synoptical ly and over the entire spawning ground. Water clarity 

 measured by the CZCS in conjunction with acoustic tracking investigation 

 of albacore has also allowed fishery scientists to demonstrate causal 

 mechanisms involved in the aggregations of albacore tuna associated with 

 ocean fronts and boundaries. In an application mode, location of ocean 

 color boundaries detected by the CZCS contributes a useful guide to 

 fisherman. This information is now being distributed by NASA's Jet 

 Propulsion Laboratory (JPL) in cooperation with the National Marine 

 Fisheries Service and National Weather Service. 



Farther offshore, an NSF-funded study of warm core eddies, shed from the 

 Gulf Stream, is now using CZCS color imagery to monitor, before, during 

 and after cruises, the positions, trajectories, and chlorophyll content 

 of low-chlorophyll boluses within slope water. Another study of mid- 

 Atlantic slope/shelf interactions, Shelf Edge Exchange Processes (SEEP) 

 funded by DOE, involves the use of meters, thermistor chains, sediment 

 traps, and in situ moored fluorometers to study the seasonal import of 

 shelf organic carbon to the bottom of the continental slope. The MAREX 

 experimental design will be the first, however, to use a combination of 

 shipboard rate measurements and moored f luorometer-aircraft time series 

 to interpret the CZCS imagery as a data set of dynamic biological 

 variables from each major continental shelf rather than as a corrobora- 

 tive snapshot of the physical properties of a local water mass. 



4.2 MAREX SHELF STUDIES 



As a function of latitudinal changes in wind forcing, and geographic 

 differences in shelf width, bottom topography, and human population cen- 

 ters, both the anthropogenic and natural nutrient inputs, as well as the 

 annual primary production, of U.S. shelves exhibit a wide range (Table 

 4-1). Within North America, the nitrate content of the Mississippi 

 River has at least doubled to ~ 150 pg- at N0 3 £~ during spring floods 

 over the past 10 years, while mean concentrations have increased from 

 ~40 yg-at Njf 1 in 1905 (Gunther, 1967), in 1935 (Riley, 1973), and in 

 1965 to +80 ug-at Hi' 1 in 1980 (Walsh et al., 1981). Data for other 

 eastern U.S. rivers which drain heavily populated areas, such as the 

 Ohio (Wolman, 1971), Potomac and Susquehanna (Carpenter et al., 1969), 

 Delaware (Kiry, 1974), and Hudson (Deck, 1981), suggest that their 



4-2 



