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@ARTICLE{Heyng:21990,
      author       = {Heyng, A.M. and Mayr, C. and Lücke, A. and Striewski, B.
                      and Wastegard, S. and Wissel, H.},
      title        = {{E}nvironmental changes in northern {N}ew {Z}ealand since
                      the {M}iddle {H}olocene inferred from stable isotope records
                      (d15{N}, d13{C}) of {L}ake {P}upuke},
      journal      = {Journal of paleolimnology},
      volume       = {48},
      issn         = {0921-2728},
      address      = {Dordrecht [u.a.]},
      publisher    = {Springer Science + Business Media B.V},
      reportid     = {PreJuSER-21990},
      pages        = {351 - 366},
      year         = {2012},
      note         = {We thank Gillian Turner and Jim Neale for coring, Markus
                      Oehlerich and Laurentius Sauer for assistance in the isotope
                      lab, Alexander Altenbach for discussions. Thomas Stephens,
                      an anonymous reviewer and the editors Thomas Whitmore and
                      Steffen Mischke provided useful comments on an earlier
                      version of this manuscript. Funding to AL and CM by the
                      German Research Foundation (grant nos. MA 4235/1-1 and LU
                      786/5-1) is gratefully acknowledged.},
      abstract     = {Maar lakes in the Auckland Volcanic Field are important
                      high-resolution archives of Holocene environmental change in
                      the Southern Hemisphere mid-latitudes. Stable carbon and
                      nitrogen isotope analyses were applied on bulk organic
                      matter and the green alga Botryococcus from a sediment core
                      from Lake Pupuke (Auckland, North Island, New Zealand)
                      spanning the period since 7,165 cal. year BP. The origin of
                      organic matter was established using
                      total-organic-carbon-to-nitrogen ratios (TOC/TN) as well as
                      organic carbon (delta C-13(OM)) and nitrogen (delta N-15)
                      isotope composition of potential modern sources. This
                      approach demonstrated that the contribution of allochthonous
                      organic matter to the lake sediment was negligible for most
                      of the record. The sedimentary TOC/TN ratios that are higher
                      than Redfield ratio (i.e. > 7) are attributed to N-limiting
                      conditions throughout the record. Variations of nitrogen and
                      carbon isotopes during the last 7,165 years are interpreted
                      as changes in the dominant processes in the lake. While
                      epilimnetic primary productivity controlled isotope
                      composition before 6,600 cal. year BP, microbial processes,
                      especially denitrification and methane oxidation, caused
                      overall shifts of the delta N-15 and delta C-13 values since
                      the Mid-Holocene. Comparisons with climate reconstructions
                      from the Northern Island suggest that changes in the
                      wind-induced lake overturn and a shift to more pronounced
                      seasonality were the most likely causes for lake-internal
                      changes since 6,600 cal. year BP.},
      keywords     = {J (WoSType)},
      cin          = {IBG-3},
      ddc          = {930},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {Terrestrische Umwelt},
      pid          = {G:(DE-Juel1)FUEK407},
      shelfmark    = {Environmental Sciences / Geosciences, Multidisciplinary /
                      Limnology},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000305959000006},
      doi          = {10.1007/s10933-012-9606-5},
      url          = {https://juser.fz-juelich.de/record/21990},
}