depth of 20-25 m. which coincides with the upwelling area, but 

 the phytopianivton population was so great that nitrate, silicate, 

 ammonium, and phosphate were reduced to 10.3, 1.2. 0.1. and 

 1 .4 |.imole/l respectively. The outer end of this transect was 

 located in the near-hottom winter shelf water as indicated by 

 the ammonium signature (Fig. 4B). 



The Chirikov basin receives water from the Gulf of Anadyr 

 after nearly complete vertical mixing occurs throughout the 

 water column in Anadyr Strait (Fig. 5). The very uniform 

 vertical nutrient concentrations on the western end of the 

 transect changes into a stratified system near the middle where 

 Bering Shelf waters and Alaskan Coastal waters are encountered. 

 The strong east-west gradients are the products of the lack of 

 flow from the deep Bering Sea and the little vertical mixing in 

 Shpanberg Strait on the east side of St. Lawrence Island. 



The Chukchi Sea receives the waters that flow through 

 Bering Strait after passing through Chirikov basin ( Fig. 6 ). The 

 nutrient content of this northward (lowing water has been 

 reduced somewhat in the Chirikov basin, but the major portion 

 remains to support primary production in the Chukchi Sea. The 

 strong east to west gradient of nutrients remains similar to the 

 more southern areas. The Chukchi transect of stations shows 

 the large near surface concentrations of nutrients which 

 corresponds to observations of the largest chlorophyll 

 concentrations. Nitrate, ammonium, and phosphate 



concentrations show enhancement near the Soviet coast, which 

 probably results from a southward tlowing Siberian Coastal 

 Current (Coachman & Shigaev, Subchapter 2. 1 . this volume). 

 The Alaskan Coastal water displays a low nutrient content 

 consistent with more southern transects except silicate, which 

 is enriched by about l()|imole/l. Even though past observations 

 have shown all nitrogen in the Yukon River was removed 

 quickly in the Chirikov basin, this nearshore increase in silicate 

 may be related to the Yukon River. This would be 

 consistent with the distribution of carbon isotope and C/N 

 ratios as reported by Scalan et al. (Subchapter 8.5.1, this 

 volume). 



The temperature-salinity diagram for all samples collected 

 on the 1988 joint cruise (Fig. 7A) shows the very cold water 

 below 0°C that falls into the salinity range of 32-32.7 7,k, . The 

 low temperature water between and 0.5°C has a salinity of 

 33-33. 5"/|,„ so this must represent water that was formed 

 during ice production, which increases the salinity. 



The nitrate-salinity diagram for all samples (Fig. 7B) on 

 the joint expedition fell predominantly in the salinity range of 

 32-32.5"/,,,. and the nitrate varied from about 0.1 to about 

 40 |ig-at/] . A few points deviated from this general distribution 

 in low salinity water in the Alaskan Coastal Current that was 

 depleted of nitrate and higher salinity samples from the deep 

 Bering Sea where nitrate concentrations exceeded 50 ^g-at/l. 



STATION NO 



STATION NO 



75 



100 



200 



DISTANCE (Km) 



300 



400 



100 



DISTANCE (Km) 



Fig. 4. The distribution of nitrate (A), ammonium (B), silicate (C) and phosphate (D) in a transect of stations across the Gulf of Anadyr. Units are 

 H mole/1. 



43 



