Class Dinophyceae — Gyiuncdiniuni wiiljfii. 



Class Cryptophyceae — Hemiselmis sp. 



Class Chrysophyceae — Disteplunuis speculum. 



Thus, due to large ceil sizes, representatives (it both 

 diatoms and peridinians dominated the biomass. 



In general, the following relationships in distribution of 

 qualitative and quantitative characteristics of phytoplankton in 

 the Bering Sea, in 1988, were noted: 



/. Depletion of the diatom and peridinian flora from north 

 to south, which can be attributed to the seasonal succession of 

 phytoplankton. 



2. As for quantitative indices, they were subject to sharp 

 variations both from station to station and at different depths, 

 which was characteristic for the region under investigation, 

 being hydrologically complex. 



5.1.2 Phytoplankton Biomass Distribution in the 

 Northern Bering Sea and Southern 

 Chukchi Sea 



WILLIAM S. ROBIE. C. PETER MCROY. and ALAN M. SPRINGER 

 liisiiiulf of Marine Science, University af Alaska. Fairbanks. Alaska. USA 



Introduction 



The ecosystem of the northern Bering Sea and southern 

 Chukchi Sea Shelf region is strongly influenced by the advection 

 of cold, nutrient-rich seawater from the edge of the deep Bering 

 Sea basin ( Springer. 1988). This conclusion resulted from data 

 collected by Inner Shelf Transfer and Recycling (ISHTAR) 

 Project investigators between 1983 and 1989 (Walsh et ai, 

 1989). The project was the first large-scale scientific study 

 attempting to elucidate the ecological processes of these northern 

 shelf waters, aregion of extremely high primary and secondary 

 productivity (McRoy et ai, 1972: Motoda & Minoda. 1974: 

 Sambrotto et ai.. 1984: Springer. 1988) leading to high upper 

 trophic level productivity (Hood & Kelley, 1974). The Third 

 Joint US-LISSR Bering & Chukchi Seas Expedition, aboard 

 iheAkadeinik Korolev. provided the first opportunity to extend 

 the ISHTAR experimental design across the whole northern 

 shelf area to examine the areal and vertical distribution of 

 phytoplankton biomass. 



Historical studies of the Bering Sea region show high 

 productivity associated with the continental shelf area in the 

 southeastern Bering Sea ( Banahan & Goering. 1 986: Sambrotto 



et ai. 1986: Schneider et al.. 1986: Smith & Vidal. 1986; 

 Walsh & McRoy. 1986) and in Bering Strait (McRoy et al., 



1972;Motoda& Minoda. 1974:Iverson<'/«/.. 1979). Zenkevitch 

 ( 1 963 ), working with many years of Soviet data, proposed that 

 cold oceanic water from the North Pacific Ocean and warm 

 shelf water from the southeastern Bering Sea create an east- 

 west biogeographical division in the northern shelf region. A 

 Japanese study by Motoda and Minoda ( 1974) also described 

 zoogeographic associations in the pelagic fauna with cold and 

 warm water masses. Kinder ef a/. (1 975) described the Bering 

 Slope Current system as a northwest, subsurface flow of North 



Pacific Ocean water entering through the Aleutian Islands and 

 continuing along the continental shelf slope bisecting at Cape 

 Navarin to form the Anadyr Stream. 



Takenouti and Ohtani (1974) and Coachman et al. (1975) 

 described the northern Bering Sea as consisting of three distinct 

 water masses: Alaskan Coastal, Bering Shelf, and Anadyr 

 water. Productivity and chlorophyll data from McRoy et al. 

 (I972),Sambrottoe?fl/.( 1984). Springer( 1988). and Whitledge 

 etal. ( 1988) showedextremely high phytoplankton production 

 in the northern Bering Sea and southern Chukchi Sea. Benthic 

 studies (Zenkevitch. 1963; Alton. 1974; Grebmeier et al.. 

 1988; Grebmeier & McRoy, 1989) revealed rich benthic fauna 

 in this region, also indicating a persistent system of intense 

 primary production in the overlying water. These studies led 

 to the hypothesis that advection of cold, nutrient-rich, oceanic 

 water (Anadyr water) onto the continental shelf of the northern 

 Bering and southern Chukchi Seas fueled the high primary 

 productivity (Walsh t'/fl/.. 1989). This production regime has 

 been described as a "continuous culture" system analogous to 

 an upwelling regime (Sambrotto et al., 1984). 



Prior to 1988, the data set describing the production 

 associated with this flow was confined to the waters east of the 

 US-USSR convention line. The joint US-USSR expedition 

 allowed expansion of the data set across the entire shelf (see 

 Frontispiece) to include the core of the Anadyr Stream. 



Study Area 



The study area extended from the South Polygon (53°N, 

 175°E) in the southern Bering Sea to the southeastern Chukchi 

 Sea near Cape Lisburne (69°N, 167°W: Frontispiece). 

 Ecological investigations began at the East Polygon (58°N, 

 1 75° W; Stations 1-5) and continued in the Gulf of Anadyr and 



123 



