Late Holocene climate and environmental changes in Kamchatka inferred from the subfossil chironomid record
Highlights
► We investigated fossilized chironomids in lake sediment core from Central Kamchatka. ► We reconstructed late Holocene climate variations using chironomid inference model. ► Before 3.7 cal ka BP reconstructed TJuly are close to present day temperatures. ► Between 3.7 and 1.1 cal ka BP two warm stages are reconstructed. ► After 1.1 cal ka BP lower than present day TJuly are reconstructed.
Introduction
The Kamchatka Peninsula shapes the eastern edge of Siberia and separates the Sea of Okhotsk from the Pacific Ocean. It is one of the least studied regions in Eurasia. The climate history of the last 400 years in Kamchatka is well documented in tree-ring and ice-core records and suggests short-term climate oscillations at centennial to decadal time scales (Solomina et al., 2007; Sano et al., 2009, 2010). Less is known about the Holocene environmental dynamics in the region (Pisaric et al., 2001; Razjigaeva et al., 2004; Fradkina et al., 2005; Kokorowski et al., 2008).
Studies of the Holocene climate in Kamchatka are limited and mainly focus on reconstruction of vegetation dynamics from pollen records in peat sections (Dirksen and Uspenskaya, 2005; Dirksen and Dirksen, 2008) or reconstructions of glacial dynamics in southern and central Kamchatka (Zech et al., 1997; Savoskul, 1999). The present study is focussed on qualitative and quantitative reconstructions of environmental changes using chironomids, which have proven to be useful indicators of environmental variations (Battarbee, 2000; Smol et al., 2005; Stief et al., 2005; Kienast et al., 2011; Self et al., 2011). Past climate can be quantified from fossil chironomid assemblages by using inference models (Larocque et al., 2001; Solovieva et al., 2005; Barley et al., 2006; Nazarova, 2012; Nazarova et al., in press), which link the present distribution and abundance of chironomids to contemporary climate. The main objective of our study is to perform a palaeoecological reconstruction of the late Quaternary climate and environment in Kamchatka from sediments of Dvuyurtochnoe Lake (Two-Yurts Lake, TYL), situated in Central Kamchatka. The specific aim is to provide reconstructions of mean July air temperature (TJuly), using the newly developed for north-eastern Russia chironomid-inferred mean July temperature model (Nazarova et al., 2011).
Section snippets
Study area
The Kamchatka is a peninsula in the Russian Far East that lies between the Pacific Ocean to the east and the Sea of Okhotsk to the west (Fig. 1). The longitudinal extent of the peninsula is approximately 1600 km and the maximum width is 500 km (Nazarova, 1999). Active volcanoes are part of the two mountain systems of the Kamchatka Peninsula: the Sredinny and the Vostochny mountain ranges. The Central Kamchatka Lowland is situated between the two mountain ranges and consists of alluvial,
Field work
The TYL was sampled in September 2007. Water depth (WD) was measured using a Garmin–Fishfinder-system echolot with a vertical resolution of ca 10 cm. Echographic surveying was conducted using a GEOPULSE Shallow Seismic 3.5-kHz-Profiler System to locate stations for sediment coring.
TYL sediment cores were obtained with a tripod-supported UWITEC piston corer from a floating platform at different locations in the lake. Two cores (1857-2 – upper core and 1857-5 – lower core) consisted of
Chironomid fauna and taxon richness
Most of the chironomid head capsules (81.55%) could be identified to species types and species group level, 4.5% to tribe level, 12.41% to genus level and 1.54% to subfamily level only. In total, we identified 83 taxa within 44 genera and 4 subfamilies. Twenty-six taxa belonged to subfamily Chironominae (12 Chironomini, 13 Tanytarsini and 1 Pseudochironomini), 52 taxa to subfamily Orthocladiinae, 8 taxa to subfamily Diamesinae and 2 to Tanypodinae. The majority (82.68%) of the specimens
Chironomid fauna
Our investigation of the subfossil chironomids from central Kamchatka revealed a rich taxonomic assemblage. The fauna is similar to that from Yakutia, but we observed a relatively high amount of head capsules from the subfamily Diamesinae in Kamchatka (not shown in Fig. 3), whereas almost none were found in Yakutia. Makarchenko et al. (2005) recorded 52 Diamesinae taxa in a catalogue of chironomid fauna of the Russian Far East. High taxonomic richness and abundance of Diamesini may be a
Conclusion
This study presents a reconstruction of the Late Holocene climate in Kamchatka based on chironomid remains from TYL. Chironomid head capsules from TYL reflect a rich and diverse fauna, which is similar to those from Yakutia and northwest North America. An unknown morphotype of Tanytarsini, Tanytarsus type klein, was found in the lake sediments. Our analysis reveals four chironomid assemblage zones reflecting four different climatic periods in the late Holocene. Between 4500 and 4000 cal years
Acknowledgements
We thank all of our Russian and German colleagues, who helped us during fieldwork in Kamchatka. Sincere thanks to anonymous reviewers for their valuable comments. This study is part of a Russian–German joint project KALMAR (Kurile-Kamchatka and Aleutian Marginal Sea-Island Arctic Systems: Geodynamic and Climate interactions in Space and Time) and the German–Russian cooperative scientific efforts of the Alfred Wegener Institute for Polar and Marine Research.
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