Reconstruction of past methane availability in an Arctic Alaska wetland indicates climate influenced methane release during the past ~12,000 years

Abstract

Atmospheric contributions of methane from Arctic wetlands during the Holocene are dynamic and linked to climate oscillations. However, long-term records linking climate variability to methane availability in Arctic wetlands are lacking. We present a multi-proxy *12,000 year paleoecological reconstruction of intermittent methane availability from a radiocarbon-dated sediment core (LQ-West) taken from a shallow tundra lake (Qalluuraq Lake) in Arctic Alaska. Specifically, stable carbon isotopic values of photosynthetic biomarkers and methane are utilized to estimate the proportional contribution of methane-derived carbon to lake-sediment-preserved benthic (chironomids) and pelagic (cladocerans) components over the last *12,000 years. These results were compared to temperature, hydrologic, and habitat reconstructions from the same site using chironomid assemblage data, oxygen isotopes of chironomid head capsules, and radiocarbon ages of plant macrofossils. Cladoceran ephippia from *4,000 cal year BP sediments have d 13 C values that range from *-39 to -31%, suggesting peak methane carbon assimilation at that time. These low d 13 C values coincide with an apparent decrease in effective moisture and development of a wetland that included Sphagnum subsecundum. Incorporation of methane-derived carbon by This is one of 18 papers published in a special issue edited by Darrell Kaufman and dedicated to reconstructing Holocene climate and environmental change from Arctic lake sediments. chironomids and cladocerans decreased from *2,500 to 1,500 cal year BP, coinciding with a temperature decrease. Live-collected chironomids with a radiocarbon age of 1,640 cal year BP, and fossil chironomids from 1,500 cal year BP in the core illustrate that 'old' carbon has also contributed to the development of the aquatic ecosystem since *1,500 cal year BP. The relatively low d 13 C values of aquatic invertebrates (as low as -40.5%) provide evidence of methane incorporation by lake invertebrates, and suggest intermittent climate-linked methane release from the lake throughout the Holocene.

Post-glacial dispersal patterns of Northern pike inferred from an 8800 year old pike (Esox cf. lucius) skull from interior Alaska

“…Twelve AMS radiocarbon analyses were previously reported from analyses of terrestrial plant material from the sediment core (Table 1), which were used to produce the chronology for the core from which the bones were removed (Wooller et al, 2012a). The bones were located at between 440 and 446 cm in the sediment core.…”

“…Since the Northern pike specimen came from a previously analyzed lake-sediment core from Quartz Lake (Wooller et al, 2012a) we are able to provide some direct paleoecological context for the specimen. There appears to have been an increase in lake production that occurred after~10,500 cal yr BP, which could have resulted from an increase in July temperature and decreased ice cover (Wooller et al, 2012a).…”

“…There appears to have been an increase in lake production that occurred after~10,500 cal yr BP, which could have resulted from an increase in July temperature and decreased ice cover (Wooller et al, 2012a). Increased autochthonous production from~10,300 cal yr BP peaked at~9500 cal yr BP (Wooller et al, 2012a) and the development of this productive lacustrine environment probably provided a habitat and food web to support an aquatic predator such as a Northern pike.…”

“…A sub-sample of the collagen was analyzed for its stable nitrogen isotope composition (expressed as d 15 N values) (Wooller et al, 2012b). We also separated cladoceran ephippia (following Wooller et al, 2012a) DNA extraction and all pre-PCR work of the specimen was performed in a dedicated ancient DNA facility at the Pennsylvania State University that is housed in a separate building from any laboratories that perform genetic analysis. Ancient DNA protocols were strictly adhered to at all stages (Cooper and Poinar, 2000;Gilbert et al, 2005).…”

The current state of knowledge of ecosystems and ecosystem services in Russia: A status report

“…Climate change processes also could stimulate or modify CO 2 and methane emissions from tundra ecosystems and underlying permafrost. These processes actively discussed in recent scientific literature (Heikkinen et al 2004;Merbold et al 2009;Hartley et al 2012;Wooller et al 2012 and many others), but results and conclusions are too diverse to be included for the assessment of ecosystem services.…”