Arctic Lakes and Streams as Gas Conduits to the Atmosphere: Implications for Tundra Carbon Budgets

Abstract

Arctic tundra has large amounts of stored carbon and is thought to be a sink for atmospheric carbon dioxide (CO(2)) (0.1 to 0.3 petagram of carbon per year) (1 petagram = 10(15) grams). But this estimate of carbon balance is only for terrestrial ecosystems. Measurements of the partial pressure of CO(2) in 29 aquatic ecosystems across arctic Alaska showed that in most cases (27 of 29) CO(2) was released to the atmosphere. This CO(2) probably originates in terrestrial environments; erosion of particulate carbon plus ground-water transport of dissolved carbon from tundra contribute to the CO(2) flux from surface waters to the atmosphere. If this mechanism is typical of that of other tundra areas, then current estimates of the arctic terrestrial sink for atmospheric CO(2) may be 20 percent too high.

Diurnal sampling reveals significant variation in CO2 emission from a tropical productive lake

“…Cole et al, 1994;Marotta et al, 2009), Lake Carioca is a small source of atmospheric carbon in comparison to higher latitude lakes. While CO 2 emissions from Lake Carioca averaged only 0.9 mmolCO 2 .m -2 .d -1 , other studies have recorded CO 2 effluxes of 20.9 mmolCO 2 .m -2 .d -1 from Arctic lakes (Kling et al, 1991), 55.6 mmolCO 2 .m -2 .d -1 from a boreal humic lake (Huotari et al, 2009), and 1200 and 90 mmolCO 2 .m -2 .d -1 from two clear-water temperate lakes (Riera et al, 1999). The registered low values of pCO 2 and CO 2 efflux from Lake Carioca are probably a consequence of its high autotrophic activity, particularly during the studied period when vertical mixing induces high production rates (640 mgC.m -2 .d -1 ; PELD Report, 2012) and scarce rainfall limits the input of allochthonous dissolved organic carbon to the lake likely reducing its respiration rates (Cole et al, 2000).…”

“…It is widely accepted that lakes are typically supersaturated with CO 2 relative to the overlying atmosphere (Kling et al, 1991;Cole et al, 1994;Duarte and Prairie, 2005). This net heterotrophic condition is believed to predominate as ecosystem respiration frequently exceeds ecosystem primary production in lakes due to the input of allochthonous organic matter from their catchments (Del Giorgio et al, 1999;Pace et al, 2004).…”

Long‐term decline in carbon dioxide supersaturation in rivers across the contiguous United States

“…Free CO 2 in ground waters is principally derived from respiration in soil environments, but can also be influenced by weathering production of DIC and alkalinity, and the resulting changes in pH. The flux of ground water enriched with terrestrially-derived (largely soil-respired) CO 2 , supplemented by the decomposition of terrestrial organic matter within streams, dominate the aquatic carbon cycle in most rivers, and makes these systems CO 2 supersaturated and net sources of CO 2 to the atmosphere [Kling et al, 1991;Cole et al, 1994;Jones andMulholland, 1998a, 1998b].…”

Holocene carbon burial by lakes in SW Greenland

“…Glaciated landscapes often have a very high density of lakes, and Oechel & Billings (1992) have estimated that C in arctic soils has a turnover time of ~500 years, which contrasts to the effective long-term burial of C by lakes spanning thousands of years (Cole et al, 2007). Some of the soil-C is released from terrestrial systems as dissolved organic carbon (DOC) and subsequently transported to streams and lakes where it is transformed and processed by microbial activity (Kling et al, 1991;Sobek et al, 2003). A portion of this C-pool is released via respiration, but some may be retained and stored in sediments.…”

“…The applicability of these C burial estimates to arctic lakes is not known, but considering the large variability among the estimates to date and the generally lower productivity of arctic lakes relative to boreal and temperate lakes (due to shorter growing season and lower nutrient availability) (Lizotte, 2008), they may be inappropriate. Thus, better regional/local estimates of C burial are needed to increase our understanding of the role of lakes in regional C budgets (Kling et al, 1991;Cole et al, 2007).…”