180 



V. Alexander et al. 



2.0 



1.6 



i. 



Q. 

 O 



1.2 



I 0.8 



0.4 



-] — I — I — 1 1 — I — 1 — I — 1 — I — I [- 



(•) Phaeo not measured 



10 20 

 Jun 



_1 I L_ 



10 20 

 Jul 



10 20 

 Aug 



Sep 



FIGURE 5-1. Chlorophyll 2l in the water of Pond B, 1971 

 and 1972. 



and an ultra-oligotrophic situation. The concentrations are comparable 

 with those found in the open ocean, in lakes at Prudhoe Bay, Alaska (0.13 

 to 1.46 Mg Chi a liter ~^), and in Ikroavik Lake (0.03 to 2.37). In lakes 

 Peters and Schrader, deep lakes in the Brooks Range, Hobbie (1959) 

 found up to 1.6 ^lg Chi a liter "^ during an under-ice bloom but 

 concentrations dropped to 0.8 ^lg during the open water period. Char Lake 

 contained 0.4 to 0.6 Mg Chi a liter ^ during the summer and 0. 1 to 0.2 Mg 

 in the winter (Kalff and Welch 1974). 



The microscopic examination confirmed the earlier work of Kalff 

 (1967a) who found that almost all of the phytoplankton were small 

 nannoplankton forms. An even earlier study of the freshwater algae of the 

 Barrow area (Prescott 1953) sampled only with a net and also used 

 formalin for a preservative. Not only do the nannoplankton pass through 

 most nets, but the flagellates are destroyed by formalin. For this reason, 

 the dominant algae we found in the ponds were not the same ones reported 

 by Prescott. In addition, the settling chamber technique reveals millions of 

 algae per liter while the net collects only a few hundred or thousand per 

 liter. This dominance of the nannoplankton over the net plankton is 

 characteristic of arctic lakes and ponds (Hobbie 1973). 



Although some variability in the species did exist from pond to pond, 

 there was a strikingly consistent pattern of early season dominance by the 

 Chrysophyta and a later shift to dominance by Cryptophyta (Figure 5-2). 

 The important Chrysophytes included Chromulina sp. and Ochromonas 

 sp., with Pseudokephyrion sp. and Mallomonas sp. also present. The 

 Cryptophytes included a number of species of Cryptomonas and 

 Chroomonas but the most abundant form was Rhodomonas minuta. All 



