Impact of toxicants on stream fish biological traits

Pour garantir une qualité d'eau appropriée à la population humaine et aux milieux naturels, l'Union Européenne a sollicité tous les états membres afin d'obtenir d'ici 2015 une qualité écologique minimale satisfaisante pour toutes les eaux de surface, définie par la nouvelle Directive Cadre sur l'Eau. Des outils basés sur des paramètres biologiques sont donc nécessaires dans ce contexte, de façon à aider les gestionnaires de l'eau à évaluer, et protéger cette importante ressource. L'objectif principal de cette thèse a été l'évaluation du statut de populations de poissons natives de quelques rivières du Sud-ouest de la France, impactés par les polluants, en utilisant des traits biologiques des poissons. La rivière Lot a été fortement touchée par une pollution historique par les métaux lourds, conséquence d'exploitations minières dans plusieurs sites du bassin versant. Les concentrations de cuivre, zinc, cadmium et plomb on été quantifiées dans le muscle et le foie de 3 espèces de poissons, ainsi que dans l'eau, les sédiments et les bryophytes, en 1987 et 2007. La situation du Lot s'est améliorée au cours des 2 dernières décennies, bien qu'il reste encore une marge de progression selon les critères établis pour la protection de la vie aquatique. Les concentrations moyennes de cadmium dans le muscle de poisson en 2007 dépassaient les niveaux maximaux, établis par le Commission Européen pour une consommation humaine sans risque. Plus de la moitié du bassin versant de l'Adour-Garonne est couvert de terres agricoles. Dans ce contexte, l'impact de la pollution agrochimique sur des populations sauvages de goujons et chevaines a été évalué. Après élimination des effets confondants (variation génétique, distance géographique, paramètres de l'eau), 4 des 17 traits morphologiques étudiés sur le goujon étaient significativement liés à la toxicité des pesticides. Des différences morphologiques sont susceptibles d'avoir lieu précocement au cours du développement, indiquant que les poissons on été en effet exposés à des facteurs de stress, comme les molécules toxiques, pendant leur croissance. Avec une augmentation des niveaux de pesticides, la condition générale des chevaines a diminué alors que la taille de leurs gonades a augmenté. Des observations histopathologiques du foie ont révélé que les chevaines des stations plus polluées présentent des réserves lipidiques réduites et des signaux de stress immunologique accrus. Afin de vérifier si les pesticides trouvés dans le bassin versant de l'Adour-Garonne ont des effets sub-létaux sur les poissons, des juvéniles de truites arc-en-ciel ont été exposés en laboratoire à de faibles teneurs d'un mélange d'herbicides (atrazine, linuron et metolachlore). Pendant l'exposition de 5 jours, le comportement des truites a été surveillé. L'augmentation de l'agressivité des poissons corrélée à un accroissement des mouvements n'a pas été observée pour les poissons exposés. Ces derniers ont tendance à occuper des zones plus profondes des aquariums. En conclusion, les truitelles exposées ont présenté une hypoactivité générale, ce qui est un handicap à long terme. Globalement, les résultats de recherches ici menées démontrent que les poissons sont appropriés en tant que bioindicateurs environnementaux, et comme organismes modèles pour tester les effets de faibles doses de mélanges de polluants, dans la nature et au laboratoire. En testant l'existence d'une relation significative entre contamination et réponse biologique, il est important de prendre en compte les facteurs confondants, tant environnementaux qu'innés aux organismes. Le lien entre la présence/magnitude de la contamination et l'effet sur l'écosystème peut donc être établi, et utilisé pour promouvoir des actions préventives et protectrices à des fins de conservation des espèces et de protection d'une ressource essentielle comme l'eau.In order to guarantee a basis for adequate water quality for humans and the natural environment, the European Union has requested that all member states attain at least good ecological and chemical water quality in all surface waters by 2015, in what is know as the Water Framework Directive. Biologically-based tools are thus needed to adequately assess the ecological status of water bodies. Such tools will aid water managers in assessing, reporting, and eventually protecting such an important resource. The main objective of this thesis work was to evaluate the status of native fish populations in toxicant-impacted rivers in South-West France using a number of fish biological traits. The historically polluted environment of the River Lot has been strongly impacted by heavy metals during and after mining activities took place in certain parts of the river basin. The concentration of copper, zinc, cadmium and lead were quantified in muscle and liver of 3 fish species, as well as in environmental samples (water, sediment, moss) in 1987 and 2007. The situation of the River Lot has improved over the last 2 decades although there is still margin for amelioration according to criterion for the protection of freshwater aquatic life. The average concentrations of cadmium in fish muscle in 2007 were above the maximum safe for human consumption defined by the European Commission. More than half of the Adour-Garonne river catchment area is covered by agricultural land. In this context, the impact of agrochemical pollution on wild gudgeon and chub populations was assessed. A set of biological traits were measured for each species and the link to pesticide toxicity levels tested. Upon removal of confounding effects (genetic variation, geographical distance, water parameters), 4 of the 17 morphological traits studied on the gudgeon were significantly linked to pesticide toxicity. Such differences in body shape are susceptible to take place during early developmental stages, thus indicating that fish were indeed exposed to change-inducing stressors such as toxicants throughout their development. Chub general condition decreased while gonad size increased with increasing toxicity. Histopathological observations of liver tissue indicate that chubs from more polluted sites have reduced lipid storage and increased immunological stress. In order to verify whether pesticides found in the Adour-Garonne river basin cause sub-lethal effects on fish, farm-raised juvenile rainbow trout were exposed in laboratory conditions to low levels of a mixture of herbicides (atrazine, linuron and metolachlor). During the 5-day exposure, trout behaviour was monitored. The increase in number of aggressions of control fish was reflected in an increase of movements per fish, whilst this relationship was not seen in exposed fish. In average, exposed fish tended to occupy lower compartments than control fish. Juvenile trout exposed to a mixture of pesticides thus presented a general hypoactivity, possibly a handicap to survival in the long term. The overall results of these investigations indicate that fish are relevant as environmental bioindicators and as model test organisms to evaluate the effect of sub-lethal levels of contaminant mixtures, in the field and in laboratory conditions. When testing whether there is a significant relationship between contamination and a biological response, it is important to take into account multiple confounding factors, both environmental as well as innate to the organism. In this way, the link between presence/magnitude of contamination and effect on the ecosystem can be clearly established, and used to promote preventive and protective measures for species conservation and the protection of a basic resource - water

The Ecotoxicity of Pyrimethanil for Aquatic Biota

Via the application of agrochemicals, farmers currently guarantee high productivity of fruit and vegetable crops. However, pest reduction using excessive amounts of such chemicals has a negative effect on aquatic organisms. The spray-drift, leaching, run-off or accidental spills occurring during or after application has become a serious and increasing problem for aquatic ecosystems. Pyrimethanil (PYR) is one of the most used fungicides. Such increase has heightened the interest in studying the potential risk and influence of PYR on the environment. In this chapter information on the PYR environmental risks for aquatic organisms was divided into three different approaches: (i) assessment of toxic effects of the pure active ingredient or the commercial formulation on primary producers, (ii) assessment of toxic effects of the pure active ingredient and PYR formulation on aquatic animals, and (iii) estimation of the role of PYR as an environmental disturber by triggering avoidance response. The available data provide evidences that PYR is potentially toxic for many aquatic species, affecting survival, reproduction, feeding, growth, and that it can disturb the environmental quality with no direct effect at the individual level by inducing organisms to migrate to less impacted areas

Copper-driven avoidance and mortality in temperate and tropical tadpoles

Amphibians have experienced an accentuated population decline in the whole world due to many factors, one of them being anthropogenic contamination. The present study aimed to assess the potential effect of copper, as a worldwide and reference contaminant, on the immediate decline of exposed population due to avoidance and mortality responses in tadpoles of three species of amphibians across climatic zones: a South American species, Leptodactylus latrans, a North American species, Lithobates catesbeianus, and a European species, Pelophylax perezi. A non-forced exposure system with a copper gradient along seven compartments through which organisms could freely move was used to assess the ability of tadpoles to detect and avoid copper contamination. All species were able to avoid copper at a concentration as low as 100 ␮g L −1 . At the lowest (sublethal) concentrations (up to 200 ␮g L −1) avoidance played an exclu-sive role for the population decline, whereas at the highest concentrations (>450 ␮g L −1) mortality was the response determining population decline. The median concentrations causing exposed population immediate decline were 93, 106 and 180 ␮g L −1 for Le. latrans, Li. catesbeianus and P. perezi, respectively. Contaminants might, therefore, act as environmental disruptors both by generating low-quality habitats and by triggering avoidance of tadpoles, which could be an important response contributing to disper-sion patterns, susceptibility to future stressors and decline of amphibian populations (together with mortality)