182 V. Alexander etal. 



told, some 105 different species were found in the ponds (Table 5-1). The 

 dominance of Chrysophytes and Cryptophytes is typical of high-latitude 

 or high-altitude bodies of water and the species found in these ponds were 

 almost all the same ones found in northern Scandinavia (Skuja 1963, 

 Holmgren 1968). Unfortunately, there were some small forms that could 

 not be given names, possibly because they are undescribed species. These 

 were lumped as 4-fim or 6-Mm flagellates, for example, and often were the 

 most abundant forms. 



In other studies in northern Alaska, Coulon and Holmgren (quoted in 

 Hobbie 1973) looked at a transect of 10 lakes from the Brooks Range to 

 the coast. They also found a dominance of Chrysophytes and 

 Cryptophytes but diatoms were particularly important in larger and 

 deeper lakes such as Chandler. Lakes Peters and Schrader, Alaska, 

 characteristically have under-ice blooms of algae. Despite the fact that 

 these lakes are similar in water chemistry and depth and are separated by a 

 narrow channel only 1.5 km long, the bloom alga in Peters was a diatom 

 (Synedra) and the bloom organisms in Schrader were Chlorophytes 

 {Chlamydomonas, Pyramidomonas and Ankistrodesmus). Comparisons 

 of these and other arctic lakes (Table 5-2) indicate that the Barrow ponds 

 are not atypical of arctic conditions and that their phytoplankton biomass 

 is even higher than the average for all arctic water bodies. Compared with 

 those of temperate lakes, these arctic phytoplankton biomass figures are 

 very low. For example, the range in the ponds is 25 to 400 Mg liter"' (but 

 two samples during spring peaks did reach 1,000). The range in the 

 eutrophic Lake Esrom is 400 to 3,000 (Jonasson 1972) and in mesotrophic 

 Lake Erken is 300 to 6,000 Mg liter " ' (Nauwerck 1963). 



The small phytoplankton algae are extremely abundant despite their 

 low total biomass. Thus, on one date in 1970 Pond C had an algal biomass 

 of 600 Mg liter ', which corresponded to 4 million cells liter " '. The range 

 over the summer was approximately from 1 to 6 million cells. As will be 

 described later, the numbers of planktonic bacteria are a thousand times 

 higher than this. 



Phytoplankton data represent a single sample taken once a week; the 

 tremendous work involved in counting one sample did not allow us to take 

 daily samples. However, in one study where tremendous effort was made a 

 dramatic day-to-day change was found in a large lake (Rodhe et al. 1958). 

 These workers attributed the changes to different water masses that were 

 transported by the wind. Hopefully, this areal heterogeneity is not a 

 problem in a small pond. There are, however, other complications as we 

 found important changes within a single day (Figure 5-3). These changes 

 are regular enough that it is doubtful that they were caused by sampling 

 error. One possible cause is that rapid reproduction is occurring and 

 indeed, the peak in algal biomass does correspond in time to the expected 

 photosynthesis peak (or perhaps the biomass peaks slightly after the 

 photosynthesis). Another possibility is that the algae are being heavily 



