reaches of estuaries are exposed to the full fluctuations in salinity because 

 they are exposed to saltwater due to flooding tides and fresh water due to 

 riverine flow and ebbing tides (Bassindale 1943). In unconsolidated 

 substrata, the infaunal species live farther upestuary than epifaunal species 

 because of the dampening effect of the sediment on salinity fluctuations 

 (Alexander et al. 1935). The extent of this dampening was shown by Boyden and 

 Little (1973) to be great in the tidally dominated Severn Estuary in England. 

 These investigators demonstrated that the nature of the substrata is more 

 important than the salinity regime in controlling the upestuary habitation of 

 intertidal infaunal species. Flats near the head of the estuary were capable 

 of harboring as many species as flats near the mouth, because the sediment 

 protected infaunal organisms from the salinity fluctuations. 



Intertidal rocky shore . Rocky shores are not as predominant in Maine 

 estuaries as they are in coastal marine waters. The preliminary NWl data 

 indicate that 5% of the estuarine intertidal area is comprised of rocky shore. 

 Rocky shore areas border many flats and emergent wetlands in intertidal areas 

 but were not delineated as areal features by NWl because of the linear nature 

 of rocky shores. 



The geologies of estuarine and marine rocky shores are nearly identical, that 

 is, the substrata of both consist of folded and faulted igneous and 

 metamorphic rocks locally invaded by granitic intrusions (plutons) and ring 

 dike complexes (a grouping of rocks arranged in a circle) of volcanic origin 

 up to a mile in diameter (TRIGOM 1974) . All of these rocks are of Paleozoic 

 and Mesozoic age. Paleozoic volcanic rocks also occupy a portion of the coast 

 of Washington County (Doyle 1967). 



Primary production on rocky shores is dependent on macroalgae (see "Rocky 

 Shore" page 4-78, in chapter 4) . Density of the brown algae knotted wrack 

 ( Ascophyllum nodosum ) and various other species of rockweed (Fucus spp.) is 

 great. Estuarine rocky shores generally support the largest individual 

 plants. Areas that are exposed to heavy waves support little macroalgal 

 growth, however, sheltered areas are subject to severe freezing and ice 

 abrasion that may reduce macroalgal populations. Wave action is minimal in 

 estuaries compared to marine systems. The area and width of the intertidal 

 zone in estuaries is less than at exposed coastal rocky shores; total 

 productivity is reduced. 



The types of benthic invertebrates encountered on protected rocky shores are 

 basically the same as those on exposed shores, but the number of species is 

 lower on protected rocky shores, presumably because of reduced habitat 

 diversity and higher environmental variability; that is, warmer temperatures 

 in summer, colder in winter, greater turbidity, and more variable salinity. 

 Ice formation may dislodge or destroy the fauna in some locales. Protected 

 rocky shores often have a layer of silt coating the surface of the rocks and 

 attached macroalgae. Grant (1977) observed that the trapped silt may smother 

 barnacles. The total number of benthic individuals in protected rocky areas 

 is much less than in exposed rocky areas, mainly because the barnacle habitat 

 is reduced in comparison to exposed areas. 



The size (slope and vertical height) of the intertidal subsystem in protected 

 rocky areas is smaller than that of the intertidal subsystem in exposed rocky 

 areas and the zones are not analogous. The upper intertidal subsystems 



5-94 



