The local primary production peaks occurring at a depth of 

 70 m at Stations 1 22 and 1 26 were probably due to the elevated 

 levels of biogenic elements present there. 



The values obtained for primary production of organic 

 matter by phytoplankton for the whole of the photosynthetic 

 zone ranged from 70 to 140 mg C/nr/day (see Table 1 ). The 

 maximum phytoplankton production ( 140 mg C/nr/day) was 

 observed at Station 116; minimum production 

 ( 70 mg C/nr/day) occurred at Station 120 (Table 1). The total 

 average levels of phytoplankton productivity in this part of the 

 Pacific during the period of our studies was in line with the 

 higher range of primary phytoplankton production values 

 typical of oligotrophic zones of the World Ocean (i.e., about 

 101 mg C/nr/day). 



For stations of the second transect, situated to the northwest 

 of the first at about 8°N, the range of variation of primary 

 production rates (90-338 mg C/nr/day) exceeded the range of 

 values for Stations 1 14-120 (Table 1). The mean primary 

 production at Stations 121-126 corresponded to the lower 

 range of productivity rates for oligomesotrophic zones of the 

 World Ocean (i.e.. about 172 mg C/nr7day) (Table 1 ). 



Comparing the primary organic-matter production values 

 measured during the 1988 expedition with those obtained 



during the 1984 expedition, which covered roughly the same 

 parts of the Pacific, we note that both primary productivity and 

 the range of variation of primary production rates were greater 

 in 1984. The rates of primary production of organic matter by 

 phytoplankton over the Marianas transect in late July-early 

 August 1984 ranged from 1 00 mg C/nr/day to 1.16gC/nr7day, 

 the mean value being about 400 mg C/nr/day . The highest 

 primary production values for phytoplankton occurred at the 

 westernmost stations of the transect. The rather high primary 

 production rates in this part of the ocean in 1 984 were probably 

 due to the seasonal arrival of waters rich in biogenic elements 

 that originated in the equatorial divergence area to the south of 

 the study area. 



Phytoplankton productivity rates for the Marianas transect 

 in 1988 were somewhat lower than those recorded in 1984. 

 The differences can probably be attributed to fluctuations in 

 the arrival of waters from the equatorial divergence region. 

 On the whole, the level of primary production of organic 

 matter in the central tropical Pacific was in keeping with 

 expectations based on previous studies ( Sorokin, 1 976 ) and on 

 the findings of the 1 984 expedition, corresponding more or less 

 to the level associated with oligomesotrophic zones of the 

 World Ocean. 



TABLE 1 



Primary production (mg C/nr/day) at different stations 

 in the central Pacific. 



3.3 Mesozooplankton 



TATIANA A. PAVLOVA and AUDREY S. KUL1KOV 



Institute of Global Climate and Ecology, State Committee for Hydrometeorology and Academy of Sciences, Moscow, USSR 



Materials and Methods 



The materials for this work were collected in the eastern 

 equatorial region of the Pacific Ocean at seven stations ( Stations 

 1 14- 120) whose coordinates ranged from 10°Sto 150°W,and 

 0°S to 178°W (Fig. 1). The zooplankton was collected in 

 daylight with a large Juday Net. with a mesh of 168 urn and a 



throat diameter of 37 cm. from the 0-50. 50-100, and 

 100-200-m levels. The samples were fixed with a 40% 

 solution of formaldehyde and were processed by the standard 

 methods (Korshenko, 1988: Tsyban et al„ 1988) under an 

 MBS-9 binocular microscope in a Bogorov chamber. The 

 sample was concentrated and poured into a Petri dish. While 

 it was being examined under the binocular microscope, the 



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