A modern snapshot of the isotopic composition of lacustrine biogenic carbonates – records of seasonal water temperature variability
Carbonate shells and encrustations from lacustrine organisms provide proxy records of past environmental and climatic changes. The carbon isotopic composition ( δ 13 C ) of such carbonates depends on the δ 13 C of dissolved inorganic carbon (DIC). Their oxygen isotopic composition ( δ 18 O ) is cont...
| Published in: | Biogeosciences |
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| Main Authors: | , , , , , |
| Format: | Text |
| Language: | English |
| Published: |
2022
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| Subjects: | |
| Online Access: | https://doi.org/10.5194/bg-19-2759-2022 https://bg.copernicus.org/articles/19/2759/2022/ |
| Summary: | Carbonate shells and encrustations from lacustrine organisms provide proxy records of past environmental and climatic changes. The carbon isotopic composition ( δ 13 C ) of such carbonates depends on the δ 13 C of dissolved inorganic carbon (DIC). Their oxygen isotopic composition ( δ 18 O ) is controlled by the δ 18 O of the lake water and by water temperature during carbonate precipitation. Lake water δ 18 O , in turn, reflects the δ 18 O of atmospheric precipitation in the catchment area, water residence time and mixing, and evaporation. A paleoclimatic interpretation of carbonate isotope records requires a site-specific calibration based on an understanding of these local conditions. For this study, samples of different biogenic carbonate components and water were collected in the littoral zone of Lake Locknesjön, central Sweden (62.99 ∘ N, 14.85 ∘ E, 328 <math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">m</mi><mspace linebreak="nobreak" width="0.125em"/><mi mathvariant="normal">a</mi><mo>.</mo><mi mathvariant="normal">s</mi><mo>.</mo><mi mathvariant="normal">l</mi><mo>.</mo></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="36pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="4bfbe43a0c86958fccfe62f96625904c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-2759-2022-ie00001.svg" width="36pt" height="10pt" src="bg-19-2759-2022-ie00001.png"/></svg:svg> ) along a water depth gradient from 1 to 8 m . Carbonate samples of living organisms and subfossil remains in surface sediments were taken from the calcifying alga Chara hispida , from bivalve mollusks of the genus Pisidium , and from adult and juvenile instars of two ostracod species, Candona candida and Candona neglecta . Our results show that neither the isotopic ... |
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