5-31 Nitrate concentration ( M) and salinity (ppt) in the 



Sheepscot estuary in September 1976 (Garaide et al. 1978) . . 5-56 



5-32 Factors controlling flushing in seven Maine estuaries, 



based on application of the model described on page 5-59 



For example, in the Kennebec estuary 40% of the estuary's 



volume is provided by river flow, about 28% by tidal 



input, and 32% is residual at low tide 5-61 



5-33 Generalized size distribution of organic carbon particles 



in seawater (adapted from Sharp 1973) 5-66 



5-34 Schematic diagram of the organic matter cycle in 



the estuarine system 5-66 



5-35 Physical conditions of the estuarine water column 

 during summer (stratified) and winter (well mixed) 

 which affect phytoplankton growth. Arrows indicate 

 mixing; N= nutrients; dots are phytoplankton (Yentsch 1977) . 5-68 



5-36 Comparison of the boundaries of the physical intertidal 

 zone and the littoral (biological intertidal) zone with 

 increasing exposure to wave action (adapted from Lewis 1964) . 5-77 



5-37 Monthly measurements of chlorophyll-a concentrations 

 (mg/m ) in upper Penobscot Bay for 1974 to 1975 

 (Bertrand 1977) 5-79 



5-38 Relation of phytoplankton species diversity to 

 phytoplankton population size in marine and 

 estuarine waters (Hulburt 1963) 5-82 



5-39 The comparative distribution of marine, brackish, and 

 freshwater species along a salinity gradient in a 

 German estuary (after Remane 1934) 5-86 



5-40 Number of marine and freshwater invertebrate 



species from the mouth to the head of the Sheepscot 



River estuary (Larsen and Doggett 1978b) 5-86 



5-41 The process of salt marsh progradation 



(adapted from Redfield 1972) 5-111 



5-42 The process of salt marsh transgression 5-111 



5-43 Salinity ranges of the bottom sediments underlying 

 the different marsh communities in New England 

 salt marshes (adapted from Chapman 1940a) 5-114 



XIV 



