Taking full advantage of modelling to better assess environmental risk due to xenobiotics—the all-in-one facility MOSAIC

Environmental Science and Pollution Research - In the European Union, more than 100,000 man-made chemical substances are awaiting an environmental risk assessment (ERA). Simultaneously, ERA of...     

Fixation du cadmium par une pseudomonadacee marine vivante ou tuee par l''ethanol ou le cyanure de potassium

The accumulation of cadmium chloride by a living, by an ethanol or potassium cyanide treated marine pseudomonad was studied. The metal uptake by the living strain was linear during the experiment and the amount of accumulated metal was high. The uptake by the treated strain was very fast during the first hours, but the amount of accumulated cadmium was lower.     

Forest dynamics modelling under natural fire cycles: A tool to define natural mosaic diversity for forest management

In natural boreal forests, disturbances such as fire and variation in surficial deposits create a mosaic of forest stands with different species composition and age. At the landscape level, this variety of stands can be considered as the natural mosaic diversity. In this paper, we describe a model that can be used to estimate the natural diversity level of landscapes. We sampled 624 stands for tree species composition and surficial deposits in eight stand-age classes corresponding to eight fire episodes in the region of Lake Duparquet, Abitibi, Québec at the southern fringe of the Boreal Forest. For six surficial deposit types, stand composition data were used to define equations for vegetation changes with time for a chronosequence of 230 years for four forest types. Using Van Wagner's (1978) model of age class distribution of stands, the proportion of each forest type for several lengths of fire cycle were defined. Finally, for real landscapes (ecological districts) of the ecological region of the Basses-Terres d'Amos, the proportion of forest types were weighted by the proportion of each surficial deposit type using ecological map information. Examples of the possible uses of the model for management purposes, such as biodiversity conservation and comparisons of different landscapes in terms of diversity and sensitivity to fire regime changes, are discussed.     

Monitoring the Conservation of Grassland Habitats, Prairie Ecozone, Canada

The Prairie Ecozone contains 5% of Canada's land area and represents 16% of the Great Plains of North America. Current estimates indicate that 25–30% of original Canadian grassland habitats remain, largely concentrated in southeastern Alberta and southwestern Saskatchewan with fragments distributed throughout southern Manitoba. The size, distribution and condition of native grasslands serve as valuable indicators of the ecological integrity and the sustainability of those landscape types. With so little native grasslands remaining, areas that conserve grasslands serve as core sites for indicators such as gaps in ecosystem and wildlife habitat protection, i.e. which ecosystems are well-represented, poorly represented or have no representation. Such gap analyses helps to determine where protection efforts need to be placed in the future. Overall, about 3.5% of the Prairie Ecozone of Canada is under some form of conservation area status. This paper reports, relative to the ecoregions and political jurisdictions of the Prairie Ecozone, on the amount and distribution of various types of conservation areas and native grasslands. Relationships between the occurrence of conservation areas and grasslands are presented. Implications for conservation area planning and management are discussed within regional, national and international contexts. The issue of which characteristics of conservation areas should be assessed and monitored to address conservation objectives for sustainability is also discussed.     

Population growth in snow geese: a modeling approach integrating demographic and survey information

There are few analytic tools available to formally integrate information coming from population surveys and demographic studies. The Kalman filter is a procedure that facilitates such integration. Based on a state-space model, we can obtain a likelihood function for the survey data using a Kalman filter, which we may then combine with a likelihood for the demographic data. In this paper, we used this combined approach to analyze the population dynamics of a hunted species, the Greater Snow Goose (Chen caerulescens atlantica), and to examine the extent to which it can improve previous demographic population models. The state equation of the state-space model was a matrix population model with fecundity and regression parameters relating adult survival and harvest rate estimated in a previous capture-recapture study. The observation equation combined the output from this model with estimates from an annual spring photographic survey of the population. The maximum likelihood estimates of the regression parameters from the combined analysis differed little from the values of the original capture-recapture analysis, though their precision improved. The model output was found to be insensitive to a wide range of coefficient of variation (CV) in fecundity parameters. We found a close match between the surveyed and smoothed population size estimates generated by the Kalman filter over an 18-year period, and the estimated CV of the survey (0.078-0.150) was quite compatible with its assumed value (approximately 0.10). When we used the updated parameter values to predict future population size, the model underestimated the surveyed population size by 18% over a three-year period. However, this could be explained by a concurrent change in the survey method. We conclude that the Kalman filter is a promising approach to forecast population change because it incorporates survey information in a formal way compared with ad hoc approaches that either neglect this information or require some parameter or model tuning.     

Mycobacteriosis-associated mortality in wild striped bass (Morone saxatilis) from Chesapeake Bay, U.S.A

The striped bass (Morone saxatilis) is an economically and ecologically important finfish species along the Atlantic seaboard of the United States. Recent stock assessments in Chesapeake Bay (U.S.A.) indicate that non-fishing mortality in striped bass has increased since 1999, concomitant with very high (>50%) prevalence of visceral and dermal disease caused by Mycobacterium spp. Current fishery assessment models do not differentiate between disease and other components of non-fishing mortality (e.g., senescence, predation); therefore, disease impact on the striped bass population has not been established. Specific measurement of mortality associated with mycobacteriosis in wild striped bass is complicated because the disease is chronic and mortality is cryptic. Epidemiological models have been developed to estimate disease-associated mortality from cross-sectional prevalence data and have recently been generalized to represent disease processes more realistically. Here, we used this generalized approach to demonstrate disease-associated mortality in striped bass from Chesapeake Bay. To our knowledge this is the first demonstration of cryptic mortality associated with a chronic infectious disease in a wild finfish. This finding has direct implications for management and stock assessment of striped bass, as it demonstrates population-level negative impacts of a chronic disease. Additionally, this research provides a framework by which disease-associated mortality may be specifically addressed within fisheries models for resource management.     

Correction to: Documenting lemming population change in the Arctic: Can we detect trends?

Ambio - In the original published article, some of the symbols in figure 1A were modified incorrectly during the typesetting and publication process. The correct version of the figure is provided...     

Repartition du cadmium dans les enveloppes cellulaires d'une bacterie marine

Investigations were made on a Gram negative marine bacterium to describe the involvement of the different envelopes in the distribution of cadmium on cells. Cadmium content decreased from the outer to the inner layers of the cell wall, suggesting a protective effect of the different envelopes.     

DIE‐OFF OF PATHOGENIC E. COLI O157:H7 IN SEWAGE CONTAMINATED WATERS1

E. coli O157:H7 is a pathogen that can be present in sewage contaminated waters. This organism poses a health risk for humans who come in contact with these waters via drinking, swimming, or shellfish consumption. A risk assessment model is needed to evaluate or quantify this risk. One possibility is the use of a computer model to simulate the fate and transport of E. coli O157:H7 downstream from a discharge point [e.g., a separate sanitary sewer overflow (SSO)]. However, this computer model would require input data regarding characteristics of this organism, which have not been previously available. One necessary input parameter is the rate at which die off of this organism occurs in a stream or river environment. Several studies were conducted to evaluate the die‐off rate of E. coli O157:H7 in an SSO impacted stream. Indicator bacteria (total coliforms, E. coli, and enterococci) were evaluated simultaneously. The results suggest that E. coli O157:H7 is not persistent — decay rates are high relative to the indicator bacteria. However, the decay plots suggest a biphasic response: initial decay is rapid, followed by an attenuated, slower decay. Hence traditional simulation methods using a single, first‐order decay rate may be inaccurate.