IV-A-5 



Day, J.W., Jr. 1973. Some trophic relationships of marsh and estuarine 

 areas. Pages 115-135 i£ R.H. Chabreck, ed., Proceedings of the coastal 

 marsh and estuary management symposium. Louisiana State University, 

 Baton Rouge. 



While true marine ecosystems are usually based on a phytoplankton 

 energy source, estuaries usually have a more diverse group of primary 

 producers which allows a more complex structure and much higher 

 production and average standing crop biomass at all trophic levels. 

 The most striking single difference in estuarine systems is the fact 

 that some contain emergent vascular plants that utilize atmospheric 

 carbon and oxygen directly without the limitations placed on utilization 

 of these materials in aquatic systems. This results in a higher order 

 of production within estuaries that have important amounts of marsh 

 or mangrove swamp as components of the system. The production from 

 emergent plants is the source of most detrital material that gives 

 the familiar detrital -based structure to estuarine food chains. 

 Detritus is also often abundant in estuaries from exogenous sources, 

 particularly larger rivers that carry organic matter from inland 

 drainage basins into the system. 



Important factors in the trophic relationships are: (1) Organic 

 detritus; (2) tides and other currents for moving organisms, food and 

 other materials; back-and-forth movement of the tide superimposed on 

 river currents, a characteristic of most estuaries; and (3) the large 

 number of seasonal (and daily) migrants. Many organisms use the 

 estuary at times when food is abundant and during fast growing stages 

 of their life cycle. More sensitive times of the life cycle are 

 spent under stable conditions, often offshore. 



Overall estuarine productivity will be maximum when: (1) The 

 estuary is formed by a major river system; (2) it is located in or 

 near the subtropical zone; (3) it is situated on a wide, shallow con- 

 tinental shelf so that there is a large area of intertidal land; 

 (4) the drainage basin of the river system is an old geologic province 

 and is large compared to the estuarine area. Large volumes of sus- 

 pended materials, nutrients, and detritus will be carried to the 

 estuary; (5) the climate of the drainage basin as well as the estuary 

 is not arid; and (6) there is a low to moderate coastal energy regime. 

 (G.S.) 



Keywords: trophic reltionships, coastal marshes, estuarine areas, 

 primary productivity, mangroves, U.S. general 



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