28 



in sand (Hickman and Round, 1970; Marshall et. al., 1971; Ferguson, et 

 al., 1980, Revsbeck et al., 1981; Sand-Jensen and Borum, 1983). Sand- 

 Jensen and Borum (1983) found in Danish waters that microbenthic algal 

 production peaked at 120 g C m~^ y~^ at 0.5 m MLW, dropped to 35 g C m~^ 

 y"-'- at 2 m MLW, and decline to low values below 5 m.. 



The production rate of periphyton declines more rapidly than 

 macrophytes. Thus, the total shallow (photic) substrate area in 

 Buzzards Bay (10,380 ha. Chapter 1) overestimates the areal extent of 

 periphyton production area, because more than 80% of this substrate is 

 covered with eelgrass beds, rock fields, or sand flats without 

 appreciable periphyton densities. If the remaining area has a mean 

 production rate of 45 g C m '^ y •^, then periphyton contribute 9 x 10 g 

 C y~^ in Buzzards Bay. 



Salt marshes 



Salt marshes cover 1900 ha in Buzzards Bay (Hankin et al , 1985). 

 These communities are productive, but they do not export appreciable 

 amounts of organic matter (Nixon, 1980) . One well studied salt marsh in 

 Buzzards Bay has a mean annual production of 160 g C m y (Valiela et 

 al., 1975), however, only 20% of its production is released into 

 Buzzards Bay (Valiela and Teal, 1979). If this marsh is typical for the 

 region, then the contribution of salt marshes to Buzzards Bay is 6.0 x 

 .10^ g C m"2 y"l. 



