The results of studies of the extensive, unpolluted estuaries at Sapelo 

 Island, Georgia, indicate that the following factors are responsible for 

 high productivity: (1) ebb-and-flow water movements resulting from tidal 

 action; (2) abundant supplies of nutrients; (3) rapid regeneration and con- 

 servation of nutrients due to activity of microorganisms and filter feeders; 

 (4) three types of primary production units (marsh grass, benthic algae, 

 and phytoplankton) , which insure maximum utilization of light at all 

 seasons; and (5) year-round production with successive crops. These factors 

 are discussed and illustrated by data obtained by various workers at the 

 University of Georgia Marine Institute. (A. A. and excerpt) 



Keywords: estuaries, primary productivity, high productivity factors, 

 Georgia 



II-A-8 



Keefe, C.W. 1972. Marsh production: 

 University of Texas Contributions 



a summary of the literature, 

 in Marine Science 16:163-181 



The paper summarizes the literature on both inland and coastal marsh 

 primary production. Discussions of production measurements, factors 

 influencing marsh production, nutrient content of marsh plants, and 

 energy flow are presented. The author points out that extensive work 

 has been done to determine net primary production and to describe the 

 reasons for high marsh production compared to production in terrestrial 

 communities. 



The physical environment of the marsh is used to advantage by the 

 marsh plants. Hybrid vigor, leaf orientation, long growing season, 

 abundant water, and other factors are important for high production. 

 Salt marsh plants support two food webs. The first web is composed of 

 primary consumers that feed on the living marsh plants. The consumers 

 of the second web feed on the plants as detritus, both on the marsh 

 floor and in the estuary. The populations of consumers supported to 

 some extent by detritus are large and would be reduced by almost 50 

 percent if there were no input of detritus from salt marsh production. 



The paper suggests that there is still a great deal of primary research 

 that needs to be done, particularly with respect to the relative contri- 

 bution of marsh detritus to freshwater ecosystems and to complex salt- 

 water ecosystems of the Chesapeake Bay type. (B.W.) 



Keywords: primary productivity, food chain, detritus, marsh plants 



31 



