Methane emissions from aquatic ecosystems are increasingly recognized as substantial, yet variable, contribution to global greenhouse gas (GHG) emissions. In the literature, fish bioturbation has resulted in both reduced and enhanced emissions GHG emissions from sediments. To explore how the frequency of disturbance impacts the levels of methane emissions and the associated microbial communities, we quantified GHG emissions in sediment microcosms treated with various frequencies of mechanical disturbance, analogous to different levels of activity in benthic feeding fish. GHG emissions were largely driven by methane ebullition and were highest for the intermediate disturbance frequency (7 days). The lowest emissions were for the highest frequency treatment (3 days). While total microbial community structure did not differ among treatments, among methanogenic Archaea, we observed a shift towards greater relative abundance of a putatively oxygen-tolerant methanogenic phylotype (ca. Methanothrix paradoxum) in the highest frequency treatments and at depths impacted by disturbance (1 cm). ca. Methanothrix paradoxum demonstrated no change in abundance, suggesting disturbance negatively and preferentially impacted other methanogen populations. However, total methane emissions were not simply a function of methanogen populations and were likely impacted by the residence time of methane. Low frequency mechanical disruption resulted in lower methane ebullition compared to higher frequency treatments, which in turn resulted in reduced overall methane release, likely through enhanced methanotrophic activities. Overall, this work contributes to understanding how animal behavior may impact variation in GHG emissions and provides insight into how frequency of disturbance may impact emissions. 

Primary Presenter: Michael Booth, University of Cincinnati (michael.booth@uc.edu)

Authors:

Annette Rowe, University of Cincinnati  (rowea2@ucmail.uc.edu)

Megan Urbanic, University of Cincinnati  ()

Leah Trutschel, University of Cincinnati  ()

John Shukle, IUPUI  ()

Greg Druschel, IUPUI  ()

Michael Booth, University of Cincinnati  (michael.booth@uc.edu)