Limnology of harding lake, alaska: A deep, subarctic lake

Abstract

Harding Lake (mean depth =16 m) located in Interior Alaska (64°25'N, 146°50'W), studied in the early 1970s in response to concerns about the impact of lakeshore development on water quality was sampled again in summer 1993 thereby providing comparative data over a 20-year period. The lake is usually dimictic but some years stratification begins under the ice and the lake misses a re-oxgenating overturn. One-third of the annual heat budget of about 19,600 cal cm2 is taken up by melting the ice cover. The lake is the common calcium-bicarbonate type but is dilute due to its relatively small watershed and dominance of siliceous material in the local lithography. Based on Secchi transparency, plant nutrients and algal chlorophyll the lake is oligotrophic, with no evidence the lake has been enriched during the study period. Annual primary productivity was estimated at 48 C m2 yr−1 and exhibited a seasonal pulse that began in early May and reached peak values just before ice-off at the end of May. Two chironomid species were identified that were indicative of oligotrophic conditions in this Nearctic lake. Data on vascular plant biomass and zooplankton are presented. © 2003 Taylor & Francis Group, LLC.