standing crop of 



S. alterniflora (g/m 2 ) 

 % of area in high marsh 

 Number of higher plant species 



Flax Pond 

 Marsh 



Great 

 Sippewissett 

 Marsh 



180 



1.5-37 

 2-6.3 



37 

 47 

 37 



975 



7 



13 



2,000 



14 

 1 



5 

 37 

 18 



350 

 18 

 22 



45 



