embayment of the Gulf of Alaska (Feder and Paul, 1977). In many cases 

 where the species are not identical or their identity is questionable, 

 the genera are the same (see Table 2.2.1). It is well known that the 

 species occurring in the Baltic are tolerant of lowered salinities, this 

 is presumably true of many of their counterparts in Alaska, even though 

 the Alaskan species usually live in full salinity sea water. While 

 salinity is known to be a major factor controlling distribution in the 

 Baltic, it apparently is not a major factor in Alaska, except in 

 isolated cases. 



However, there are also important differences between the two 

 regions which must be kept in mind when comparisons are made. The 

 Baltic is nearly a-tidal, whereas the tidal range in most Alaskan waters 

 is generally large. This gives the shorelines entirely different physical 

 and biological characteristics. Also, due to the absence of tides and a 

 relatively short fetch across the Baltic, turbulent mixing is lower. 

 This results in the rapid warming of Baltic surface waters in late 

 spring to early summer, with the thermocline forming at about 15-20 m 

 depth. The surface layer generally reaches temperatures of 15-18 C in 

 summer, but inshore, and in exceptional summers even offshore, tempera- 

 tures may temporarily exceed 20 C. Although there are locations in 

 Alaska where some of the physical conditions of the surface water are 

 similar to those in the Baltic (for example, the narrow tidal range in 

 the Beaufort Sea) , community level comparisons will probably be best in 

 the deeper (below 15-20 m) zones (the soft bottoms). 



The salinity characteristics of the two regions clearly differ, 

 with the only analogous areas in Alaska being at the head of estuaries 

 and fjords adjacent to glaciers, where melt-water and runoff will at 

 times create mesohaline conditions similar to the Baltic. However, the 

 Baltic is unlike most estuarine areas of lowered salinity (including 

 those in Alaska), because the salinities vary little during the year 

 (generally less than ±1 o/oo S). This allows some species of marine 

 origin to penetrate to surprisingly low salinities. 



A final differentiating feature of the Baltic is the salinity 

 stratification of the Baltic proper (also observed in some bays of the 



34 



