Technical note: Novel triple O<sub>2</sub> sensor aquatic eddy covariance instrument with improved time shift correction reveals central role of microphytobenthos for carbon cycling in coral reef sands
<p>The aquatic eddy covariance technique stands out as a powerful method for benthic <span class="inline-formula">O<sub>2</sub></span> flux measurements in shelf environments because it integrates effects of naturally varying drivers of the flux such as curren...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2021-10-01
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| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/18/5381/2021/bg-18-5381-2021.pdf |
| _version_ | 1818716328237727744 |
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| author | A. Merikhi P. Berg M. Huettel |
| author_facet | A. Merikhi P. Berg M. Huettel |
| author_sort | A. Merikhi |
| collection | DOAJ |
| description | <p>The aquatic eddy covariance technique stands out as a powerful method for benthic <span class="inline-formula">O<sub>2</sub></span> flux measurements in shelf environments because it
integrates effects of naturally varying drivers of the flux such as current flow and light. In conventional eddy covariance instruments, the time
shift caused by spatial separation of the measuring locations of flow and <span class="inline-formula">O<sub>2</sub></span> concentration can produce substantial flux errors that are
difficult to correct. We here introduce a triple <span class="inline-formula">O<sub>2</sub></span> sensor eddy covariance instrument (3OEC) that by instrument design eliminates these
errors. This is achieved by positioning three <span class="inline-formula">O<sub>2</sub></span> sensors around the flow measuring volume, which allows the <span class="inline-formula">O<sub>2</sub></span>
concentration to be calculated at the point of the current flow measurements. The new instrument was tested in an energetic coastal environment with highly permeable
coral reef sands colonised by microphytobenthos. Parallel deployments of the 3OEC and a conventional eddy covariance system (2OEC) demonstrate that
the new instrument produces more consistent fluxes with lower error margin. 3OEC fluxes in general were lower than 2OEC fluxes, and the nighttime
fluxes recorded by the two instruments were statistically different. We attribute this to the elimination of uncertainties associated with the time
shift correction. The deployments at <span class="inline-formula">∼</span> 10 <span class="inline-formula">m</span> water depth revealed high day- and nighttime <span class="inline-formula">O<sub>2</sub></span> fluxes despite the relatively low
organic content of the coarse sediment and overlying water. High light utilisation efficiency of the microphytobenthos and bottom currents increasing
pore water exchange facilitated the high benthic production and coupled respiration. 3OEC measurements after sunset documented a gradual transfer of
negative flux signals from the small turbulence generated at the sediment–water interface to the larger wave-dominated eddies of the overlying water
column that still carried a positive flux signal, suggesting concurrent fluxes in opposite directions depending on eddy size and a memory effect of
large eddies. The results demonstrate that the 3OEC can improve the precision of benthic flux measurements, including measurements in environments
considered challenging for the eddy covariance technique, and thereby produce novel insights into the mechanisms that control flux. We consider the
fluxes produced by this instrument for the permeable reef sands the most realistic achievable with present-day technology.</p> |
| first_indexed | 2024-12-17T19:17:31Z |
| format | Article |
| id | doaj.art-22ccf39c3f0747e9810095a09e7789c6 |
| institution | Directory Open Access Journal |
| issn | 1726-4170 1726-4189 |
| language | English |
| last_indexed | 2024-12-17T19:17:31Z |
| publishDate | 2021-10-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Biogeosciences |
| spelling | doaj.art-22ccf39c3f0747e9810095a09e7789c62022-12-21T21:35:43ZengCopernicus PublicationsBiogeosciences1726-41701726-41892021-10-01185381539510.5194/bg-18-5381-2021Technical note: Novel triple O<sub>2</sub> sensor aquatic eddy covariance instrument with improved time shift correction reveals central role of microphytobenthos for carbon cycling in coral reef sandsA. Merikhi0P. Berg1M. Huettel2Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, FL 32306-4520, USADepartment of Environmental Sciences, University of Virginia, Charlottesville, VA 22904-4123, USADepartment of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, FL 32306-4520, USA<p>The aquatic eddy covariance technique stands out as a powerful method for benthic <span class="inline-formula">O<sub>2</sub></span> flux measurements in shelf environments because it integrates effects of naturally varying drivers of the flux such as current flow and light. In conventional eddy covariance instruments, the time shift caused by spatial separation of the measuring locations of flow and <span class="inline-formula">O<sub>2</sub></span> concentration can produce substantial flux errors that are difficult to correct. We here introduce a triple <span class="inline-formula">O<sub>2</sub></span> sensor eddy covariance instrument (3OEC) that by instrument design eliminates these errors. This is achieved by positioning three <span class="inline-formula">O<sub>2</sub></span> sensors around the flow measuring volume, which allows the <span class="inline-formula">O<sub>2</sub></span> concentration to be calculated at the point of the current flow measurements. The new instrument was tested in an energetic coastal environment with highly permeable coral reef sands colonised by microphytobenthos. Parallel deployments of the 3OEC and a conventional eddy covariance system (2OEC) demonstrate that the new instrument produces more consistent fluxes with lower error margin. 3OEC fluxes in general were lower than 2OEC fluxes, and the nighttime fluxes recorded by the two instruments were statistically different. We attribute this to the elimination of uncertainties associated with the time shift correction. The deployments at <span class="inline-formula">∼</span> 10 <span class="inline-formula">m</span> water depth revealed high day- and nighttime <span class="inline-formula">O<sub>2</sub></span> fluxes despite the relatively low organic content of the coarse sediment and overlying water. High light utilisation efficiency of the microphytobenthos and bottom currents increasing pore water exchange facilitated the high benthic production and coupled respiration. 3OEC measurements after sunset documented a gradual transfer of negative flux signals from the small turbulence generated at the sediment–water interface to the larger wave-dominated eddies of the overlying water column that still carried a positive flux signal, suggesting concurrent fluxes in opposite directions depending on eddy size and a memory effect of large eddies. The results demonstrate that the 3OEC can improve the precision of benthic flux measurements, including measurements in environments considered challenging for the eddy covariance technique, and thereby produce novel insights into the mechanisms that control flux. We consider the fluxes produced by this instrument for the permeable reef sands the most realistic achievable with present-day technology.</p>https://bg.copernicus.org/articles/18/5381/2021/bg-18-5381-2021.pdf |
| spellingShingle | A. Merikhi P. Berg M. Huettel Technical note: Novel triple O<sub>2</sub> sensor aquatic eddy covariance instrument with improved time shift correction reveals central role of microphytobenthos for carbon cycling in coral reef sands Biogeosciences |
| title | Technical note: Novel triple O<sub>2</sub> sensor aquatic eddy covariance instrument with improved time shift correction reveals central role of microphytobenthos for carbon cycling in coral reef sands |
| title_full | Technical note: Novel triple O<sub>2</sub> sensor aquatic eddy covariance instrument with improved time shift correction reveals central role of microphytobenthos for carbon cycling in coral reef sands |
| title_fullStr | Technical note: Novel triple O<sub>2</sub> sensor aquatic eddy covariance instrument with improved time shift correction reveals central role of microphytobenthos for carbon cycling in coral reef sands |
| title_full_unstemmed | Technical note: Novel triple O<sub>2</sub> sensor aquatic eddy covariance instrument with improved time shift correction reveals central role of microphytobenthos for carbon cycling in coral reef sands |
| title_short | Technical note: Novel triple O<sub>2</sub> sensor aquatic eddy covariance instrument with improved time shift correction reveals central role of microphytobenthos for carbon cycling in coral reef sands |
| title_sort | technical note novel triple o sub 2 sub sensor aquatic eddy covariance instrument with improved time shift correction reveals central role of microphytobenthos for carbon cycling in coral reef sands |
| url | https://bg.copernicus.org/articles/18/5381/2021/bg-18-5381-2021.pdf |
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