Sediment Record of Biogeochemical Responses to Anthropogenic Perturbations of Nutrient Cycles in Lake Ontario

Two sediment cores collected from the Rochester basin of Lake Ontario were dated with 210Pb and stratigraphic correlation and analyzed to determine whether nutrient accumulation with time was consistent with previous computer-simulated total phosphorus (TP) loadings. Relative increases in TP and nonapatite inorganic phosphorus (NAIP) accumulation were less than the fivefold increase in TP loading from 1800 to 1950 predicted independently from Chapra's simulation model. In addition, increases in TP accumulation occurred mainly after 1940 and the proportion of NAIP relative to TP increased in one core and decreased in the other. Of the nutrients studied, only increases in organic carbon (OC) paralleled the increases in modelled TP loadings. The relative increase in inorganic carbon (IC) was greatest, with accumulation increasing an order of magnitude after 1940 in one core. This large increase in IC, amounting to 20% calcite in recent sediments, was attributed to biologically induced calcite precipitation, a secondary consequence of increased planktonic photosynthetic removal of carbon dioxide that resulted from accelerated eutrophication after 1940 when modelled TP concentrations increased rapidly. Biogenic silica (BSi) accumulation, an indicator of increased diatom production, peaked between 1850 and 1870 when increases in TP and NAIP fluxes were minimal. Results provide evidence that historic biogeochemical responses inferred from OC, IC, and BSi accumulation in the sediment record provide stronger signals of phosphorus enrichment effects than can be inferred directly from changes in accumulation of different forms of phosphorus in the sediment record.

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VISCOELASTIC PROPERTIES OF SILICONE-BASED MAGNETORHEOLOGICAL ELASTOMERS

International Journal of Modern Physics B ◽

10.1142/s0217979207045670 ◽

2007 ◽

Vol 21 (28n29) ◽

pp. 4790-4797 ◽

Cited By ~ 73

Author(s):

HOLGER BÖSE

Keyword(s):

Magnetic Field ◽

Smart Materials ◽

Viscoelastic Properties ◽

Magnetic Particles ◽

Relative Increase ◽

Matrix Composites ◽

Mechanical Stiffness ◽

Storage And Loss Moduli ◽

Order Of Magnitude ◽

Reported Data

Magnetorheological (MR) elastomers are composite materials consisting of magnetic particles in elastomer matrices, whose mechanical properties can be influenced by applying a magnetic field. Main parameters which determine the behavior of these smart materials are the concentration of the magnetic particles and the mechanical stiffness of the elastomer matrix. The viscoelastic properties of silicone-based MR elastomers are outlined in terms of their storage and loss moduli. The mechanical behavior of the material is also influenced by a magnetic field during the curing of the elastomer matrix, which leads to materials with anisotropic microstructures. The storage modulus of soft elastomer matrix composites can be increased in the presence of a magnetic field by significantly more than one order of magnitude or several hundreds of kPa. The relative increase exceeds that of all previously reported data. A shape memory effect, i. e. the deformation of an MR elastomer in a magnetic field and its return to original shape on cessasion of the magnetic field, is described.

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Blooms of Toxic Cyanobacterium Nodularia spumigena in Norwegian Fjords During Holocene Warm Periods

Toxins ◽

10.3390/toxins12040257 ◽

2020 ◽

Vol 12 (4) ◽

pp. 257

Author(s):

Robert Konkel ◽

Anna Toruńska-Sitarz ◽

Marta Cegłowska ◽

Žilvinas Ežerinskis ◽

Justina Šapolaitė ◽

...

Keyword(s):

Dna Sequences ◽

Phytoplankton Community ◽

Sediment Cores ◽

Specific Chemical ◽

Nodularia Spumigena ◽

History Of ◽

Recent Sediments ◽

Species Specific ◽

Ecosystem Changes ◽

Deep Sediments

In paleoecological studies, molecular markers are being used increasingly often to reconstruct community structures, environmental conditions and ecosystem changes. In this work, nodularin, anabaenopeptins and selected DNA sequences were applied as Nodularia spumigena markers to reconstruct the history of the cyanobacterium in the Norwegian fjords. For the purpose of this study, three sediment cores collected in Oslofjorden, Trondheimsfjorden and Balsfjorden were analyzed. The lack of nodularin in most recent sediments is consistent with the fact that only one report on the sporadic occurrence and low amounts of the cyanobacterium in Norwegian Fjords in 1976 has been published. However, analyses of species-specific chemical markers in deep sediments showed that thousands of years ago, N. spumigena constituted an important component of the phytoplankton community. The content of the markers in the cores indicated that the biomass of the cyanobacterium increased during the warmer Holocene periods. The analyses of genetic markers were less conclusive; they showed the occurrence of microcystin/nodularin producing cyanobacteria of Nostocales order, but they did not allow for the identification of the organisms at a species level.

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Polycyclic Aromatic Hydrocarbons and Mercury in Sediments from Two Isolated Lakes in Central and Northern Canada

Water Science & Technology ◽

10.2166/wst.1993.0602 ◽

1993 ◽

Vol 28 (8-9) ◽

pp. 43-52 ◽

Cited By ~ 17

Author(s):

W. L. Lockhart ◽

P. Wilkinson ◽

B. N. Billeck ◽

G. J. Brunskill ◽

R. V. Hunt ◽

...

Keyword(s):

Sediment Cores ◽

Hudson Bay ◽

Atmospheric Fallout ◽

Long Period ◽

The North ◽

Northwestern Ontario ◽

Forest Region ◽

Rate Of Increase ◽

Polycyclic Aromatic ◽

Recent Sediments

Sediment cores were taken from two isolated Canadian lakes, a southern lake in the boreal forest region of northwestern Ontario and a northern one in the tundra on the west coast of Hudson Bay, for the purpose of comparing current and historical loadings of several contaminants. There are no sources of anthropogenic contaminants within either basin, yet both lakes showed increases in polycyclic aromatic hydrocarbon and mercury in more recent sediments as compared with older, deeper sediments. We have interpreted these as indications of increased loadings as a result of atmospheric fallout. When compared on the basis of the sum of sixteen PAHs, both lakes showed peak inputs in the middle years of this century, followed by more recent declines; although current values still exceed those from deep slices. With respect to mercury, the concentrations found in the southern lake were somewhat higher than those in the northern lake, and loadings were clearly greater in the south. Both lakes showed enrichment of mercury in top layers of the cores relative to bottom layers, and this enrichment was proportionately greater in the north. Both mercury profiles showed a slow rate of increase for a long period before 1850, suggesting influences from areas industrialized before North America. The northern lake also showed increases in PAH loadings prior to 1850, but the southern lake did not.

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Induction of metallothionein synthesis by cadmium and zinc in cultured rabbit kidney cells (RK-13)

Biochemical Journal ◽

10.1042/bj2920609 ◽

1993 ◽

Vol 292 (2) ◽

pp. 609-615 ◽

Cited By ~ 26

Author(s):

M Wan ◽

P E Hunziker ◽

J H R Kägi

Keyword(s):

Metal Tolerance ◽

Regulation Of Gene Expression ◽

Relative Increase ◽

Rabbit Kidney ◽

Kidney Cells ◽

Induction Process ◽

Order Of Magnitude ◽

Cellular Tolerance ◽

Toxic Concentrations ◽

In Cells

The effects of increasing concentrations of Zn(II) and Cd(II) on the expression of the four isometallothioneins (isoMTs), namely MT-1a, MT-2a, MT-2d and MT-2e, in rabbit kidney cells (RK-13) and the development of cellular tolerance to these metal ions were studied. The results showed that, whereas in parental cells MT concentration was low and composed nearly exclusively of MT-2a and MT-1a, all four isoMTs increased massively in abundance when the cells were exposed to toxic concentrations of Zn(II) or Cd(II), the relative increase being largest in the two minor isoforms MT-2d and MT-2e. While the response of the four isoMTs to the challenge by Zn(II) or Cd(II) was qualitatively comparable, there were differences in sensitivity and delay time, Cd(II) being the more efficient inducer and much faster in eliciting the onset of isoMT synthesis. An even larger production of isoMTs resulted when RK-13 cells were cultured in the presence of a series of metal concentrations yielding sub-lines of increased metal tolerance. In this instance too, there were marked differences in the response to Cd(II) and Zn(II). Thus, in cells of sub-lines selected for tolerance to moderate concentrations of Cd(II) the kinetic analysis of isoMT accretion gave indications of a saturable induction process while no such evidence was forthcoming for Zn(II). In sub-line cells selected for tolerance to the highest concentrations of Cd(II) or Zn(II) isoMT formation was increased by another order of magnitude, reaching for some isoforms a 100- to 1000-fold augmentation over the amounts measured in cells of the unexposed parental cells. A potentiation of this magnitude goes beyond the range of ordinary regulation of gene expression. It is to be viewed instead as an enlargement of the capacity of isoMT synthesis acquired by a variety of mechanisms in the surviving cells.

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Radiometric dating of the United Kingdom SWAP sites

Philosophical Transactions of the Royal Society of London Series B Biological Sciences ◽

10.1098/rstb.1990.0057 ◽

1990 ◽

Vol 327 (1240) ◽

pp. 233-238 ◽

Cited By ~ 40

Keyword(s):

Sediment Cores ◽

Radiometric Dating ◽

Recent Sediment ◽

Accumulation Rates ◽

Water Acidification ◽

Sediment Record ◽

The United Kingdom ◽

Surface Water Acidification ◽

Study Sites ◽

Gamma Assay

Measurements of 210 Pb by direct gamma assay have been used to date sediment cores from Surface Water Acidification Project (SWAP) study sites in the U.K. The results were checked against additional dating evidence from the artificial fallout isotopes 137 Cs and 241 Am. At one of the sites, Devoke Water in Cumbria, the 137 Cs and 241 Am data were crucial in identifying a recent sediment hiatus. At sites with recently afforested catchments the sediment record indicated substantial increases in accumulation rates.

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The Distribution of Mercury in the Sediments of Lake Ontario

Canadian Journal of Earth Sciences ◽

10.1139/e72-054 ◽

1972 ◽

Vol 9 (6) ◽

pp. 636-651 ◽

Cited By ~ 110

Author(s):

R. L. Thomas

Keyword(s):

Mercury Concentration ◽

Lake Ontario ◽

Average Concentration ◽

Sediment Type ◽

Lake Basin ◽

Niagara River ◽

Fine Sediments ◽

High Mercury ◽

Main Lake ◽

Recent Sediments

Total mercury has been analysed in the surface 3 cm of sediment taken from 287 sample stations on an 8 km grid on Lake Ontario during 1968. The mercury distribution shows well-defined trends which can be related to sediment type; the concentration of mercury increasing from the shallow nearshore coarse sediments outwards, into the central, deep-water basin sediments composed of fine silty clays and clays. The average concentration of mercury in the nearshore sediments is 355 ppb, in the basin sediments 997 ppb and the average for the whole lake is 651 ppb. Regions of high mercury concentration (in the order of 2000 ppb) occur along the southern margin of the main lake basin and in the western (Niagara) basin of the lake. The dispersion pathways of these two regions point to the Niagara River as the prime source of mercury input to Lake Ontario. Most of this mercury is believed to be of industrial origin. An additional area of high mercury concentration with values up to 20 000 ppb, occurs at the eastern end of Lake Ontario (Kingston Basin) in the region of the lake close to the outlet to the St. Lawrence River. These high values in organic-rich, fine sediments are likely related to processes of biological concentration. The concentrations of mercury observed in the recent sediments of Lake Ontario can be accounted for by an average minimum daily input of 125 lb (56.7 kg) of mercury of which an estimated 42 lb (19.0 kg) is of natural origin and the remaining 83 lb (37.6 kg) is from industrial sources. The vertical distribution of mercury in a selected sediment core suggests that industrial mercury input commenced about the turn of the century, rose rapidly to circa 1943 and, since then, has shown a slow but continued rise to the time of core retrieval in 1970.

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A new 30 000-year chronology for rapidly deposited sediments on the Lomonosov Ridge using bulk radiocarbon dating and probabilistic stratigraphic alignment

Geochronology ◽

10.5194/gchron-2-81-2020 ◽

2020 ◽

Vol 2 (1) ◽

pp. 81-91

Author(s):

Francesco Muschitiello ◽

Matt O'Regan ◽

Jannik Martens ◽

Gabriel West ◽

Örjan Gustafsson ◽

...

Keyword(s):

Accumulation Rate ◽

Ice Core ◽

Sediment Cores ◽

Monte Carlo Algorithm ◽

Stratigraphic Correlation ◽

Lomonosov Ridge ◽

14C Dating ◽

High Accumulation ◽

Radiocarbon Age ◽

Age Estimates

Abstract. We present a new marine chronostratigraphy from a high-accumulation rate Arctic Ocean core at the intersection of the Lomonosov Ridge and the Siberian margin, spanning the last ∼ 30 kyr. The chronology was derived using a combination of bulk 14C dating and stratigraphic correlation to Greenland ice-core records. This was achieved by applying an appositely developed Markov chain Monte Carlo algorithm for Bayesian probabilistic alignment of proxy records. The algorithm simulates depositionally realistic alignments that are consistent with the available radiocarbon age estimates and allows deriving uncertainty bands associated with the inferred alignment. Current composite chronologies from this region are reasonably consistent with our age model during the Holocene and the later part of deglaciation. However, prior to ∼ 14 kyr BP they yield too old age estimates with offsets that linearly increase up to ∼ 40 kyr near the onset of Marine Isotope Stage (MIS) 2. Our results challenge the robustness of previous regional chronostratigraphies and provide a new stratotype for correlation of sediment cores from this sector of the Lomonosov Ridge and East Siberian slope. In particular, they call for a re-interpretation of events in recent sea-ice proxy reconstructions (Xiao et al., 2015) inaccurately attributed to MIS 3 and the Last Glacial Maximum.

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60CO and 137CS Activity of Nearshore Lake Ontario Sediments in the Vicinity of the Pickering Nuclear Generating Complex

Water Quality Research Journal ◽

10.2166/wqrj.1988.029 ◽

1988 ◽

Vol 23 (3) ◽

pp. 396-407 ◽

Cited By ~ 1

Author(s):

D. W. Rodgers ◽

R. S. McKinley

Keyword(s):

Cation Exchange Capacity ◽

Lake Ontario ◽

137Cs Activity ◽

Distribution Coefficients ◽

Exchange Capacity ◽

Gamma Activity ◽

Widespread Distribution ◽

Adsorption Affinity ◽

Order Of Magnitude ◽

60Co Activity

Abstract Detectable 137Cs activity (<1 - 27 Bq/kg dry wt.) was widely distributed in sediments from a series of nearshore transects along Lake Ontario near Pickering Nuclear Generating Station (NGS) ‘A’. In contrast, detectable 60Co activity (<1 - 14 Bq/Kg dry wt.) was largely restricted to transects located near the discharge of Pickering ‘A’ NGS. The widespread distribution of 137Cs is consistent with diffuse input of the radionuclide through fallout, while the restricted distribution of 60Co indicates a localized input of this radionuclide. Adsorption distribution coefficients (Kd’s) of 60Co and 137Cs varied by more than an order of magnitude among representative sediments. Although Kd’s of both radionuclides were correlated with cation exchange capacity and particle size, neither the observed gamma activity nor the corresponding Kd were important in describing 60Co or 137Cs Kd’s. Thus factors other than adsorption affinity alone may be required to account for the distribution of these radionuclides in nearshore Lake Ontario sediments.

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A late Holocene Record of sediment dynamics obtained from Lake Altaussee (Salzkammergut, Austria).

10.5194/egusphere-egu21-1963 ◽

2021 ◽

Author(s):

Jasper Moernaut ◽

Sebastian Wagner ◽

Julia Rechenmacher ◽

Markus Fiebig ◽

Marcel Ortler ◽

...

Keyword(s):

Sediment Cores ◽

Mass Movement ◽

Sediment Dynamics ◽

Coastal Sediments ◽

Coarse Grained ◽

Lake Basin ◽

Stratigraphic Correlation ◽

X Ray ◽

The University ◽

Subbottom Profiling

Sedimentary records in inner-Alpine lakes typically show a rich history of changes in sediment dynamics and the occurrence of various geohazards. Lake Altaussee (712 m asl; 2.4 x 1.0 km; max. 72 m deep) is a dimictic, moderately-sized glacigenic lake located in the Northern Calcareous Alps. Currently, it has no major river inflow and most water input comes from several subaqueous springs, forming large and deep craters (max. 60 m diameter and 22 m deep) on the lake bottom. Since 2019, a wide suite of investigations (hydrogeology, microplastics, hydroacoustics, geomorphology, sedimentology) started under the framework of the Walter Munk Foundation for the Oceans (WMFO) and the University of Natural Resources and Life Sciences (BOKU) Vienna. In 2020, the University of Innsbruck (UIBK) became a project partner to undertake joint research on its sedimentary infill.We present preliminary results from lacustrine morphological mapping of high-resolution multibeam bathymetry (Kongsberg EM2040), seismic-stratigraphic analysis of subbottom profiling data (Innomar SES-2000 and Kongsberg GEOPULSE), and sedimentological/geochemical analysis on 22 short cores (60-170 cm long). Stratigraphic correlation between the 22 cores is based on visual detection of marker layers in Multi-Sensor Core Logging (MSCL), X-Ray CT and X-ray fluorescence (XRF) core scanning data.The sediment cores mainly exhibit slowly-accumulating organic-rich sediments, typical for lake systems that lack significant fluvial sediment input. One unit of finely-laminated clastic carbonate-rich sedimentation can be traced back to an episode in which a major creek &#8722;draining an area of active salt mining&#8722; was flowing into the western part of the lake. In medieval times, this creek was artificially diverted and depositional conditions in the lake returned to organic-rich sedimentation.&#160;The hydroacoustic data show a scattered pattern of large-scale blocks up to 50-70 m diameter in the eastern half of the lake basin. This suggests the occurrence of one or more large gravitational mass movements, which potentially originated at the steep rock slopes at the northern and eastern end of the lake. A megaturbidite (>1-2 m thick) can be traced over the entire basin floor in both subbottom profiling data and sediment cores, and directly overlies the blocks in the deep basin. Isopach mapping of this megaturbidite hints at sediment transport from both the eastern and western slopes, which we interpret to have occurred as the results of a mass-movement induced impulse wave that eroded coastal sediments at the opposite side of the lake and transported these to the deeper basin. On the shallower western plateau, the presence of an outstanding coarse-grained stratigraphic unit with an erosive base further supports this hypothesis, as it is stratigraphically coeval to the megaturbidite. Biogenic gas accumulation at the base of the megaturbidite prevents further penetration on the subbottom profiles, but some acoustic windows visualize up to 15 m of infill.Upcoming research involves the establishment of 14C-based age-depth models, the acquisition of single-channel airgun seismics to visualize the entire infill of the lake through the gas blanket, and long piston coring to investigate the sediment dynamics and geohazards recorded in the Holocene sedimentary infill.

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Dynamic environmental response to the Younger Dryas cooling in the sediment record of Lake Gościąż

10.5194/egusphere-egu2020-742 ◽

2020 ◽

Author(s):

Daniela Müller ◽

Rik Tjallingii ◽

Birgit Plessen ◽

Mateusz Płóciennik ◽

Arne Ramisch ◽

...

Keyword(s):

Regional Climate ◽

Sediment Cores ◽

Younger Dryas ◽

Major Change ◽

Lake Basin ◽

Environmental Response ◽

Last Deglaciation ◽

Sediment Record ◽

Proxy Responses ◽

Environmental Responses

The last deglaciation in the northern hemisphere was interrupted by several short cold setbacks of which the Younger Dryas (YD) was the last and most pronounced. This abrupt and extreme cold period provides valuable insights into regional climate and environmental responses. To decipher the rate of such rapid changes continuous climate archives of annually laminated (varved) sediments are crucial.Lake Go&#347;ci&#261;&#380; (central Poland) exhibits an iconic varved lake sediment record that is one of the few European lake records preserving varves throughout the complete YD. To re-investigate this archive, 10 new sediment cores have been obtained along a N-S transect through the deepest part of the lake basin. We used a combination of continuous microfacies analyses, XRF element core scanning, &#181;-XRF mapping, and high-resolution chironomid-inferred mean July air temperature as well as analyses of stable oxygen and carbon isotopes.Lacustrine sedimentation begins in the late Aller&#248;d, is briefly interrupted by a slump during the early YD and proceeds continuously afterwards. Here, we present a first continuous microfacies investigation of the complete YD in Lake Go&#347;ci&#261;&#380;. Varve composition during the YD is the most complex and variable one, featuring primarily diatom frustules, calcite, re-worked and re-suspended material. Contrastingly, the simpler structured varves during the early Preboreal and late Aller&#248;d are characterized predominantly by calcite, rhodochrosite and dissolved organic matter. The change in microfacies at both YD transitions occurs not simultaneously with the other proxy responses.Causes of and differences in proxy responses in regard to the dynamics of environmental change during a major change in climate are discussed. Further, we conduct a proxy comparison at both YD transitions and provide a detailed documentation of the transitions through &#181;-XRF mapping.This study is a contribution to the Virtual Institute of Integrated Climate and Landscape Evolution Analysis (ICLEA) of the Helmholtz Association (grant number VH-VI-415). It is further a contribution to a scientific project financed by the National Science Centre, Poland &#8211; No. UMO-2015/19/B/ST10/03039.

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