Journal of Geophysical Research: Biogeosciences
© American Geophysical Union
Impact Factor: 3.318
ISI Journal Citation Reports © Ranking: 2015: 27/184 (Geosciences Multidisciplinary)
Online ISSN: 2169-8961
Associated Title(s): Journal of Geophysical Research
Sources and sinks of methane in Lake Kivu
Africa' s Lake Kivu, which borders Rwanda and the Republic of the Congo, contains huge amounts of methane (an estimated 60 km3) as well as carbon dioxide (an estimated 300 km3). Although the methane could provide a source of energy if it could be tapped, the high concentration of gases pose a risk of dangerous gas eruptions, threatening the local population. Furthermore, it has been reported that concentrations of methane have risen by as much as 15% in the past 30 years. Scientists need to learn more about the sources and sinks of methane in Lake Kivu to better assess the risk of catastrophic outgassing and sustainability of methane harvesting. Pasche et al. (2011) studied present-day formation and oxidation of methane. By analyzing isotopes of carbon in samples from the lake, they determined that an unusually high proportion of methane (65%) in the deep parts of the lake is derived from geologic sources or produced biologically from geogenic carbon dioxide entering the lake through subaquatic springs. A significant amount of methane also comes from degrading organic material. Accumulation of such material has been increasing in recent decades as a result of factors such as the introduction of nonnative fish, enhanced internal recycling of nutrients due to increased discharges of subaquatic springs, and increased levels of nutrients caused by rising human populations. In addition, researchers found that oxidation of methane by aerobic bacteria is the main process preventing methane from escaping into the atmosphere, with anaerobic methane oxidation playing a minor role.