. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder . 40 80 Distance (km) 40 80 Distance (km) 120 Figure 58-10. Distribution of nitrate and ammonium (idg atoms N/1) in outer Bristol Bay south of the Pribilof Islands along a northern transect extending from 55°'N-168°'W to 56°'N-167°'W (Acona cruise 242, 13-28 May 1977). 8 1 1 1 1 1 7 _ Open symbol: Shelf Stat on . ( 6 h ⢠Closed symbol: + July Deep Stat 1971 on - 4< i D ⢠⢠⢠O July D July 1975 1978 - 3( 2l 5 1 1 1 J â â ⢠⢠1 ⢠+ ⢠â 1 ⢠â 1 ⢠1 10 NO,- 15
. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder . 40 80 Distance (km) 40 80 Distance (km) 120 Figure 58-10. Distribution of nitrate and ammonium (idg atoms N/1) in outer Bristol Bay south of the Pribilof Islands along a northern transect extending from 55°'N-168°'W to 56°'N-167°'W (Acona cruise 242, 13-28 May 1977). 8 1 1 1 1 1 7 _ Open symbol: Shelf Stat on . ( 6 h ⢠Closed symbol: + July Deep Stat 1971 on - 4< i D ⢠⢠⢠O July D July 1975 1978 - 3( 2l 5 1 1 1 J â â ⢠⢠1 ⢠+ ⢠â 1 ⢠â 1 ⢠1 10 NO,- 15 20 25 (ng at N/l) Figure 58-11. Relationship between nitrate concentrations in the surface layer and ammonium concentrations in the sub-surface layer in the Bering Sea and the northern North Pacific (after Saino et al. 1979). Data sources: Hattori 1973, 1977, 1979. +: July 1971; o: July 1975; d: July 1978. Open symbols refer to shelf stations and closed symbols deep stations. that the nitrite maximum, like ammonium in the outer-shelf domain and the deep Bering Sea, is near the bottom rather than near the top of the seasonal thermocline (Fig. 58-12). Ubiquitous occurrences in the open ocean of the subsurface nitrite maximum and its close association with chlorophyll maxima are known. However, concen- trations of nitrite in its maximum layer in the Bering Sea are several times higher than those observed in the tropical and subtropical North Pacific (Hattori 1973, 1975; Kiefer et al. 1976). Two sources of subsurface nitrite have been con- sidered: production of nitrite during nitrate reduc- tion by phytoplankton, and production during ammonium oxidation by nitrifying bacteria (Carlucci et al. 1970, Miyazaki et al. 1973, Kiefer et al. 1976). Experiments conducted using '^N-labeled nitrate and ammonium in the northwestern North Pacific suggest that the former is mainly responsible for nitrite production in boreal seas (Miyazaki et al. 1975). Unfortuna
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