L'utilisation de souches de micro-organismes de collection pour l'etude de la biodegradabilite des pesticides

Use of Microbial strains from collection in the study of pesticide biodegradability. 5 different herbicides and 1 metabolite of herbicide were subjected to biodegradation by different microbial strains and simultaneously by soil suspensions.To take account of possible co-metabolisme a supplementary source of carbon was added in the culture media. Results were discussed.     

Sustainable livelihoods and people’s vulnerability in the face of coastal hazards

The present study investigates into the link between people’s vulnerability in the face of coastal hazards and sustainable livelihoods. It focuses on the town of Borongan in the Philippines and draws on questionnaire-based surveys and focus group discussions. This research shows that local fishermen are often compelled to go out fishing despite pending typhoon or storm surge to sustain the daily needs of their family. Its also demonstrates that the capacity of these people to protect themselves from the threat is constrained by poor and fragile livelihoods. In the event of a crisis, the study argues that people resort to a range of adjustments on their daily life which is rooted in the strength and diversity of their livelihoods. To reduce people’s vulnerability and enhance capacities to face coastal hazards, the study fosters Community-Based Disaster Risk Reduction with special emphasis to sustainable livelihoods.     

Effects of a major municipal effluent on the St. Lawrence River: A case study

The St. Lawrence River (SLR) is the second largest waterway in North America. The discharge of the City of Montreal wastewater treatment plant (WWTP) represents the largest volume of treated wastewaters being released into the river. It also ranks as the largest sewage treatment plant of its kind in North America. Over the last decade, intensive multidisciplinary research has focused on assessing the impacts of Montreal wastewater effluents on the SLR. We describe the major findings of these investigations, including the determination of the fate of contaminants, bioaccumulation in fish and invertebrates, ecotoxicological measurements of aquatic animal health, evaluation of endocrine disruption, parasitism in fish, and combined effects of multiple stressors on the SLR. Impacts of the effluents from the WWTP on aquatic organisms from the SLR are both toxicological and ecological, demonstrating the need for an integrated view of the impacts of municipal effluents on aquatic ecosystems.     

Biological denitrification in a closed seawater system

Build-up of high nitrate concentrations in closed seawater systems where primary productivity is undesirable and water changes are impractical presents unique problems. Nitrate concentration in Ocean Tank at the New Jersey State Aquarium reached 9500 microM after 6 years of operation. A biological denitrification system was installed in 1998 and nitrate concentration in the aquarium decreased to 7000 microM within the first 100 days of operation. The system offers additional benefits by increasing the pH and alkalinity of seawater and providing a reducing environment to balance the oxidizing disinfection environment in the aquarium. The initial performance of the denitrification system was monitored and two semi-empirical models were developed: one based on the actual methanol additions, and another based on the daily amounts of nitrogen gas removed. The first model predicts a net nitrate decrease of 39 microM/day in the aquarium. The second model predicts a net decrease of 25 microM/day, in good agreement with the empirical value of 23 microM/day. This indicates that nitrogen gas removal is the controlling factor during denitrification in this facility, and the second model can be used to predict and optimize the operation of the system.     

Fish production and the marine ecosystems of the Scotian Shelf,eastern Canada

Fishery production and food webs have been studied on the Scotian Shelf and upper continental slope along a transect running 270 km SE of Halifax, Canada. The area (TCNAF Division 4W) supports a fishery of roughly 0.15x10⁶ metric tons. Overall primary production of the shelf waters is 102 g C m^-2 year^-1 and of the slope wacers about 128 g C m^-2 year^-1. Demersal fish production (average 4.1 kcal m^-2 year^-1) is highest over the shelf and declines in an offshore direction, while pelagic fish production (average 16 kcal m^-2 year^-1) is highest over the slope and declines in an inshore direction. Hypothetical food webs of these two intergrading ecosystems have been constructed, based on data for primary production, fish catches, and the biomasses of zooplankton and macrobenthos. These lead us to suggest that there are basic differences in food chains and efficiencies between the two ecosystems that account for their differences in production. Although primary production is 17% higher on an average on the Nova Scotian transect than in the North Sea, the apparent zooplankton and macrobenthos production is 31% lower and macrobenthos production may also be lower. Overall fish catch from the Scotian Shelf and slope is about 47% lower per unit area than the catch in the North Sea, despite the fact that the demersal catches are identical. This is accounted for by a much lower overall pelagic catch from the Nova Scotian area, centered in a region that is small compared to the total area. Fish production in different regions cannot be predicted merely on the basis of differences in level of primary production, but must take into account differences in the structure of the ecosystems.     

A new test of random walks in heterogeneous environments

Environmental heterogeneities can change animal movement in two different manners. First, they can modify movement characteristics (move lengths or turning angles), in which case the movement remains of the diffusive kind. Second, they can bias displacement towards a particular direction in which case it becomes non-diffusive. We propose in this paper a simple method that only requires computing the mean length of a sample of trajectories in some bounded area to distinguish between these two kinds of movement. We show through simulations that the method allows to detect the presence of heterogeneities that orient animal movement. We apply it to experimental trajectories of Messor sancta ants engaged in corpse aggregation to show that their displacement is oriented at the contact of the formed corpse piles and that their trajectories become non-diffusive.     

Immune response of earthworms (Lumbricus terrestris, Eisenia andrei and Aporrectodea tuberculata) following in situ soil exposure to atmospheric deposition from a cement factory

In order to reduce their energy costs, many cement plants use fuel product substitutes (old tyres and used oil). The combustion of these products generates a metal increase (e.g. Cu, Cd, Pb and Zn) in the atmospheric emissions. After their release, these elements are deposited into the environment and could eventually accumulate up to concentrations of concern. At the Saint-Laurent cement factory (Joliette, QC, Canada), maximum deposition of these elements occurs in the direction of prevailing winds (North-East). We evaluated the potential impact of these depositions upon the immune system of three earthworm species (Lumbricus terrestris, Eisenia andrei and Aporrectodea tuberculata) exposed in a natural environment. The exposure sites were 0.5, 1.0, and 2.0 km downwind from the cement factory, along with an upwind reference site. The immune parameters studied were the cell viability and phagocytic potential of the immune cells (coelomocytes). For both L. terrestris and E. andrei, after 7 d exposure, none of the measured parameters showed significant differences among the sites. On the other hand, for the indigenous worm A. tuberculata, in the most exposed zone (at 0.5 km), we observed an increase in cell viability and phagocytic potential. This increase could possibly be attributed to physicochemical effects such as the alkaline pH of the soil, or alternatively, it could result from beneficial effects induced by an increased calcium supply.     

Distribution of carbon 14 in the terrestrial environment close to French nuclear power plants

For 10 years, (14)C measurements have been performed around French nuclear power plant sites, both in zones influenced and zones not influenced by gaseous releases. Examining the results from these measurements in the terrestrial environment shows that the discharges have a very slight impact on the radiocarbon level (with a relative increase in the specific activity of the order of 3 Bqkg(-1)C in the influenced areas). In correlation, there is a near-negligible increase in dose, on average less than 0.1 microSvyr(-1), with reference to a dose from background radiation, which is of the order of 10 microSvyr(-1). The deltaC13 values are very similar between the influenced zone and the non-influenced zone, with a mean of -27 per thousand. The mean DeltaC14 varies from 101 per thousand in the non-influenced zone to 123 per thousand in the influenced zone. Moreover, a general reduction in (14)C concentration was found, with a time constant of the order of 95 years. The current level of (14)C specific activity in terrestrial environment is estimated to be 242+/-6 Bqkg(-1)C.