234 



WOODWELL, RICH, AND HALL 



x 



H 

 a. 



LU 



Q 



6 5 4 3 2 1 



TIME, 10 3 years before the present 



Fig. 5 Relationship between age and depth of high marsh peat at Barnstable, 

 Mass. (Alfred C. Redfield, Estuaries, p. 113, American Association for the 

 Advancement of Science, Washington, 1967.) 



accumulate probably approximates the rate of net productivity. The import of 

 fixed C from uplands and from the coastal ocean might increase the rate locally 

 above the net production under extraordinary circumstances. 



Fisheries 



The fish populations of estuaries are higher than those of freshwater bodies 

 and commonly higher (sometimes 1000 times) than in other coastal waters 

 (Fig. 6). Standing crops in segments of Flax Pond occasionally exceed 100 g (dry 

 weight)/m 2 . Productivity of fish in estuaries often ranges from 5 to 15 g (dry 

 weight) m 2 year" 1 and is probably the highest of any water bodies. (Dry weight 

 of fish is approximately 20% of wet weight.) The total contribution of estuaries 

 to oceanic fisheries has been documented. 1 2 ' 20 Of the estimated 3 X 10 6 metric 

 tons of fish and shellfish caught in western Atlantic continental shelf waters, 

 about two-thirds are from species believed to be estuarine dependent at some 

 stage in their life history. Stroud 21 calculated that each hectare of estuary 

 contributes more than 550 kg fish each year to coastal fisheries, either directly 

 or by serving as nursery grounds for the young of fish captured offshore. The 



