Methane (CH4), the second most dominant greenhouse gas next to CO2, is estimated to be responsible for about one-fifth of man-made global warming. According to Bastviken et al. (2011), freshwaters are the primary natural source of atmospheric CH4 by emitting 103 Tg per year, which is 0.65 Pg of carbon. Tropical lakes possess high potential for CH4 production in anoxic deep waters and sediment due to high water temperatures and thermal stratification throughout the year. Studies regarding CH4 processes in the temperate and subtropical lakes suggest that variations in CH4 emissions should be estimated on a global scale and should be accounted together with the mixing status and possible recycling pathways (i.e. assimilation by methane-oxidizing bacteria and subsequent predation by animals, such as plankton and fish, involve in the lakes’ food webs) to suggest better water resource management, aid in CH4 reduction, and help in climate change mitigation. The overall effects of a changing climate on CH4 emission from tropical lakes is poorly understood and no account of studies on Philippine lakes can be found.

To fill this gap, this project focuses on providing insights on how ongoing climate change will affect CH4 emissions from Lakes Yambo and Pandin - two of the seven maar lakes in San Pablo, Luzon Island, Philippines and compare them with other lakes at a wider latitudinal scale. These lakes are characterized by having vertically stratified layers that either wholly or partly mix annually, based on our preliminary analyses. These lakes will be good candidates for comparison with other lakes with the same quantified data (Lake Biwa in Japan and Fei-tsui reservoir in Taiwan).