Some biogeochemicals , particularly carbon, may be present in abundance and 

 readily available from the environment. Storage of these elements in peat 

 does not seriously affect their availability as new sources are continually 

 formed. Figure 8-6 illustrates the cycling of carbon in a palustrine wetland. 

 The supply of other biogeochemicals may be affected significantly when they 

 are incorporated into peat, depending upon: 



1. How much of the element is locked up in a given quantity of peat; 



2. How fast the peat is being formed; 



3. The rate at which a new supply of the element enters the system 

 (Moore and Bellamy 1974). 



Shortages of phosphorus and nitrogen for plant nutrition are likely to develop 

 in palustrine areas where rapid peat deposition occurs. These areas are 

 isolated from nutrient-bearing groundwaters by the peat "barrier." Plants 

 growing on peat deposits are largely dependent upon rainwater (or sources such 

 as dust and captured insects) for nutrients; consequently their growth is 

 limited. The nitrogen budget is of particular interest in the study of palus- 

 trine biogeochemicals. Elemental nitrogen is abundant in the atmosphere but 

 plants require a reduced form of nitrogen, such as nitrates. This reduction 

 of nitrogen is accomplished chiefly through the action of nitrogen-fixing 

 bacteria. In many palustrine areas of coastal Maine nitrogen-fixing bacteria, 

 which live symbiotically with the bog myrtle ( Myrica gale ) and speckled alder 

 ( Alnus rugosa ) , seem to be important to the nutrient budget (Sculthorpe 1967). 

 Conditions of rapid peat deposition and a deep peat substrate do not favor the 

 growth of these two plants and the supply of nitrogen is further limited. A 

 model of phosphorus and nitrogen flow in a palustrine wetland is presented in 

 figure 8-7. Many plants commonly found in bogs are adapted to the acid, low 

 nutrient environment. 



In summary, the slow rate of decomposition in palustrine wetlands of coastal 

 Maine results in nutrients being bound in peat. Thus, nutrient cycling is 

 limited, which results in deficiencies in already nutrient-poor ecosystems. 

 The slow-moving waters of many palustrine areas render their biogeochemical 

 cycles closed compared to those of lotic (swiftly moving) waters. In Maine 

 wetlands the greatest period of nutrient exchange occurs during the spring, 

 when palustrine systems usually are flushed by high water. 



BIOTA 



The organisms inhabiting palustrine areas have evolved over billions of years 

 and each is fitted to the its available supply of biogeochemicals, and the 

 flow of energy within ecosystems. The biota of palustrine systems can be div- 

 ided into three groups: the producers, the consumers, and the decomposers. 

 The producers include most plants and certain forms of bacteria that synthe- 

 size organic matter from inorganic materials. The consumers are animals 

 (e.g., beaver) that feed on producers (living or in some stage of 

 decomposition) and/or other consumers. The decomposers (largely bacteria and 

 fungi) transform dead organic matter into recyclable constituents. Data on 

 the biotic component of palustrine systems in the Maine coastal zone are 

 sparse. A review of information concerning the composition and function of 

 palustrine trophic levels follows. 



8-19 



10-80 



