Lake Water Salinity and Periphytic Diatom Succession in Three Subarctic Lakes, Yukon Territory, Canada

Abstract

Seasonal changes in water chemistry and periphytic diatom assemblages were monitored for a saline, a subsaline, and freshwater lake in the central Yukon Territory. Athalassic saline lakes, such as these, are believed to be extremely rare in arctic regions. All three study lakes exhibited a gradual shoreline retreat over the season (28 May to 22 August 1992) due to evaporative water loss. As the season progressed, the saline lake exhibited a marked increase in conductivity and salinity, similar to changes observed for inland salt lakes in more southern regions. The seasonal changes in water chemistry were less pronounced in the subsaline and freshwater lakes. The periphytic diatom populations of the saline lake closely tracked changes in the lake's salinity, exhibiting a successional shift from taxa with low salt tolerances (e.g., Nitzschia cf. commutata and N. cf. palea) to those with high salt tolerances (e.g., Amphora acutiuscula) over the study period. Periphytic diatoms in the subsaline and freshwater lakes also exhibited marked successional changes, shifting to almost complete dominance by a single species (Cocconeis placentula and Achnanthes minutissima respectively), but these shifts were not related to lake water salinity alone.

Key words: lakes, diatoms, seasonal succession, saline, subarctic, Yukon