Methanotrophic Activity, Abundance, and Diversity in Forested Swamp Pools: Spatiotemporal Dynamics and Influences on Methane Fluxes
Abstract:Methane oxidation (methanotrophy) in the water column and sediments of forested swamp pools likely control seasonal and annual emission of CH4from these systems, but the methanotrophic microbial communities, their activities, locations, and overall impact, is poorly understood. Several techniques including14CH4oxidation assays, culture-based most probable number (MPN) estimates of methane-oxidizing bacteria (MOB) and protozoan abundance, MOB strain isolation and characterization, and PCR techniques were used to investigate methanotrophy at a forested swamp near Ithaca, New York. The greatest methanotrophic activity and largest numbers of MOB occurred predominantly at the low oxygen sediment/water interface in the water column. Seasonally, methanotrophic activity was very dynamic, ranging from 0.1 to 61.9μmoles CH4d−1g−1dry sediment, and correlated most strongly with dissolved inorganic carbon (r=0.896). Incorporation of methanotrophic variables (abundance and activity) into existing CH4flux regression models improved model fit, particularly during mid summer when CH4fluxes were most dynamic. Annually integrated methane flux and methanotrophic activity measurements indicate that differences in methanotrophic activity at the sediment/water interface likely accounted for differences in the annual CH4emission from the field site. Direct isolations of MOB resulted in the repeated isolation of organisms most closely related toMethylomonas methanicaS1. A single acidophilic, type II MOB related toMethylocella palustrisK was also isolated. Using a PCR-based MPN method and 16S rRNA genome copy number from isolates and control strains, type I and type II MOB were enumerated and revealed type I dominance of the sediment-associated MOB community.
Document Type: Research Article
Publication date: June 1, 2004