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- Title
Assessment of carbon isotopic signature of Daphnia ephippia as a proxy for past carbon transfers to pelagic food webs in Jura lakes.
- Authors
Essert, Valentin; Millet, Laurent; Verneaux, Valérie; Millet, Jules; Masclaux, Hélène
- Abstract
Previous studies suggested that past changes in carbon sources and pathways in pelagic food webs can be investigated using carbon isotopic analysis (δ13C) of ephippia, resting-eggs produced by Daphnia. However, ephippia are known to be produced by Daphnia within a relatively short time window. Moreover, δ13CDaphnia value may vary considerably over the annual cycle of lakes due to seasonal variations in the availability of the different carbon sources for pelagic consumers, such as phytoplankton or methanogenic carbon, under the effect of stratification and turnover mechanisms. As a result, the information provided by δ13Cephippia can mainly depend on the timing of ephippia production with respect to the timing of lake autumnal turnover. Nevertheless, there is still limited information in the literature about the timing of ephippia production in relation to the seasonal variability of δ13CDaphnia. However, it may have important implications for the use of carbon isotopic signature of ephippia as a paleoecological proxy of pelagic carbon transfers in stratified lakes. In this study, we combine a limnological survey on nine French lakes with a paleolimnological approach on three sediment cores to identify the factors controlling the integration period of δ13Cephippia and to assess the relevance of using δ13Cephippia as a proxy for pelagic carbon transfers in paleolimnological studies. Our limnological survey of nine lakes suggests that δ13Cephippia depends mainly on the timing of autumnal turnover. Lakes with the earliest turnover had lower ephippia δ13C due to methanogenic carbon transfer in the pelagic food web after autumnal turnover, whereas lakes with later autumnal turnover had higher δ13Cephippia, mainly reflecting phytoplankton consumption by Daphnia during stratification period. Consequently, potential shifts over time in lake turnover timing relative to ephippia production period may lead to the misinterpretation of δ13Cephippia variations in sediment records. Our paleolimnological study on three lakes shows that complementary δ13C analysis of other Daphnia remains like claws, reflecting a time-integrated average isotopic signature of the Daphnia source population, can help to identify potential changes in the integration period of δ13Cephippia and avoid misinterpretation of stratigraphic and temporal δ13Cephippia trends regarding carbon sources fuelling pelagic consumers.
- Subjects
JURA Mountains (France &; Switzerland); CARBON isotopes; DAPHNIA; ISOTOPIC signatures; FOOD chains; LAKES; ISOTOPIC analysis
- Publication
Journal of Paleolimnology, 2023, Vol 70, Issue 4, p331
- ISSN
0921-2728
- Publication type
Article
- DOI
10.1007/s10933-023-00297-6