Relationship between Chrysophyte Assemblages and Environmental Variables in Seventy-Two Sudbury Lakes as Examined by Canonical Correspondence Analysis (CCA)

1989 ◽  
Vol 46 (10) ◽  
pp. 1667-1676 ◽  
Author(s):  
Sushil S. Dixit ◽  
Aruna S. Dixit ◽  
John P. Smol
Keyword(s):  
Correspondence Analysis ◽  
Canonical Correspondence Analysis ◽  
Surface Sediment ◽  
Important Variable ◽  
Great Promise ◽  
Calibration Model ◽  
Ph Indicator ◽  
History Of ◽  
Inferred Ph ◽  
Almost All

Relationship between surface sediment chrysophyte scales and limnological variables in 72 Sudbury lakes was examined using canonical correspondence analysis (CCA). CCA is a recently developed multivariate direct gradient analysis that has many advantages over indirect gradient analyses. Lakewater pH was identified as the most important variable influencing the distribution of scaled chrysophytes in Sudbury lakes. Almost all common chrysophyte taxa can be assigned a pH indicator value. In addition to pH, many chrysophyte taxa are sensitive to metal concentrations. A calibration model was developed to predict chrysophyte inferred pH using CCA. The model proved to be far superior to traditionally used models derived from multiple regression of pH indicator chyrsophyte assemblages. Applicability of the predictive pH equation was examined by reconstructing the recent pH history of Lohi Lake. The study provides compelling evidence that canonical correspondence analysis offers great promise in surface sediment calibration and pH reconstruction studies.

Surface-sediment chrysophytes from 35 Quebec lakes and their usefulness in reconstructing lake-water pH

1989 ◽  
Vol 67 (7) ◽  
pp. 2071-2076 ◽  
Author(s):  
Aruna S. Dixit ◽  
Sushil S. Dixit
Keyword(s):  
Surface Sediment ◽  
Lake Water ◽  
Predictive Ability ◽  
Strong Relationship ◽  
Ph Indicator ◽  
Ph Values ◽  
Water Ph ◽  
History Of ◽  
Inferred Ph ◽  
Water Acidity

Chrysophyte scales from surface sediment samples of 35 Quebec lakes were analyzed to examine their relationship with lake-water pH. The percent composition of common chrysophyte taxa were plotted against the measured lake-water pH. The distribution of many taxa was found to be closely associated with pH. The pH indicator status and abundance-weighted mean pH values of the majority of taxa of the studied region agreed with the published work. Chrysophyte counts were quantified to establish a predictive pH model using multiple regressions of pH indicator chrysophyte assemblages with lake-water pH. A strong relationship (r2 = 0.72) was observed between measured and inferred pH values. The pH predictive ability of chrysophytes was further corroborated by reconstructing the recent pH history of Lake Bonneville. Over the last 30 years, the inferred pH of this lake has declined ≈ 1 pH unit. The present study accentuates that stratigraphic analysis of chrysophytes will provide useful measurements of the extent of lake-water acidity in Quebec.

Relationships between surface sediment diatom assemblages and water chemistry gradients in saline lakes of the Vestfold Hills, Antarctica

1996 ◽  
Vol 8 (4) ◽  
pp. 331-341 ◽  
Author(s):  
D. Roberts ◽  
A. McMinn
Keyword(s):  
Water Chemistry ◽  
Correspondence Analysis ◽  
Canonical Correspondence Analysis ◽  
Surface Sediment ◽  
Saline Lakes ◽  
Diatom Assemblages ◽  
Antarctic Region ◽  
Inference Models ◽  
Vestfold Hills ◽  
The Relationship

The relationship between surface sediment diatom assemblages and measured limnological variables in 33 coastal Antarctic lakes was examined by constructing a diatom-water chemistry dataset. Canonical correspondence analysis revealed that salinity and silicate each explain significant amounts of variation in the distribution and abundance of the surface sediment diatom taxa. Salinity has the strongest influence, revealing its value for limnological inference models in this coastal Antarctic region.

Scaled Chrysophytes (Chrysophyceae) as Indicators of pH in Sudbury, Ontario, Lakes

1988 ◽  
Vol 45 (8) ◽  
pp. 1411-1421 ◽  
Author(s):  
Sushil S. Dixit ◽  
Aruna S. Dixit ◽  
R. Douglas Evans
Keyword(s):  
Lake Water ◽  
Ph Indicator ◽  
Related Factors ◽  
Scaled Chrysophytes ◽  
Calibration Equation ◽  
Water Ph ◽  
History Of ◽  
Inferred Ph ◽  
Relationship Of ◽  
The Relationship

Surface sediment chrysophytes (Chrysophyceae) of 30 Sudbury, Ontario, lakes were analyzed to investigate the relationship of these algal microfossils with the limnological characteristics of the study lakes. The distribution of the majority of common chrysophyte taxa is correlated closely with lake water pH, pH-related factors, or both. Chrysodidymus synuroideus, Synura echinulata, Mallomonas hamata, M. acaroides var. muskokana, and Chrysosphaerella longispina appear to be indicators of strongly to moderately acidic waters whereas M. pseudocoronata and M. caudata are indicators of circumneutral to alkaline waters. Using multiple regression of pH indicator chrysophyte assemblages against the measured lake pH, a calibration equation was developed to compute chrysophyte-inferred pH. Chrysophyte-inferred pH values were closely related with measured lake water pH (r2 = 0.74). The study indicates that in the absence of historical pH data, stratigraphic analysis of scaled chrysophytes would provide useful information about the history of lake acidification in the Sudbury area. There is some indication that high metal concentrations, in addition to pH, may influence chrysophycean species distribution in acidic lakes.

scholarly journals Metagenomic screening of global microbiomes identifies pathogen-enriched environments

2018 ◽  
Author(s):  
Xiaofang Li
Keyword(s):  
Correspondence Analysis ◽  
Canonical Correspondence Analysis ◽  
Quantitative Estimate ◽  
Bioinformatic Analysis ◽  
Polluted Water ◽  
Ocean Water ◽  
Human Pathogens ◽  
Precautionary Measures ◽  
Enriched Environments ◽  
Almost All

AbstractBackgroundHuman pathogens are widespread in the environment, and examination of pathogen-enriched environments in a rapid and high-throughput fashion is important for development of pathogen-risk precautionary measures.MethodsIn this study, a Local BLASTP procedure for metagenomic screening of pathogens in the environment was developed using a toxin-centered database. A total of 27 microbiomes derived from ocean water, freshwater, soil, feces, and wastewater were screened using the Local BLASTP procedure. Bioinformatic analysis and Canonical Correspondence Analysis were conducted to examine whether the toxins included in the database were taxonomically associated.ResultsThe specificity of the Local BLASTP method was tested with known and unknown toxin sequences. Bioinformatic analysis indicated that most toxins were phylum-specific but not genus-specific. Canonical Correspondence Analysis implied that almost all of the toxins were associated with the phyla ofProteobacteria,NitrospiraeandFirmicutes. Local BLASTP screening of the global microbiomes showed that pore-forming RTX toxin and adenylate cyclase Cya were most prevalent globally in terms of relative abundance, while polluted water and feces samples were the most pathogen-enriched.ConclusionsA Local BLASTP procedure was established for rapid detection of toxins in environmental samples. Screening of global microbiomes in this study provided a quantitative estimate of the most prevalent toxins and most pathogen-enriched environment.

Diatom-inferred pH calibration of lakes near Wawa, Ontario

1986 ◽  
Vol 64 (6) ◽  
pp. 1129-1133 ◽  
Author(s):  
Sushil S. Dixit
Keyword(s):  
Multiple Regression ◽  
Surface Sediment ◽  
Lake Water ◽  
Ph Indicator ◽  
Lake Region ◽  
Water Ph ◽  
Sedimentary Diatoms ◽  
Inferred Ph ◽  
Ph Calibration

In the absence of long-term pH records for lakes, sedimentary diatoms have often been used to detect the extent of recent lake acidification. Although various methods have been used to relate surface-sediment diatom remains to contemporary lake-water pH, their usefulness and selection criteria have not been clearly defined for Canadian lakes. Surface-sediment diatoms of 28 lakes (pH 4.0–8.13) located northeast of Lake Superior were identified and enumerated. Lake-water pH estimates were made using multiple regression analyses of selected diatom taxa and Hustedt's pH indicator groups, as well as by index α and index B. Multiple regression, using the abundance of pH indicator assemblages, appears to be the most suitable method for the studied lake region. Discrepancies associated with other methods are discussed in details.

Weed communities associated with arable Saskatchewan farm management systems

2000 ◽  
Vol 80 (1) ◽  
pp. 177-185 ◽  
Author(s):  
J. Y. Leeson ◽  
J. W. Sheard ◽  
A. G. Thomas
Keyword(s):  
Life History ◽  
Correspondence Analysis ◽  
Canonical Correspondence Analysis ◽  
Management System ◽  
Management Practices ◽  
Farming System ◽  
Management Systems ◽  
Weed Communities ◽  
History Of ◽  
The Impact

The objective of this study was to determine the impact of a range of management systems on weed communities in cropped fields on farms in Saskatchewan. Farms (n = 28) with management systems defined by a combination of different cropping histories and chemical input levels were selected. Fields were surveyed on each farm in 1995, 1996, and 1997 after any post-emergent weed control to ensure that their weed communities reflected the impact of all agronomic management practices typical of the management system. Canonical correspondence analysis was used to determine whether weed communities were significantly correlated with management system after removal of variance due to ecoregion and year. The largest difference in weed communities attributable to farming system was between the systems with annual cropping histories and those that included perennials in the cropping history. Thus, the life history of the weeds reflected the life history of the crops. Herbicide use was correlated with the next largest difference between systems. A significant association between weed communities and different management systems indicates that weed species are being selected for by these systems. If such selection pressure continues, these species may become a threat to the system's sustainability. Key words: Weed communities, chemical input level, cropping history, canonical correspondence analysis, correspondence analysis, farming system

From the Tower of London to the Thomas More Society of Buenos Aires: “Give me thy grace, good Lord, to set the world at nought”

Moreana ◽  
2005 ◽  
Vol 42 (Number 164) (4) ◽  
pp. 187-206
Author(s):  
Clare M. Murphy
Keyword(s):  
Buenos Aires ◽  
Short History ◽  
Thomas More ◽  
Tower Of London ◽  
Hebrew Poetry ◽  
Prayer Book ◽  
The World ◽  
History Of ◽  
Book Of Hours ◽  
Almost All

The Thomas More Society of Buenos Aires begins or ends almost all its events by reciting in both English and Spanish a prayer written by More in the margins of his Book of Hours probably while he was a prisoner in the Tower of London. After a short history of what is called Thomas More’s Prayer Book, the author studies the prayer as a poem written in the form of a psalm according to the structure of Hebrew poetry, and looks at the poem’s content as a psalm of lament.

scholarly journals An Emulation of Randomized Trials of Administrating Antipsychotics in PTSD Patients for Outcomes of Suicide-Related Events

2021 ◽  
Vol 11 (3) ◽  
pp. 178
Author(s):  
Noah R. Delapaz ◽  
William K. Hor ◽  
Michael Gilbert ◽  
Andrew D. La ◽  
Feiran Liang ◽  
...  
Keyword(s):  
Randomized Clinical Trials ◽  
Previous History ◽  
Current Treatment ◽  
Careful Consideration ◽  
P Value ◽  
Post Traumatic Stress ◽  
Increased Risk ◽  
History Of ◽  
Almost All

Post-traumatic stress disorder (PTSD) is a prevalent mental disorder marked by psychological and behavioral changes. Currently, there is no consensus of preferred antipsychotics to be used for the treatment of PTSD. We aim to discover whether certain antipsychotics have decreased suicide risk in the PTSD population, as these patients may be at higher risk. A total of 38,807 patients were identified with a diagnosis of PTSD through the ICD9 or ICD10 codes from January 2004 to October 2019. An emulation of randomized clinical trials was conducted to compare the outcomes of suicide-related events (SREs) among PTSD patients who ever used one of eight individual antipsychotics after the diagnosis of PTSD. Exclusion criteria included patients with a history of SREs and a previous history of antipsychotic use within one year before enrollment. Eligible individuals were assigned to a treatment group according to the antipsychotic initiated and followed until stopping current treatment, switching to another same class of drugs, death, or loss to follow up. The primary outcome was to identify the frequency of SREs associated with each antipsychotic. SREs were defined as ideation, attempts, and death by suicide. Pooled logistic regression methods with the Firth option were conducted to compare two drugs for their outcomes using SAS version 9.4 (SAS Institute, Cary, NC, USA). The results were adjusted for baseline characteristics and post-baseline, time-varying confounders. A total of 5294 patients were eligible for enrollment with an average follow up of 7.86 months. A total of 157 SREs were recorded throughout this study. Lurasidone showed a statistically significant decrease in SREs when compared head to head to almost all the other antipsychotics: aripiprazole, haloperidol, olanzapine, quetiapine, risperidone, and ziprasidone (p < 0.0001 and false discovery rate-adjusted p value < 0.0004). In addition, olanzapine was associated with higher SREs than quetiapine and risperidone, and ziprasidone was associated with higher SREs than risperidone. The results of this study suggest that certain antipsychotics may put individuals within the PTSD population at an increased risk of SREs, and that careful consideration may need to be taken when prescribed.

scholarly journals Ecological Risk Assessment and Contamination History of Heavy Metals in the Sediments of Chagan Lake, Northeast China

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 894
Author(s):  
Panfeng Liu ◽  
Chaojie Zheng ◽  
Meilan Wen ◽  
Xianrong Luo ◽  
Zhiqiang Wu ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Principal Component Analysis ◽  
Ecological Risk ◽  
Surface Sediment ◽  
Northeast China ◽  
Principal Component ◽  
Potential Ecological Risk ◽  
210Pb Dating ◽  
History Of ◽  
Chagan Lake

The study deals with the spatio-temporal distribution of heavy metals in the sediments of Chagan lake, Northeast China. The pollution history of heavy metals is studied simultaneously through the 210Pb dating method by analyzing the characteristic of As, Hg, Cd, Cr, Ni, Cu, Pb, and Zn concentration-depth profiles. The potential ecological risk index (RI) and geo-accumulation index (Igeo) were used to evaluate the contamination degree. Principal component analysis (PCA), based on the logarithmic transformation and isometric log-ratio (ilr) transformed data, was applied with the aim of identifying the sources of heavy metals. The element concentrations show that the heavy metals are enriched in the surface sediment and sediment core with a varying degree, which is higher in the surficial residue. The results of Igeo indicate that the Cd and Hg in the surface sediment have reached a slightly contaminated level while other elements, uncontaminated. The results of RI show that the study area can be classified as an area with moderate ecological risk in which Cd and Hg mostly contribute to the overall risk. For the sediment core, the 210Pb dating results accurately reflect the sedimentary history over 153 years. From two evaluation indices (RI and Igeo) calculated by element concentration, there is no contamination, and the potential ecological risk is low during this period. The comparative study between raw and ilr transformed data shows that the closure effect of the raw data can be eliminated by ilr transformation. After that, the components obtained by robust principal component analysis (RPCA) are more representative than those obtained by PCA, both based on ilr transformed dataset, after eliminating the influence of outliers. Based on ilr transformed data with RPCA, three primary sources could be inferred: Cr, Ni, As, Zn, and Cu are mainly derived from natural sources; the main source of Cd and Hg are associated with agricultural activities and energy development; as for Pb, it originated from traffic and coal-burning activities, which is consistent with the fact that the development of tourism, fishery, and agriculture industries has led to the continuous increasing levels of anthropogenic Pb in Chagan Lake. The summarized results and conclusions will undoubtedly enhance the governmental awareness of heavy metal pollution and facilitate appropriate pollution control measures in Chagan Lake.

Sign in / Sign up

Export Citation Format

Share Document