Lakes Could be an Unsuspected Source of Methane

Evaluating methane production under oxic conditions.

Lakes Could be an Unsuspected Source of Greenhouse Gases
Summer 2015, beginning of the field study on Lake Hallwil, in the Swiss canton of Argovia. (DR)

Until now, it had been thought that methane could only be produced in oxygen-deprived environments, such as the sedimentary layers found at the bottom of lakes. But, in reality, surface water even can produce a significant amount of methane.

Scientists at the University of Geneva (UNIGE), Switzerland have recently disclosed that this aspect is still largely unknown. They enlighten it by measuring the methane concentration and production in the surface water (the top five meters) of Lake Hallwil in the Swiss canton of Argovia.

Scientists measured methane concentration at different depths in lakes with low organic matter content. They mainly observed the thermocline layer, where the water temperature drops sharply. While doing this, they ignored methane production in the lake surface layer, especially the top five meters.

They found that the mechanical accumulation of methane in the lake surface cannot explain the concentrations that the scientists observed. The blending of the surface water makes a constant, one-path trade with the climate, and the methane escapes from the water into the air. The fixation should, along these lines, be much lower, and the rates watched must be clarified by the way that the gas is being delivered in the surface layer.

Daniel McGinnis, co-authors of the study said, “Something huge is going on in the surface water, and nobody has been paying attention to it so far. In short, though there is less area covered by freshwater than oceans, the contribution from lakes is the same.”

The result suggests that a similar wonder happens in different lakes with comparative attributes. However, a large portion of the methane framed in the silt vanishes through oxidation as it rises in the lake water, the same isn’t valid for the methane produced close to the surface: this departure specifically into the environment. It is conceivable, at that point, that lakes could be gigantic makers of methane, substantially bigger makers, truth be told than already evaluated.

McGinnis said, “Another hypothesis is that the bacteria that take part in the methane oxidation process are inhibited by light, and their action would, therefore, be non-existent near the surface.”

“The methane produced in lake surface water is probably the result of several factors, and may not even be produced by bacteria. It could be the by-product of another, yet unknown process.”