Secondary Productivity 



Secondary productivity applies to the production of animal tissue, that is, 

 the growth of trophic levels above the primary producers. It is a measure of 

 energy flow through the various components of the ecosystem. Data on 

 secondary productivity in coastal Maine estuarine systems are lacking. 



Biomass or standing stock is the weight or volume of animal tissue in a given 

 area (e.g., per square meter) and it is often used as a crude indication of 

 productivity, on the assumption that biomass and secondary productivity are 

 correlated directly. This is not necessarily true because communities of 

 large, long-lived molluscs have a high biomass but low secondary productivity 

 because of their small turnover rate. Conversely, a community dominated by 

 small, short-lived species, such as amphipods and polychaetes , has low biomass 

 and high productivity. If, however, two communities are composed of the same 

 types of organisms, biomass comparisons ought to reflect differences in 

 productivity. Limited biomass data are available on animals in the 

 characterization area. Sherman (1968) compared zooplankton biomass along the 

 Maine coast and found lesser amounts in northeastern Maine (region 6). Such a 

 pattern is unexpected, because the biomass of other groups, benthos, birds, 

 marine mammals and herring, is assumed to be high in region 6. Larsen (1979) 

 presents biomass values for the shallow water benthos of the Sheepscot River 

 estuary, which are similar to those of other shallow water areas (see 

 "Estuarine Unconsolidated Bottom" below). 



CLASS LEVEL DISCUSSIONS WITH INTRODUCTION TO THE SUBTIDAL AND INTERTIDAL 

 SUBSYSTEMS 



Estuaries consist of subtidal and intertidal subsystems that are separated by 

 physical boundaries. The intertidal subsystem is that area between extreme 

 high and extreme low tides that varies during the month (lunar cycle; see 

 chapter 4, page 4-18). The subtidal subsystem extends into the estuary beyond 

 the extremes of low water. 



The biological boundaries of the intertidal subsystem, which often differ from 

 the physical boundaries, enclose the area called the littoral zone where the 

 biotic assemblages grade from the subtidal to terrestrial environment. The 

 difference between the physical intertidal zone and the littoral zone is shown 

 schematically in figure 5-36. The width of the littoral zone is greater than 

 the width of the physical zone in wave exposed areas. Waves and their spray 

 wet the higher intertidal levels and allow for the development of intertidal 

 communities in these areas. The areas of subtidal subsystem and intertidal 

 subsystem were calculated as comprising 51% (66,693 acres; 27,001 ha) and 49% 

 (63,382 acres; 25,661 ha), respectively, of the estuarine system in coastal 

 Maine, based on NWI measurements. 



The Subtidal Subsystem 



The estuarine subtidal subsystem is permanently flooded by ocean waters but 

 has lower salinities (<30 ppt) than offshore coastal waters. The four types 

 of habitats in the subtidal area are the water column, rock bottoms, 

 unconsolidated bottoms, and aquatic beds. Fifty percent of the subtidal area 

 of coastal Maine is in regions 2 (28%; 18,711 acres; 7575 ha) and 6 (22%, 

 14,163 acres; 5734 ha). Regions 1, 3, 4, and 5 have 5908 acres (239 ha; 9%), 



5-76 



