. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder. Oceanography Bering 986 Plankton ecology needed to assess which is more important in the eastern Bering Sea is still lacking. In the mid-shelf domain, a nitrite maximum is not evident in the sub-surface layer. Instead, rela- tively high concentrations of nitrite are found near the bottom, coinciding with the maximum concen- tration of ammonium. This nitrite probably is a product of nitrifying bacteria. However, there are living plants near the sea bed in the mid-shelf domain (Fig. 5
. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder. Oceanography Bering 986 Plankton ecology needed to assess which is more important in the eastern Bering Sea is still lacking. In the mid-shelf domain, a nitrite maximum is not evident in the sub-surface layer. Instead, rela- tively high concentrations of nitrite are found near the bottom, coinciding with the maximum concen- tration of ammonium. This nitrite probably is a product of nitrifying bacteria. However, there are living plants near the sea bed in the mid-shelf domain (Fig. 58-14), and these may possibly reduce nitrate to nitrite. The large concentrations of oxygen in these waters probably inhibit the reduction of nitrate to nitrite by bacteria. In the coastal domain both ammonium and nitrite concentrations are uniformly low throughout the water column. In this area the water is shallow enough for wind and tidal mixing to overlap, and the result is a thoroughly mixed water column. HORIZONTAL DISTRIBUTION OF NITRATE AND AMMONIUM IN SURFACE WATERS OF THE UNIMAK PASS REGION Alaskan Stream water enters into the Bering Sea through Unimak and other Aleutian passes and bathes the continental slope of the southeastern corner of the Bering Sea basin (Coachman and Charnell 1979). Detailed information about nutrient distributions in the Unimak Pass region can be of use in identifying the role played by Alaskan Stream water in the fertility of the southeast Bering Sea. In Fig. 58-17 the simultaneous measurements of temperature, salinity, nitrate, ammonium, and chlorophyll a are presented for a R/V Hakuho Maru cruise tract (Fig. 58-18) extending about 125 km southwest of Unimak Pass (Koike et al. 1979). During the transect the ship moved southeastward approximately parallel to the bathymetry at a con- stant speed of ca. 11 kn. Therefore, the tidal current (~1 kn) effects can be disregarded. Near the Aleutian Islands, nitrate concentrations were high (>10 iig
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