Limnological properties of permafrost thaw ponds in northeastern Canada

• Published in: Canadian journal of fisheries and aquatic sciences 2009-10, Vol.66 (10), p.1635-1648
• Main Authors: Breton, Julie, Vallières, Catherine, Laurion, Isabelle
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Applied ecology; Aquatic ecosystems; Aquatic sciences; Biological and medical sciences; Cold regions; Dissolved organic matter; Exploitation and management of natural biological resources (hunting, fishing and exploited populations survey, etc.); Fresh water ecosystems; Freshwater; Frozen ground; Fundamental and applied biological sciences. Psychology; Global warming; Greenhouse gases; Hypolimnion; Hypoxia; Limnology; Nutrients; Oil and gas production; Optical properties; Organic soils; Permafrost; Photosynthesis; Ponds; Properties; Synecology
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/F09-108

Arctic warming has recently accelerated, triggering the formation of thaw ponds and the mobilization of a carbon pool that has accumulated over thousands of years. A survey of 46 thaw ponds in the Canadian arctic and subarctic regions showed that these ecosystems have high concentrations of dissolved organic matter (DOM) and nutrients and are relatively productive. This activity was reflected in the optical properties of DOM that indicated a dominance of allochthonous sources but a significant contribution of low molecular weight compounds. Several subarctic ponds were stratified in summer, resulting in a hypoxic hypolimnion. Most ponds were supersaturated in CO 2 and CH 4 , with higher gas concentrations in bottom waters. However, arctic thaw ponds colonized by benthic microbial mats showed lower CO 2 concentrations, likely caused by active photosynthesis. CO 2 was correlated with both the quantity and the optical properties of DOM, suggesting the significant role of dissolved compounds from melting organic soils and catchment vegetation on the balance between heterotrophy and autotrophy. The large variability observed in limnological properties of this series of ponds precludes generalisations about their role in greenhouse gas production. However, the fact that all thaw ponds were supersaturated in CH 4 underscores the importance of estimating their global significance.