The most damaging effects on the marine system are caused by the chronic low 

 level inputs of petroleum hydrocarbons. These remain in the sediments and may 

 be metabolized by or accumulated within the tissue of benthic species and 

 passed through the food chain to the commercially important species. 



Fish, marine mammals, and birds are affected by spills through external oiling 

 (especially birds) and the ingestion of oil (through the food chain and during 

 preening). In addition, oiling significantly reduces the hatchability of bird 

 eggs (see Chapters 11, 13, and 14, "Fishes," "Marine Mammals," and 

 "Waterbirds" respectively). 



Dams 



A significant potential exists for low-head hydropower development in coastal 

 Maine. The U.S. Army Corps of Engineers (1979), in a recent inventory of 

 potential hydropower sites, identified 276 dam sites in coastal Maine (see 

 atlas for locations), which constitutes 20% of all the dams in the State. 

 Most of these are on rivers or the outlets of lakes. The possibility also 

 exists for generating power at dams constructed in tidal waters along the 

 eastern coast. The impacts of impoundments are discussed below. 



Effects of dams on marine and estuarine systems . Dams and impoundments 

 can have major effects on marine and estuarine systems (Copeland and Dickens 

 1974). These structures typically alter the volume and rate of freshwater 

 flow into estuaries. Alterations, in turn, can change the physical qualities 

 of the receiving waters, especially circulation, salinity, sedimentation, 

 temperature, shoreline erosion, flushing, ice-formation, and nutrient levels. 

 Impoundments also can act as settling basins, reducing sediment load and, 

 thus, reducing nutrient and sediment supply to intertidal areas and beaches. 

 Such changes in hydrography, geology, and chemistry can alter estuarine biota 

 significantly. The characteristics and magnitude of these changes depend on 

 the nature and duration of the induced alterations and on specific physical 

 and biological characteristics of estuaries receiving the modified inflow. 



Tidal power projects are of two general types: dams utilizing both incoming 

 and outgoing tidal currents, and impoundments using incoming tides to store 

 water until power is needed later. Both types can alter tidal dynamics, water 

 temperature, wave action, surface and bottom currents, sedimentation, and 

 erosion patterns. These changes subsequently can influence aquatic biota. 

 For example, if the Fundy Tidal Power Project (Bay of Fundy, Canada) is built 

 the mean high water level in the bay would decrease 1.3 to 2.9 feet (0.4 to 

 0.9 m) . The low water level would rise so as rarely to fall below existing 

 mean low water, causing mean sea level to rise approximately 9 feet (2.8 m; 

 figure 3-2; Hodd 1977). These changes would cause a vertical compression of 

 the intertidal zone, halving the tidal excursion and thus changing intertidal 

 zonation. In turn, the latter change would bring about a partial displacement 

 of intertidal macroalgae, salt marsh and epibenthic algae, and associated 

 fauna. Much of the intertidal habitat would be altered and its productivity 

 would be impaired greatly. About half of the intertidal plant communities 

 would cease to be productive. 



Numerous ecological changes also could take place in the impounded tidal 

 water, resulting in biological alterations. Decreased wave exposure along 

 impoundment fringes would favor Aseophyllum over Fucus (seaweeds) in rocky 



3-44 



