Distribution of Atmospheric Methane Oxidation and Methanotrophic Communities on Hawaiian Volcanic Deposits and Soils

Abstract

Hawaiian volcanic deposits offer ideal opportunities to assess methanotrophic bacterial colonization of new substrates, and to determine the relative significance of methanotrophy during ecosystem succession. Activity and molecular ecological surveys indicated that significant methanotrophic activity was restricted to vegetated ecosystems characterized by closed-canopy forests and significant soil accumulation. In these systems, atmospheric methane oxidation rates (0.7-1.8 mg CH₄ m^-2 d^-1) were comparable to the lower end of values reported for continental soils. No trends in activity related to deposit age or type were evident at ambient or elevated methane levels. Analyses of clone libraries based on particulate methane monooxygenase and ammonia monooxygenase (pmoA/amoA) genes revealed largely novel sequences, with distinct assemblages for each of two sites. Remarkably, sequences from a 300-yr old forest soil were most closely related to sequences from Arctic soils. Collectively, the evidence indicates that methanotrophs colonize volcanic substrates slowly and likely depend on interactions with plant and other microbial communities.