ENERGY FLOW IN THE SALT MARSH ECOSYSTEM 



by 



John M. Teal 

 University of Georgia 



In order to evaluate the role of the salt marsh in the estuary -mar sh sys- 

 tem along the Georgia coast and to understand the trophic relationships of the 

 various organisms living in the marsh, I have, with the admittedly incomplete 

 data available, constructed an energy flow diagram for the marsh. The diagram 

 in Figure 16 shows the energy flow in kilocalories per square meter per year and 

 was constructed in the following manner: 



The value for total light energy was taken from Kimball (1929) and divided 

 equally between the two primary producers on the marsh, Spartina alterniflora , 

 and the algae living on the mud surface. The values represented by question 

 marks have not been measured. Data for Spartina production were taken from 

 measurements made by Ragotzkie and Smalley of the standing crop of grass in 

 the Sapelo Island marshes. The data for the algae were taken from the paper by 

 Pomeroy in this publication. The assimilation and transformation of energy by 

 insects was taken directly from the paper by Smalley. 



The marsh grass that is not eaten by insects is changed into detritus by 

 the action of bacteria. Data for the calculation of the magnitude of this step 

 were taken from Burkholder and Bornside (1957). Fifty-six percent of the marsh 

 grass is composed of material available for bacterial metabolism and of this, 

 20 percent is built into bacterial substance while 80 percent is respired. This 

 bacterial action does not all take place in the marsh, but also in the waters flow- 

 ing in and out of the marsh. A part of the detritus energy is extracted from the 

 energy flow as far as the marsh animals are concerned by the feeding of aquatic 

 forms. There are errors in this calculation due to incomplete use of the avail- 

 able Spartina by the bacteria and to turnover within the bacterial populations. 



Bacteria, detritus and algae form the food of the fiddler crabs, snails, 

 nematodes and mussels. The fiddler crabs' respiration was measured through- 

 out the year at the temperatures to which the crabs were acclimated. Multiply- 

 ing population size be respiratory rate showed that an average of 133 KC/m'^/yr 

 was respired by the crabs. Since crabs grow to adulthood in a out one year, 

 production was taken to be equal to the maximum standing crop, an average of 

 Z7 KC/m''/yr. The respiration of the snail population, 72 KC/m''/yr is from 

 the work of Smalley and the production of 8KC/m^/yr was calculated on the 

 assumption of a 10 percent growth efficiency arrived at by combining theoret- 

 ical considerations with Smalley' s measurements of the growth of young snails. 

 Using the data of Kuenzler for respiration and population size of the mussels and 

 assunning a complete population turnover in one year, I found the mussels re- 

 spired 49 KC/m^/yr and had a production of 20 KC/m^/yr. From some prelim- 

 inary nematode samples, and using data from Nielson (1949) for respiration and 

 turnover rate, I calculated respiration of 43 KC/m^/yr and a production of 



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