Carbon fixation by photosynthetic mats along a temperature gradient in a Tengchong hot spring

Geothermal hot springs, widely distributed on Earth, are important geological green-house gas sources which contribute large amounts of CO2 emission to the atmosphere. Exploring microbial carbon fixation in these springs is vital to fully understand the carbon budget in these terrestrial aquatic systems. In this study, carbon fixation rate by photosynthetic mats was determined with a 13C labeling approach along a gradient of temperature (~69 - ~75 oC) in a geothermal pool at Rehai Park in Tengchong, Yunnan Province, China. Light experiments were performed to determine carbon fixation rate by both photosynthesis and chemosynthesis, while dark experiments were performed by chemosynthesis. The results showed that the highest carbon fixation rate (about 4,637 μg C/g TOC/h) was obtained in light at the lowest temperature (~69 oC) in the afternoon (1:00 to 6:00 pm), most of which (96.7%) was contributed by photosynthesis. The lowest carbon fixation rate (138 μg C/g TOC/h) was measured at the ...