Diatom-inferred lake level from near-shore cores in a drainage lake from the Experimental Lakes Area, northwestern Ontario, Canada (original) (raw)
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A diatom-inferred water depth reconstruction for an Upper Peninsula, Michigan, lake
Journal of Paleolimnology, 1998
Transects of surface sediment samples were taken in 4 lakes from the Sylvania Wilderness Area, Upper Peninsula of Michigan. These surface samples were compared with diatom samples from a core taken in the Northwest basin of Crooked Lake, also from the Sylvania Wilderness Area. Weighted Averaging calibration was used to reconstruct lake depths in Crooked Lake using the diatom microfossils from the core and the surface samples to infer past lake depth. During the early Holocene the lake was dominated by planktonic species and diatom-inferred water depth was large -approx. 13 m. At about 6700 BP inferred water depth was 2 m and samples were dominated by Fragilaria construens var. venter -a species characteristic of shallow parts of the surface sample transects. From 6700 to 5000 BP reconstructed water level was at its shallowest. From 5000 to 3000 BP it increased. This rise in water level was marked by increasing abundances of Aulacoseira ambigua and occurred at the same time increasing percentages of hemlock pollen indicate increasing available moisture. Modern water depth was reached about 3000 BP. The water level changes at Crooked Lake are consistent with regional climate changes in the Upper Midwest during the Holocene. The lake was shallowest during the mid-Holocene warm period documented by other investigators. It deepened as the Midwestern climate became cooler and wetter during the late Holocene.
Journal of Paleolimnology, 2011
Diatom assemblages in recent versus preindustrial sediments were examined in 40 relatively undisturbed lakes from the Experimental Lakes Area (ELA). The ELA region of northwestern Ontario receives low amounts of acidic deposition and the lakes have been minimally disturbed by watershed development or other human activities. Consequently, this region represents an important location to detect possible changes in lakes due to climate change. In over half of the lakes, planktonic taxa (especially Discostella stelligera) increased between 10 and 40% since pre-industrial times. Changes in diatom assemblages are consistent with taxa that would benefit from enhanced stratification and a longer ice-free season. We hypothesized that there should be a relationship between stratification and measured chemical and physical characteristics of the study lakes. Multiple correlation analysis was undertaken to see the relationship between planktonic taxa and D. stelligera since pre-industrial times and the physical and chemical characteristics of the study lakes. Lake depth was consistently identified as an important variable. The timing of the increase in planktonic taxa within cores from these lakes will be needed to rule out other possible regional changes that may also be occurring in the ELA region.
2002
A fossil diatom record covering the past 3000 cal. years BP was analyzed from a small lake in northwesterń Quebec near the northern limit of present-day tree-line. Fragilaria virescens var. exigua Grunow in Van Heurck was the dominant species throughout the core with abundances ranging between 13-35% of the total valve count. There was a replacement of alkaliphilous taxa by acidophilous taxa beginning ca. 1300 cal. yr ago, probably reflecting long-term, natural acidification processes. A diatom-based transfer function was used to provide quantitative estimates of variations in lakewater dissolved organic carbon (DOC). These inferred values showed 21 that DOC concentrations have remained stable over the past 3000 years (mean 6 S.D. 5 5 6 0.43 mg C l ), suggesting relatively constant allochthonous carbon inputs and underwater light conditions during the late Holocene. The reconstructed DOC data were compared to the palynological record from the same lake. Our study indicates that, in contrast to paleolimnological records from lakes in central and western Canada, climatic variations and associated vegetational shifts have been too subtle to cause pronounced variations in DOC in thiś northern Quebec site.
Journal of Phycology, 1998
Water quality degradation is a serious concern for the St. Lawrence River. While some environmental data are available for the St. Lawrence ecosystem, long-term monitoring data are generally lacking. To infer past environmental changes, we undertook a paleolimnological assessment of diatom assemblages preserved in four 210 Pb-and 137 Cs-dated sediment cores from two fluvial lakes in the river, and used diatom transfer functions to infer past shoreline habitat characteristics. At sites in Lake Saint-François, a fluvial lake downstream from Cornwall, water quality decreased this century in response to human impacts (e.g. macrophyte density and nutrient levels increased). These trends were apparent from an increase in epiphytic diatom taxa, followed by an increase in eutrophic planktonic taxa. Water quality, however, appears to have improved somewhat in response to rehabilitation measures during the last two decades. From a sediment core near Montréal (Lake Saint-Louis), we also noted a large proportion of eutrophic and epiphytic taxa, but less evidence was recorded of a recent improvement in water quality. The diatom-based inference model for habitat characteristics appeared to reconstruct environmental conditions in the St. Lawrence River during the last century. The most notable shift has been an increase in diatom taxa commonly associated with macrophyte substrates. Trends in some of the planktonic diatoms were similar to those recorded in paleolimnological investigations from Lake Ontario, but cores from the river also may be reflecting local environments. This study shows that diatom-based paleolimnological studies are possible in large river systems, if coring sites (e.g. fluvial lakes) are carefully selected.
The Holocene, 2021
The paleolimnological record of diatoms and climate, spanning the last 2800 years, was investigated in a small subarctic lake (Pocket Lake) that from AD 1948 to 2004 was contaminated by gold smelting waste. An age-depth model was constructed using a combination of 210Pb, 14C, and tephra to determine a 2800 year history of lake ontogeny (natural aging), biological diversity, and regional climate variability. Diatoms form six strong paleoecological assemblages over time in response to changes in local hydrological and sedimentological conditions (including metals). Selected environmental variables explained 28.8% of the variance in the diatom assemblages, with Fe, Ca, and sediment end member distribution being important indicators. The diatom assemblages correlated to the Iron Age Cold Epoch (2800–2300 cal BP), Roman Warm Period (2250–1610 cal BP), Dark Age Cold Period (1500–1050 cal BP), Medieval Climate Anomaly (ca. 1100–800 cal BP), and the Little Ice Age (800–200 cal BP). The disa...
Aquatic Sciences, 2005
Baseline and historical environmental data are sparse in high-altitude regions. Diatom assemblages preserved in lake sediment records can, however, provide proxy data of past environmental and biological conditions. Sediment cores were retrieved from 209 high altitude lakes from 11 countries in Europe. Diatoms were extracted and counted from surface-sediment samples and sediments representing pre-industrial conditions. Regional changes in diatom assemblages covering at least the last c. 150 years are discussed and quantified using ordination techniques and dissimilarity indices. Distinct changes in diatom composition are identified and regional patterns highlighted, with two lake regions showing particularly large changes in diatom composition (Central Swiss Alps and the Pyrenees). Several driving mechanisms that might have caused the changes in the diatom community are discussed. Pre-industrial and present-day lake-water pH are inferred from the diatom assemblages and their prediction accuracy compared to contemporary water-chemistry measurements for each lake. Regional pH changes are minimal with no lake region exceeding 0.27 pH units of change in the period covering the last c. 150 years. The majority of lakes studied show an increase in planktonic diatom species over the period covering the past c. 150 years. We hypothesise that changes in the ratio of planktonic to non-planktonic diatoms within the study lake-regions are related to changes in climate and to associated changes in nutrients, ice-cover and erosion caused by climate warming.
Post-glacial diatom-inferred aquatic changes in Sicamous Creek Lake, British Columbia, Canada
Revue des sciences de l'eau, 2014
Diatom analyses of sediments from a high elevation lake situated in an Engelmann Spruce - Subalpine Fir (ESSF) forest of south-central British Columbia, Canada, reveal long-term climate and water chemistry change. During the transition from the late-glacial / Pleistocene to the xerothermic early Holocene, small, benthic Fragilaria diatoms species that grew under low light conditions in Sicamous Creek Lake gave way to planktonic Cyclotella species that require open-water conditions. Warm temperatures in the mesothermic Holocene are indicated by smaller Cyclotella species and large, benthic pennate diatoms. Diatom communities reflected Neoglacial cooling in the late Holocene, with abundant Nitzschia fonticola and Achnanthes minutissima. Small, benthic Fragilaria regained abundance, suggesting cooling and conditions similar to the late-glacial interval. Diatom community composition responded to the deposition of the Mt. Mazama and Mt. St. Helens tephras, though the Mazama eruption caus...
A Holocene paleosalinity diatom record from southwestern Saskatchewan, Canada: Harris Lake revisited
1997
Fossil diatoms were analysed from a 10.3 m core from Harris Lake, Cypress Hills, Saskatchewan, and a diatomsalinity transfer function was used to construct a history of Holocene salinity changes for the lake. The diatom paleosalinity record indicates that Harris Lake remained fresh (<0.5 g l 1 ) throughout the Holocene, with only slight increases in salinity between approximately 6500 and 5200 years BP. This interval corresponds to the only period in the lake's history when planktonic diatoms were abundant; benthic Fragilaria taxa, mainly F. pinnata, F. construens and F. brevistriata were dominant throughout most of the Holocene.