LIMNOLOGY OF HIGH ARCTIC PONDS (CAPE HERSCHEL, ELLESMERE ISLAND, NWT)

We monitored limnological changes over four field seasons in 36 high a rctic ponds, located on Cape Herschel (78-degrees 37' N, 74-degrees 42 ' W), east-central Ellesmere Island. The ponds freeze completely for a t least 10 months of the year; however, during the short summers, wate r temperatures warm substantially (to a recorded maximum of 17-degrees -C) and fluctuate diurnally. All the ponds are shallow (Z(max) < 2 m), clear, and oligotrophic. With the exception of one site (Paradise Pon d, pH = 6.5), the ponds are alkaline (pH range = 7.4-8.6), reflecting the presence of calcareous tills overlying granitic bedrock. Conductiv ity values fluctuated seasonally, but were generally between 100 and 3 00 muS. The only exceptions were one tidally influenced brackish pond, with conductivity measured at 10,393 muS, and the dilute Paradise Pon d, with a minimum conductivity of 22 muS. Major ion concentrations are relatively similar amongst the remaining sites, although environmenta l gradients exist (reflecting, for example, differences in local drain age basins and proximity to the sea). Ca2+ and Na+ are the major catio ns, whereas Cl- is the major anion. Ionic concentrations change over t he summer, due to the combined effects of cryoconcentration, snowmelt dilution, evaporation, and other variables. High arctic ponds such as these may be especially sensitive monitors of future environmental cha nge.