Seasonality of cladoceran and bryozoan resting stage δ13C values and implications for their use as palaeolimnological indicators of lacustrine carbon cycle dynamics

Morlock, M. A. and Schilder, J. and van Hardenbroek, M. and Szidat, S. and Wooller, M. J. and Heiri, O.. (2017) Seasonality of cladoceran and bryozoan resting stage δ13C values and implications for their use as palaeolimnological indicators of lacustrine carbon cycle dynamics. Journal of Paleolimnology, 57 (2). pp. 141-156.

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Official URL: https://edoc.unibas.ch/67693/

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The stable carbon isotope composition, expressed as delta C-13 values, of chitinous resting stages of planktivorous invertebrates can provide information on past changes in carbon cycling in lakes. For example, the delta C-13 values of cladoceran ephippia and bryozoan statoblasts have been used to estimate the past contribution of methane-derived carbon to lake food webs and variations in the delta C-13 value of planktonic algae. Limited information, however, is available concerning seasonal variations in delta C-13 values of these organisms and their resting stages. We measured the seasonal variation in delta C-13 values of Daphnia (Branchiopoda: Cladocera: Daphniidae) and their floating ephippia over a 2-year period in small, dimictic Lake Gerzensee, Switzerland. Floating ephippia of Ceriodaphnia (Branchiopoda: Cladocera: Daphniidae) and statoblasts of Plumatella (Phylactolaemata: Plumatellida: Plumatellidae) were analysed during parts of this period. Furthermore, delta C-13 values of remains from all three organism groups were analysed in a 62-cm-long sediment core. Throughout the year, Daphnia delta C-13 values tracked the delta C-13 values of particulate organic matter (POM), but were more negative than POM, indicating that Daphnia also utilize a relatively C-13-depleted carbon source. Daphnia ephippia delta C-13 values did not show any pronounced seasonal variation, suggesting that they are produced batch-wise in autumn and/or spring and float for several months. In contrast, delta C-13 values of Ceriodaphnia ephippia and Plumatella statoblasts followed variations in delta C-13(POM) values, Ceriodaphnia values being the most negative of the resting stages. Average cladoceran ephippia delta C-13 values in the flotsam agreed well with ephippia values from Gerzensee surface sediments. In contrast, average Plumatella statoblast delta C-13 values from the flotsam were 4aEuro degrees more negative than in the surface sediments. In the sediment core, delta C-13 values of the two cladocerans remained low (mean -39.0 and -41.9aEuro degrees) throughout the record. In contrast, Plumatella had distinctly less negative delta C-13 values (mean -32.0aEuro degrees). Our results indicate that in Gerzensee, Daphnia and Ceriodaphnia strongly relied on a C-13-depleted food source throughout the past 150 years, most likely methane-oxidising bacteria, whereas this food source was not a major contribution to the diet of bryozoans.
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften > Geowissenschaften > Geoökologie (Heiri)
UniBasel Contributors:Heiri, Oliver
Item Type:Article, refereed
Article Subtype:Research Article
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:19 Feb 2019 16:45
Deposited On:19 Feb 2019 16:45

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