1 Chaoborus spp. transport CH4 from the sediments to the surface

2Department of Biological Systems Engineering, Virginia Tech, Blacksburg, ... Tg CH4 yr-1 to the atmosphere via diffusive fluxes from their surface wa...
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Chaoborus spp. transport CH from the sediments to the surface waters of a eutrophic reservoir, but their contribution to water column CH concentrations and diffusive efflux is minor 4

Cayelan C. Carey, Ryan P. McClure, Jonathan P. Doubek, Mary E. Lofton, Nicole K. Ward, and Durelle Scott Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b04384 • Publication Date (Web): 20 Dec 2017 Downloaded from http://pubs.acs.org on January 3, 2018

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Environmental Science & Technology

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Chaoborus spp. transport CH4 from the sediments to the surface waters of a eutrophic reservoir,

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but their contribution to water column CH4 concentrations and diffusive efflux is minor

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Cayelan C. Carey1*, Ryan P. McClure1, Jonathan P. Doubek1, Mary E. Lofton1, Nicole K.

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Ward1, Durelle T. Scott2

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Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, USA

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Department of Biological Systems Engineering, Virginia Tech, Blacksburg, Virginia, USA

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*Corresponding author. Email: [email protected]; Phone: +1-540-231-8938

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Authorship Contributions: CCC conceived the original idea for the manuscript. All authors

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collected field data; CCC led the Chaoborus incubations; RPM led GHG analyses; JPD

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conducted the zooplankton microscopy; and all authors contributed to data analysis and

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interpretation. CCC led the writing of the manuscript, and all authors provided feedback and

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approved the final version.

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Submitted as a Research Article to ES&T

ACS Paragon Plus Environment

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Environmental Science & Technology

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Abstract:

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Chaoborus spp. (midge larvae) live in the anoxic sediments and hypolimnia of freshwater

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lakes and reservoirs during the day and migrate to the surface waters at night to feed on plankton.

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It has recently been proposed that Chaoborus take up methane (CH4) from the sediments in their

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tracheal gas sacs, use this acquired buoyancy to ascend into the surface waters, and then release

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the CH4, thereby serving as a CH4 “pump” to the atmosphere. We tested this hypothesis using

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diel surveys and seasonal monitoring, as well as incubations of Chaoborus to measure CH4

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transport in their gas sacs at different depths and times in a eutrophic reservoir. We found that

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Chaoborus transported CH4 from the hypolimnion to the lower epilimnion at dusk, but the

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overall rate of CH4 transport was minor, and incubations revealed substantial variability in CH4

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transport over space and time. We calculated that Chaoborus transport ~0.1 mmol CH4 m-2 yr-1 to

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the epilimnion in our study reservoir, a very low proportion (