Evolution of cadmium tolerance and associated costs in a Gammarus fossarum population inhabiting a low-level contaminated stream

Abstract

Deciphering evolutionary processes occurring within long-term contaminated wild populations is essential for the ecological risk assessment of persistent chemical contaminations. Using field populations of Gammarus, a commonly-used genus in aquatic ecotoxicology, the present study sought to gain insights into the extent to which long-term exposure to metals in the field could effectively lead to shifts in toxicological sensitivities. For this, we identified a Gammarus population inhabiting a stream contaminated by cadmium (Cd). We compared the Cd-exposure and Cd-sensitivity of this population to those of five reference populations. Active biomonitoring determined in different years and seasons that significant levels of Cd were bioavailable in the contaminated site. Laboratory sensitivity tests under common garden conditions established that this long-term field exposure led to the development of a moderate Cd tolerance, which was maintained after a 3-week acclimatization in the laboratory, and transmitted to offspring produced under clean conditions. The potential physiological costs of tolerance were assessed by means of feeding rate measurements (in the laboratory and in situ). They revealed that, unlike for reference populations, the feeding activity of organisms from the tolerant population was greatly decreased when they were maintained under laboratory conditions, potentially indicating a high population vulnerability to environmental perturbations. Because dissolved Cd concentrations in water from the contaminated site were low (averaging 0.045 µg L(-1)) and below the current European environmental quality standard for Cd for inland surface waters (fixed at 0.08 µg L(-1) in soft water environments), this case study sheds light onto the extent to which current environmental quality standards are protective against potential adverse outcomes of adaptive and micro-evolutionary processes occurring in contaminated environments.

Mothers and not genes determine inherited differences in cadmium sensitivities within unexposed populations of the freshwater crustacean Gammarus fossarum

“…; Vigneron et al. ), 20 μg Cd L −1 gave rise to mortalities scattered from 12 h to 10 days of exposure, while only few death occurred in the controls. Survival was monitored every day until all individuals died.…”

“…; Vigneron et al. ). Gammarus fossarum were kick‐sampled using a hand net and quickly transported to the laboratory in plastic bottles containing ambient freshwater.…”

“…This population had developed Cd tolerance that is transmissible to offspring, even when genitors were placed in an uncontaminated environment (Vigneron et al. ). Moreover, tolerance and associated costs in that population have evolved for water Cd concentrations that are ten times lower than concentrations for which the phenomenon of microevolution in response to contaminants has already been reported (De Coninck et al.…”

Ecosystem Vulnerability Review: Proposal of an Interdisciplinary Ecosystem Assessment Approach

“…A disturbance or shock could have consequences of similar severity for an ecosystem as an enduring or increasing stress perceived as nearing a threshold or tipping point (Redman 2014). Examples in our literature sample of these exposures were effects of climate change (e.g., Moe et al 2013;Okey et al 2015), land use changes like deforestation or urbanization (e.g., Ventura and Lana 2014), invasive species (e.g., Arianoutsou et al 2013;Olden et al 2011), and effects from pesticides (van Gestel 2012), oil spill (Cai et al 2015) or other toxicants (e.g., Vigneron et al 2015). According to Ippolito et al (2010), the different stressors should be addressed by single and separate vulnerability assessments as long as the combining effects and interrelations are not yet fully understood.…”

“…A longterm exposure to one stress may lead to the development of increased tolerance (or decrease in sensitivity), but potentially increases the vulnerability to other environmental changes. This could mean, for example, that according to micro-evolutionary processes the resulting population, which successfully survived a first stress from a toxicant, is less competitive for foraging and likely to be more affected to another stress like a nourishment-poor period (Vigneron et al 2015). The sensitivity could be determined by specific indicators according to the ecosystem and exposure under investigation.…”