. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder. Oceanography Bering 169° 165° 161' Figure 22-3. Distribution of pC02 in surface water in PROBES study area, May 1976. Nitrate-chlorophyll-pC02 relationships A plot comparing the average nitrate values of the top 35 m of the 1976 study area with PCO2 is pre- sented in Fig. 22-6. The circled dots in the top figure show zero nitrate values at the surface where PCO2 was measured, but higher values at depth. The clus- tering of points of near-zero nitrate values at ApC02 values of less t
. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder. Oceanography Bering 169° 165° 161' Figure 22-3. Distribution of pC02 in surface water in PROBES study area, May 1976. Nitrate-chlorophyll-pC02 relationships A plot comparing the average nitrate values of the top 35 m of the 1976 study area with PCO2 is pre- sented in Fig. 22-6. The circled dots in the top figure show zero nitrate values at the surface where PCO2 was measured, but higher values at depth. The clus- tering of points of near-zero nitrate values at ApC02 values of less than —135 juA in the top figure, which represents 1976 data, and —110 juA for the middle figure, which represents 1978 data, is of considerable physiological interest. These data indicate that the photosynthesizing plants are capable of removing all the nitrate from the water column relatively uninflu- enced by the concentration of molecular carbon dioxide. It may be that other forms of CO2 (, HCO3) are being utilized; if so, the stoichiometric ef- fect on the PCO2 is the same as for direct utilization (Fig. 22-1). The chlorophyll a content appears to bear little direct relation to PCO2 content, probably because these two physiologically important compo- nents are functioning on different time scales. A high chlorophyll content is associated with a low PCO2, but the recovery time for CO2 is slow (because of limited atmospheric exchange capacity and depen- dence on respiration of fixed carbon for recovery) and the photosynthesis which caused its decrease had ceased to occur long enough before the analysis was made that the plants and their chlorophyll a had disappeared. The utilization of ammonia, present in 5. H "> 170 W O 3 -70 2 -140 1 -200 O 55 12 8 46 44 42 41] Station No. o' o a z (m9 A/i) 12 48 10 40 8 32 (0 o 0) 6 24 ^ 4 16 3 Figure 22-4. Cross section 55°50'N eastern Bering Sea shelf in June 1976. All parameters
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