. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder . 40 80 120 160 Distance (km) Station 18 19 20 21 22 46 40 £ 80 a 03 o 120 - • • • • • • J: ' G • • • • • G • • • • AMMONIUM (;^g at 1 1 N/l) 40 80 120 Distance (km) 160 Figure 58-9. Distribution of nitrate and ammonium (/ig atoms N/l) in outer Bristol Bay south of the Pribilof Islands along a southern transect extending from 55° 'N-167°' to 55°'N-165°'W (Acona cruise 242, 13-26 May 1977). shelf during winter. With the onset of spring surface heating, the water column stabi
. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder . 40 80 120 160 Distance (km) Station 18 19 20 21 22 46 40 £ 80 a 03 o 120 - • • • • • • J: ' G • • • • • G • • • • AMMONIUM (;^g at 1 1 N/l) 40 80 120 Distance (km) 160 Figure 58-9. Distribution of nitrate and ammonium (/ig atoms N/l) in outer Bristol Bay south of the Pribilof Islands along a southern transect extending from 55° 'N-167°' to 55°'N-165°'W (Acona cruise 242, 13-26 May 1977). shelf during winter. With the onset of spring surface heating, the water column stabilizes, the spring bloom commences, and nutrients are consumed. The more intense spring and summer storms influence total seasonal productivity by mixing the water column to sufficient depths so that new nutrients are supplied to the euphotic zone (Fig. 58-13). By the end of summer, however, nutrient depletion is a common feature of the euphotic zone in all shelf domains. The role of the oceanic fronts in transporting nutri- ents from deep water to the Bering shelf euphotic zone is not clear. However, various studies of fronts on other shelves have demonstrated that they are important sites of vertical transport of nutrients into the euphotic zone (Pingree et al. 1977, Fournier et al. 1977), and this is probably also true of the Bering Sea shelf fronts. There appear to be two distinct copepod communi- ties on the southeastern Bering Sea shelf (Cooney 1978, Iverson et al. 1979). A shelf group consisting of a small standing stock of small animals such as Pseudocalanus spp. and Acartia spp. is confined to the region shoreward of the middle front. An oceanic group consisting of a large standing stock of euphau- siids and large calanoid copepods is confined to the outer-shelf domain because of hydrographic condi- tions which do not allow extensive exchange of outer-shelf water with mid-shelf water. These two communities produce an across-shelf diffe
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