TABLE 8 



Abundance of organisms (speciniens/m') 



in tiie neuston and subneuston layers 

 of the Chuicchi Sea. 9-15 August 1988. 



Similar to the Chirikov Gulf in the Bering Sea, the Chukchi 

 Sea was dominated by copepods, bivalve larvae, and tunicates 

 making up 50%, 26%, and 17%. coirespondingly. from the 

 total number of organisms. Besides, protozoa, rotatoria, 

 hydrozoans, polychaete larvae, cirripeds, ophiurians, marine 

 urchins, cladocereans. euphausiids. decapod larvae, fish eggs, 

 and larvae were encountered. 



Thus, the number of organisms in the neuston layer in 

 comparison to the subneuston layer in the Bering Sea (East 

 Polygon, 80%; South Polygon, 33%; Gulf of Anadyr, 38%; 

 Chirikov Gulf, 75%) prevailed on the average in 63% of the 

 cases; in the Chukchi Sea, 86%. The distribution of the number 

 of organisms in the neuston and subneuston layers of the 

 Bering and Chukchi Seas is illustrated in Fig. 1. Taking into 

 consideration the dominance of organisms (%) in these two 

 layers, seven regions less favorable for the development of 

 neuston in comparison to others have been distinguished 

 (Fig. 2). 



It is known that wind and surface water circulation have a 

 great influence on the development and distribution of neuston. 

 According to the general scheme of surface water circulation in 

 the Bering and Chukchi Seas, the regions pertain to zones of 

 mixing of waters of different origin, such as: I-II — warm 

 Pacific and Bering marine waters; III-IV — warm Pacific and 

 cold fresh Anadyr waters; V — cold fresh Anadyr and cold 

 Chukchi marine waters; VI — warm Pacific and Bristol waters; 

 and VII — warm Pacific and cold Chukchi marine waters. 



The data received, at first glance, do not coincide with 

 Zaitsev's concept (1977), where it has been stated that a rich 

 community of neuston develops on the boundaries between 

 different water masses. Probably, the main factor here is the 

 velocity of water currents. At small velocities a concentration 

 of organisms occurs, initiating the development of hydrobionts; 



CHUKCHI 

 PENINSULA 



Concentration (%) in 

 Neuston layer (0-5 cm). 

 SubNueston I, 



LgN.no'm 



Fig. 1 . Distribution of organisms in the near surface microlayers and relation 

 to abundance in stations in the Bering and Chukchi Seas. 



at greater speeds, organic matter promoting their development 

 is carried out with the currents. 



The following explanation may also hold. The regions do 

 not coincide with the areas of convergence of heterogeneous 

 waters but with the centers of circulation of surface currents 

 where funnels are formed and organisms are sucked into them 

 entering the lower layers of the pelagic zone. This explanation, 

 probably, is closer to the truth, as the regions with a higher 

 density of organisms in the neuston layer (Fig. 3), when 

 compared to regions unfavorable for the development of 

 zooneuston. confimi that they are adjacent to one another, but 

 the former overlap with marginal regions of circulation of 

 surface currents. 



Five areas of distribution of organisms in the neuston layer 

 of the Bering and Chukchi Seas having high abundance are 

 distinguished: southwest of the southern region (South Polygon), 

 southeast of the eastern region (East Polygon), the northwest of 

 the Gulf of Anadyr, the north and east of Chirikov Gulf, and the 

 east and north of the Chukchi Sea. 



The average abundance of organisms in the neuston layer 

 of the Bering Sea is 68,658 specimens/m', and 

 43,464 specimens/m' in the Chukchi Sea. The most diverse in 

 number was the eastern region in the Bering Sea ( East Polygon ), 

 1 18,234 specimens/m\ while the lowest numbers were found 

 in the Gulf of Anadyr, 17,238/m\ 



