COASTAL MARSH ECOSYSTEMS 

 PRODUCTIVITY IN COASTAL MARSHES 



A marsh means many things to many people depending on the point of 

 view of the individual. To some it is an evil smelling eyesore, a 

 treacherous bog infested with mosquitoes. To others it represents a 

 piece of valuable real estate with great aesthetic value. To many others, 

 hunters and naturalists, it is a haven for a variety of wildlife. And 

 recently, to a growing body of scientists, it represents a dynamic 

 system of unique biological, geological and ecological interest and 

 importance (Matthiessen 1962). 



Regardless of how a marsh is described, the fact remains that it is 

 one of the most productive types of natural ecosystems in the world. Marsh 

 vascular vegetation, such as grasses, rushes, and sedges, produces an 

 enormous amount of organic material that enables marshes to equal or exceed 

 the productivity of most terrestrial communities of comparable size, even 

 some of the most intensively managed cropland. A great quantity of litera- 

 ture, of both a scientific and non-scientific nature, has been published 

 during the last decade on the subject of tidal marshes. Much of this 

 literature extols the biological productivity of the marsh environment 

 and emphasizes the important role this type of environment plays in the 

 fertility of estuarine and coastal marine ecosystems. 



The high fertility of tidal marshes is due basically to physical 

 phenomena and biological processes unique to marsh estuaries (Odum 1961). 

 Nutrient-rich estuarine waters periodically bathe these intertidal zones. 

 Dissolved organic nutrients (e.g., phosphates and nitrates) and detrital 

 materials enter the marsh-estuary from inflowing rivers. The saltwater 

 wedge pushed along the estuary bottom by the incoming tide brings in other 

 nutrients of near-shore marine origin. Currents and tides circulate and 

 recirculate fresh and salt water, thus distributing, and to a certain 

 extent trapping, dissolved and suspended matter. Deposition of suspended 

 materials and flocculation of dissolved substances fertilize the marsh 

 substrate. The plant life of the marsh, which flourishes in the nutrient- 

 rich waters, is thus geared to year-round high production. This plant life 

 includes vascular vegetation (grass, rush, and sedge), benthic algae 

 (diatoms), epiphytic and mud-encrusting algae, and submerged grasses on 

 intertidal sediments. 



Vascular plants growing in marshes periodically die and enter the 

 aquatic food chain in the form of particulate detritus, which is laden 

 with bacteria and other microorganisms. During low tides, runoff waters 

 and interstitial water seeping out of the mud transport high concentrations 

 of dissolved substances such as silica, phosphate, bicarbonate, and ammonia. 

 The estuarine waters are therefore enriched in return by the high oroduc- 

 tion processes on the marshes. 



