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A sediment sequence was taken from a closed, high altitude lake (informal name Olive-backed Lake) in the central mountain range of Kamchatka, in the Russian Far East. The sequence was dated by radi ...

We investigated chironomid fauna of surface sediments and a short sediment core (Bol’shoy Kharbey Lake) from Pechora river basin, Northern Russia. Twenty three investigated lakes have thermokarst, glacial or floodplain origin and are characterised by low mineralization, mostly hydrocarbon-calcium type of water and low concentration of nutrients. Most of the lakes have circumneutral pH around ≤7 and only two lakes are slightly more acidic with pH ≤ 6. Ninety six chironomid taxa were identified in the surface sediments. Distribution of chironomids in the studied region is driven by continentality, mean TJuly and рН. Chironomid communities from the core of the B. Kharbei Lake demonstrate the highest similarity with the fauna of the deeper lakes of the glacial origin. The glacial lakes have the highest indices of continentality and the lowest winter temperatures within the investigated data set. The chironomid fauna of the glacial lakes is composed of the profundal, oligotrophic and cold-stenotherm taxa. The fauna of the floodplain and thermokarst lakes is more closely related to TJuly and is composed of littoral and phytophilic taxa of meso – or eutrophic waters and moderate temperature conditions. The fauna of the acidic thermokarst lakes considerably differs from the other lakes. Chironomid communities here are represented by tolerant to acidification taxa, and by the typically littoral and shallow water acid-tolerant taxa that apparently also can tolerate acidification. Studied sediment record covers ca last 200 years. The reconstructed TJuly during the entire period remain slightly below the modern temperatures. From 1970 reconstructed TJuly shows steady increase to the modern level. The reconstructed water depths (WDs) of the lake are higher than today till 1980. The highest WDs are reconstructed for ca 1970. After that the WDs gradually decrease to the modern level. Changes of the WDs are most probably related to changes in the precipitation rate.

The premise of this article is that climate effects on lakes can be quantified most effectively by the integration of process-oriented limnological studies with paleolimnological research, particularly when both disciplines operate within a common conceptual framework. To this end, the energy (E)-mass (m) flux framework (Em flux) is developed and applied to selected retrospective studies to demonstrate that climate variability regulates lake structure and function over diverse temporal and spatial scales through four main pathways: rapid direct transfer of E to the lake surface by irradiance, heat, and wind; slow indirect effects of E via changes in terrestrial development and subsequent m subsidies to lakes; direct influx of m as precipitation, particles, and solutes from the atmosphere; and indirect influx of water, suspended particles, and dissolved substances from the catchment. Sedimentary analyses are used to illustrate the unique effects of each pathway on lakes but suggest that interactions among mechanisms are complex and depend on the landscape position of lakes, catchment characteristics, the range of temporal variation of individual pathways, ontogenetic changes in lake basins, and the selective effects of humans on m transfers. In particular, preliminary synthesis suggests that m influx can overwhelm the direct effects of E transfer to lakes, especially when anthropogenic activities alter m subsidies from catchments.

The Pechora Region (PR) has extensive natural resources supporting forestry, oil and gas industries. The objective of this integrated study was to identify if local and long range pollution and bio ...

The study was supported by the Swedish Research Council through grants 621-2004-5224 and 621-2005-4444 to K.D. Bennett. A. Self and N. Solovieva acknowledge S. Brooks and V. Jones and were supported by NERC grant NE/H008160/1. A sediment record from a small lake in the north-eastern part of the Kamchatka Peninsula has been investigated in a multi-proxy study to gain knowledge of Holocene climatic and environmental change. Pollen, diatoms, chironomids and selected geochemical parameters were analysed and the sediment record was dated with radiocarbon. The study shows Holocene changes in the terrestrial vegetation as well as responses of the lake ecosystem to catchment maturity and multiple stressors, such as climate change and volcanic eruptions. Climate change is the major driving force resulting in the recorded environmental changes in the lake, although recurrent tephra deposition events also contributed. The sediment record has an age at the base of about 10,000 cal yrs BP, and during the first 400 years the climate was cold and the lake exhibited extensive ice-cover during winter and relatively low primary production. Soils in the catchment were poor with shrub alder and birches dominating the vegetation surrounding the lake. At about 9600–8900 cal yrs BP the climate was cold and moist, and strong seasonal wind stress resulted in reduced ice-cover and increased primary production. After ca. 8900 cal yrs BP the forest density increased around the lake, runoff decreased in a generally drier climate resulting in decreased primary production in the lake until ca. 7000 cal yrs BP. This generally dry climate was interrupted by a brief climatic perturbation, possibly attributed to the 8.2 ka event, indicating increasingly windy conditions with thick snow cover, reduced ice-cover and slightly elevated primary production in the lake. The diatom record shows maximum thermal stratification at ca. 6300–5800 cal yrs BP and indicates together with the geochemical proxies a dry and slightly warmer climate resulting in a high productive lake. The most remarkably change in the catchment vegetation occurred at ca. 4200 cal yrs BP in the form of a conspicuous increase in Siberian dwarf pine (Pinus pumila), indicating a shift to a cooler climate with a thicker and more long-lasting snow cover. This vegetational change was accompanied by marked shifts in the diatom and chironomid stratigraphies, which are also indicative of colder climate and more extensive ice-cover. Publisher PDF

A sediment core from Chuna Lake (Kola Peninsula, northwest Russia) was studied for pollen, diatoms and sediment chemistry in order to infer post-glacial environmental changes and to investigate responses of the lake ecosystem to these changes. The past pH and dissolved organic carbon (DOC) of the lake were inferred using diatom-based transfer functions. Between 9000 and 4200 cal. yr BP, slow natural acidification and major changes in the diatom flora occurred in Chuna Lake. These correlated with changes in regional pollen, the arrival of trees in the catchment, changes in erosion, sediment organic content and DOC. During the past 4200 yr diatom-based proxies showed no clear response to changes in vegetation and erosion, as autochthonous ecological processes became more important than external climate influences during the late Holocene. The pollen stratigraphy reflects the major climate patterns of the central Kola Peninsula during the Holocene, i.e. a climate optimum between 9000 and 5400/5000 cal. yr BP when climate was warm and dry, and gradual climate cooling and an increase in moisture during the past 5400/5000 yr. This agrees with the occurrence of the north–south humidity gradient in Fennoscandia during the Holocene. Copyright © 2002 John Wiley & Sons, Ltd.

Fifty-five paleolimnological records from lakes in the circumpolar Arctic reveal widespread species changes and ecological reorganizations in algae and invertebrate communities since approximately anno Domini 1850. The remoteness of these sites, coupled with the ecological characteristics of taxa involved, indicate that changes are primarily driven by climate warming through lengthening of the summer growing season and related limnological changes. The widespread distribution and similar character of these changes indicate that the opportunity to study arctic ecosystems unaffected by human influences may have disappeared.