Methane ebullition and diffusion from northern ponds and lakes regulated by the interaction between temperature and system productivity
Methane (CH₄) emissions from aquatic systems should be coupled to CH₄ production, and thus a temperature-dependent process, yet recent evidence suggests that modeling CH₄ emissions may be more complex due to the biotic and abiotic processes influencing emissions. We studied the magnitude and regulat...
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| Published in: | Limnology and oceanography 2016-11, Vol.61 (S1), p.S62-S77 |
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| Main Authors: | , , , , |
| Format: | Article |
| Language: | eng |
| Online Access: | Request full text |
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| Summary: | Methane (CH₄) emissions from aquatic systems should be coupled to CH₄ production, and thus a temperature-dependent process, yet recent evidence suggests that modeling CH₄ emissions may be more complex due to the biotic and abiotic processes influencing emissions. We studied the magnitude and regulation of two CH₄ pathways—ebullition and diffusion—from 10 shallow ponds and 3 lakes in Québec. Ebullitive fluxes in ponds averaged 4.6 ± 4.1 mmol CH₄ m-2 d-1, contributing ~56% to total (diffusive + ebullitive) CH₄ emissions. In lakes, ebullition only occurred in waters < 3 m deep, averaging 1.1 ± 1.5 mmol CH₄ m-2p d-1, and when integrated over the whole lake, contributed only 18% to 22% to total CH₄ emissions. While pond CH₄ fluxes were related to sediment temperature, with ebullition having a stronger dependence than diffusion (Q10, 13 vs. 10; activation energies, 168 kJ mol-1 vs. 151 kJ mol2-1), the temperature dependency of CH₄ fluxes from lakes was absent. Combining data from ponds and lakes shows that the temperature dependency of CH₄ diffusion and ebullition is strongly modulated by system trophic status (as total phosphorus), suggesting that organic substrate limitation dampens the influence of temperature on CH₄ fluxes from oligotrophic systems. Furthermore, a strong phosphorus-temperature interaction determines the dominant emission pathway, with ebullition disproportionately enhanced. Our results suggest that aquatic CH₄ ebullition is regulated by the interaction between ecosystem productivity and climate, and will constitute an increasingly important component of carbon emissions from northern aquatic systems under climate and environmental change. |
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| ISSN: | 0024-3590 1939-5590 |