Evidence for past variations in methane availability in a Siberian thermokarst lake based on δ 13 c of chitinous invertebrate remains

• Published in: Quaternary Science Reviews
• Main Authors: van Hardenbroek, M., Heiri, O., Parmentier, Frans-Jan W., Bastviken, D., Ilyashuk, B. P., Wiklund, J. A., Hall, R. I., Lotter, A. F.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2013
• Subjects: Chironomids; Chitinous remains; Invertebrates; Lake sediment; Methane; Stable carbon isotopes; Thermokarst; Siberia
• Online Access: https://pure.au.dk/portal/da/publications/evidence-for-past-variations-in-methane-availability-in-a-siberian-thermokarst-lake-based-on-13c-of-chitinous-invertebrate-remains(2984abcc-edb6-4eb9-beca-e5344c4b2f08).html; https://doi.org/10.1016/j.quascirev.2012.04.009; http://www.scopus.com/inward/record.url?scp=84881372403&partnerID=8YFLogxK

Understanding past methane dynamics in arcticwetlands and lakes is crucial for estimating future methane release. Methane fluxes from lake ecosystems have increasingly been studied, yet only few reconstructions of past methane emissions from lakes are available. In this study,we develop an approach to assess changes in methane availability in lakes based on δ 13 c of chitinous invertebrate remains and apply this to a sediment record from a Siberian thermokarst lake. Diffusive methane fluxes from the surface of ten newly sampled Siberian lakes and seven previously studied Swedish lakes were compared to taxon-specific δ 13 c values of invertebrate remains from lake surface sediments to investigate whether these invertebrates assimilated 13 C-depleted carbon typical for methane. Remains of chironomid larvae of the tribe Orthocladiinae that, in the study lakes, mainly assimilate plant-derived carbon had higher δ 13 c than other invertebrate groups. δ 13 c of other invertebrates such as several chironomid groups (Chironomus, Chironomini, Tanytarsini, and Tanypodinae), cladocerans (Daphnia), and ostracods were generally lower. δ 13 c of Chironomini and Daphnia, and to a lesser extent Tanytarsini was variable in the lakes and lower at sites with higher diffusive methane fluxes. δ 13 c of Chironomini, Tanytarsini, and Daphnia were correlated significantly with diffusive methane flux in the combined Siberian and Swedish dataset (r1=-0.72, p = 0.001, r = 0.53, p = 0.03, and r1\4;0.81, p < 0.001, respectively), suggesting that δ 13 c in these invertebrates was affected by methane availability. In a second step, we measured δ 13 c of invertebrate remains from a sediment record of Lake S1, a shallow thermokarst lake in northeast Siberia. In this record, covering the past ca 1000 years, δ 13 c of taxa most sensitive to methane availability (Chironomini, Tanytarsini, and Daphnia) was lowest in sediments deposited from ca AD 1250 to ca AD 1500, and after AD 1970, coinciding with warmer climate as indicated by an independent ...