of mixed species of grasses, rushes, and sedges and may be categorized 

 as salt flat, salt meadow, and irregularly flooded salt marsh commu- 

 nities. The regularly flooded Spartina alterniflora marsh common in 

 the south Atlantic coast and in the Louisiana deltas occurs in Missis- 

 sippi in rather limited patches, forming a narrow discontinuous band 

 in the low tide zones of river mouth banks and certain exposed beaches 

 fronting the Mississippi Sound. Except for one report on the primary 

 production of Juncus roemerianus marsh, there had not been any pro- 

 ductivity studies on the Mississippi marshes until this one was conducted. 



In this study, square-meter quadrat samples harvested monthly during 

 1971 to 1972 provided data on the species composition, standing 

 stock, and net primary aerial production of a salt marsh community in 

 St. Louis Bay Estuary, Mississippi. Although a total of 34 species 

 of marsh plants were identified, Juncus roemerianus , Spartina cynosuroides , 

 Scirpus americanus and Distichlis spicata were found to be the most 

 dominant in all the quadrats sampled. Maximum biomass of alive, dead, 

 and partially decayed plants was observed in July, August and January, 

 respectively. Total biomass obtained by reharvesting previously 

 clipped quadrats in various ages of regrowth revealed a seasonal 

 pattern of growth rate with a maximum during late summer. (G.S.) 



Keywords: primary productivity, Spartina , salt marshes, Mississippi 



II-B-12 



Odum, E.P., and M.E. Fanning. 1973. Comparison of the productivity of 



Spartina alterniflora and Spartina cynosuroides in Georgia coastal 

 marshes. Bulletin of the Georgia Academy of Science 31(1):1-12. 



The purpose of this paper is to compare the net primary production 

 of the salt marsh Spartina alterniflora with the fresh or brackish 

 marsh Spartina cynosuroides in an optimum habitat for each; or, in 

 other words, to compare production in areas where each species grows 

 most vigorously. The general theory being tested was that given a 

 favorable tidal irrigation "energy subsidy," stands of S. alterniflora 

 would be able to equal or exceed the primary production of stands of 

 S. cynosuroides . 



As a result of the research, net production of S. alterniflora was 

 estimated to be two to three times that of S^ cynosuroides . The paper 

 further determined that the productivity of S. alterniflora can be 

 very high under conditions of high salinity, exceeding that of a related 

 species growing in fresh water, wherever there is abundant, daily tidal 

 flow. Thus, the paper concluded that such tidal action does provide 

 an "energy subsidy" that reduces the metabolic cost of coping with 

 the stressful environment. In this sense, salt marshes in Georgia 

 convert "tidal power" into organic food. (L.H.) 



Keywords: primary productivity, Spartina alterniflora , Georgia 



41 



