Martens, C., J. Val Klump. 1979. Biogeochemical cycling in an organic-rich coastal marine basin-I. Methane sediment-water exchange processes. Elsevier 44:471-490.
I chose this article because I was very interested in seeing how methane affects the earth, especially since it is being released more and more due to the thawing of permafrost. I was also very intrigued when we learned about the frozen methane bubbles in the lakes during one of our earlier lectures. After learning a little bit about methane in cold environments, such as Fairbanks, I thought it would be interesting to compare it to a warmer environment which this article does. It takes a look at how methane is produced through different mechanisms in bodies of water in North Carolina. I thought this would be interesting because the temperature changes in North Carolina aren’t nearly as extreme and the changes in Fairbanks, so I was interested in learning if the difference in temperature made a difference.
Methane produced in anoxic organic-rich sediments of Cape Lookout Bight, North Carolina, enters the water column via two seasonally dependent mechanisms: diffusion and bubble ebullition. Diffusive transport measured in situ with benthic chambers averages 49 and 163 Î¼mol · m âˆ’2 · hr âˆ’1 during November—May and June—October respectively. High summer sediment methane production causes saturation concentrations and formation of bubbles near the sediment-water interface. Subsequent bubble ebullition is triggered by low-tide hydrostatic pressure release. June—October sediment-water gas fluxes at the surface average 411 ml (377 ml STP: 16.8 mmol) · mâˆ’2 per low tide. Bubbling maintains open bubble tubes which apparently enhance diffusive transport. When tubes are present, apparent sediment diffusivities are 1.2—3.1-fold higher than theoretical molecular values reaching a peak value of 5.2 Ã— 10âˆ’5 cm2 · secâˆ’1. Dissolution of 15% of the rising bubble flux containing 86% methane supplies 170Î¼mol · mâˆ’2 · hrâˆ’1 of methane to the bight water column during summer months; the remainder is lost to the troposphere. Bottom water methane concentration increases observed during bubbling can be predicted using a 5—15 Î¼m stagnant boundary layer dissolution model. Advective transport to surrounding waters is the major dissolved methane sink: aerobic oxidation and diffusive atmospheric evasion losses are minor within the bight.