Introduction and Site Description 47 



The algae of the plankton are all nannoplankton, mostly 

 cryptophytes, chrysophytes, and greens. Productivity is low, usually 1 to 

 30 g C m ■^ yr ' . Zooplankton are never abundant and only one calanoid 

 copepod, one cyclopoid copepod, and one cladoceran are present while the 

 most oligotrophic lakes have either only one species of copepod or no 

 zooplankton at all. Fish are always present except where the body of water 

 freezes solid. In shallow ponds, the absence offish permits the fairyshrimp 

 and large Daphnia to thrive. Chironomid larvae dominate the bottom 

 fauna and may live for several years. Oxygen is usually close to saturation 

 during the open water season but decreases during the winter and may 

 disappear in the deepest part of a lake. Other primary producers (rooted 

 plants, benthic algae) have not been studied, although mosses are 

 abundant in deep, clear lakes. 



In northern Alaska there are a few deep lakes (50 m) in mountain 

 valleys, a few more moderately deep lakes (25 m) in the foothills, and tens 

 of thousands of shallow lakes (2-3 m) on the coastal plains. Hundreds of 

 thousands of shallow ponds have formed on the coastal plain in former 

 lake beds. There are a number of rivers as well but these are virtually 

 unstudied. The deep lakes are dominated by planktonic processes. Several 

 receive glacial rock flour so they are quite turbid. The lack of stratification 

 during open water causes poor conditions for algal growth; as a result, the 

 maximum productivity occurs in the spring beneath the ice cover (light 

 penetrates the ice sheet when the snow cover is less than 10 cm thick). 



The shallow lakes research in northern Alaska has concentrated on 

 the origin and development of the oriented lake basins (north-south). This 

 orientation or elongation is caused by differential erosion by wind-driven 

 currents. A non-oriented lake near Barrow (Imikpuk Lake) has been 

 sampled extensively for microbes, algae, chemistry, and zooplankton. The 

 few species of cladocera and copepoda enabled several life cycles to be 

 worked out in detail. The chemistry and biology (taxonomy) of small lakes 

 have been investigated at Cape Thompson. 



Ponds near Barrow have been investigated by two projects which 

 concentrated on nutrients, phytoplankton, and zooplankton. Primary 

 productivity was extremely low, around I g C m~^ yr~'; different 

 nutrients stimulated primary productivity at different times of the year. 

 The dominant Daphnia species, D. middendorffiana and D. pulex, have 

 only females in the population. The resting eggs, which overwinter, need to 

 be frozen before they will hatch in the spring. 



In a small watershed near Barrow, most of the runoff occurred in the 

 spring melt period; summer precipitation was balanced by evapo- 

 transpiration. Large rivers, which have been little studied, contain 

 virtually no plankton, but do harbor fish which breed in smaller streams 

 and overwinter in deep pools or in streams near springs. 



Air temperatures average below freezing so that permafrost underlies 

 the area to a depth of 400 m. Some 20 to 50 cm of soil thaws each summer 

 but the permafrost is impervious and water cannot drain. Low-lying soils 



