Dominique Vallod

Is eutrophication really a major impairment for small waterbody biodiversity

Eutrophication remains a major stress for freshwater biodiversity. Its deleterious consequences on biodiversity are well documented for large waterbodies. However, the impact of eutrophication may differ in smaller waterbodies, such as ponds and small lakes, which generally support naturally high levels of nutrients in lowlands. Furthermore, this response could depend on the scale considered, from local (individual waterbody, alpha diversity) to regional (the network of waterbodies, gamma diversity). It is also unclear whether the richness of threatened species responds in the same way as the richness of the whole assemblage. The present study investigates local- and regional-scale consequences of eutrophication on taxonomic richness (all taxa) and conservation value (threatened taxa) in temperate lowland small waterbodies. Five taxonomic groups were investigated: macrophytes, gastropods, water beetles, adult dragonflies and amphibians, in a set of natural waterbodies and a set of enriched waterbodies covering a large nutrient gradient from mesotrophic to hypertrophic conditions. Globally, our study did not reveal consistent, systematic responses to eutrophication. For macrophytes, the richness and conservation value suffered from eutrophication at both local and regional scales. In contrast, for amphibians and gastropods, eutrophication did not impair biodiversity at the local nor the regional scale. Dragonflies and water beetles showed intermediate situations, with an impairment by eutrophication varying according to the type of waterbodies considered. At the regional scale, each trophic status, even the nutrient richest, brought an original contribution to biodiversity. Synthesis and applications. The management of eutrophication for small lowland waterbodies has to be considered differently than for lakes. For an individual waterbody (the local scale), nutrient enrichment is not necessarily a major impairment and its impact depends on the taxonomic group considered. Conversely, at the landscape scale, eutrophication is a major pressure on small waterbody biodiversity, especially because nutrient-rich small waterbodies are dominant in the landscape. Therefore, conservation efforts should integrate the notion of pond regional networks or ‘pondscapes’, where the regional biodiversity is supported by a mosaic of trophic conditions, and promote the presence of less rich waterbodies.

Eutrophication and drought disturbance shape functional diversity and life-history traits of aquatic plants in shallow lakes

Theories that link plant strategies and abiotic filters discriminate between three strategies: competitive, ruderal or stress-tolerant species, and suggest that functional diversity is higher at intermediate values along the gradients of productivity and disturbance. The mechanism by which abiotic filters screen plant traits in aquatic plant communities has been poorly tested and has led to contrasting results. The present study aimed to test whether functional diversity and abundance of life-history traits corresponding to morphology, fecundity and longevity of aquatic plants were linked to disturbance and productivity. Fifty-nine shallow lakes that were arranged along a gradient of productivity (estimated through total phosphorus concentration) and drought-disturbance frequency were sampled for aquatic plants. Species traits were documented and functional diversity was calculated (richness, dispersion and evenness) for each lake. Increasing total phosphorus concentration was associated with decreased functional richness and dispersion but not functional evenness. Functional diversity did not differ according to disturbance frequency, regardless of the index that was measured. High productivity favoured floating species with storage organs and vegetative reproduction, especially at low disturbance frequency. For all disturbance frequencies, low productivity favoured small species without storage organs and sexual reproduction. The present study partly supports the theoretical model. At high productivity levels, because phytoplankton is a better competitor for light than aquatic plants, plant traits are screened stringently, and species with traits that allow them to reach the photic zone are selected.

Analysis of the off-flavor risk in carp production in ponds in Dombes and Forez (France)

Off-flavors represent one of the most economically significant problems encountered in continental aquaculture. The appearance of a repulsive odor, or taste, in fish may cause a major reduction in the consumption of the products. Carp farmers and processors are aware of this problem and wish to keep it under control. A first cross-disciplinary study was carried out in France in 2002–2003, following three approaches: (1) estimation of water quality and composition of the phytoplankton community in carp ponds, (2) sensory analysis of carp, (3) quantification of odoriferous volatile compounds in carp. The results show that strongly off-flavor carp were found in ponds colonized by cyanobacteria, mainly Anabaena spp. in summer. The quantification of odorous compounds was not effective in the fish samples, but sensory evaluation confirmed the existence of off-flavors in the carp tested. The most commonly used descriptors associated with geosmin, referred to a waste water, earthy/musty odor and taste, were those identified by the panel of testers. Such results led us towards a new strategy of carp fishing, stocking and processing during the summer.

Varied impact of land use on water and sediment parameters in fish ponds of the Dombes agro-ecosystem, France

Abstract Agricultural land use in the area of water bodies is generally considered to increase the nutrient status of the water body water and sediments, but is this also the case for already nutrient-rich fish ponds? We studied 83 fish ponds in the Dombes region, France, where 1100 ponds are located in a heterogeneous agricultural landscape. Different water and sediment parameters were analysed for ponds and in ditches after rainfall events. Land use was studied in the primary catchment of ponds and in a 100-m zone around ponds. Soil parameters of different land-use types were analysed and farmers interviewed about agricultural practices. Increasing cropping area in the catchment of the ponds is significantly correlated to higher PO4 3- concentration of pond water and to a lower degree, also to NO3 −, but only in certain years with higher rainfall and with a more uneven distribution in spring. Sediment parameters were not significantly influenced. High NO3- concentration in the water of a ditch during significant rainfall events was found for a cropland dominated catchment. Citation Wezel, A., Arthaud, F., Dufloux, C., Renoud, F., Vallod, D., Robin, J., and Sarrazin, B., 2013. Varied impact of land use on water and sediment parameters in fish ponds of the Dombes agro-ecosystem, France. Hydrological Sciences Journal, 58 (4), 854–871.

Using biodiversity to valorise local food products: the case of fish ponds in a cultural landscape, their biodiversity, and carp production

Today, we need to produce sufficient food and simultaneously conserve biodiversity. But, could biodiversity associated with certain food production practices also be used in marketing products? We analyse this possibility for creating a food quality label for carp raised in the Dombes territory, a cultural landscape of fish ponds in France. The biodiversity of 99 fish ponds was studied in the Dombes territory by analysing aquatic vegetation, dragonflies, amphibians, macroinvertebrates, habitats around ponds, and water quality. In addition, a survey with 200 questionnaires and interviews was conducted with consumers to investigate fish and carp consumption and knowledge about quality labels and biodiversity. Findings reveal that fish production practices conserve remarkable species diversity, particularly for aquatic vegetation, dragonflies and amphibians, and habitats around the ponds. This relatively high level of biodiversity is found in spite of having very nutrient-rich fish pond systems, systems for which normally a low level of biodiversity is expected. Nevertheless, currently this biodiversity cannot be valorised for setting up a quality label for locally produced carp. Firstly, few consumers have adequate knowledge about carp and are interested in eating it. Secondly, most of them have less knowledge about the quality label which wanted to be established for carp from the Dombes. Thirdly, only less than one-third of the consumer is familiar with the term “biodiversity”. Fourthly, the stakeholder network of the supply chain is presently not able to communicate the message of biodiversity as they themselves lack a sufficient knowledge about biodiversity of their systems.

Influence des pratiques agropiscicoles sur la biodiversité des étangs de la Dombes (Ain, France) en vue d'une valorisation de produits du terroir

Dans le cadre d’un programme de recherche conduit en France pour produire des references alimentant le debat agriculture et biodiversite, une equipe de chercheurs de l’ISARA-Lyon mene un travail sur les relations entre pratiques agricoles et biodiversite dans une region d’etangs a vocation piscicole. Il s’agit de la Dombes, vaste region presentant une surface de pres de 11 000 ha en eau. Ces etangs sont inscrits dans un paysage agricole constitue de cultures intensives, de prairies et de forets. Ils representent une richesse ecologique et patrimoniale certaines et la question de l’influence des pratiques agricoles sur les elements constitutifs de la biodiversite est au cœur de ce projet. Une deuxieme question porte sur l’insertion socio-economique du systeme de production et l’utilisation potentielle de la biodiversite pour valoriser l’image de la production piscicole issue de ces etangs. Les premiers resultats mettent en avant la diversite specifique importante observee (macrophytes, odonates et amphibiens) et montrent que les pratiques agricoles traditionnelles en place entretiennent la richesse biologique de ces milieux, crees par l’homme.