Maine salt marshes have developed on a coastline forged by glaciation. They 

 are built on marine peat, marine silt, sand, gravel, cobbles and, in some 

 instances, over the remains of fresh water bogs in which stumps of old pine 

 trees ( Pinus strobus ) can be found (Chapman 1940a; and Thompson 1976). 

 Redfield (1972) discovered in his examination of the salt marsh peat in 

 Barnstable Marsh, Massachusetts, that the upper and lower peat fringes of the 

 marsh sediments were dominated by the heavier material (sand) but that the 

 peats within the marsh were composed of fine-grained silty material. The 

 sediment distribution indicates that the salt marsh acts as a buffer against 

 wave energy by absorbing it and slowing the movement of the waters. As the 

 wave energy is dissipated in the grass, the small silt and clay particles no 

 longer held in suspension by the wave are deposited on the marsh surface. 

 Thus, marshes absorb energy and act as buffers for upland systems, while at 

 the same time capturing fine-grained material to maintain themselves. 



Salt marshes have two major requirements for existence: a source of sediment 

 (sand and peat) and a sheltered (low energy) location. Salt marshes cannot 

 form without the accumulation of depositional material. In Maine, the hard 

 rocky coast is relatively resistant to marine erosion (consequently, a major 

 source of sediments is lacking) and marsh development depends upon the highly 

 limited quantities of silt from rivers and from decayed plant material (peat). 

 In northeastern Maine, particularly, the numerous drowned river valleys and 

 inlets have not accumulated an abundance of sediment material suitable for 

 salt marsh formation. Most of the fine clays and silts (which are little) 

 transported by rivers are not trapped in the estuaries but move into the deep 

 water of the Gulf of Maine. These factors limit the availability of suitable 

 substrate for salt marshes in Maine. 



Salt marshes in Maine require natural protective structures if they are to be 

 maintained. Since salt marshes usually form on fibrous marine peat they 

 cannot exist in high-energy situations (characterized by waves). Sandy 

 barrier beaches and islands are the most common protective structures for salt 

 marsh formation but the scarcity of sand and sand sources in Maine limits the 

 formation of such protective structures. 



In areas in Maine where sediment supplies and protective structures exist 

 (sand spits or barrier beach structures), protected intertidal sand flats may 

 become colonized with cordgrass. Salt marsh vegetation may become established 

 by seeding, lateral growth of rhizomes, and by rafting by ice (Redfield 1972). 



Salt marsh plant propagation by lateral growth of rhizomes and by seeding is 

 common. Ice rafting is a unique colonization feature of northern latitude 

 salt marshes. Ice, which moves in and out of intertidal regions during winter 

 and spring, is capable of transporting plants or plant particles frozen in it 

 to locations far from the parent source. Salt marsh turfs 10 feet (3 m) in 

 diameter that rafted high into the marsh in Barnstable Marsh, Massachusetts, 

 were observed by Redfield (1972) and smaller blocks were observed stranded on 

 bare sand flats. Cordgrass rafted to unvegetated sand flats potentially could 

 initiate marsh development. 



If sedimentation rates continually exceed the rise in sea level over time 

 cordgrass may spread over the accumulated sediment and accrete laterally over 

 formerly open-water areas as depicted in figure 5-41 (Chapman 1960; and 

 Redfield and Rubin 1972). Areas in which cordgrass previously grew will 



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10-80 



