northwestern Europe, which have been more fully studied, or by applying 

 general concepts true for Maine. 



Research needs are addressed at the end of the chapter. All literature used 

 to produce this chapter is listed under "References" at the end of the chapter 

 and in the Data Source Appendix (volume 4). In addition, many other data 

 sources were reviewed but are not cited. These are included in the Data 

 Source Appendix. 



Information on the location and extent of estuarine habitats compiled by the 

 NWI is incorporated. NWI has mapped habitat units at a minimum resolution of 

 about 3 to 5 acres (1 to 2 ha; personal communication from R. W. Tiner, Jr., 

 U.S. Fish and Wildlife Service, Newton Corner, MA; March, 1979). Habitats <3 

 acres (1.2 ha) generally were not mapped. A particular estuarine habitat may 

 contain more than one class and a particular estuarine class may contain areas 

 of other classes <3 acres. For example, an area mapped as a 5-acre (2 ha) 

 flat may consist of a sand or mud flat surrounded by emergent wetland and 

 rocky shore with an aquatic bed or mussel reef in the lower intertidal area. 

 If each of these habitat types (rocky shore, emergent wetland, reef, and 

 aquatic bed) were 3 to 5 acres or larger, they would be mapped as distinct 

 units. Small-scale variations in abiotic factors affecting estuarine areas 

 may result in several estuarine classes being found in the same area. These 

 classes may intergrade into one another, adding to the difficulty of precise 

 classification. 



In the intertidal classification, all reflective areas were considered part of 

 the intertidal zone. An estimated 34% of the rocky intertidal acreage 

 classified by NWI is above the zone where macroalgae are found (personal 

 communication from J. Topinka, Bigelow Laboratory for Ocean Sciences, West 

 Boothbay Harbor, ME; December, 1979). Other intertidal classes include flats, 

 beach/bars, emergent wetlands, aquatic beds, and reefs. 



The NWI provides the user with the most detailed data to date on the 

 distribution of estuarine habitats of coastal Maine. These data provide a 

 baseline against which the future status of estuarine habitats can be 

 measured. 



DISTRIBUTION OF THE ESTUARINE SYSTEM 



The total area (130,075 acres; 52,662 ha) and distribution of the estuarine 

 system in the six regions of the characterization area are given in table 5-2. 

 Major estuaries for each region are mapped in figures 5-1 to 5-6. Estuarine 

 systems are most abundant in regions 2 (33,419 acres; 12,530 ha) and 6 (28,103 

 acres; 11,378 ha). Region 2 is dominated by the interconnected 

 Kennebec/Sheepscot/Back River estuary complex and region 6 is dominated by 

 Cobscook Bay and the St. Croix River estuary. Complete data on the St. Croix 

 River are not available. The estuarine system is divided about equally 

 between subtidal and intertidal areas. The majority of open water habitat 

 (bottom type undetermined) probably is underlain by unconsolidated bottom. 

 Rock bottom and aquatic beds account for a small percentage of the identified 

 subtidal habitat. Flats occupy the largest area of any single intertidal 

 class and account for 66% of the intertidal area and 32% of the total 

 estuarine area. With the exception of the beach/bar class, most of the 

 intertidal classes are distributed evenly among the regions. The beach/bar 



5-12 



