daily rates of primary production. As discussed, the accuracy of the 

 14 r method for measuring primary productivity in nutrient-poor, open- 

 ocean regions recently has been questioned; research on assessing error 

 for these regions is currently ongoing. In coastal waters, the 14^ 

 method is representative of the actual rate of carbon fixation. Due to 

 the great spatial and temporal variability, however, large errors in 

 primary production estimates exist in these waters where undersampling 

 in a heterogeneous environment exists. This situation will be resolved 

 with the MAREX biomass data set. 



A second historical approach for determining primary productivity has 

 been through mathematical models, ranging from single process models of 

 photosynthesis through ecosystem simulation with complex coupled 

 biological-physical numerical modes. These models all share a common 

 parameterization of primary production as some function of an initial 

 concentration of phytoplankton biomass. Early models of primary produc- 

 tion over Georges Bank, an important commercial fishing ground, included 

 the concept of regulation of photosynthesis by light and nutrients; 

 these models were limited by the state-of-the-art view of photosynthetic 

 regulation (Riley, 1946). 



The utility of the more sophisticated recent models in predicting 

 regional primary productivity is still largely hindered by the current 

 meager knowledge of the coupling of physical dynamics with biological 

 processes on the appropriate time and space scales. MAREX proposes to 

 measure the temporal change of biomass and productivity at 1 km inter- 

 vals over at least two years, as frequently as possible on those con- 

 tinental shelves within the Mid-Atlantic Bight, the Georgia Bight, the 

 Gulf of Mexico, the California Current, and the Bering Sea (Table 4- 

 2). With this comparative information, the fate of nitrogen and carbon 

 on U.S. and perhaps world shelves can be specified, with respect to the 

 MAREX objectives involving C0~ sinks, fish yields, waste disposal, and 

 anthropogenic nutrient stimulation. 



4.3 RELIABILITY OF INDIVIDUAL MEASUREMENTS 



Recent advances in the basic understanding of photosynthesis and the 

 modulating role of environmental parameters on phytoplankton 



4-5 



