fishes, and terrestrial mammals; figure 1-2). The major processes (e.g., 

 energy flow and biogeochemical cycling) are discussed at each level: the four 

 levels are outlined below. For organizational purposes six regions were 

 delineated along the coast (figure 1-1). These regions are not necessarily 

 physiographically distinct but are subject to similar environmental forces, 

 such as geologic, hydrologic, and climatic. 



THE ECOSYSTEM 



Several major forcing functions operate throughout the ecosystem, including 

 climate, geology, hydrology, and the socioeconomy . The influences of these 

 factors are greatly interrelated. Climatic and geological events influence 

 the topography, soils, sediments, and hydrology of the entire coast. Changes 

 in substrata and hydrology affect vegetation, which in turn affects the fauna. 

 Socioeconomic activities both influence and are influenced by the physiography 

 of the ecosystem. Human activities can change in a short time what natural 

 processes have created over centuries. Chapter 2 describes the geography of 

 the Maine coast and examines the influences of these forcing functions on the 

 ecosystem. Chapter 3 discusses human impacts on the ecosystem. 



THE SYSTEM 



A system is a particular type of habitat that is influenced by a unique set of 

 hydrologicai , geomorphological , chemical, and biological factors. The clas- 

 sification of the Maine coast by system, subsystem, and class is based on the 

 U.S. Fish and Wildlife Service's (FWS) Classification of Wetlands and 

 Deepwater Habitats of the United States (Cowardin et al. 1979) and Maine State 

 Planning Office's Classification System For Land Cover in Maine (figure 1-3). 



The systems are reviewed individually in chapters 4 through 10 and each is 

 described in terms of characteristic components, functions, and interactions. 

 To illustrate the functions of and interactions between systems, four major 

 aspects of the ecosystem will be examined: 



1 . energy flow 



2. biogeochemical cycles 



3. biota 



4. abiota 



These do not function exclusively but overlap and complement each other. They 

 are outlined briefly below and illustrated in figure 1-4. 



Energy flow 



Ecosystems require energy to support life, and the ultimate source of energy 

 for all natural ecosystems is the sun. Through a process known as 

 photosynthesis, green plants capture solar energy and use it to transform car- 

 bon dioxide and nutrients into utilizable forms (carbohydrates). External 

 forces affecting this transfer of solar energy include hydrologicai factors 

 (currents, tides, and freshwater flows), climatic factors (wind, insolation, 

 and ice formation), geological factors (soil type and composition), and chemi- 

 cal factors (ionorganic and organic nutrients). Human activities (pollution, 

 habitat modification, and natural resource utilization) also affect energy 

 transfer. 



1-2 



