224 



WOODWELL, RICH, AND HALL 



TABLE 1 



AREAS OF ESTUARY AND ESTUAR1NE MARSH IN THE UNITED STATES* 



•Source: National Estuarine Pollution Study, Report of the Secretary of the Interior to the U. S. Congress, 

 March 1970. 



THE FUNCTION OF ESTUARIES 



Data in support of a comprehensive appraisal of the function of estuaries are 

 also fragmented and incomplete. The most comprehensive studies of function 

 have been made at Sapelo Island, Ga., and in the bays along the Texas coast. 



These and other studies, few in number, lead to the contemporary view that 

 estuaries are highly "productive" of both fixed carbon and fish. The assumption 

 has seemed reasonable that estuaries serve as centers of "outwelling" of nutrients 

 and fixed carbon into the coastal ocean. 1 1 Their contribution to fisheries 

 through spawning and nurture is widely recognized, 1 2A but data in support of 

 their net role in the biospheric carbon cycle are limited. 



One interpretation of the major routes of carbon movement in estuaries 

 appears in Fig. 2, which was drawn specifically for Flax Pond, an estuarine 

 marsh on the north shore of Long Island. Major exchanges occur here with Long 

 Island Sound, with the uplands, with the sediments, and with the atmosphere, 

 which are the four sides of the diagram. Within the estuary, there is net fixation 

 of carbon by the Spartina marsh, by phytoplankton, benthic algae, and other 

 plants. A major fraction of this fixed carbon enters detritus pathways in various 

 forms, including "dissolved" and particulate organic matter (DOM, POM), and 

 much of this ultimately participates in the complex oxidation— reduction 

 exchanges of the sediments. But the possibility exists that the carbon flux of 

 estuaries is dominated by large exchanges of fixed carbon with the land and with 

 coastal waters. In Flax Pond the major exchange is with Long Island Sound. 



The potential importance of large exchanges of fixed carbon between 

 estuaries and other ecosystems nearby makes interpretation of the function of 



