Diatom responses to 20th century climate warming in lakes from the northern Urals, Russia (original) (raw)
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Journal of Paleolimnology, 2017
A sediment core from the Arctic Revvatnet (Hornsund area, SW Spitsbergen, Svalbard) provided data on environmental changes over the last 3100 years. Diatom analysis showing the domination of planktonic Cyclotella forms suggested good edaphic conditions until the middle of the nineteenth century, even during the Little Ice Age. A thermally stratified and relatively stable water column with good mixing allowed small, less heavily silicified Cyclotella sensu lato to develop during this time. The climate warming at the beginning of the twentieth century induced intensification of erosion processes in the catchment of the lake and caused an increase in the sedimentation rate. These processes have caused a lack of thermal stratification by disturbances in the water column and an increase of nutrients, consequently driving changes in the diatom species composition, which became dominated by benthic forms. In this period, almost all planktonic taxa disappeared or abruptly decreased in frequency. Higher temperatures accelerated the melting of nearby glaciers, which caused an increase in the activity of diatoms typical of running waters. Also a few Cladocera species appeared at the first time in the youngest samples.
Diatom response to mid-Holocene climate in three small Arctic lakes in northernmost Finnmark
The Holocene
Palaeoclimatic reconstructions from lake sediment biological records can be challenging, due to variation in non-climatic factors, which alter ecosystem responses. To consider this, it is important to replicate a study regionally, so as to gain information on spatial variability of ecosystem response and the influence of site-specific conditions. Previous pollen-based palaeoclimatic records from three well-dated Arctic lake sites highlight the response of regional Scots Pine ( Pinus sylvestris) and Mountain Birch ( Betula pubescens ssp. czerepanovii) forest-tundra transition to Holocene climatic variability and suggest the northernmost Peninsulas of Finnmark to be climatically sensitive. This study analysed dated sediment sequences between c. 3970 and c. 6200 cal. yr BP from these three previously published shallow lakes: Liten Čap’pesjav’ri (LCJ), over Gunnarsfjorden (OGF) and over Kobbkrokvatnet (OKV), for freshwater diatoms. Diatom assemblages showed an increase in the planktonic...
PLOS One, 2010
Background: Although arctic lakes have responded sensitively to 20 th -century climate change, it remains uncertain how these ecological transformations compare with alpine and montane-boreal counterparts over the same interval. Furthermore, it is unclear to what degree other forcings, including atmospheric deposition of anthropogenic reactive nitrogen (Nr), have participated in recent regime shifts. Diatom-based paleolimnological syntheses offer an effective tool for retrospective assessments of past and ongoing changes in remote lake ecosystems.
1998
Recent environmental change in Lake Baikal has been attributed to anthropogenic influences on the ecosystem, especially through pollution and cultural eutrophication. These hypotheses are tested in this paper principally by diatom analyses in 20 short sediment cores. Most of the cores were collected with a new type of box corer specifically designed for use on Lake Baikal. Most cores contain a good sediment record but turbidites occur in some sediment profiles which may be best recognized using a combination of techniques, such as radiometric dating and percentage dry weight analyses. The most recent sediments, especially those in the southern basin and in the very north of Baikal, contain a record of anthropogenic contamination in the form of lead and spheroidal carbonaceous particles, which confirms that the southern basin of Baikal is most affected by atmospheric sources of pollution. However, there is no sedimentary diatom evidence indicating offshore water quality deterioration in Baikal owing to air pollution or eutrophication. Small increases in diatoms which indicate nutrient enrichment (e.g. Stephanodiscus minutulus, Synedra acus v. radians and Synedra acus v. acus) may reflect local eutrophication of the shallow waters close to the Selenga Delta and certain coastal sites in the southern basin near to the Baikalsk paper and pulp mill. By using numerical techniques, Lake Baikal can be split into at least four regions on the basis of its surface sediment flora: the south, middle and north basins, and the shallow waters surrounding the Selenga Delta region. Diatom analyses reveal that the endemic flora of Lake Baikal has been constantly changing over at least the last 2000 years and that these fluctuations are probably responses to natural climatic variability. Recent sediments of Baikal may be affected by taphanomic processes (e.g. dissolution) and turbidite deposition, and these must be taken into account when interpreting the sedimentary diatom record. The diatom flora of the lake is currently dominated by several species, such as Aulacoseira baicalensis, A. islandica, Cyclotella minuta and Stephanodiscus binderanus v. baicalensis. All these species, except for C. minuta, have become more common in the lake in approximately the last 130 years, and we hypothesize that these changes may be attributed to a number of different processes linked to an ameliorating climate after the end of the Little Ice Age. The results presented here have important implications for this recently designated World Heritage Site, with regard to future pollution controls and catchment management policies.
Diatom Research, 1999
Knowledge of the composition and ecological preferences of diatom assemblages in northern regions is important for paleoenvironmental reconstructions of variables related to climate andor anthropogenic disturbances. Relatively little is presently known about diatoms from circumpolar treeline areas, especially for lakes located in northern Russia. Our study set included lakes in the Siberian tundra, forest-tundra, and boreal forest regions close to Norilsk, of which nine sites were subject to anthropogenic disturbances, such as mining and housing developments. We enumerated surficial sediment diatom assemblages and used multivariate statistical techniques to investigate which environmental variables were important in explaining the variation in diatom assemblages within our lake set. Deeper lakes were associated with higher abundances of planktonic centric taxa, such as Cyclotellu Kiitzing species. Warmer, higher conductivity forested lakes were associated with higher abundances of planktonic pennate taxa, such as Frugiluriu nanuna Lange-Bertalot. Diatom assemblages in the colder tundra lakes were significantly different from those in forested regions, and were dominated by small benthic Frugiluriu Lyngbye species. Disturbed lakes near the Norilsk smelters exhibited slightly higher metal (Cu) concentrations and conductivities, and were associated with pollution-tolerant Nitzschiu Hassall taxa, as well as species associated with higher electrolyte concentrations, such as Nuvicula cupitutu Ehrenberg. However, in comparison with diatom assemblages from other regions of intense mining (e.g. Sudbury, Canada), the assemblages appear relatively unaffected by mining activities, most likely reflecting the suppression of aqueous metal concentrations due to the alkaline nature of these lakes. Overall, diatom assemblages were very similar to those found in northern Canadian and Fennoscandian lakes, suggesting that the Siberian taxa are representative of a circumpolar arctic diatom flora.
Russian Geology and Geophysics, 2016
We studied the upper 0–1000 mm of the bottom sediment core from the underwater Sofia Lepneva Ridge of Lake Teletskoye. The core sediments accumulated with a rate of 0.3 mm/year (with regard to their humidity, with a rate of 0.45 mm/year) and have an age of about 2000 years. A total of 194 species (212 varieties and forms) of diatoms have been revealed. Analysis of diatom composition in tanatocoenoses showed prevalence of species inhabiting the bottom and periphyton, widely distributed geographically, indifferent to salinity, and preferring a weakly alkaline environment, as well as beta-mesosaprobionts. The number of diatom valves ranged from 0.86 to 64.4 mln valves/g, with an average of 22.90 ± 0.78 mln valves/g. Over the last millennium, the peaks of the abundance of diatoms, especially representatives of the cold-water assemblage, including the main dominant Aulacoseira subarctica (O. Müll.) Haw., are referred to the periods with low water temperature. The pH value for the period ...
Climate drivers of diatom distribution in shallow subarctic lakes
Freshwater Biology, 2017
1. Global warming can induce profound changes to the functioning of northern freshwater ecosystems. Diatom (Bacillariophyceae) communities often provide early warning signs of associated ecological regime shifts, responding sensitively to alterations in underwater light climate, nutrient regimes, habitat availability and lake water acid-base balance. The underlying mechanisms are manifold and may be mediated via direct climate impact on the physical and chemical properties of lakes or via changes in the terrestrial environment and catchment-lake coupling. 2. To address catchment-mediated climate effects on diatom community composition, spatial diatom distribution in the surface sediments of 31 subarctic treeline lakes displaying a broad gradient in terrestrial dissolved organic matter (tDOM) was contrasted with limnological indices of light climate, nutrient availability and lake water pH. To evaluate direct and indirect climate impacts on the long-term development of benthic phototrophic communities at the subarctic treeline, fossil diatom assemblages in the sediments of a shallow oligotrophic lake were examined against established temperature variability and inferences of terrestrial influence over the past 600 years. The regional lake set was used to test local calibration models for reconstructing dissolved organic carbon as well as lake water pH that is a fundamental environmental determinant for diatom distribution and may echo temperature variability in dilute lakes. 3. Across the treeline, lake water pH imposed primary control over the benthicdominated surface sediment diatom communities. The pH influence was connected to catchment geomorphology, soils and vegetation cover and, together with habitat controls, largely superseded tDOM impact on underwater light attenuation and nutrient levels. Similarly, temporal changes in diatom distribution in the sediment core appeared to be relatively little affected by tDOM variability. The species shifts were subtle yet occurred in distinct synchrony with centennial temperature fluctuations, attributed to changing length of the ice cover period and associated effects on lake water chemistry, nutrient regimes and physical habitats. 4. Our results suggest that diatom flora in shallow lakes at the subarctic Fennoscandian treeline may be comparatively resilient towards climate-driven
Ecological Indicators, 2020
Alpine mountain lake biota are adapted to harsh conditions making them particularly vulnerable to global change. However, as each mountain lake has a different limnology, there are supposed to be differential responses and degrees of resilience to climate change. In this study, 23 lakes in the Bavarian-Tyrolian Alps differing in altitude, size and geology were examined for their diatom community response to climate warming. Subfossil data were related to 210 Pb and 137 Cs-dated sediment cores. Correspondence and regression analyses revealed five different assemblage developments depending on lake depth, altitude and origin. Planktic species, especially Cyclotella, dominated deeper and lower-altitude mountain lakes earlier and stronger. This depends on the stability and temperature of the epilimnion which in turn determines the tipping point. Instead, shallow lakes exhibit higher species reorganizations of diatom assemblages. Mountain lakes of lower altitudes or affected by water level fluctuations (WLF) establish complex substrata and Achnanthidium accompanied by epiphytic species or Denticula tenuis in WLF-lakes replace dominating Staurosira. Conversely, alpine shallow lakes lack directional shifts and Staurosira dominate, but approach the tipping point of macrophyte establishment. In a deep doline lake, Diploneis species replace Nitzschia denticula with negligible planktic proportions. In mountain lakes with direct anthropogenic influence, enhanced nutrient supply disguises diatom response to global warming. These findings revealed deep mountain lakes with low nutrient levels to be more resilient to climate change than shallow lakes with a higher trophic status as the onset of the response to rising temperatures is earlier and thus smoother. In conclusion, subfossil diatom analyses can provide a powerful tool for climate change assessment and other anthropogenic impacts on mountain lakes.
2005
The mainly endemic phytoplankton record of Lake Baikal has been used in this study to help interpret climate variability during the last 1000 years in central Asia. The diatom record was derived from a short core taken from the south basin and has been shown to be free from any sedimentary heterogeneities. We employ here a diatom-based inference model of snow accumulation on the frozen lake for the first time (r2boot=0.709; RMSEP=0.120 log cm). However, palaeoenvironmental reconstructions have been improved by the use of correction factors, specifically developed for the dominant phytoplankton (Aulacoseira baicalensis, Aulacoseira skvortzowii, Cyclotella minuta, Stephanodiscus meyerii and Synedra acus) in the south basin of Lake Baikal. Cluster analysis identifies three significant zones in the core, zone 1 (c. 880 AD–c. 1180 AD), zone 2 (c. 1180–1840 AD) and zone 3 (c. 1840–1994 AD), coincident with the Medieval Warm Period (MWP), the Little Ice Age (LIA) and the period of recent warming, respectively. Our results indicate that S. acus dominated the diatom phytoplankton within zone 1 coincident with the MWP. S. acus is an opportunistic species that is able to increase its net growth when A. baicalensis does not. During this period, conditions are likely to have been unfavourable for the net increases in A. baicalensis growth due to the persistence of warm water in the lake, together with an increased length of summer stratification and delay in timing of the autumnal overturn. In zone 2, spring diatom crops blooming under the ice declined in abundances due in part to increased winter severity and snow cover on the lake. Accumulating snow on the lake is likely to have arisen from increased anticyclonic activity, resulting in prolonged winters expressed during the LIA. Thick, accumulating snow cover inhibits light penetration through the ice, thereby having negative effects on cell division rate and extent of turbulence underneath the ice. Consequently, only taxa whose net growth occurs during autumn overturn (C. minuta) predominate in the lake at this time. Diatom census data and reconstructions of snow accumulation suggest that warming in the Lake Baikal region started as early as c. 1750 AD, with a shift from taxa that bloom during autumn overturn to assemblages that begin to grow underneath the frozen lake in spring. Very recent increases and subsequent decline of S. acus in the surface sediments of the lake mirror monitoring records of this species over the last 50 years. Our study confirms that, over the last 1000 years, physical processes are important in determining planktonic diatom populations in the lake and highlights the value of integrated plankton, trap, and sediment studies for improving quantitative palaeoenvironmental reconstructions from fossil material.