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| Titel: |
Nitrogen stable isotopes of ammonium and nitrate in high mountain lakes of the Pyrenees |
| Auteur: |
M. Bartrons L. Camarero J. Catalan |
| Verschenen in: |
Biogeosciences discussions |
| Paginering: | Jaargang 6 (2009) nr. 6 pagina's 11479-11499 |
| Jaar: |
2009 |
| Inhoud: |
Nitrogen stable isotopes (δ<sup>15N) are increasingly used to trace food web relationships and the flow of matter in lakes. However, there is high variability in δ<sup>15N among primary producers and other primary energy resources that can eventually propagate throughout the lake food web. To increase our understanding of the origin of this variability, we measured ammonium and nitrate δ<sup>15N in atmospheric deposition (AD), epilimnetic water (EW), deep chlorophyll maximum water (DCMW), and sediment porewater (SPW) in eight mountain lakes. A general δ<sup>15N (−3.4‰) for AD was estimated as the signature for AD ammonium and nitrate did not differ. All lakes showed similar high δ<sup>15N-NH4<sup>+ values for SPW (ca. 2.2‰). In contrast, the variability among lakes in water column values was high, although differences between EW and DCMW within a lake were low. δ<sup>15N-NO3<sup>- correlated with the altitude of the lakes, and its variability was interpreted as the influence of catchment nitrification, which is higher in talus landscapes. δ<sup>15N-NH4<sup>+ distribution had two modes, positive values (ca. 3‰) were associated to DCMW of shallow lakes, and probably reflect the SPW influence. Lower values (ca. −3‰) occur in EW and DCMW of deep lakes, and its variability was related to the degree that NO3<sup>- was up taken by primary producers and recycled within the food-web when NH4<sup>+ availability was low compared to demand. Overall, altitude, lake depth and seasonal cumulative primary production largely explain the patterns of δ<sup>15N variability observed in nitrogen dissolved compounds. |
| Uitgever: |
Copernicus GmbH (provided by DOAJ) |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 89 van 146 gevonden artikelen
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