Effects of long-term natural acidification on the algal communities of tundra ponds at the Smoking Hills, N.W.T., Canada

Abstract

Epipelic and planktonic algal communities have been examined periodically for 3 years from four tundra ponds which have very low pH values (1.8–3.6) and high heavy metal concentrations due to long-term fumigation by sulphur dioxide and sulphuric acid aerosols from nearby lignite burns. These communities have been compared with those of control ponds which are situated further from the burns and have alkaline waters (pH 8) due to calcareous marl soils. The 90 species identified from the control ponds are members of nine classes of algae. In contrast, 14 species have been observed in the fumigated ponds which are representatives of four classes, the Chlorophyceae, Euglenophyceae, Bacillariophyceae, and Cryptophyceae. The plankton of the control ponds is typical of tundra ponds in that it is dominated by small flagellates, particularly the cryptomonad Chroomonas minuta. Diatoms such as Amphora, Navicula and Surirella species, are the major components of the epipelic periphyton of these ponds, accounting for 67 to 90% of the biomass. Most of the primary productivity and biomass of the algae in the acidified ponds is benthic (3.7 versus 0.17 mg C m−2 h−1 for epipelon and plankton, respectively). The dominant species in the fumigated ponds include Chlamydomonas acidophila, Euglena mutabilis, Nitzschia communis, Eunotia arcus, and Eunotia glacialis. Fine structural examination of Euglena and Nitzschia indicates that these species are healthy under conditions of pH 1.8 and high heavy metals. These results show that the flora of the fumigated ponds is atypical of tundra ponds but rather is similar to that of very acidic temperate waters such as those draining coal-mined areas or volcanic lakes.