Carbon Sources and Sinks in Freshwater and Estuarine Environments of the Arctic Coastal Plain.

Abstract:

The source, fate and transport of terrestrially derived carbon as it moves through multiple landscape components (i.e. groundwater, rivers, ponds, wetlands, lakes, lagoons) on a path from land to sea in permafrost-dominated watersheds is poorly understood. Critical to our understanding of Arctic carbon budgets are small, but numerically abundant watersheds that dominate the landscape of the Alaskan Arctic Coastal Plain (ACP), which appears to be changing rapidly in response to climate warming and other environmental changes. This study was designed to understand the contribution of freshwater ecosystems in the Arctic to regional carbon budgets. pCO2 was logged continually in ponds, lakes and streams sites near Barrow, AK and recorded across transects in Elson Lagoon, a coastal lagoon on the Beaufort coast. Average pCO₂ of the pond over 2 weeks in August (1196 µatm) was double that of lakes and streams, and four times higher than Elson Lagoon (216 µatm); thus, the Lagoon was acting as a small sink while the pond was a substantial source of CO₂ to the atmosphere. The uptake of CO₂ in Elson Lagoon, combined with an oversaturation of O₂, may be due to enhanced primary productivity caused by freshwater nutrient inputs. Conversely, pCO₂, chlorophyll-a and DOC increased substantially in the pond after a large rain event, suggesting that run-off introduced large amounts of terrestrially-derived carbon from groundwater. Further studies are required to elucidate the fate and transport of carbon in the numerically abundant smaller watersheds of the Arctic.