schedules should remain flexible enough to incorporate segments dedicated to intensive, 

 experimental studies at selected locations, or for responding to unique sampling opportunities 

 such as repeated sampling of discrete eddies. These complementary objectives require cruises 

 of ca. 15-20 days duration at minimum. 



Information collected semi-continuously by moored instruments will be used to 

 extrapolate transformation rate measurements to expanded temporal scales. This extrapolation 

 has proved difficult in the past, but is essential. Therefore, in the OMP experiment, 

 transformation cruises will be tightiy coupled to deployment of new in-situ measurement 

 technologies. 



In order to understand the transformation of carbon among its various pools, a suite of 

 measurements must be obtained that describe the oceanographic setting. These accompanying 

 measurements must be made at the same time as more process-oriented transformations are 

 monitored, and thus must be obtained on all transformation cruises. In particular, nutrients 

 exercise a fundamental control over carbon cycling. The transformation of DIC to and from 

 organic carbon will occtu- in conjunction with transformation of nutrients, and seasonal nutrient 

 signals are tracers of production and respiration processes. Field measurements of a broad suite 

 of nutrients are vital, both to characterize vertical and lateral fluxes from hydrographic surveys 

 (and potentially from moorings), and to support experiments conducted to determine 

 transformation rates of carbon. Thus, measurements of nitrate, phosphate, silicate, ammonia, 

 nitrite and urea concentrations through the euphotic zone are needed on all transformation 

 cruises. 



A. Primary Production 



Primary production will be assayed via ^'*C02 uptake for samples obtained at various 

 depths throughout the photic zone using temperature and light quality/quantity-controlled deck 

 incubators. These measurements will be conducted at selected stations. Because the euphotic 

 zone may extend to the sea floor, benthic primary production rates must also be determined. 

 At stations representing the inner shelf, middle shelf and shelf /slope boundary, process studies 

 will be conducted on consecutive days. In each of these experiments, phytoplankton carbon 

 specific growth rates and carbon biomass will be determined using ^'^C labeUng of 

 photosynthetic pigments. In some cases, post-incubation size-fractionation experiments will be 

 conducted to determine production, growth rates and biomass of specific size ranges. 



In addition, primary production wiU be modeled by determining photosynthesis-irradiance 

 parameters (P-I; alpha and P^aj). Using this approach, P-I parameters can be considered in 

 conjunction with mooring-sensed chlorophyll distributions in the study region and 

 measurement of incident irradiance, to estimate the production of organic carbon in the study 

 region, both at specific process study sites and for the region as a whole. 



Measurements of primary productivity will also be made using the Fast Repetition Rate 

 (FRR) fluorometer. This will allow estimation of primary productivity over the entire shelf 

 from synoptic FRR measurements, and from the moored FRR measurements. Another goal is 

 to identify the factors limiting primary productivity on the continental shelf, and to design 

 molecular probes indicative of in-situ growth limitation. The study requires two FRR 

 fluorometers, one operating in a profiling mode (interfaced to a CTD), and another being 

 operated aboard a ship. The profiling instrument will provide real-time measurements of 



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