Carbon and nitrogen stable isotope ratios in surface sediments from lakes of western Ireland: Implications for inferring past lake productivity and nitrogen loading

Woodward, Craig A., Potito, Aaron P. and Beilman, David W. (2012) Carbon and nitrogen stable isotope ratios in surface sediments from lakes of western Ireland: Implications for inferring past lake productivity and nitrogen loading. Journal of Paleolimnology, 47 2: 167-184. doi:10.1007/s10933-011-9568-z


Author Woodward, Craig A.
Potito, Aaron P.
Beilman, David W.
Title Carbon and nitrogen stable isotope ratios in surface sediments from lakes of western Ireland: Implications for inferring past lake productivity and nitrogen loading
Journal name Journal of Paleolimnology   Check publisher's open access policy
ISSN 0921-2728
1573-0417
Publication date 2012-02
Year available 2011
Sub-type Article (original research)
DOI 10.1007/s10933-011-9568-z
Volume 47
Issue 2
Start page 167
End page 184
Total pages 18
Place of publication Dordrecht, Netherlands
Publisher Springer
Collection year 2012
Language eng
Formatted abstract
We used statistical analyses to determine which subset of 36 environmental variables best explained variations in surface sediment δ13C and δ15N from 50 lakes in western Ireland that span a human-impact gradient. The factors controlling lake sediment δ13C and δ15N depended on whether organics in the lake sediment were mostly derived from the lake catchment (allochthonous) or from productivity within the lake (autochthonous). Lake sediments with a dominantly allochthonous organic source (high C:N ratio sediments) produced δ13C and δ15N measurements similar to values from catchment vegetation. δ13C and δ15N measurements from lake sediments with a dominantly autochthonous organic source (low C:N ratio sediments) were influenced by fractionation in the lake and catchment leading up to assimilation of carbon and nitrogen by lacustrine biota. δ13C values from lake sediment samples in agricultural catchments were more negative than δ13C values from lake sediment samples in non-impacted, bogland catchments. Hypolimnetic oxygen concentrations and methane production had a greater influence on δ13C values than fractionation due to algal productivity. δ15N from lake sediment samples in agricultural catchments were more positive than δ15N in non-impacted bogland catchments. Lower δ15N values from non-impacted lake catchments reflected δ15N values of catchment vegetation, while higher δ15N values in agricultural catchments reflected the high δ15N values of cattle manure and inorganic fertilisers. The influence of changing nitrogen sources and lake/catchment fractionation processes were more important than early diagenesis for lake sediment δ15N values in this dataset. The results from this study suggest a possible influence of bound inorganic nitrogen on the bulk sediment δ15N values. We recommend using a suitable method to control for bound inorganic nitrogen in lake sediments, especially when working with clay-rich sediments. This study confirms the usefulness of δ13C and δ15N from bulk lake sediments, as long as we are mindful of the multiple factors that can influence these values. This study also highlights how stable isotope datasets from lake surface sediments can complement site-specific isotope source/process studies and help identify key processes controlling lake sediment δ13C and δ15N in a study area.
Keyword Lake sediments
Stable carbon isotopes
Stable nitrogen isotopes
Paleolimnology
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Published online: 1 December 2011

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Geography, Planning and Environmental Management Publications
Official 2012 Collection
 
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