dominated by small short-lived species, such as amphipods and polychaetes, 

 will have a low biomass and high productivity. If, however, two communities 

 are composed of the same types of organisms, biomass comparisons should 

 reflect productivity differences. Biomass data for coastal Maine are limited. 

 Sherman (1968) compared zooplankton biomass along the Maine coast and found 

 reduced amounts in eastern Maine. Such a pattern is unexpected, because the 

 biomass of other groups, benthos, birds, marine mammals, and herring, is high 

 in region 6. Larsen (1979) presented biomass values for the shallow-water 

 benthos of the Sheepscot River estuary that are comparable with other shallow- 

 water areas (see "Estuarine Unconsolidated Bottom," page 5-81 in chapter 5). 

 This suggests that, since other parts of the Sheepscot River are more densely 

 populated than the estuary, the secondary productivity of the Sheepscot is 

 high. Data on this subject are lacking, however. 



CLASS LEVELS AND AN INTRODUCTION TO THE SUBTIDAL AND INTERTIDAL SUBSYSTEMS 



Introduction 



Two ecologically distinct but related subsystems make up the marine system: 

 the subtidal and intertidal zones. The physical subtidal zone includes marine 

 habitats extending beyond the extremes of low water. The area of the 

 intertidal zone varies during the month (see "Hydrography" above). The 

 physical boundaries of the zone are defined as the area between extreme high 

 tide and extreme low tide. 



The biological boundaries of the zones (which correspond to the NWI subsystem 

 boundaries) often differ from their physical boundaries. The biological 

 boundaries are defined by the grading of the biotic assemblages from subtidal 

 to terrestrial areas, and the area between these boundaries is called the 

 littoral zone. The difference between the physical intertidal zone and 

 littoral zone (NVI intertidal zone) is shown schematically in figure 4-20. 

 The littoral zone, is narrower than the physical zone in protected areas and 

 is wider and higher than the physical zone in wave-exposed areas. Wave surge 

 and spray wet higher intertidal levels and allow for the raised and widened 

 development of intertidal communities. The subtidal subsystem and intertidal 

 subsystems were calculated as making up 65% (112,130 acres; 45,397 ha) and 35% 

 (60,576 acres; 24,525 ha), respectively, of the marine system. (Limitations 

 of these calculations are discussed in "Data Sources and Compilation of Data" 

 above. ) 



The Subtidal Subsystem 



The marine subtidal zone is the area that is continually immersed by the ocean 

 and has high constant salinities. Four types of habitats are found in the 

 marine subtidal zone of coastal Maine: aquatic bed, rock bottom, water 

 column, and unconsolidated bottom. These habitats, except aquatic beds, are 

 discussed below. Aquatic beds are discussed in chapter 5, "The Estuarine 

 System." The available information on this habitat is not sufficient to 

 determine whether the beds differ between the estuarine and marine systems. 



Eighty-five percent of the subtidal system in the characterization area is in 

 the northeastern section. Regions 4, 5, and 6 have 40,167 acres (16,262 ha; 

 36%), 25,180 acres (10,194 ha; 22%), and 29,740 acres (12,040 ha; 27%) 

 respectively. These regions are large and encompass large bays. The subtidal 



4-59 



10-80 



