Organochlorine Concentrations in the Plankton of Lakes in Southern Ontario and Their Relationship to Plankton Biomass

1991 ◽  
Vol 48 (10) ◽  
pp. 1960-1966 ◽  
Author(s):  
W. D. Taylor ◽  
J. H. Carey ◽  
D. R. S. Lean ◽  
D. J. McQueen
Keyword(s):  
Total Phosphorus ◽  
Atmospheric Transport ◽  
Negative Relationship ◽  
Dilution Effect ◽  
Common Source ◽  
Contaminant Concentration ◽  
Southern Ontario ◽  
Refractory Compounds ◽  
Plankton Biomass ◽  
Organochlorine Contaminants

Hydrophobic organochlorine contaminants were surveyed in net plankton from 33 lakes in southern Ontario. Organochlorines were detected in all lakes. The relative concentrations of 12 common organochlorines were generally similar, suggesting that they derive from a common source, probably atmospheric transport. Variability in relative abundances of these contaminants increased with contaminant concentration, while contaminant concentration was related to plankton biomass, total phosphorus, and conductivity. Lakes with low plankton biomass had high organochlorine concentrations in that biomass, indicating that a large portion of the variation among lakes in the concentration of contaminants in plankton can be ascribed to variable planktonic biomass. This negative relationship with plankton biomass, or biomass dilution effect, was strongest for the more hydrophobic and refractory compounds.

A Candide response to Panglossian accusations by Randolph and Dobson: biodiversity buffers disease

Parasitology ◽  
2013 ◽  
Vol 140 (10) ◽  
pp. 1196-1198 ◽  
Author(s):  
RICHARD S. OSTFELD
Keyword(s):  
Infectious Disease ◽  
Disease Risk ◽  
Negative Relationship ◽  
Dilution Effect ◽  
Widespread Phenomenon ◽  
High Diversity

SUMMARYRandolph and Dobson (2012) criticize the dilution effect, which describes the negative relationship between biodiversity and infectious disease risk. Unfortunately, their commentary includes distortions, errors of omission, and errors of commission, which are rebutted herein. Contrary to their claims, the dilution effect is not a ‘mantra’ that asserts that reduced disease risk is a ‘universal’ outcome of high diversity. Although universality of the dilution effect has not been claimed, and conditions under which diversity can amplify disease risk have been described, the growing literature indicates that the dilution effect is indeed a widespread phenomenon.

Disruption of a host-parasite system following the introduction of an exotic host species

Parasitology ◽  
2005 ◽  
Vol 130 (6) ◽  
pp. 661-668 ◽  
Author(s):  
S. TELFER ◽  
K. J. BOWN ◽  
R. SEKULES ◽  
M. BEGON ◽  
T. HAYDEN ◽  
...  
Keyword(s):  
Bank Vole ◽  
Host Species ◽  
Negative Relationship ◽  
Dilution Effect ◽  
Wood Mouse ◽  
Clethrionomys Glareolus ◽  
Infection Prevalence ◽  
Wood Mice ◽  
Effect Hypothesis ◽  
Host Parasite

The potential of biological invasions to threaten native ecosystems is well recognized. Here we describe how an introduced species impacts on native host-parasite dynamics by acting as an alternative host. By sampling sites across an invasion front in Ireland, we quantified the influence of the introduced bank vole (Clethrionomys glareolus) on the epidemiology of infections caused by flea-transmitted haemoparasites of the genusBartonellain native wood mice (Apodemus sylvaticus).Bartonellainfections were detected on either side of the front but occurred exclusively in wood mice, despite being highly prevalent in both rodent species elsewhere in Europe. Bank vole introduction has, however, affected the wood mouse-Bartonellainteraction, with the infection prevalence of bothBartonella birtlesiiandBartonella tayloriideclining significantly with increasing bank vole density. Whilst flea prevalence in wood mice increases with wood mouse density in areas without bank voles, no such relationship is detected in invaded areas. The results are consistent with the dilution effect hypothesis. This predicts that for vector-transmitted parasites, the presence of less competent host species may reduce infection prevalence in the principal host. In addition we found a negative relationship betweenB. birtlesiiandB. tayloriiprevalences, indicating that these two microparasites may compete within hosts.

Lean-team effectiveness through leader values and members’ informing

2016 ◽  
Vol 36 (11) ◽  
pp. 1530-1550 ◽  
Author(s):  
Desirée H. van Dun ◽  
Celeste P.M. Wilderom
Keyword(s):  
Operations Management ◽  
Team Effectiveness ◽  
Negative Relationship ◽  
Equation Modeling ◽  
Future Research ◽  
Common Source ◽  
Content Type ◽  
Team Members ◽  
Conservation Values ◽  
Self Transcendence

Purpose Although empirical tests of effective lean-team leadership are scarce, leaders are often blamed when lean work-floor initiatives fail. In the present study, a lean-team leader’s work values are assumed to affect his or her team members’ behaviors and, through them, to attain team effectiveness. Specifically, two of Schwartz et al.’s (2012) values clusters (i.e. self-transcendence and conservation) are hypothesized to be linked to team members’ degree of information and idea sharing and, in turn, to lean-team effectiveness. The paper aims to report the examination of these hypotheses. Design/methodology/approach Survey responses (n=429) of both leaders and members of 25 lean-teams in services and manufacturing organizations were aggregated, thereby curbing common-source bias. To test the six hypotheses, structural equation modeling was performed, with bootstrapping, linear regression analyses, and Sobel tests. Findings The positive relationship between lean-team effectiveness and leaders’ self-transcendence values, and the negative relationship between lean-team effectiveness and leaders’ conservation values were partly mediated by information sharing behavior within the team. Research limitations/implications Future research must compare the content of effective lean-team values and behaviors to similar non-lean teams. Practical implications Appoint lean-team leaders with predominantly self-transcendence rather than conservation values: to promote work-floor sharing of information and lean-team effectiveness. Originality/value Human factors associated with effective lean-teams were examined, thereby importing organization-behavioral insights into the operations management literature: with HRM-type implications.

The diversity–disease relationship: evidence for and criticisms of the dilution effect

Parasitology ◽  
2016 ◽  
Vol 143 (9) ◽  
pp. 1075-1086 ◽  
Author(s):  
Z. Y. X. HUANG ◽  
F. VAN LANGEVELDE ◽  
A. ESTRADA-PEÑA ◽  
G. SUZÁN ◽  
W. F. DE BOER
Keyword(s):  
Species Diversity ◽  
Host Species ◽  
Disease Risk ◽  
Current Knowledge ◽  
Risk Measures ◽  
Extinction Risk ◽  
Meta Analysis ◽  
Negative Relationship ◽  
Dilution Effect ◽  
Landscape Fragmentation

SUMMARYThe dilution effect, that high host species diversity can reduce disease risk, has attracted much attention in the context of global biodiversity decline and increasing disease emergence. Recent studies have criticized the generality of the dilution effect and argued that it only occurs under certain circumstances. Nevertheless, evidence for the existence of a dilution effect was reported in about 80% of the studies that addressed the diversity–disease relationship, and a recent meta-analysis found that the dilution effect is widespread. We here review supporting and critical studies, point out the causes underlying the current disputes. The dilution is expected to be strong when the competent host species tend to remain when species diversity declines, characterized as a negative relationship between species’ reservoir competence and local extinction risk. We here conclude that most studies support a negative competence–extinction relationship. We then synthesize the current knowledge on how the diversity–disease relationship can be modified by particular species in community, by the scales of analyses, and by the disease risk measures. We also highlight the complex role of habitat fragmentation in the diversity–disease relationship from epidemiological, evolutionary and ecological perspectives, and construct a synthetic framework integrating these three perspectives. We suggest that future studies should test the diversity–disease relationship across different scales and consider the multiple effects of landscape fragmentation.

scholarly journals LEAD SOURCE ASSESSMENT BY ISOTOPIC AND ELEMENTARY COMPOSITION IN THE TRANSITION FROM PRISTINE TO POLLUTED CONDITION OF COASTAL SEDIMENTS / AVALIAÇÃO DAS FONTES DE PB PELAS COMPOSIÇÕES ISOTÓPICAS E ELEMENTARES DE SEDIMENTOS COSTEIROS NA TRANSIÇÃO DE CONDIÇÕES NATURAIS PARA POLUÍDAS

2018 ◽  
Vol 3 (1) ◽  
pp. 46-53 ◽  
Author(s):  
Bruno Cunha ◽  
Wilson Machado ◽  
Ariadne Marra ◽  
Daniel Araújo ◽  
Jérémie Garnier ◽  
...  
Keyword(s):  
Negative Relationship ◽  
Dilution Effect ◽  
Isotopic Signature ◽  
Coastal Sediments ◽  
Coastal Zones ◽  
Potential Influence ◽  
Elementary Composition ◽  
Marine Carbonate ◽  
Lead Source ◽  
Predominance Diagrams

The source assessments of metal contaminants are critical for a consistent management of coastal zones. In this work, lead (Pb) concentration and isotopic composition were determined in sediments from Angra dos Reis coast (Brazil) to evaluate the potential influence of contamination sources on Pb distribution. Estimated Pb enrichment factor superior to 1.64 suggested natural source predominance. Diagrams of 206Pb/207Pb ratio plotted against 208Pb/206Pb and 1/Pb ratios indicated a binary source mixing that was explained by marine and terrigenous influences. Only some specific sites fall close to anthropogenic Pb isotopes signatures (e.g., from urban effluents and gasoline). The lower Pb concentrations were associated with a marine carbonate dilution effect, as indicated by a negative relationship between Pb and Ca. Past dredging activities contributed to explain a diffuse occurrence of anthropogenic Pb isotopic signature. The overall results reveal the beginning of a transition from pristine to slightly-polluted condition. ResumoA avaliação das fontes dos contaminantes metálicos é fundamental para um bom gerenciamento das zonas costeiras. Neste trabalho, as concentrações e composições isotópicas do chumbo (Pb) foram determinadas em sedimentos do litoral de Angra dos Reis (Brasil) para avaliar a potencial influência das fontes de contaminação na distribuição de Pb. Fatores de enriquecimento de Pb de até 1,64 sugeriram predominância de fontes naturais. Diagramas da razão 206Pb/207Pb plotados contra as razões 208Pb/206Pb e 1/Pb indicaram uma mistura binária de fontes, que foi explicada por influências marinhas e terrígenas. Apenas alguns locais específicos possuem assinaturas isotópicas similares às antropogênicas (por exemplo, de efluentes urbanos e gasolina). As concentrações mais baixas de Pb foram associadas a um efeito de diluição pelo carbonato marinho, como indicado por uma relação negativa entre Pb e Ca. Atividades de dragagem no passado contribuíram para explicar uma ocorrência difusa da assinatura isotópica de Pb antropogênico. Os resultados, em geral, revelam o início de uma transição da condição natural para levemente poluída.

Polycylindrichnus: possible Silurian tunicate burrows from southern Ontario

1980 ◽  
Vol 17 (6) ◽  
pp. 738-743 ◽  
Author(s):  
Judith A. Fournier ◽  
S. George Pemberton ◽  
Michael J. Risk
Keyword(s):  
Bedding Plane ◽  
Trace Fossil ◽  
Common Source ◽  
Southern Ontario

Several specimens of a new trace fossil, Polycylindrichnus prolifer, n. gen., n. sp., have been collected from the Middle Silurian Thorold Formation in Hamilton, Ontario. Traces are multiple burrows, originating from a common source at depth, budding into several cylindrical to conical, subhorizontal burrows. Burrow openings lie on a common bedding plane. Traces are tentatively attributed to the activities of infaunal tunicates.

A Test of a Simple Nutrient Budget Model Predicting the Phosphorus Concentration in Lake Water

1974 ◽  
Vol 31 (11) ◽  
pp. 1771-1778 ◽  
Author(s):  
P. J. Dillon ◽  
F. H. Rigler
Keyword(s):  
Total Phosphorus ◽  
Additional Data ◽  
Nutrient Budget ◽  
Phosphorus Loading ◽  
Phosphorus Concentration ◽  
Total Phosphorus Concentration ◽  
Southern Ontario ◽  
Budget Model ◽  
Phosphorus Budgets ◽  
Quantitative Changes

The total phosphorus budgets for a number of lakes in the Haliburton–Kawartha region of southern Ontario were measured over a 20-mo period. These data, combined with the lakes' morphometry and water budgets, were used to test a simple nutrient budget model similar to that proposed by Vollenweider (1969) purporting to predict the total phosphorus concentration in lakes. Except in the case of two very shallow lakes [Formula: see text], the concentrations predicted by the model were very close to those measured in the lakes at spring overturn. Additional data from the literature supported the belief that this model could be used effectively for oligotrophic and mesotrophic lakes. Its value lies in the fact that quantitative changes in phosphorus loading can be interpreted in terms of changes in phosphorus concentration, which in turn, can be related to changes in parameters that reflect the lake's trophic state such as summer chlorophyll a concentration.

Trends in Nutrients, Major Ions and Physical Water Quality Parameters in the Niagara River During the 1977–87 Period

1990 ◽  
Vol 25 (1) ◽  
pp. 15-32
Author(s):  
K.W. Kuntz ◽  
I.K. Tsanis
Keyword(s):  
Total Phosphorus ◽  
Major Ions ◽  
Dilution Effect ◽  
Quality Parameters ◽  
Specific Conductance ◽  
Physical Parameters ◽  
Niagara River ◽  
Annual Variations ◽  
Nitrogen Concentrations ◽  
High Concentrations

Abstract This paper presents the seasonal and annual variations of the physical parameters, nutrients and major ions in the Niagara River for a period of eleven years, 1977–87. The discharge during this period was found to be steadily increasing and as a consequence the specific conductance was decreasing due to the higher dilution effect, as well as the lower concentrations of chloride and sodium. High concentrations of total phosphorus during the winter months corresponded with high turbidity. In addition, a steady decrease in total phosphorus concentrations was observed until 1984, while during the rest of the period concentrations were increasing. Nitrate nitrogen concentrations were found to be steadily increasing during the entire period except for 1987. Seasonal cycles of specific conductance, calcium, alkalinity, magnesium, and sulphate all showed decreases in April, May and June, during the high discharge period. Both chloride and sodium concentrations have decreased substantially during the 1977–85 period, the result of upstream industrial input decreases, but concentrations since then have levelled out.

Phosphorus and Metal Contaminant Transport in Two Southern Ontario Rivers: the Grand River and its Tributary, the Nith River

1996 ◽  
Vol 31 (1) ◽  
pp. 119-152 ◽  
Author(s):  
T. Mayer ◽  
E. Delos Reyes
Keyword(s):  
Heavy Metals ◽  
Water Quality ◽  
Great Lakes ◽  
Total Phosphorus ◽  
Water Samples ◽  
Suspended Solids ◽  
Suspended Sediments ◽  
Southern Ontario ◽  
High Flows ◽  
Grand River

Abstract Water samples and suspended sediments from two southern Ontario rivers, the Grand River and its tributary, the Nith River, were analyzed to investigate the role of suspended sediments in the transport of phosphorus and metals from tributaries. Water samples were analyzed for total suspended solids, total phosphorus, total dissolved phosphorus, chloride and heavy metal concentrations. Suspended sediments were analyzed for forms of phosphorus, total and organic carbon, and heavy metals. Concentrations of total phosphorus and heavy metals in water were elevated during high flows (spring snowmelt and episodes of intensive rain events), which are characterized by high concentrations of suspended solids. On average, about half of the total phosphorus in the water (60 and 54% in the Grand and Nith rivers, respectively) was transported in the particulate form, of which about 20% is in a form that would be potentially available for biological utilization upon depletion of soluble P. Biologically inert apatite-P accounted for 25 and 19% of the total particulate P in suspended sediments from the Grand and Nith rivers, respectively, indicating that between one-fifth and one-quarter of the tributary particulate P flux is of little environmental significance. This form of particulate P showed positive correlation with discharge, indicating increased contribution of this form of P during high flows due to the channel scouring and bank erosion. This finding has important implications for the refinement of P load calculations, since it is during the wet years that P loads to the Great Lakes exceed target loads stipulated by the Great Lakes Water Quality Agreement, mainly because of increased tributary P contributions. Except for apatite-P in suspended sediments from the Grand River, no statistically significant intersite differences were found in water and sediment chemistry, suggesting that there are no important sources or sinks of available phosphorus and metals between the monitored sites. River inputs from sewage treatment plants and urban runoff appear to have little effect on water quality. The lack of significant site differentiation in suspended sediments chemistry also reflects the absence of any significant chemical and/or biological processing of particles in transit and the similarity of sediment sources.

scholarly journals Ice core records of levoglucosan and dehydroabietic and vanillic acids from Aurora Peak in Alaska since the 1660s: a proxy signal of biomass-burning activities in the North Pacific Rim

2020 ◽  
Vol 20 (1) ◽  
pp. 597-612 ◽  
Author(s):  
Ambarish Pokhrel ◽  
Kimitaka Kawamura ◽  
Bhagawati Kunwar ◽  
Kaori Ono ◽  
Akane Tsushima ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Biomass Burning ◽  
Atmospheric Transport ◽  
Ice Core ◽  
Dehydroabietic Acid ◽  
Common Source ◽  
Tropospheric Temperature ◽  
Historical Trends ◽  
Emission Frequency ◽  
The North

Abstract. A 180 m long (343 years) ice core was drilled in the saddle of Aurora Peak in Alaska (63.52∘ N, 146.54∘ W; elevation: 2825 m) and studied for biomass-burning tracers. Concentrations of levoglucosan and dehydroabietic and vanillic acids exhibit multidecadal variability, with higher spikes in 1678, 1692, 1695, 1716, 1750, 1764, 1756, 1834, 1898, 1913, 1966 and 2005 CE. Historical trends of these compounds showed enhanced biomass-burning activities in the deciduous broadleaf forests, boreal conifer forests, and/or tundra woodland and mountain ecosystems before the 1830s and after the Great Pacific Climate Shift (GPCS). The gradually elevated level of dehydroabietic acid after the GPCS is similar to p-hydroxybenzoic acid (p-HBA) from the Svalbard ice core, suggesting common climate variability in the Northern Hemisphere. The periodic cycle of levoglucosan, which seemed to be associated with the Pacific Decadal Oscillation (PDO), may be more involved with the long-range atmospheric transport than other species. These compounds showed significant correlations with global lower-tropospheric temperature anomalies (GLTTAs). The relations of the biomass-burning tracers with the PDO and GLTTA in this study suggest that their emission, frequency and deposition are controlled by the climate-driven forces. In addition, historical trends of dehydroabietic and vanillic acids (burning products of resin and lignin, respectively) from our ice core demonstrate the Northern Hemispheric connections to the common source regions as suggested from other ice core studies from Svalbard, Akademii Nauk and Tunu Greenland in the Northern Hemisphere.

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