THE IMPORTANCE OF BIOGENIC METHANE AND SEDIMENTATION TO BENTHIC CHIRONOMID LARVAE IN FOUR RESERVOIRS

The biogenic production and subsequent oxidation of methane in aquatic sediments are important microbial processes that contribute to the global carbon cycle and play a significant role in the natural flux of methane to the atmosphere. I studied the importance of biogenic methane to the diet of benthic Chironomus as well as the effects of sedimentation on Chironomus carbon signatures through the use of stable isotope analysis. Results suggest benthic Chironomus are obtaining a portion of their carbon (4 – 89%) from biogenically produced methane via methane-oxidizing bacteria (MOB). Core incubation experiments showed significant levels of methane production (up to 1,514.7 mg/m2/day) and methane oxidation (up to 1101.0 mg/m2/day). Sedimentation rates, measured with vertical-suspended sediment traps, were variable by site, reservoir and thermal profile. Linear regression analysis found a significant negative correlation between total sedimentation and the percent organic matter in the sediment and a positive relationship between inorganic sedimentation and the δ13C values of Chironomus. In conclusion, biogenic methane and sedimentation are important to Chironomus in these reservoirs, and the production and oxidation of biogenic methane in these reservoirs is significant