Although few estimates of estuarine primary production by phytoplankton exist, 

 phytoplankton dominate total estuarine primary production. Estuarine 

 phytoplankton productivity in Maine has been estimated at approximately 150 g 

 C/m /year by standard C,, assimilation techniques. Although productivity 

 varies considerably among estuaries, this estimate represents a value between 

 gross and net primary productivity, which is suitable for rough estimates of 

 estuarine phytoplankton production. The above estimate of productivity is 

 applied below to the estuarine areas identified by the NWI . 



NWI data on the total estuarine subtidal area have been employed in estimating 

 the extent of subtidal phytoplankton habitat. Phytoplankton, however, are 

 also present in waters overlying intertidal regions. The intertidal zone 

 represents a large percentage (407o to 60%) of total estuarine area among the 

 regions. The phytoplankton productivity of waters overlying intertidal 

 bottoms was assumed to be approximately 40% of that in deep estuarine regions. 

 This productivity in intertidal areas represents a large percentage (27%) of 

 total estuarine phytoplankton productivity. Estuarine phytoplankton is the 

 dominant estuarine producer in regions 1 and 2 and accounts for a large 

 percentage (42%) of total estuarine production (table 5-4). 



Emergent wetland areas are often highly productive. Productivity per unit 

 area is examined under "Emergent Wetlands" below. Emergent wetlands that were 

 measured in the NWI included both salt marsh and brackish water marsh. For 

 the sake of productivity determinations, salt marsh represents the major type 

 of marsh and is dominated by cordgrass ( Spartina alternif lora ) . It is 

 possible therefore to make salt marsh productivity estimations based on 

 emergent wetland area data from the NWI and productivity data for cordgrass. 



Maximum biomass data give a minimum average productivity of 1216 g dry 

 weight/m^/year for cordgrass in Maine (Vadas et al. 1976). Assuming that 

 40.77% of this dry weight is carbon (Burkholder and Bornside 1957) annual 

 carbon production is 496 g/m^ . Salt marsh production is presented in table 

 5-4 and accounts for about 20% of estuarine production. Salt marsh 

 productivity in Maine will be discussed further below. In regions 1 and 2, 

 salt marsh production accounts for approximately one-third of the total 

 production (table 5-4). 



In comparison with the estuarine phytoplankton habitat, intertidal seaweed 

 beds and salt marshes occupy relatively small areas. Areas supporting 

 intertidal seaweeds and salt marshes are nevertheless important because their 

 productivity per unit area is great. This is in contrast to estuarine 

 phytoplankton which occupy large areas but the productivity per unit area of 

 which is relatively low. 



Although it is clear that the phytoplankton, intertidal seaweeds, and salt 

 marshes all make important contributions to estuarine production, other plant 

 groups, such as the subtidal benthic algae, salt marsh algae, mudflat algae, 

 and eelgrass populations also may be important contributors to primary 

 production. Much research needs to be done before estuarine and inshore 

 coastal productivity can be better defined. 



5-75 



10-80 



