Thursday, 3 April 2014

The pond gas detective: tupperware and hi-tech

The new field season is underway at Druridge Bay. Pete has been experimenting with measurements of carbon dioxide and methane fluxing in and out of the wetlands. This needs a delicate mix of high-tech gas analysing kit cunningly attached to an upside down plastic sandwich box wrapped round with an old bicycle tyre inner-tube as a flotation device. Here is Pete gently positioning the floating box over the grassy shallows of a pond in a grazing meadow. The red and blue tubes allow gasses to be pumped through the analyser sitting snuggly in its black case perched on a plastic box (it does not like water), which records the changing concentrations. Pete's design uses a small floating chamber so that we can position the box over the distinct plant communities such as amphibious grasses or submerged pondweed in the ponds. There is something very immediate about watching the measures tick up on the digital displays. Suddenly the invisible chemistry is brought to life, the molecules in the air made apparent, complementing the seeping cold and the calls of the last winter geese, who did not approve of all this fiddling about in their field. The technology is, as usual, temperamental and easy to de-calibrate with one push of the wrong button but also very impressive when it switches from prima donna to primary data collection. Pete's first try outs showed steady carbon dioxide release with methane too, although at much lower concentrations. As Spring builds and the plant growth surges he will be aiming to capture gas fluxes from different pond types and plant communities. Early results show some pond types pumping out carbon dioxide whilst others are much less active. As with their plant and animal communities it seems that ponds represent a fine-grained diversity of geochemical drivers. If we can combine the flux measures for different pond types with data on the organic carbon trapped in the sediments we should be able to identify the wetlands that make the most powerful carbon sinks, perhaps even the role of different plant communities in these processes. Just so long as the wrong button does not get pressed.....

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