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16 results for “paleolimnology”
Paleolimnology of Lakes in Central New England from 2000 BP to Present
Paleolimnological studies of three small watersheds in central New England were undertaken to determine the influence of deforestation and agriculture on lake systems, as well as the response of the lakes to agricultural abandonment and reforestation, or the cessation of disturbance. Sites were chosen to represent a range of past land-use activities, while keeping other site factors constant. The study was designed to complement the historical and paleoecological studies of the central Massachusetts area of Fuller et al. (1998) and Foster et al. (1998). Changes in terrestrial vegetation were documented using the pollen record from each lake, and changes in aquatic systems were documented through fossil chironomid assemblages (Chironomidae: Diptera) and sediment chemistry. Dated cores were analyzed for pollen, fossil chironomids, percent organic matter, carbon and nitrogen, and sedimentation changes. Increased sedimentation rates occurred in all lakes during the settlement period, and small increases in productivity changes resulted from the increased runoff. Productivity changes, as indicated by organic material, C:N ratios, and chironomid assemblages, are more pronounced in North Round and Wickett Ponds than in Pecker Pond, even though agricultural activity was most intense at Pecker Pond. North Round and Wickett Ponds are more shallow than Pecker, and were more affected by sediment and nutrient inputs from the watershed. North Round Pond was the least impacted site, with only minimal logging and no agriculture, but still significant changes occurred during the settlement period. The sedimentation rates and productivity continue to be higher than pre-settlement levels, indicating that the systems have not returned to pre-disturbance states. This is similar to the response of forest vegetation studied by Fuller et al. (1998) in the Central Massachusetts study. The low intensity agricultural practices of the 19th Century and small watershed sizes contributed to the f
Paleolimnological assessment of a hyper-eutrophic lake (Nowlans Lake, N.S., Canada) Cladoceran communities
<p>Mink fur farming was once a widespread agricultural activity in southwestern Nova Scotia. Some freshwaters near mink fur farm operations now show severe water quality issues. Notably, the watershed of Nowlans Lake (southwestern Nova Scotia, Canada) once contained six mink farms as well as a fish meal feed processing plant. It is now one of the most productive lakes in Atlantic Canada, with exceedingly high measured Total Phosphorus concentrations.</p> <p>Here, we provide data from a paleolimnological investigation on the long-term environmental changes that occurred in Nowlans Lake, and how these changes have impacted cladoceran communities. First, we identify abundances of cladoceran taxa throughout the sediment core, corresponding to assemblages from the ~1900s to present day (determined by 210Pb dating analyses – see Table 1 of cited manuscript), and provide raw counts. We detected shifts in the dominant pelagic cladoceran taxa beginning in the early 1900s, with decreases in small-bodied bosminids, while taxa such as <em>Chydorus brevilabris</em> and <em>Daphnia pulex</em> spp. increased. We identified assemblage "zones" using a constrained hierarchal clustering analysis, denoting three distinct assemblage groups (Script 03). We then provide empirical measures of the body sizes of bosminids in each sediment interval, as body sizes of cladocerans are good proxies of shifts in predation. We identified bottom-up ecological factors as the likely drivers of these assemblage shifts, as body sizes were found to be consistent through time with a Mann Kendall Monotonic Trend Analysis (Script 02). Finally, we reconstructed and provide data on trends in sedimentary chl-a concentrations using visible reflectance spectroscopy (VRS). After conducting a PCA on cladoceran assemblages and extracting PC1 scores, we observed a strong relationship by VRS chl-a and PC1 scores, suggesting similar timing between increases in lake productivity and major cladoceran changes (Script 01).</p>
Figure 2 in First record of Parochlus kiefferi (Garrett, 1925) in a sediment sequence from a Slovak mountain lake with notes on paleolimnological interpretation
Figure 2. Detail of the head capsule of Parochlus kiefferi found in lake Vrbické pleso. Photo: Martina Jambrović.
Cyanobacterial blooms in a warming climate: Paleolimnological assessments of three Boreal Shield lakes in central Ontario, Canada
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Paleolimnological assessment of a hyper-eutrophic lake (Nowlans Lake, N.S., Canada) Cladoceran communities
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Multi-proxy paleolimnological records provide evidence for a shift to a new ecosystem state in the Northern Great Plains, USA
<p>Wetlands in the Prairie Pothole Region of the North American Northern Great Plains perform multiple ecosystem services and are biodiversity hotspots. However, climatological changes can result in sudden shifts in these important ecosystems. For example, marked increases in precipitation in the last few decades have resulted in a widespread shift in wetlands across the Prairie Pothole Region to a new ecohydrological state. We used multi-proxy analyses (diatom community composition and invertebrate stable isotopes) of 210Pb-dated sediment cores from two adjacent, but morphologically and hydrologically different, prairie-pothole wetlands to assess the effects of hydroclimatic variability on these wetland ecosystems. Our results provide evidence that the recent ecohydrological shift in the region's wetlands is unprecedented over the past ca.178 years. Oxygen stable isotopes in chironomid head capsules provide a record of paleo-hydrology changes. The most recent sediments (i.e., those deposited after the state shift) from both wetlands revealed novel changes in diatom communities that differed greatly from earlier community compositions. Additionally, a depleted signal in deuterium and 13C carbon stable isotopes observed in chironomid head capsules and Daphnia ephippia, respectively after 1993 is likely related to an increase in methane production in these wetlands. Our study highlights the importance of considering basin morphometry including whether a wetland has an overflow point, and multiple biological indicators to study climate-change influences on freshwater ecosystems. Research using these techniques can lead to an improved understanding of recent ecosystem shifts, an understanding that will be essential for future climate-change adaptation and mitigation in this ecologically important region.</p>
Figure 1 in First record of Parochlus kiefferi (Garrett, 1925) in a sediment sequence from a Slovak mountain lake with notes on paleolimnological interpretation
Figure 1. View of lake Vrbické pleso. Photo: Ladislav Hamerlík.
Multi-proxy paleolimnological records provide evidence for a shift to a new ecosystem state in the Northern Great Plains, USA
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A 140-year paleolimnological record of climatically and anthropogenically driven eutrophication in Utikuma Lake, Alberta, Canada
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Datasets from PhD thesis: "Integrating classical and DNA-based approaches to advance the field of paleolimnology: Case studies of a warm monomictic lake"
<p>The general objectives of my PhD were to evaluate the advantages and limitations to using DNA-based methods in paleolimnology and to evaluate the ecological trajectory of Cultus Lake, British Columbia, using both classical paleolimnological and DNA-based approaches. The datasets therein were generated for my PhD thesis.</p> <p>Firstly, a 36-month sediment trap time series was developed to evaluate which DNA taxa can be deposited in the sediments and potentially be used as indicator taxa in paleolimnological studies. Congruence between morphological and DNA identification in water and sediment trap samples was also assessed specifically for diatoms and crustaceans. The data generated include mass accumulation rate and carbon accumulation rate, carbon and nitrogen percentage, morphological counts for diatoms and cladocerans in the sediment traps, DNA quantity for water and sediment trap samples, metabarcoding of a fragment of the V7 region of the 18S rRNA gene.</p> <p>Secondly, a multi-proxy paleolimnological study was developed to evaluate the ecological changes in Cultus Lake and the potential drivers of the changes. From this study, sedimentary delta 15N, delta 13C, percentage of carbon, percentage of nitrogen, pigments were measured and diatoms and cladoceran remains were counted and identified from a sediment core collected in 2008. The data for this project are part of a publication accepted in May 2020 in Journal of Paleolimnology: Gauthier et al (In press) Ecological dynamics of a peri-urban lake: a multi-proxy paleolimnological study of Cultus Lake (British Columbia) over the past ~200 years. doi: 10.1007/s10933-020-00147-9.</p> <p>Thirdly, a paleo-genetic project was developed to compare the ecological changes observed with sedimentary DNA with those observed with classical paleolimnological approaches. The same fragment of the V7 region of the 18S rRNA gene was targeted, percentage of carbon and nitrogen were also measured as well as DNA quantity for all intervals subsampled in a sediment core collected in 2017.</p> <p>The datasets usually come with a description of the data and meaning of abbreviations whether needed. DNA datasets will be publicly released upon acceptance of the manuscripts. For more information about the projects, methods and results, please refer to my PhD thesis published at McGill University. The number in front of the name of each file represents the chapter for which the data were generated.</p>
Data from: Paleolimnological assessment of wildfire-derived atmospheric deposition of trace metal(loid)s and major ions to subarctic lakes (Northwest Territories, Canada)
<p>Wildfires release terrestrial elements to the atmosphere as aerosols, and these events are becoming more frequent and intense in the Arctic boreal forest as the climate is warming. We quantified the impact of atmospheric deposition of aerosols from local wildfires on metal(loid) fluxes using macroscopic charcoal accumulation rates, historical fire mapping, and element concentrations in <sup>210</sup>Pb‐dated lake sediment from five subarctic lakes with small catchments. Lake sediments showed small but significant increases in fluxes (median = 5–10%) for 22 trace metals, metalloids, or major ions following fire events. The impact of wildfire aerosols on element fluxes was mostly due to short‐term (≤2 years) increasing sedimentation rate (6 ± 41% increase), whereas sediment element concentrations were not strongly impacted. Wildfire‐associated deposition to lake sediments was mainly composed of Ca, Al, Fe, Mg, K, Mn, and Na, which are major constituents of ash from burned biomass, but changes in sediment flux were greatest for Sb, As, Ni, Ba, Mn, Mo, and Sr compared to pre‐disturbance conditions. Compared to anthropogenic sources of pollution, wildfire‐associated atmospheric fluxes of metal contaminants to the lakes (e.g., Hg, Pb, As, Sb, and Cd) were low. This study provides quantitative estimates of wildfire impacts on atmospheric geochemical fluxes to subarctic lakes, which can be used for modeling larger‐scale impacts under changing fire regimes.</p>
Data from: Paleolimnological assessment of wildfire-derived atmospheric deposition of trace metal(loid)s and major ions to subarctic lakes (Northwest Territories, Canada)
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A 520-year paleolimnological grain size and ITRAX record from Harvey Lake, New Brunswick, Canada
<p>This grain size data was derived from a 250 mm long gravity Glew Maxi core (HL-2017-GC-2) collected from near the mouth of Herbert's Cove, Harvey Lake, New Brunswick Canada (45°43'42.535" N; 67°01'23.739" W) at a water depth of 4.5 m. The core was subsampled on-site at 2 mm resolution using a Glew core extruder before transport to Carleton University for subsequent analysis. Subsamples were analyzed using a Beckman Coulter LS 13 320 laser diffraction grain size analyzer equipped with a universal liquid module. The resultant triplicate grain size data were averaged using a script within Matlab which generated the data archived here. The data was then analyzed using End Member Mixing Analysis and three distinct end members were recognized EM01, Mode = 05 μm; EM02, Mode = 27μm; EM03, Mode = 58 μm). Subsequent radiocarbon dating revealed that deposition spanned the last 520 years of deposition. During this interval there were 12 major storms (EM03) and analysis of precipitation data from the Harvey climate station indicated that ~110 mm of rain was required for the deposition of EM01 in Harvey Lake. The deposition of EM02 was derived from the yearly spring freshet runoff.</p>
Data from: Long-term dynamics in microbial eukaryotes communities: a paleolimnological view based on sedimentary DNA
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A 520-year paleolimnological grain size and ITRAX record from Harvey Lake, New Brunswick, Canada
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Two millennial-scale paleolimnological records from San Salvador Island, Bahamas
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