The Methane Cycle in Shallow Lakes

Friday 26 May 2023, 12:30 pm
PhD student
T.P.A. Nijman MSc.
prof. dr. L.P.M. Lamers, dr. C.U. Welte
dr. A.J. Veraart

Methane is the second most important greenhouse gas and is responsible for around 20 percent of global warming. Unlike carbon dioxide (CO2), most methane comes from natural systems, and more specifically from shallow lakes. Yet as a society we have a huge impact on this, because nutrients from agriculture production and increases in temperature that are caused by climate change increase methane emissions. However, why this is so, and whether this process can be reversed, is not yet clear. This PhD thesis therefore focused on the methane cycle in lakes, and the way in which this is influenced by warming, nutrients and carbon. 

Evidence showed that warming causes a different type of methane-consuming bacteria in lake beds, which resulted in less methane being consumed. Extra nutrients increased methane consumption, but only at low concentrations. Methane production is therefore likely to increase at high concentrations, which would cause a greater emission of methane. Extra carbon increased methane production but did not affect methane consumption. It was ultimately found that methane emissions from shallow lakes can be cut down by control measures that reduce nutrients in shallow lakes. 

Although global warming is a universal problem, increases in nutrients and carbon are mostly caused by local factors. As a result, it is vital that their availability in shallow lakes is locally reduced in order to cut methane emissions and combat climate change. 

Tom Nijman obtained his Master’s degree in Forest and Nature Management from Wageningen University in 2017. The following year, he began his PhD research at Radboud University’s Department of Aquatic Ecology and Environmental Biology, where he previously obtained his Bachelor’s degree in Biology in 2015. Tom is now working as a postdoctoral researcher in the same department where he conducted his PhD research and is currently researching CO2 emissions from peatlands.