simulation of primary production for a static water column vs. a dynamic 

 rapidly mixing water column. Phytoplankton following a complex 

 trajectory and experiencing a wide range of light intensities in the 

 mixing water column are capable of a high level of primary productivity. 

 Scatterometer wind stress measurements, coupled with increasing sophis- 

 tication in turbulence models for the upper mixed layer, will provide 

 information on the intensity and effect of vertical mixing. 



Finally, the rates of vertical mixing have a third implication for 

 calculating primary productivity from chlorohyll a concentrations: 

 specifically by the influence of light history on the molecular organi- 

 zation of chlorophyll into discrete functional photosynthetic units. 

 Phytoplankton grown at low light intensities (less than I ) tend to have 

 large functional photosynthetic units with 800 to 1400 chlorophyll 

 molecules, while cells grown at high light intensities (greater than I ) 

 tend to have smaller units of 400 to 600 chlorophyll molecules. 

 Although the larger units are more efficient per unit at low intensities 

 than the smaller units, the individual chlorophyll molecules are 

 actually less efficient in the larger units. Figure 4-5 indicates the 

 trend in the value of a as a function of the size of the functional 

 photosynthetic unit. Changes in the size of these units and 

 concommittant changes in values of a are predictable as a function of 

 varying light intensities with time ( Falkowski , 1981; Marra , 1980). 



The results of recent research on the control of photosynthesis by these 

 environmental parameters—temperature nutrients, light intensity, and 

 light history--all give improved accuracy to primary production models. 

 Ongoing research in these areas will continue to improve our abilities 

 to determine instantaneous shelf primary production from single 

 measurements of remotely sensed data on phytoplankton chlorophyll con- 

 centration, oceanic optical properties, temperature, and wind stress. 

 Because the wind event source of habitat varibility is present on the 

 shelves and not the open ocean (Walsh, 1976), however, the MAREX experi- 

 mental design must certainly resolve the wind event frequency (3 to 5 

 days) and hopefully that of cell division (0.25 days) in order to detect 

 causal changes in primary production. 



4-13 



