Appendix 2. Estuary notes 



Compared to the Atlantic coast south of Cape Cod, 

 estuaries in the North Atlantic region have colder and 

 deeper waters, little seasonal variation in temperature, 

 significant freshwater inflowfrom only a few large rivers 

 (Figure 9), stronger tides, and a predominantly cold- 

 temperate fauna (Gosner 1 971 , TRIGOM-PARC 1 974, 

 Berrill and Berrill 1 981 , NOAA 1 990, Anonymous 1 991 , 

 Ayvazian et al. 1992). The Gulf of Maine consists of a 

 deep central basin enclosed by Georges Bank, with 

 water circulating counterclockwise through the gulf; 

 entering through the Northeast Channel and Browns 

 Bank and exiting via Great South Channel and Nan- 

 tucket Shoals. The northern coastline is mostly rocky, 

 consisting primarily of granite, schist, and gneiss. In 

 many regions the consolidated rocks are overlaid by 

 glacial till, or sand/gravel deposits. The estuaries of this 

 area are dominated by submerged, glacier-scoured 

 river valleys with unmodified mouths, but there are 

 some exceptions (e.g., Boston Harbor, Wells Harbor). 

 Tides are semidiurnal and peak freshwater inflow 

 occurs during April and May due to the spring runoff. 

 Average precipitation across the region is 40-46 inches/ 

 yr. Cape Cod is generally considered to be the biogeo- 

 graphic boundary between the Virginian province to 

 the south and the Scotian province to the north (Briggs 

 1 974). However, it is considered to act as a "selective 

 filter" rather than an absolute barrier (Gosner 1971) 

 because many of the cold-temperate, boreal fauna that 

 dominate the North Atlantic have ranges extending 

 south of the cape and several eurythermal migrants 

 from the south enter the Gulf of Maine seasonally. 



For a general description of the physical and hydrologi- 

 cal characteristics of individual estuaries the reader is 

 referred to NOAA 1985, NOAA 1990, Anonymous 

 1 99 1 , and Larsen and Dogget 1 976. Average daily flow 

 is one of the primary determinants of the salinity 

 distribution and stratification in each system, while 

 surface area and depth (approximated at mean tide 

 level) describe the relative size of the estuaries (NOAA 

 1990, NOAA 1993). The Penobscot, Kennebec/ 

 Androscoggin, Merrimack and St. Croix 

 (Passamaquoddy Bay) Rivers have the highest aver- 

 age daily freshwater inflow and contribute more fresh 

 water to the Gulf of Maine than the remaining thirteen 

 watersheds combined (Figure 9). Massachusetts and 

 Cape Cod bays have the highest average depth and 

 surface area, however, several of the eastern Maine 

 systems (e.g., Penobscot, Blue Hill, and 

 Passamaquoddy bays) are also comparatively large. 

 The comparatively smaller systems (e.g., Wells Har- 

 bor, Great Bay, and Merrimack River) occur in the mid- 

 western portion of the Gulf of Maine (Figure 9). To 

 assist in the interpretation of ELMR data, unique fea- 

 tures of certain estuaries and the rationale for their 



inclusion to our database are presented below. Modi- 

 fications to specific National Estuarine Inventory (NEI) 

 maps (NOAA 1985) are also listed; however, a more 

 complete revision of the NEI is in progress. 



• Passamaquoddy Bay: Extremely strong tidal cur- 

 rents make the salinity zone boundaries highly variable 

 within the system. Intrusion of lower Bay of Fundy 

 water often makes Passamaquoddy Bay warmer than 

 neighboring systems just to the west, and causes 

 certain biological processes (e.g., herring spawning) to 

 occur earlier than in those estuaries (Thomas 1983). 

 Refer to NEI map 1.01 (Passamaquoddy Bay) and 

 NOAA charts # 13328 or 13398 for more information. 



• Penobscot Bay: According to regional hydrological 

 work, the seawater zone boundary should be relocated 

 in NEI map 1 .05 (Penobscot Bay) to the area between 

 Fort Point and West Penobscot (Normandeau 1975). 

 Refer to NOAA chart #1 3309 for help in locating these 

 landmarks. 



• Damariscotta River: This system was differentiated 

 from the large estuary depicted in NEI map 1.07 

 (Sheepscot Bay) due to its distinct hydrology. A small 

 tidal fresh zone is usually present just below the head 

 of tide dam at Damariscotta Mills. Manual closure of 

 the dam's sluiceway during exceptionally dry seasons, 

 however, may result in the disappearance of the fresh- 

 water lens. McAlice (1977) provides the only detailed 

 hydrological information for the estuary. The system's 

 seaward boundary is a straight line from Pemaquid 

 Point to Ocean Point. Referto NOAA chart #1 3293 for 

 help in locating the landmarks mentioned. 



• Sheepscot River: This system was differentiated 

 from the estuary depicted in original NEI map 1.07 

 (Sheepscot Bay) due to its distinct hydrology. It is 

 separated from the Kennebec/Androscoggin estuary 

 by Upper Hell Gate on the Sasanoa River and by the 

 marshland at the southern end of Hockomock Bay. 

 Also, in the original NEI, the seawater zone is errone- 

 ously drawn through the entire Back River/Montsweag 

 Bay branch. Hydrographic data from Maine Yankee 

 Nuclear Power Company (1978) and Stickney (1959) 

 indicate that brackish water fills most of this system, 

 from Bailey Point southward through Knubble Bay. 

 Paradoxically, the seawater zone extends up through 

 the lower Sheepscot River mainstem, as indicated in 

 the NEI. The Back River/Montsweag Bay complex 

 exhibits lower salinities because it is diluted from 

 Kennebec water entering through the Sasanoa River. 

 Head of tide is at the dam in Head Tide village and the 

 system's seaward boundary is a line from Ocean Point 

 toCapeNewagento Indian Point. Refer to NOAA chart 

 #13293 for help in identifying the landmarks men- 

 tioned. 



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