Empirical Hypothesis to Explain the Restricted Distribution of Hyalella azteca (Amphipoda) in Anthropogenically Acidified Lakes

1987 ◽  
Vol 44 (6) ◽  
pp. 1112-1121 ◽  
Author(s):  
Robert L. France ◽  
Bruce D. LaZerte
Keyword(s):  
Littoral Zone ◽  
Time Trend ◽  
Population Decline ◽  
Hyalella Azteca ◽  
Ecological Data ◽  
Short Term ◽  
Restricted Distribution ◽  
Empirical Hypothesis ◽  
Acidified Lakes ◽  
Plastic Lake

A simple and speculative model is proposed to explain the restricted distribution of Hyalella azteca (Amphipoda) within acidified Ontario lakes. The model integrates field chemical and ecological data with results from laboratory toxicological experiments. Frequent spring depressions of pH to below 5.0, measured in the littoral zone of Plastic Lake during 1982, were predicted to cause a mortality of 35.2% to a theoretically constructed amphipod population. A time trend simulation suggested that population decline of H. azteca in similar anthropogenically acidified lakes could be caused by such direct mortality due to short-term pH fluctuations. Assumptions and factors not considered by the model which could exacerbate or mitigate the effects of acidic snowmelt to H. azteca are discussed.

Lake Acidification as a Limiting Factor in the Distribution of the Freshwater Amphipod Hyalella azteca

1986 ◽  
Vol 43 (2) ◽  
pp. 288-292 ◽  
Author(s):  
M. Stephenson ◽  
G. L. Mackie
Keyword(s):  
Surface Water ◽  
Hyalella Azteca ◽  
Lake Acidification ◽  
Limiting Factor ◽  
Short Term ◽  
Natural Surface ◽  
Bioassay Data ◽  
Plastic Lake

The distribution of the freshwater amphipod Hyalella azteca in 79 Ontario lakes suggests that its absence may be a good indicator of lake acidification. Hyalella azteca was present in 69 of 71 nonacidified lakes, and absent in 8 of 8 lakes which either are now ar recently were considered acidified. Bioassay data indicate a 96-h LC50 of pH 4.4 and a 10-d threshold LC50 of pH 4.5 for H. azteca in a natural surface water. Hyalella azteca is extremely rare in Plastic Lake, which undergoes severe short-term acidification in spring, and recruitment is delayed 2 wk in Heeney Lake which undergoes similar short-term acidification, in Dickie, Harp, Red Chalk, and Blue Chalk lakes, where springtime pH depressions below pH 4.7 were not recorded, H. azteca is abundant.

Do koalas really get the blues? Critique of ‘Aversive behaviour by koalas (Phascolarctos cinereus) during the course of a music festival in northern New South Wales, Australia'

2017 ◽  
Vol 39 (1) ◽  
pp. 108 ◽  
Author(s):  
Sean I. FitzGibbon ◽  
Amber K. Gillett ◽  
Ben J. Barth ◽  
Brendan Taylor ◽  
William A. Ellis
Keyword(s):  
New South ◽  
Behavioural Response ◽  
Ecological Data ◽  
Short Term ◽  
Music Festival ◽  
Data Analyses ◽  
South Wales ◽  
Unpublished Report ◽  
The Impact ◽  
Sound Data

It is imperative that the reported results of scientific studies are based on sound data analyses and unbiased interpretation, especially where they may be used to guide government policy and regulation. A recent paper by Phillips (2016) evaluated the behavioural response of radio-collared koalas to an inaugural large music festival held in 2010 in northern New South Wales. The study concluded that six of seven koalas showed an aversive response. However, we regard the paper as misleading because it contains serious errors in the examination of koala home ranges and in the subsequent assessment of ‘aversive behaviour’ during the music festival. We conclude that Phillips’ paper is based on sufficient data to state that three, not six, of the koalas he studied displayed a short-term behavioural response to the music festival. These koalas temporarily moved outside of their estimated ranges during the festival period (10–80 m). Further, Phillips fails to report crucial ecological data regarding the high level of disease and mortality he recorded, which are presented in their entirety in the author’s prior, unpublished report. For the two deaths that are reported, no mention is made that these koalas had pre-existing disease. Rather, the author raises the possibility that the mortalities may have been related to festival-induced stress. The omission of such key data is prejudicial to the interpretation of results. The reported short-term impact of the festival upon some of the study animals is indeed noteworthy; however, it is apparent that the impact has been considerably overstated due to errors of analysis and the omission of critical ecological data. Our critique highlights our concerns by drawing on the author’s unpublished report as well as our own research at the same site over the past five years. Our aim is to ensure that debate over the impact of music festivals on wildlife is based on sound data analyses and unbiased interpretation, to provide guidance to relevant regulators and land managers.

scholarly journals Harvest impacts on caribou population dynamics in South West Greenland

Rangifer ◽  
2011 ◽  
pp. 135-145
Author(s):  
Lars Witting ◽  
Christine Cuyler
Keyword(s):  
Population Dynamics ◽  
Population Model ◽  
Population Decline ◽  
Short Term ◽  
Target Density ◽  
West Greenland ◽  
Total Absence ◽  
South West ◽  
The Future

We examined the effects of hunting on caribou populations in South West Greenland from year 1999 to 2007. In the Ameralik area a reported average annual harvest of 2950 caribou coincided with a population decline from 31 000 (90% CI: 22 000 - 44 000) animals in 1999 to 8900 (90% CI: 5800 - 13 000) in 2007. A survey estimate from 2006 indicates that a suggested target caribou density of 1.2 / km2 was met. A Bayesian population model estimates the annual replacement for Ameralik at minus 170 individuals (90% CI: -550 - 460), which indicates that the target density may or may not be maintained even in the total absence of a hunt. For the Qeqertarsuatsiaat area an average annual harvest of 230 caribou appears to have left the density unaffected, remaining steady on target with an abundance of approximately 5000 individuals. The harvest in this area increased from 100 animals in 2000 to 440 in 2006. With an estimated 2007 replacement of 190 (90% CI: -190- 960) caribou per year the target density may not be maintained in the future unless hunting restrictions are implemented. The density of caribou in Qeqertarsuatsiaat may, however, be maintained over the short term if the emigration of animals from Ameralik into Qeqertarsuatsiaat continues.

Life Stage and Population Variation in Resistance and Tolerance of Hyalella azteca (Amphipoda) to Low pH

1987 ◽  
Vol 44 (6) ◽  
pp. 1102-1111 ◽  
Author(s):  
R. L. France ◽  
P. M. Stokes
Keyword(s):  
Genetic Basis ◽  
Life Stage ◽  
Population Decline ◽  
Acid Tolerance ◽  
Hyalella Azteca ◽  
Low Ph ◽  
Population Variation ◽  
Population Differences ◽  
Physiological Plasticity ◽  
Neutral Water

Lethality experiments revealed that resistance of Hyalella azteca (Amphipoda) to low pH was directly related to size and developmental stage. Exposure of adults to water below pH 5.0 during pulses of acid snowmelt, or of juveniles to below pH 5.5 through gradual lake acidification, could result in population decline. Hyalella azteca from moderately acidic Ontario lakes (pH 5.6–5.7) survived longer at lethal pH than did amphipods from circumneutral lakes (pH 6.4–7.2) where spring pH depressions do not occur. Resistance and tolerance to low pH was neither readily lost by tolerant amphipods exposed to neutral water for 10 d nor readily gained by nontolerant amphipods exposed to sublethal low pH for a similar duration. This absence of physiological plasticity of individual H. azteca suggests that population differences in acid tolerance may result from processes of selective mortality with or without a genetic basis.

Black smoke air pollution and daily non-accidental mortality in Nis, Serbia

Open Medicine ◽  
2006 ◽  
Vol 1 (3) ◽  
pp. 292-297 ◽  
Author(s):  
Dragan Bogdanovic ◽  
Dragana Nikic ◽  
Zoran Milosevic ◽  
Aleksandra Stankovic
Keyword(s):  
Air Pollution ◽  
Poisson Regression ◽  
Time Trend ◽  
Linear Models ◽  
Short Term ◽  
Generalised Linear Models ◽  
Respiratory Mortality ◽  
Daily Number ◽  
Black Smoke ◽  
Cent Increase

AbstractThe short-term effects of ambient black smoke concentrations on total non-accidental, cardiovascular and respiratory mortalities in Nis, during the 2000-2003 period, were investigated.Daily measurements for black smoke (BS), as well as the daily number of deaths have been collected. Generalised linear models extending Poisson regression were applied. The e.ects of time trend, seasonal variations, days of the week, temperature, humidity and air pressure were adjusted.The per cent increase in the daily number of total deaths associated with a 10 μg/m3 increase in BS was 1.13% (0.08–2.20%). The e.ect size was slightly higher for cardiovascular mortality (1.25%, 95% CI: 0.53–1.97%). There was no signi.cant association between air pollution and respiratory mortality.These results indicate that current levels of ambient BS have signi.cant e.ects on total and cardiovascular mortalities in Nis.

Politics clouds Central Europe’s short-term outlook

2019 ◽  
Keyword(s):  
Family Policy ◽  
Population Decline ◽  
Short Term ◽  
Fiscal Stimulus ◽  
Content Type ◽  
Court Of Justice ◽  
European Court ◽  
The Supreme Court ◽  
Polish Government ◽  
The Eu

Significance Last year ended dramatically, with the European Court of Justice (ECJ) ordering the Polish government to suspend its reform of the Supreme Court, and the European Commission announcing that subsidies to major Czech agricultural conglomerate Agrofert, owned by Prime Minister Andrej Babis, would be suspended until allegations of conflict of interest were resolved. Tensions between the EU and Central Europe (CE) are expected to escalate ahead of the European Parliament (EP) elections due on May 23-26. Impacts The slowdown’s severity will vary among countries, with robust fundamentals, cheap borrowing and lower government debt all positives. A hit to private consumption from higher inflation could dampen the popularity ratings of leading parties absent additional fiscal stimulus. In Hungary, Fidesz may launch a ‘pro-family’ policy to win back popularity; reversing population decline was an election campaign pledge.

scholarly journals Pathogenicity of the hymenolepidid cestode Microsomacanthus hopkinsi in its intermediate host, Hyalella azteca: implications for transmission, host fitness, and host populations

2006 ◽  
Vol 84 (1) ◽  
pp. 32-41 ◽  
Author(s):  
T Kokkotis ◽  
J D McLaughlin
Keyword(s):  
Intermediate Host ◽  
Hyalella Azteca ◽  
Experimental Period ◽  
Host Population ◽  
Intermediate Hosts ◽  
Short Term ◽  
Host Fitness ◽  
Negative Effect ◽  
Larval Parasites

Infection by larval parasites can have severe consequences on intermediate hosts that affect transmission, fecundity and fitness of the host, and host population structure. This study examines the pathogenic effects of cysticercoid larvae of the hymenolepidid cestode Microsomacanthus hopkinsi (Schiller, 1951) on its amphipod intermediate host, Hyalella azteca Saussure, 1858. There was a significant, positive relationship between oncosphere consumption, cysticercoid burden, and age in short-term experiments in which groups of H. azteca were exposed individually to single egg packets of M. hopkinsi during instars 1, 2, 3, 4, 6, 8, and 9; however, there was no correlation between oncosphere consumption and the intensity of infection in the amphipod hosts within each instar. The mean number of moults over a 14 day experimental period was significantly less in infected amphipods than in their respective controls. In short-term experiments, the greatest mortality appeared to be limited to amphipods exposed during the earliest instars; little mortality was observed in amphipods exposed during instar 4 or later. Long-term experiments revealed a significant negative effect of infection on the overall life span of both male and female H. azteca exposed individually to a single egg packet during instar 4. Of 72 females infected during instar 4 and provided with mates during instar 6, only 1 and 4 produced broods in instars 8 and 9, respectively, compared with 58 and 57 of 72 control females. Broods produced by infected females were significantly smaller than those of control females. Infected individuals were less likely to mate successfully. The results are discussed in terms of their consequences for transmission, host fitness, and potential effects on host populations.

Effects of Predation Risk and Parasitism on the Feeding Ecology, Habitat Use, and Abondance of Lacustrine Threespine Stickleback (Gasterosteus aculeatus)

1988 ◽  
Vol 45 (3) ◽  
pp. 426-431 ◽  
Author(s):  
Per Johan Jakobsen ◽  
Geir Helge Johnsen ◽  
Petter Larsson
Keyword(s):  
Predation Risk ◽  
Salmo Salar ◽  
Littoral Zone ◽  
Gasterosteus Aculeatus ◽  
Population Decline ◽  
Length Distribution ◽  
Threespine Stickleback ◽  
Selective Predation ◽  
Restricted Area ◽  
High Predation

From 1980 to 1985, we investigated a lacustrine population of threespine stickleback (Gasterosteus aculeatus) with respect to densities, individual length, distribution, diet, frequency of parasitism by Schistocepbalus solidus, and selective predation by Atlantic salmon (Salmo salar). From these investigations we concluded the following. (1) When stickleback are forced into the littoral zone by salmon, competition in this restricted area increases, or alternatively, stickleback distribute themselves in an area with less profitable prey. This, combined with predation from salmon, results in a population decline and reduced growth of the stickleback. (2) At least in autumn, parasitized stickleback distribute themselves in areas with high predation risk from salmon; when exposed to salmon predation, parasitized stickleback are preyed upon at a higher rate than healthy ones. Hence, parasitized individuals have almost disappeared from the stickleback population in Lake Kvernavann, Norway.

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