Comme ils conduisent à des modifications de sensibilité toxicologique et de traits d'histoire de vie au sein des populations naturelles exposées, les phénomènes d'adaptation à la contamination questionnent la pertinence de l'évaluation du risque environnemental lié au rejet de contaminants chimiques et sont devenus un champ de recherche important à développer en écotoxicologie. Centrés sur l'étude des capacités d'adaptation de l'amphipode d'eau douce Gammarus fossarum, les travaux présentés ici ont eu pour objectif d'avancer dans la compréhension des effets d'une exposition à long terme au cadmium à l'échelle populationnelle et en milieu naturel. En recourant à des méthodologies de biomonitoring par encagement, de culture et d'exposition au laboratoire et de suivi démographique in situ, une démarche couplant études a priori et rétrospectives sur populations naturelles, a permis d'identifier un phénomène d'augmentation de la tolérance et de modification de traits d'histoire de vie chez une population exposée historiquement au cadmium. Des approches de génétique quantitative conduites sur trois populations ont dans un deuxième temps mis en évidence (1) une faible héritabilité de la sensibilité au cadmium au sein de populations naïves ; et (2) un rôle majeur des effets parentaux induits par l'exposition comme mécanisme populationnel soutenant l'évolution de la tolérance chez cette espèce. Enfin, la caractérisation de la variabilité de la sensibilité au cadmium au sein du genre Gammarus (dix-sept populations) et la mise en regard de la divergence de la population tolérante vis-à-vis de cette variabilité, ont permis de discuter des implications de ces processus évolutifs induits par des expositions environnementales pour l'évaluation du risque lié aux substances chimiques. Ainsi, il apparaît nécessaire de prendre en compte les réponses adaptatives induites par la contamination des milieux comme source de variabilité et d'incertitude afin de proposer une évaluation du risque pertinente intégrant pleinement l'ensemble des impacts des contaminations environnementales sur les populations naturelles / Because they lead to changes in toxicological sensitivities and life history traits within field populations, evolutionary processes supporting adaptation to contamination challenge the relevance of environmental risk assessment of chemical contaminants. Hence their study becomes an important developing field of research in ecotoxicology. Focusing on the study of adaptive capacity of the freshwater amphipod Gammarus fossarum, this work aimed to gain insight into the effects of long term exposure to cadmium at the population scale in the field. By means of biomonitoring methodologies (caging), population demographic sampling, culture and exposure in the laboratory we identified a phenomenon of increased tolerance and modification of life history traits in a natural population historically exposed to cadmium. Quantitative genetics experiments conducted on three populations secondly demonstrated (1) a low heritability of sensitivity to cadmium in naïve populations ; and (2) a major role of parental effects induced by exposure as populational mechanism supporting the development of tolerance in this species. Finally, the characterization of the variability of cadmium sensitivity in the genus Gammarus (seventeen populations), and the analysis of the divergence of the tolerant population in comparison to this variability led us to discuss about the implications of these evolutionary processes induced by environmental exposure for risk assessment of chemicals. Thus, from these results it appears necessary to take into account adaptive responses induced by environmental contamination as a source of variability and uncertainty in order to provide a relevant risk assessment fully integrating all the impacts of environmental contamination on natural populations

La toxicité potentielle des nanomatériaux présente un intérêt sociétal et scientifique élevé en raison de la promesse d'innovations pour de nombreuses applications techniques. Cependant, elle n’est pas forcément liée à la taille réelle, à la masse, à la surface des nanoparticules (NP) ou à leurs agglomérats. La toxicité des NPs pourrait être fortement influencée par d'autres propriétés inhérentes et encore incomprises telles que le relargage d’ions, de la particule elle-même, sa surface, ou des molécules adhérentes à la surface, qui interfèreraient avec l'absorption cellulaires des NPs. Le projet « NANOGAM» étroitement lié au projet « FNR CORE2012 NANION », vise à définir certains processus et facteurs impliqués dans l'absorption des NPs et leur toxicité. Une telle compréhension est une condition préalable au développement des nanomatériaux, fondement de la philosophie « safer-by-design ». Les objectifs de ce projet de thèse sont multiples. En tenant compte des caractéristiques des principaux paramètres physico-chimiques tels que la taille et l’aspect de la surface, l’étude a porté sur l'absorption de NPs d'argent et d'or, et leurs effets biologiques via une approche multi-biomarqueurs (mortalité, effets comportementaux, effets physiologiques, effets transcriptomiques, etc.) sur une espèce sensible, Gammarus fossarum (Crustacea Amphipoda). Le but de cette investigation est de comprendre si la toxicité des nanomatériaux est inhérente aux propriétés intrinsèques des NPs ou plutôt aux ions relargués, ce qui contribuera à la prédiction de la toxicité des NPs en rapport avec leurs propriétés physico-chimiques et ce afin de limiter le nombre d’essais répétitifs sur de nouveaux nanomatériaux. G. fossarum ont été exposés à de faibles concentrations d'AgNPs et AuNPs pendant 72h à jeun et 15 jours nourris. Les résultats obtenus ont montré que (i) la nature de l’enrobage de surface est le principal facteur responsable de l'absorption d'AgNPs et d'AuNPs par G. fossarum ; (ii) les ions libérés et les NPs elles-mêmes jouent un rôle dans la toxicité des AgNPs et AuNPs étudiées ; (iii) la composition chimique des NPs a conduit à des effets différents aux niveaux sub-individuels (transcriptomique), ainsi qu’à une distribution différente dans les tissues selon la nature métallique de la NP. Les AgNPs ont été localisées dans les branchies de G. fossarum tandis que les AuNPs ont été observées dans les caeca intestinaux. Cette étude a également révélé que Gammarus sp. est un excellent modèle pour l'étude de la toxicité et des effets des AgNPs et des AuNPs / The potential toxicity of nanomaterials is of high societal and scientific interest due to the promise of ground-breaking innovations for many technical applications. However, toxicity can often not be related to the actual size, mass or surface area of the single nanoparticles (NPs) or the NP agglomerates. Therefore, it can be proposed that the toxicity is greatly influenced by other inherent and non-understood properties of the particles to which ions dissolving from the particle, surface or molecules adhering to the surface interfering with the uptake of NPs into cells, may have important contributions. The PhD project “NANOGAM”, closely linked up to CORE2012 NANION project that aims to obtain knowledge to understand some of the processes and factors involved in NP uptake and toxicity as such understanding is a prerequisite for the development of nanomaterials following the safer-by-design philosophy. This PhD project aims to investigate, based on known characteristics of the key physico-chemical parameters; as size and surface functionalities, of a well-chosen list of silver and gold NPs, the uptake, and dependent biological effects of different complexity (mortality, behavioural effects, physiological effects, transcriptomic effects, etc.), on a sensitive species; Gammarus fossarum (Crustacea Amphipoda), in order to understand to which extent toxicity of nanomaterials is due to intrinsic material properties or ion leaching. Such understanding will contribute to the prediction of toxicity based on material properties rather than repetitive testing of an indefinite number of new nanomaterials. G. fossarum were exposed at low concentrations of AgNPs and AuNPs for 72h or 15 days in presence or absence of food. The obtained results showed that (i) surface coating is the main factor governing AgNPs and AuNPs uptake by G. fossarum, (ii) both released ions and NPs themselves play a role in the potency of the studied AgNPs and AuNPs and (iii) chemical composition led to different effects at the sub-individual levels (target genes expression) and different tissue distribution as AgNPs were found in G. fossarum gills while AuNPs were found in the intestinal caeca. Additionally, this work shows that Gammarus sp. are valuable models for the study of the effects of AgNPs and AuNPs

The series of experiments that comprises this thesis consider the use of prebiotics and probiotics to improve success in European lobster Homarus gammarus culture. Research was conducted at the National Lobster Hatchery and The University of Plymouth, UK between April 2007 and March 2010. Great potential was revealed for the application of biotics as dietary supplements in the culture of larval and juvenile H. gammarus. Specific biotics, namely; prebiotic mannon oligosaccharide (MOS) and probiotic Sanolife® (Bacillus spp.) were revealed to increase growth and survival during the culture of early lobster life stages. Lobsters that showed enhanced development and/or survival were found to possess improved feed conversion, immune status and/or stress tolerance. Furthermore it was found that biotic fed lobsters displayed shifts in gastrointestinal (GI) microbiology and enhanced physical GI structures, which may account for improved feed conversion and consequently growth. The work presented thus demonstrates that by making positive changes in GI structure and bacterial community composition combined with influencing immune status culture success can be positively enhanced through the biotic supplementation of diets. However, it must be considered that the outcome of dietary biotic supplementation is heavily influenced by the situation in question.

Stable isotope analysis (SIA) is a valuable tool in ecotoxicology because δ13C and δ15N may provide insights into the trophic transfer of contaminants in a food web. The relationship between a species’ trophic position (TP, determined from δ15N) and internal concentration of biomagnifying contaminants can be established and used for regulatory purposes. However, the exposure of organisms to xenobiotics incurs physiological costs, and the stable isotope signature of a consumer reflects not only diet but also a physiological state. The latter raises questions regarding the interpretation of stable isotope signatures in contaminated areas. Therefore, the aim of this Thesis was to evaluate the behaviour of consumers’ stable isotope signatures in stressed systems, with a primary focus on the effects of environmental contaminants. In paper I, the physiological costs of chemical exposure were found to alter incorporation rates of dietary nitrogen and carbon in a consumer by influencing both growth and metabolic turnover, with resulting changes in isotope signatures relative to a control system. In paper II, the diet-consumer discrimination factors for 15N and 13C were confirmed to increase under chemical exposure mediated via increased metabolic costs. However, the physiological response was low and translated into only minor shifts in the δ13C and δ15N. The predictability of exposure effects on the stable isotope signature was demonstrated in paper III, in which animals exposed to a chemical with a known mode of action presented expected effects on elemental composition, body size, biomarkers of oxidative stress and the stable isotope signatures. Moreover, consumers’ oxidative balance was found to be related to their δ15N values, thus providing evidence of the kinetic isotope effect on the oxidative status. However, despite the alterations in stable isotope signatures observed in laboratory settings (papers I-III), the effect of xenobiotics on the TP estimates was nil or minor in the field-collected animals. Moreover, the TP values were not significantly different between the animals in the contaminated and the reference habitats because of the high overall uncertainties in the TP estimates (paper IV). Also, the TP estimates based on δ15N in bulk material were more similar between the contaminated and the reference systems than TP estimates based on δ15N values in amino acids. Therefore, the latter method appears more sensitive towards xenobiotics (and, possibly, other environmental stressors) and thus less suitable for TP assessment in contaminated areas. This Thesis improved the overall understanding of the applicability of SIA in stressed systems by establishing relationships between various exposure regimes, physiological responses and the stable isotope signatures in consumers. In model species at low trophic levels, the exposure to xenobiotics was found to significantly affect δ13C and δ15N values, which can be expected whenever physiological responses are detected. However, because of the overall high uncertainty in TP estimates, no significant differences between contaminated and control systems were detected, although the estimated TP were consistently higher in the contaminated systems. Future research should focus on higher trophic levels, in which effects of a greater magnitude can be expected. Moreover, the effects in entire food webs should be addressed rather than single prey–consumer relationships as well as other environmental variables that may contribute to the stable isotope variability in and among systems under various environmental pressures. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.</p>

<p>Abstract</p><p>In Oneida Lake, New York, USA, three species of amphipods are present: Hyalella azteca is native, Gammarus fasciatus is invasive and was first observed sometime before 1940 and Echinogammarus ischnus was introduced in 2001 in shallow water. The purpose of this study was to investigate the spatial and temporal abundance of amphipods in Oneida Lake. In the Great Lakes, the invasive E. ischnus has outcompeted G. fasciatus and this was also expected to be occur in Oneida Lake. Quantitative field sampling of transects that extended from the shore to deeper water (3.8 m) at six sites around Oneida Lake showed that the abundance of all amphipod species had a positive correlation to the abundance of zebra mussels (Dreissena polymorpha). Echinogammarus ischnus were observed at low densities (mean, 18 no./m2) in shallow water (<0.6 m) areas with cobbles covered with zebra mussels, whereas just a few individuals were found in deep water. At all depths, G. fasciatus were found at high densities (mean 950 no./m2), and H. azteca were present at low densities (mean 77 no./m2). The main factor limiting E. ischnus and its coexistence with G. fasciatus is the lack of favourable habitat i.e. too few cobble areas and too much Cladophora spp. and other macrophyte species growing in the lake. In addition, exposure of shallow water habitats every fall and winter as a consequence of water level manipulations produces unfavorable habitat for E. ischnus.</p> / <p>Sammanfattning</p><p>I sjön Oneida Lake, New York, USA, finns tre arter av märlkräftor (Amphipoda): Hyalella azteca är naturligt förekommande i sjön, Gammarus fasciatus hittades för första gången någon gång före år 1940 och Echinogammarus ischnus hittades för första gången 2001 på grunt vatten. Syftet med studien var att undersöka märlkräftornas utbredning och abundans över tid i Oneida Lake. I de Stora sjöarna (the Great Lakes) i Nordamerika har den invaderande E. ischnus konkurrerat ut G. fasciatus och samma sak förväntades att finna i Oneida Lake. I fält togs kvantitativa stickprover i transekter från strandlinjen och ut till djupt vatten (3,8 m), dessa visade att samtliga märlkräftsarter hade en positiv abundans korrelation med zebra musslor (Dreissena polymorpha). E. ischnus hittades i låga densiteter (medel 18 st/m2) på stenar täckta med zebra musslor på grunt vatten (<0,6 m) och endast ett fåtal individer hittades på djupt vatten. I Oneida Lake på alla djup hittades G. fasciatus i höga densiteter (medel 950 st/m2) medan H. azteca endast fanns i låga densiteter (medel 77 st/m2). Största anledningen till E. ischnus begränsning till samexistens med G. fasciatus är avsaknaden av gynnade habitat i sjön, det vill säga för få områden med stenar, samt att det växer för mycket alger (Cladophora spp.) och andra växter i sjön vilket missgynnar E. ischnus. Även vattennivåreglering under höst och vinter är ogynnsam för E. ischnus, då habitat på grunt vatten blir exponerande.</p>

Abstract In Oneida Lake, New York, USA, three species of amphipods are present: Hyalella azteca is native, Gammarus fasciatus is invasive and was first observed sometime before 1940 and Echinogammarus ischnus was introduced in 2001 in shallow water. The purpose of this study was to investigate the spatial and temporal abundance of amphipods in Oneida Lake. In the Great Lakes, the invasive E. ischnus has outcompeted G. fasciatus and this was also expected to be occur in Oneida Lake. Quantitative field sampling of transects that extended from the shore to deeper water (3.8 m) at six sites around Oneida Lake showed that the abundance of all amphipod species had a positive correlation to the abundance of zebra mussels (Dreissena polymorpha). Echinogammarus ischnus were observed at low densities (mean, 18 no./m2) in shallow water (&lt;0.6 m) areas with cobbles covered with zebra mussels, whereas just a few individuals were found in deep water. At all depths, G. fasciatus were found at high densities (mean 950 no./m2), and H. azteca were present at low densities (mean 77 no./m2). The main factor limiting E. ischnus and its coexistence with G. fasciatus is the lack of favourable habitat i.e. too few cobble areas and too much Cladophora spp. and other macrophyte species growing in the lake. In addition, exposure of shallow water habitats every fall and winter as a consequence of water level manipulations produces unfavorable habitat for E. ischnus. / Sammanfattning I sjön Oneida Lake, New York, USA, finns tre arter av märlkräftor (Amphipoda): Hyalella azteca är naturligt förekommande i sjön, Gammarus fasciatus hittades för första gången någon gång före år 1940 och Echinogammarus ischnus hittades för första gången 2001 på grunt vatten. Syftet med studien var att undersöka märlkräftornas utbredning och abundans över tid i Oneida Lake. I de Stora sjöarna (the Great Lakes) i Nordamerika har den invaderande E. ischnus konkurrerat ut G. fasciatus och samma sak förväntades att finna i Oneida Lake. I fält togs kvantitativa stickprover i transekter från strandlinjen och ut till djupt vatten (3,8 m), dessa visade att samtliga märlkräftsarter hade en positiv abundans korrelation med zebra musslor (Dreissena polymorpha). E. ischnus hittades i låga densiteter (medel 18 st/m2) på stenar täckta med zebra musslor på grunt vatten (&lt;0,6 m) och endast ett fåtal individer hittades på djupt vatten. I Oneida Lake på alla djup hittades G. fasciatus i höga densiteter (medel 950 st/m2) medan H. azteca endast fanns i låga densiteter (medel 77 st/m2). Största anledningen till E. ischnus begränsning till samexistens med G. fasciatus är avsaknaden av gynnade habitat i sjön, det vill säga för få områden med stenar, samt att det växer för mycket alger (Cladophora spp.) och andra växter i sjön vilket missgynnar E. ischnus. Även vattennivåreglering under höst och vinter är ogynnsam för E. ischnus, då habitat på grunt vatten blir exponerande.

The ecology behind evolutionary diversification is a well studied area of research, whereas the effects of evolution on ecosystems get little attention. In line with ecological theory, evolutionary diversification of a species could influence different ecosystem aspects such as food web composition, energy flow, nutrient cycling etc. The main objective of this study was to investigate whether two diverging ecotypes (reed and chara) of Asellus aquaticus differ regarding their role in two aquatic ecosystem processes: decomposition of terrestrial leaves and grazing of periphyton. Their role in ecosystem process as well as treatment effects on fitness, measured as growth and survival, were investigated in a laboratory experiment with various levels of intra-specific competition and inter-specific interactions with the amphipod Gammarus pulex. The isopods were collected from two Swedish lakes: Lake Tåkern and Lake Fardume. These two lakes represent different history of ecotype divergence. The experimental design consisted of 2-L aquaria, each providing elm leaves (Ulmus glabra), oak leaves (Quercus roburleaves) and periphyton as food sources. Ten treatments with five replicates were applied for each lake and the experiment lasted for four weeks. The study showed that there was no significant difference between chara and reed ecotype in their functional role. However, the rate of ecosystem processes per individual decreased in competitive interactions. In high density, decomposition per dry weight consumer was low and total algae biomass was high at the end of four weeks due to intra-specific competition. Moreover, ecosystem processes were lowest in inter-specific competition between Gammarus pulex and each ecotype. Present study also shows that ecotypes from the different lakes, having different history, had different responses to mortality and growth.

Freshwater ecosystems worldwide are being altered by multiple stressors. One of the most important stressors is biological invasion---the introduction of exotic species, which can contribute to the loss of native species. The effects of an introduced species are correlated with its abundance and typically vary across ecosystems, suggesting that its impact on native species is mediated by its environment, i.e. the physical habitat and the recipient community. However, there are few studies that explore the effects of environment on the interactions between exotic and native species. My thesis examines the influence of physical habitat variables and community interactions on the relative abundance of exotic and native freshwater crustaceans in the St. Lawrence River. / The Eurasian amphipod Echinogammarus ischnus invaded the Great Lakes-St. Lawrence River system in the mid-1990s and has replaced the native North American Gammarus fasciatus as the dominant amphipod in littoral areas throughout Lake Erie and Lake Ontario.

No description available.

Predator cues can influence how aquatic organisms respond to anthropogenic contaminants. This study examined the effects of predator cues on behavior, metabolic rate, and sulfate (as Na2SO4) toxicity in amphipods (Gammarus minus). Predator cues included alarm cue (macerated conspecifics) and kairomone from mosquitofish (Gambusia affinis). Amphipods decreased activity and increased time in refuge when exposed to alarm cue, and increased time in refuge when exposed to kairomone. While median lethal concentrations (96-h LC50) were not influenced by predator cues, analysis of dose response curves indicated that kairomone exposure increased amphipod sensitivity to mid-range concentrations of sulfate (500-1,000 mg/L). Amphipods increased oxygen consumption in response to kairomone but not alarm cue. The influence of predator cues on contaminant lethality can be dependent on the type of cue, and physiological endpoints such as metabolic rate may help explain the basis of observed interactions.