124 R. T. Prentki et al. 



differences exist between interpolygonal troughs (Pond G and Soil 23 in 

 Table 4-18) and low-center polygon areas, (Ponds B and C, Soil 22) and 

 these differences transcend the aquatic-terrestrial divisions. The high 

 inorganic phosphorus in the sediment of troughs parallels the generally 

 high dissolved reactive phosphorus concentrations in the water of troughs 

 as compared to low-centered polygon ponds. There are broad patterns, 

 both in solution and sediments, which correlate with iron and other 

 parameters; these will be discussed later. 



Sediment surface layers in samples from the central basins of the 

 intensively studied ponds usually contain about 1100 Mg P (g dry wt) ' 

 with a range from 662 to 1530. The underlying reduced sediments contain 

 less phosphorus and only Pond B sediment averages more than 750 ng P (g 

 dry wt)^ over the first 10 cm. Organic phosphorus constitutes 10 to 87% 

 (1 17 to 805 Mg P (g dry wt sediment)"') of the total phosphorus present; 

 the lowest values occur in a surface fioc which covers up to 25% of the 

 sediment surface. If no floe is present, then amounts increase with depth 

 and toward plant stands. Total inorganic phosphorus has been measured 

 at 1074 Mg P (g dry wt sediment) ~ ' in the surface floe covering portions of 

 Pond B, but ranged between 200 and 400 in the other Pond B and C 

 samples. This floe appears to precipitate out of the water column and 

 accumulate along the downwind shore of ponds as summer progresses. In 

 Pond C, the total P in the sediments was 25,000 mg m "^ to a depth of 10 

 cm, the total P in interstitial water was 2 mg P m ~^ and the total P in the 

 water column (20 cm) was 5 mg P m ^ 



Pond Phosphorus Budget 



Over the long term the phosphorus status of the ponds is dependent 

 on the net balance of phosphorus entering and leaving the pond basins, 

 although the retention or loss of specific forms of phosphorus is influenced 

 strongly by pond processes. The events and processes involved in 

 phosphorus movement through the ponds are rather well understood in a 

 qualitative fashion; however, a synthesis of our insight into how the system 

 operates, together with the actual field measurements of concentrations 

 and rates, results in a budget which is distinctly speculative. This is in part 

 due to the difficulties in the measurement of water movement and in part 

 due to the paucity of phosphorus data, particularly in such things as 

 surface runoff during the summer and suspended particulates during 

 runoff. Hydrologic factors related to precipitation and water balance vary 

 greatly both within season and between years, and these factors strongly 

 influence the phosphorus budget. Warm, dry summers concentrate 

 phosphorus in the ponds at the expense of surrounding tundra while heavy 

 winter si\owpack results in high loss of phosphorus from the tundra and in 

 an even greater loss from the ponds. Insofar as possible, this budget is 



