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| Titel |
Spatial and temporal CO2 exchanges measured by Eddy Covariance over a temperate intertidal flat and their relationships to net ecosystem production |
| VerfasserIn |
P. Polsenaere, E. Lamaud, V. Lafon, J.-M. Bonnefond, P. Bretel, B. Delille, J. Deborde, D. Loustau, G. Abril |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 1 ; Nr. 9, no. 1 (2012-01-12), S.249-268 |
| Datensatznummer |
250006663
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| Publikation (Nr.) |
 copernicus.org/bg-9-249-2012.pdf |
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| Zusammenfassung |
| Measurements of carbon dioxide fluxes were performed over a temperate
intertidal mudflat in southwestern France using the micrometeorological Eddy
Covariance (EC) technique. EC measurements were carried out in two
contrasting sites of the Arcachon flat during four periods and in three
different seasons (autumn 2007, summer 2008, autumn 2008 and spring 2009).
In addition, satellite images of the tidal flat at low tide were used to
link the net ecosystem CO2 exchange (NEE) with the occupation of the
mudflat by primary producers, particularly by Zostera noltii meadows. CO2 fluxes
during the four deployments showed important spatial and temporal
variations, with the flat rapidly shifting from sink to source with the
tide. Absolute CO2 fluxes showed generally small negative (influx) and
positive (efflux) values, with larger values up to −13 μmol m−2 s−1
for influxes and 19 μmol m−2 s−1 for effluxes. Low
tide during the day was mostly associated with a net uptake of atmospheric
CO2. In contrast, during immersion and during low tide at night, CO2 fluxes where positive, negative or close to zero, depending on the season
and the site. During the autumn of 2007, at the innermost station with a
patchy Zostera noltii bed (cover of 22 ± 14% in the wind direction of
measurements), CO2 influx was −1.7 ± 1.7 μmol m−2 s−1 at low tide
during the day, and the efflux was 2.7 ± 3.7 μmol m−2 s−1 at low tide during the night. A gross primary
production (GPP) of 4.4 ± 4.1 μmol m−2 s−1 during
emersion could be attributed to microphytobenthic communities. During the
summer and autumn of 2008, at the central station with a dense eelgrass bed
(92 ± 10%), CO2 uptakes at low tide during the day were
−1.5 ± 1.2 and −0.9 ± 1.7 μmol m−2 s−1, respectively.
Night time effluxes of CO2 were 1.0 ± 0.9 and 0.2 ± 1.1 μmol m−2 s−1
in summer and autumn, respectively, resulting in a
GPP during emersion of 2.5 ± 1.5 and 1.1 ± 2.0 μmol m−2 s−1, respectively, attributed primarily to the seagrass community. At
the same station in April 2009, before Zostera noltii started to grow, the CO2 uptake
at low tide during the day was the highest (−2.7 ± 2.0 μmol m−2 s−1). Influxes of CO2 were also observed during immersion
at the central station in spring and early autumn and were apparently
related to phytoplankton blooms occurring at the mouth of the flat, followed
by the advection of CO2-depleted water with the flooding tide.
Although
winter data as well as water carbon measurements would be necessary to
determine a precise CO2 budget for the flat, our results suggest that
tidal flat ecosystems are a modest contributor to the CO2 budget of the
coastal ocean. |
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