FISHERY BULLETIN: VOL. 69, NO. 4 



was near the bottom of the photic zone 30 m 

 below the nannoplankton maximum; the net- 

 plankton chlorophyll concentration and net/nan- 

 no ratio were still high; and NO3-N concentra- 

 tions were greater than 2 /jlU throughout most 

 of the photic zone. 



GEOGRAPHIC VARIATIONS IN THE 

 CALIFORNIA CURRENT 



ENVIRONMENTAL FACTORS 



Four transects across the core of the Current 

 were made for this study (Figure 1). Tran- 

 sects 1-A, 2, and 3 were made during late July 

 and August 1970, and transect 1-B was made 

 during the first week of November 1970. Cal- 

 COFI station 3 in Monterey Bay was the inshore 

 station for transects 1-A and B. The hydro- 

 graphic conditions observed along these tran- 

 sects are summarized in Table 3 and Figures 8 

 and 9. 



The July-August transects were made during 

 a period of coastal upwelling and were charac- 

 terized by shoreward rising isotherms and ni- 

 trate isopleths. Based on the upward slope of 

 these isopleths, upwelling was least intense at 



the southernmost inshore station and most in- 

 tense at the northernmost station, which is typi- 

 cal for this time of year (Reid et al., 1958). 

 Nitrate concentrations were high in the upper 

 half of the photic zone at the three inshore sta- 

 tions and low at the two outermost stations of 

 each transect. Ammonium concentrations were 

 relatively high (>1 /ixM NH4-N) in the photic 

 zone at the stations of transect 1-A but were 

 low (typically 0.1 to 0.5 fiM) throughout the 

 water column at most of the remaining stations. 

 The surface mixed layer was never observed to 

 extend below the photic zone, inshore or oflfshore. 

 An undercurrent was present below the thermo- 

 cline between stations 5 and 8 of transect 1-A 

 as indicated by the spreading isotherms (cf. 

 Wooster and Gilmartin, 1961). Based on the 

 temperature (Figure 8) and nitrate profiles 

 ( Figure 9 ) , the stations along each transect were 

 divided into three groups: 



1. Stations within about 100 km of the coast 

 were classified as inshore (stations 3, 61, 

 and 63), 



2. Stations between 100 and 250 km offshore 

 were classified as transitional (stations 8, 

 55, and 67), 



Table 3. — Environmental factors monitored concurrently with measurements of productivity and standing crop in 

 the California Current system between lat 35° and 50° N. 



a CalCOFI station 3. 



808 



