Greenhouse gases emissions via DOM photodegradation in tropical peatlands and eutrophic lakes, Indonesia

Dissolved organic matter (DOM) photodegradation is one of the major sources for greenhouse gases (GHGs; CO₂, CH₄, CO) from the aquatic ecosystems to the atmosphere. However, little is known about estimations of GHGs emissions via DOM photodegradation. Studies, especially in the tropical regions, remain limited despite the more intense solar radiation than other regions. In this study, to estimate rates and potentials of GHGs emissions via DOM photodegradation in the tropical aquatic ecosystems, we conducted the photodegradation experiments using Indonesian bog (River Sabanga) and eutrophic lake (Lake Rawa Besar) waters under an artificial sunlight simulator. In bog and lake waters, three GHGs emissions were observed under light. In bog water, CO₂ rate and potential were the highest, followed by CO, with very low CH₄. CH₄ rate and potential in lake water were very low but CO₂ and CO were high and not significantly different between them. CO₂ rate in bog water was significantly higher than in lake water, while no significant difference was observed for the CH₄ and CO between the two waters. CH₄ potential in lake water was significantly higher than bog water. Meanwhile, under dark, all GHGs emission rates were negligible except for CO₂ in lake water. In Lake Rawa Besar, cyanobacterial blooms have been observed, suggesting CO₂ release via DOM biodecomposition due to abundant bioavailable and low-molecular weight DOM. This study demonstrated that eutrophication is very important not only for water quality deterioration but also for GHGs emissions.

Presentation Preference: Poster

Primary Presenter: KENSUKE WATANABE, Toho University (6125028w@st.toho-u.ac.jp)

Authors:

Yukiko Senga, Toho University  (yukiko.senga@sci.toho-u.ac.jp)