nature of the benthic invertebrates in unconsolidated bottoms. For this 

 reason definitive statements on the other estuaries must await further study. 



A variety of fish commonly are found in subtidal unconsolidated bottom 

 habitats (and intertidal flats and beaches at high tide) in Maine estuarine 

 systems. Representative fishes include American sand lance, alligatorf ish, 

 wrymouth, lumpfish, Atlantic cod, Atlantic tomcod, the flounders, the skates, 

 sturgeon, and silver hake. 



Rock bottom . Subtidal rock bottoms in estuaries are not as extensive as 

 they are in the marine system. The NWl places <1% of estuarine bottom in this 

 class, although much of the rock bottom habitat was classified as open water 

 and the bottom type was not specificed. 



Subtidal rock bottoms originated from the submergence of exposed bedrock. 

 Most bedrock bottoms are relatively clear of sediment because most of it has 

 been removed by ocean waves. Wave-generated subtidal currents may continue to 

 remove surficial sediment from as yet uncovered bedrock in depths up to about 

 20 m, which is the limit of storm wave depth influence along the Maine coast 

 (Farrell 1972). 



Rock bottoms in the higher salinity portions of estuaries provide stable 

 substrata for macroalgal attachment. These bottoms are similar to marine rock 

 bottoms and are very productive (see chapter 4) . The vegetation is dominated 

 by the perennial brown laminarians (kelps), principally of the genus 

 Laminaria . Red and green algae also are present, although the red algae are 

 limited to the lower portions of estuaries. Irish moss ( Chondrus crispus ) may 

 be abundant locally. Little attempt has been made to quantify the subtidal 

 flora of Maine, but subtidal flora would be expected to account for the 

 majority of estuarine macroalgal biomass and production. Due to a paucity of 

 information on estuarine subtidal macroalgae, no attempt will be made to 

 consider their geographic variations. Large-scale variations do not apear to 

 exist in marine flora between Cape Elizabeth and Eastport. The character of 

 the flora is consistent, with fucoids dominating intertidal rocky areas and 

 laminarians dominating subtidal areas. 



In rocky areas not colonized by macroalgae the magnitude of organic matter 

 flux depends chiefly upon input of organic matter (detritus) from elsewhere. 

 In areas scoured clean by currents, films of microorganisms on the surfaces of 

 rocks interact principally with dissolved organic material in the water. 

 Undisturbed areas receiving sinking detritus and excreta from resident fauna 

 support larger microheterotrophic populations than do the wave-scoured areas. 



Investigations of the invertebrates of rock bottoms in the characterization 

 area are limited to those of Stickney (1959; table 5-7). He examined subtidal 

 rock surfaces from both high salinity and low salinity areas of the Sheepscot 

 Estuary. On the rocks in the high salinity portions he found 32 species 

 including sponges, coelenterates , polychaetes, molluscs, crustaceans, 

 echinoderms, and chordates. In low salinity areas he found only half as many 

 species belonging to the coelenterates, molluscs, and crustaceans. Three of 

 these, the American oyster and two species of xanthid crabs ( Rhithropanopeus 

 harrisi and Neopanope texana ) , are considered by many researchers to be 

 "relict" populations of more southern species that only occur in warm-water 

 pockets in Maine. 



5-88 



