84 R. T. Prentki et al. 



concentrations in 1970 (Figure 4-5c) showed a large peak in all ponds in 

 mid-July. However, in 1971 there was no peak and the overall 

 concentrations were about 5-fold lower than in 1970. 



Kalff (1965) has presented very similar water chemistry data for other 

 Barrow ponds, Lamar (1966) and Watson et al. (1966a) made some 

 chemical measurements in several ponds at Cape Thompson, and Reed 

 (1962) has reported water chemistry for ponds along the Colville River. 

 Calcium concentrations in the Colville River ponds are 3 to 5 times higher 

 than in either Cape Thompson or Barrow ponds. The Barrow ponds are 

 strongly affected by their nearness to the ocean and as a result these ponds 

 have 2 times higher sodium and chloride levels and at least 3 to 10 times 

 lower sulfate levels than do ponds at Cape Thompson to the west or 

 Colville River area ponds to the east. Kalff (1968) found that the high 

 chloride waters extended farthest inland south of Barrow, but that 

 bicarbonate generally replaced chloride as the dominant ion as one moved 

 inland from the northern coast of Alaska. Kalff also concluded that the 

 concentrations of ions in surface water of northern Alaska and Canada 

 were similar to those in low conductivity temperate waters. 



The silica in the Barrow ponds is very low; in fact, the concentrations 

 are the lowest of any ponds or lakes listed by Hobbie (1973) in a recent 

 review of arctic limnology. Livingstone et al. (1958) also found the Barrow 

 ponds to be low in silica. Concentrations are so low in these ponds that it is 

 doubtful that diatoms can grow. Diatoms have been reported to stop their 

 growth when the concentration of Si fell below 0.5 mg liter ' (Lund 1964) 

 and the ponds never reach this level. Indeed, the plankton does not contain 

 any diatoms but they are the dominant forms in the sediments. If we 

 assume a Si:C ratio of 0.4, and a primary production of the benthic algae 

 of 10 g C, then the amount of Si used by the sediment algae is about 4 g 

 m " yr \ This is equivalent to a demand of 13 mg Si liter ^^ yr '• While 

 most of this Si must come from the sediments, it is clear that there is a 

 strong biological demand for this element in the ponds. Unfortunately, we 

 do not have any data on the transfer of Si from the water to the sediments. 



Iron concentrations in the ponds are high, at least 3-fold higher than 

 in arctic coastal lakes; however they do fall within the range given in 

 Hutchinson (1957) for brown water lakes. 



Sediment Chemistry 



Investigations in the sediment have been limited to analyses of three 

 interstitial water samples, to measurements of the chemical composition 

 of two cores, and to analyses of iron-phosphorus parameters which will be 

 discussed later. 



Calcium, sodium, potassium, magnesium, and iron were determined 

 by atomic absorption spectrometry. Sediments for cation analysis were 

 digested in perchloric acid. 



