The limnology, diatom autecology, and paleolimnology of lakes and ponds from Alert, Ellesmere Island, Isachsen, Ellef Ringnes Island, and Mould Bay, Prince Patrick Island, Canadian High Artic

The limnological characteristics of lakes and ponds were established for previously unexplored high arctic sites from Alert, Ellesmere Island, Isachsen, Ellef Ringnes Island, and Mould Bay, Prince Patrick Island. The Alert lakes and ponds were typically oligotrophic, low in dissolved organic carbon (DOC), and very alkaline, similar to the characteristics of the freshwaters across most of the Canadian High Arctic. Differences in water chemistry between the large lakes and the shallow ponds illustrated the different responses of these two types of water bodies to environmental changes, with ponds typically characterized by higher nutrient and solute concentrations than lakes. Isachsen lakes and ponds had strikingly diverse water chemistry characteristics, with ranges often exceeding those found from the entire High Arctic. In general, these sites were slightly acidic. The characteristics of Mould Bay freshwaters were strongly influenced by the atypically high vegetation levels and soil development of the local landscape. Sites were typically mesotrophic, weakly alkaline, and high in DOC.; The diverse diatom assemblages from the 90 sites reflected the diverse limnological characteristics of these three regions. 352 diatom taxa were identified, and multivariate analyses indicated that species compositions were most strongly related to specific conductivity and pH. The autecological characteristics of diatom taxa were used to develop inference models for the reconstruction of these two important variables. These models were then used to infer past limnological trends from fossil diatoms preserved in dated sediment cores.; Analysis of sediment cores from Alert and Isachsen revealed relatively stable community composition for centuries to millenia, followed by marked assemblage changes in the mid-18th century in two shallow Isachsen ponds, and ∼1920 in Self Pond, a lake near Alert. Diatom models inferred an increase of 0.5 to 0.8 pH units corresponding to these assemblage changes, which were strongly correlated with Alert temperature records for the last ∼30 years.