Patterns and drivers of carbon dioxide concentrations in aquatic ecosystems of the Arctic coastal tundra.

Multiple aquatic ecosystems (pond, lake, river, lagoon, and ocean) on the Arctic Coastal Plain near Utqia & x121;vik, Alaska, USA, were visited to determine their relative atmospheric CO2 flux and how this may have changed over time. The nearshore coastal waters and large freshwater lakes were small sinks of atmospheric CO2, whereas smaller waterbodies were substantial sources. pCO(2) was linked to dissolved organic carbon concentrations across broad spatial and temporal scales, with greater concentrations found in smaller freshwater systems (i.e., ponds and rivers). On a day-to-day basis, water temperatures appeared to be the strongest driver of pCO(2) levels in tundra ponds, where warmer temperatures likely stimulated microbial mineralization of carbon in both aquatic and hydrologically linked terrestrial environments. Large rainfall events, which may lead to inflow of carbon-rich groundwater into these ponds, also were associated with increased daily average pCO(2). Based on comparison to historical data, we estimate that CO2 concentrations in tundra ponds have increased more than 1.8 times over the past 40 years. Quantifying CO2 flux from these abundant aquatic ecosystems on the Arctic Coastal Plain and elsewhere in the high northern latitudes will likely have important implications for furthering understanding of landscape-level and nearshore carbon dynamics in the Arctic.