Acute toxicity of two insecticides to tubificid worms, Tubifex tubifex and Limnodrilus hoffmeisteri

Acute toxicity and presumable harmless concentration of two commercial insecticides, Furadan 3G and Malataf 50E were reported for tubificid worms, Tubifex tubifex and Limnodrilus hoffmeisteri. L. hoffmeisteri were found more susceptible to both the insecticides; the Furadan was found to be more toxic than Malataf to tubificid worms. Analysis of variants showed a significant difference between safe concentrations of the same insecticide to different species.     

Acute toxicity of herbicides to freshwater fish and midge larvae, Chironomus tentans

Acute toxicity of three herbicides, tafazine, bladex, and aresin, were studied for three species of freshwater teleost, namely, Labeo rohita, Mystus vittatus, and Cirrhinus mrigala, and benthic macroinvertebrate, midge larvae, Chironomus tentans, L. rohita and C. mrigala were found susceptible to all three herbicides as compared to M. vittatus and C. tentans, which were more susceptible to the tafazine toxicity. The toxicity of the three herbicides was in order of tafazine>bladex>aresin. Investigation leads to the conclusion that some herbicides, though quickly degradable, form hazards for aquatic life even at very low levels. Their application must be monitored to prevent aquatic pollution.     

Socio-environmental implications of process-based restoration strategies in large rivers: should we remove novel ecosystems along the Rhône (France)?

River restoration efforts require interdisciplinary approaches involving fluvial geomorphology, hydraulic engineering, ecology, sedimentology, chemistry, social geography, and sociology. We investigated the functioning of artificial structures called “Casiers Girardon” (groyne fields) in the Rhône River. We assessed potential benefits and risks linked to removing the Rhône groyne fields in a restoration context, with particular focus on the potential for increased bank erosion. Hydraulic, morphological, chemical, ecological, and social issues resulting from dismantlement were studied for terrestrialized and aquatic Casiers Girardon. Only 10% of Casiers Girardon have maintained their aquatic features, whereas most of the Casiers are terrestrialized. Our results help to confirm the effectiveness of restoration actions; however, they also indicate uncertainties and additional knowledge needs, especially in regard to potential incompatibilities between Casier restoration and conservation. Then, an interdisciplinary conceptual model was developed to identify interventions to be considered in Casiers Girardon, according to their terrestrialization rate and physiochemical characteristics (connectivity, amount of gravel vs. fine sediment, contamination level). This model synthetizes scientific results and expert judgment and provides management recommendations based on ecological and sociological expectations about the restoration of Casiers Girardon. The model highlights high heterogeneity in functioning and ecological potential between terrestrialized and aquatic Casiers. Dismantling of terrestrialized Casiers has strong potential to provide multiple benefits, whereas aquatic Casiers could be maintained as valuable backwaters. The managing guidelines for the Casiers Girardon of the Rhône River should be adapted according to local conditions, as well as expected benefits and needs, and conducted in co-ordination with all actors involved in and affected by the restoration.