PhD proposal:
Plasticity of toxicological sensitivity and life history traits as a driver of aquatic invertebrate species vulnerability to metallic contamination

Host Laboratory: INRAE, UR RiverLy, Laboratoire d’écotoxicologie, Lyon-Villeurbanne.
www6.ara.inrae.fr/lyon-riverly-ecotox

Contact : Arnaud Chaumot [email protected]

Keywords : Ecotoxicology, aquatic macroinvertebrates, experimentation, multi-generation, adaptation, comparative biology.

Chemical contamination is now clearly identified as one of the major environmental pressures on biological communities within ecosystems. For continental aquatic environments, some studies have attempted to correlate indicators of the toxic risk due to the presence of certain micropollutants with the alteration of the composition of river ecological communities, predicting in particular contrasting response patterns between species (Beketov et al 2013 , Malaj et al 2014 ). In these approaches, toxic risk assessment is based on species sensitivities defined a priori in the laboratory during ecotoxicological tests implemented on model species chosen as proxies of natural communities. One of the drawbacks is that it ignores the possibility of physiological, developmental, genetic, evolutionary, processes at the individual or multi-generational time scale that may lead to changes in the toxicological sensitivity or life history traits of exposed natural populations. The objective of the proposed thesis is to question the role of the plasticity of the sensitivity of aquatic species in their ability to maintain populations in the face of contamination gradients.
We have begun to document this issue with the exposure of aquatic macroinvertebrates to trace metal elements. Using the active biomonitoring approach developed in the crustacean Gammarus fossarum to assess the bioavailable contamination of hydrosystems, we have been able to reveal the effect of metal contamination of national rivers on the density of invertebrates (Ciliberti et al 2017 , Alric et al 2019 ). In particular, we have shown that the levels of metallic contamination impacting densities depend on species (Figure 1). But it appears that these empirically revealed differences are only partly explained by the differences in sensitivity known in the laboratory between these species families. Moreover, by focusing on the model species of our laboratory – Gammarus fossarum – known to be sensitive to metallic exposure, we were able to reveal locally the possibility of tolerance acquisition in a case of historical natural exposure to cadmium (geochemical background) (Vigneron et al 2015 ). The hypothesis of genetic adaptation has been rejected in favour of plasticity induced by transgenerational effects of parental exposure that would support a non-genetic inheritance of tolerance and modification of certain life history traits of the offspring. (Vigneron et al 2016 , 2019 ).
With the aim of generalizing these results on the plasticity of species sensitivity, three lines of work could be developed during the thesis : 1/ an experimental approach of multi-generation exposure in the laboratory to chronic levels of metallic contaminants to test the mechanistic hypotheses raised in Gammarus; 2/ a comparative approach of sensitivity to contaminants and life history traits between natural Gammarus populations in order to evaluate the importance of these plasticity processes in the maintenance of populations along the contamination gradient identified at the national level; 3/ the development of a complementary approach to compare biological traits between populations in other invertebrate species that will be selected with regard to their ability to maintain themselves in highly contaminated environments.

Candidate profile:
Training and experience in ecotoxicology or ecophysiology / population biology, with a strong interest for experimental approaches (laboratory and field).

Application:
Send your CV and cover letter by e-mail by 20 May 2020 at the latest.
[email protected]

REF:
– Alric B et al (2019) Multisubstance Indicators Based on Caged Gammarus Bioaccumulation Reveal the Influence of Chemical Contamination on Stream Macroinvertebrate Abundances across France. Environmental Science & Technology, 53(10):5906-5915.
– Beketov MA et al (2013) Pesticides reduce regional biodiversity of stream invertebrates. PNAS, 110(27):11039-11043.
– Ciliberti A et al (2017) Caged Gammarus as biomonitors identifying thresholds of toxic metal bioavailability that affect gammarid densities at the French national scale. Water Research, 118:131-140.
– Malaj E et al (2014) Organic chemicals jeopardize the health of freshwater ecosystems on the continental scale. PNAS, 111(26):9549.
– Vigneron A et al (2015) Evolution of cadmium tolerance and associated costs in a Gammarus fossarum population inhabiting a low-level contaminated stream. Ecotoxicology, 24:1239-1249.
– Vigneron A et al (2016) Mothers and not genes determine inherited differences in cadmium sensitivities within unexposed populations of the freshwater crustacean Gammarus fossarum. Evolutionary Applications, 9(2):355-366.
– Vigneron A et al (2019) Nongenetic inheritance of increased Cd tolerance in a field Gammarus fossarum population: Parental exposure steers offspring sensitivity. Aquatic Toxicology, 209:91-98.

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