A study on methane cycling in aquatic ecosystems at different latitudes

April 19, 2013 • Filed under: News — melanie.rohr

Join us this Friday, April 19, 2013, for the last seminar of the spring semester. Karla Martinez-Cruz will present her research on methane cycling in aquatic ecosystems and present current findings from Mexico City and Alaska.

Friday Seminar Series

  • What: Methane cycling in aquatic ecosystems: Alaska and Mexico as case studies
  • Who: Karla C. Martinez-Cruz, PhD candidate. Cinvestav, Mexico, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Germany and Water and Environmental Research Center, USA.
  • When: 3:30-4:30 p.m., Friday, April 19
  • Where: 531 Duckering

Methane (CH4) is one of the most important greenhouse gases (GHG); it contributes for about 30% to the total net anthropogenic radiative forcing of GHG. Previous studies have demonstrated that freshwater ecosystems are important sources of CH4, being responsible for approximately 6 to 16% of global methane emissions. Methane emissions in freshwater ecosystems are controlled by CH4 oxidation processes. It has been estimated that more than 60% of total produced CH4 in sediments is oxidized in the water column, before it enters the atmosphere.
We have been studying the methane cycling in aquatic ecosystems at different latitudes in order to better understand the processes involved in methane cycling. First, we measured the CH4 emissions from aquatic ecosystems in Mexico City in order to contribute with the governmental plan of finding sources of GHG and methods for mitigating them. Additionally, we assessed the oxidation of CH4 in these aquatic ecosystems to estimate methane budget. We found that the aquatic ecosystems in Mexico City contribute with 2 to 11% of the total CH4 emission from Mexico City, and that about 73% of net CH4 produced in lake sediments is oxidized in the water column.
On the other hand, it has been suggested that boreal lakes could contribute as much as 6% of global atmospheric CH4 sources annually. However, the magnitude and variability of CH4 production and oxidation in boreal lakes in the context of global CH4 cycling needs to be further constrained, particularly in northern latitudes, where lakes are a prominent feature of the landscape and where CH4 oxidation has been scarcely reported. We determined CH4 oxidation and emissions along a north-south transect in 30 Alaskan lakes during summer and winter seasons. The results showed a seasonal variation and a clear relationship between type of permafrost and CH4 oxidation rates.