Céline Bertrand

No association between the use of Bti for mosquito control and the dynamics of non-target aquatic invertebrates in French coastal and continental wetlands

The environmental safety of Bacillus thuringiensis subsp. israelensis (Bti) is still controversial, mainly because most of the previous field studies on its undesired effects were spatially limited and did not address the relationship between community similarity and application time and frequency. No general statement can therefore be drawn on the usage conditions of Bti that insure protection of non-target organisms. The present study was conducted in eight sites distributed over the main geographical sectors where mosquito control is implemented in mainland France and Corsica. Changes in non-target aquatic invertebrates were followed at elapsed time after repeated applications of two Bti formulations (VectoBac® WDG or 12AS) up to four consecutive years. We examined the influence of both larvicide treatments and environmental variables on community dynamics and dissimilarity between treated and control areas. As it can be argued that chironomids are the most vulnerable group of non-target invertebrates, we scrutinised potential Bti-related effects on the dynamics of their community. The use of VectoBac® WDG and 12AS in coastal and continental wetlands had no immediate or long-term detectable effect on the taxonomic structure and taxa abundance of non-target aquatic invertebrate communities, including chironomids. This applied to the main habitats where mosquito larvae occur, regardless of their geographic location. Flooding, whose frequency and duration depend on local meteorological and hydrological conditions, was identified as the main environmental driver of invertebrate community dynamics. Our findings add support to the environmental safety of currently available Bti formulations when following recommended application rates and best mosquito control practices.

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.

Preface: Vulnerability and resilience of freshwater and marine ecosystems

The 3rd International Limnology and Oceanography Conference (JILO) was held at the Aix Marseille University, Marseille, France, from 21–23 May 2014 and it was co-organised by the French Limnological Association (AFL) and the Union of French Oceanographers. The conference was attended by scholars as well as scientists, students, stakeholders and manufacturers. 210 Participants came from 13 countries, France, Britain, Poland, Spain, Switzerland, Algeria, Burkina Faso, Cameroun, Cote d’Ivoire, Morocco, South Africa, Tunisia, Brazil, and presented 39 oral and 61 poster communications. The main ecological theme of this conference was the Vulnerability and resilience of freshwater and marine ecosystems. Vulnerability is a theoretical concept that is being considered more and more frequently by both researchers and stakeholders from a wide variety of disciplines in the global change context. Vulnerability to climate change can be defined as ‘‘the degree to which a system is susceptible to, or unable to cope with, adverse effects of climate change, including variability and extremes. It’s a function of the character, magnitude, and rate of climate variation to which a system is exposed, its sensitivity, and its adaptive capacity’’ (IPCC, 2007). The concept of resilience is part of vulnerability and it can be compared with the ability to adapt to changes by exploiting instability phenomena, which implies the ability to cope and adapt without necessarily returning to its exact prior state. Studying the vulnerability and resilience of freshwater, brackish water and marine ecosystems implies to be simultaneously concerned with the following two issues: the limitation of water resources and the loss of the ecological function associated with these ecosystems such as changes in biodiversity. This conference was proposed to explore knowledge relating biodiversity to functioning of freshwater, brackish water and marine ecosystems in order to understand how this scientific approach of vulnerability and resilience can benefit planning and public decision-making. Guest editors: Céline Bertrand, Evelyne Franquet, Ivan Dekeyser & Christophe Piscart / Vulnerability and Resilience of Freshwater & Marine Ecosystems