170 R. T. Prentki et al. 



no planktonic diatoms. There are diatoms in the sediment, however, and 

 their production would reduce the concentration of silica in the water. 



The pond sediments are iron-rich peats. Concentrations of all ions 

 except potassium in the interstitial water are higher than in the water 

 column but are within the range of pore water from the Barrow terrestrial 

 site. Particulate iron concentrations are exceptionally high, up to 133,000 

 ppm, while the low manganese suggests both a differential mobilization of 

 iron by humic compounds and a lack of secondary mineral formation. 



Trace metal analyses revealed that the pond water was similar to sea 

 water; there was 1.0 ^g Cu liter"', 0.7 ng Pb liter"', and 4.9 ^g Zn 

 liter"'. 



Inorganic Carbon 



The alkalinity was low, between 0.32 and 0.45 meq liter ' after the 

 effect of the meltwater disappeared. The pH was low early in the summer 

 but stabilized in the range 7.05 to 7.62. Because of the low buffering 

 capacity, photosynthesis changed the alkalinity by 0.02 meq liter"' and 

 the pH by 0.5 during a single day. Total inorganic carbon varied from 1 .43 

 to 8.08 mg C liter"' and averaged 4.10, 5.01, and 2.73 over the 3 years. 

 These are low values (one-seventh of seawater). 



Continuous measurements of the partial pressure of COj in the water 

 (PCO2) were carried out for 6 weeks in 1971. The PCO2 ranged from 450 

 to more than 1500 ppm so the pond was always supersaturated compared 

 with 320 ppm in water in equilibrium with air. This does not imply a large 

 amount of CO2. For example, in this pond when the total CO2-C is 4.45 

 mg liter"' (from alkalinity and pH), most of the carbon is found as 

 HCO3. When the PCO2 is 320 ppm, then the dissolved CO2 is 0.37 mg C 

 liter"'. A PCO2 of 640 ppm equals 0.74 mg CO2-C liter"'. In the pond 

 water in 1971, the difference between the saturation value (320 ppm) and 

 the measured PCO2 averaged 397 ppm. This implies that there was a 

 continual transfer of CO 2 from the water to the air as a result of the excess 

 of respiration (mostly in the sediments) over photosynthesis. Also, the 

 transfer rate is relatively slow as the pond's CO 2 is not in equilibrium with 

 the air. The PCO2 was directly related to the sediment temperature and 

 indirectly related to wind speed. There was higher microbial and root 

 respiration at higher temperatures. 



An evasion coefficient of 0.34 ±0.1 7 mg C02-Ccm"^ atm"' min"' 

 was measured under a variety of wind and temperature conditions. This 

 gave an average rate of transfer of 0.53 g CO 2-C m " " day ' . The average 

 is likely conservative even though it is about twice the estimated value 

 based on studies of the respiration of separate groups of organisms. Much 

 of the CO 2 transferred to the air may arise from the respiration of roots 

 but this rate is poorly known. 



