Short-Term and Long-Term Biological Effects of Chronic Chemical Contamination on Natural Populations of a Marine Bivalve

Abstract

Understanding the effects of chronic chemical contamination on natural populations of marine organisms is complex due to the combined effects of different types of pollutants and environmental parameters that can modulate the physiological responses to stress. Here, we present the effects of a chronic contamination in a marine bivalve by combining multiple approaches that provide information on individual and population health. We sampled variegated scallops (Mimachlamys varia) at sites characterized by different contaminants and contamination levels to study the short and long-term (intergenerational) responses of this species to physiological stress. We used biomarkers (SOD, MDA, GST, laccase, citrate synthase and phosphatases) as indicators of oxidative stress, immune system alteration, mitochondrial respiration and general metabolism, and measured population genetic diversity at each site. In parallel, concentration of 14 trace metals and 45 organic contaminants (PAHs, PCBs, pesticides) in tissues were measured. Scallops were collected outside and during their reproductive season to investigate temporal variability in contaminant and biomarker levels. Our analyses revealed that the levels of two biomarkers (Laccase-type phenoloxidase and malondialdehyde) were significantly correlated with Cd concentration. Additionally, we observed significant seasonal differences for four of the five biomarkers, which is likely due to the scallop reproductive status at time of sampling. As a source of concern, a location that was identified as a reference site on the basis of inorganic contaminant levels presented the same level of some persistent organic pollutants (DDT and its metabolites) than more impacted sites. Finally, potential long-term effects of heavy metal contamination were observed for variegated scallops as genetic diversity was depressed in the most polluted sites.

First data on three bivalve species exposed to an intra-harbour polymetallic contamination (La Rochelle, France)

“…Species identification of scallops was performed with a portion of the mitochondrial gene coding for cytochrome c oxidase I (cox1) using primers specifically designed for Mimachlamys spp. : forward primer Cox1F3 (5′-GGGTTTGGrAACTGGCTTCT-3′) and reverse primer Cox1R-long (5′-CCAAAAACMCGAATCTTCTT-3′) (Breitwieser et al, 2016). The PCR profile was: 94°C for 2 min, followed by 30 cycles of 30 s at 94°C, 30 s at 54°C, and 30 s at 72°C and a final extension of 7 min at 72°C.…”

“…Branch support was assessed using 1000 bootstrap replicates and the Tamura-Nei (Tamura and Nei, 1993) model of substitution was applied as in Gerard et al (2008). Scallop haplotypes were compared to previously sampled M. varia cox1 haplotypes (across 477 bp) obtained for the same geographic area and described in Breitwieser et al (2016) to evaluate the presence of the same lineages across different years.…”

“…The evaluation of the impact of pollutants in the environment is now a major concern, with the aim of reaching a good chemical and ecological state of the littoral zone. Previous studies (Milinkovitch et al, 2015;Lacroix et al, 2015;Luna-Acosta et al, 2011;Breitwieser et al, 2016) showed the risks of chronic chemical contamination and the consequences in the bivalves Mimachlamys varia, Crassostrea gigas and Mytilus edulis in an open coastal environment. In this context, the objective of this project was to assess the impacts of pollution (heavy metals) on the macrofauna of a semi-closed environment: a marina in La Rochelle (France).…”

“…Lipid peroxidation indicates the damage to cellular membrane lipids caused by ROS and is useful for assessing exposure to and the effects of pollutants in marine species. Moreover, there is a depletion of key enzymes such as laccase involved in the modulation of immune system in bivalve in presence of contaminants (Luna-Acosta et al, 2010, 2011Milinkovitch et al, 2015;Breitwieser et al, 2016).…”

Enhanced trace element concentrations in tissues of the clam <em>Ruditapes decussatus</em> transplanted to areas influenced by human activities (Ria Formosa, Portugal)

“…Trace elements may interfere with the variation of physiological parameters related to the organism's wellbeing (Yatoo et al 2013). In the case of bivalves, several works have reported high consumption of glycogen, lipids and proteins in response to environmental contamination (Hamza-Chaffai 2014, Luna-Acosta et al 2015, leading to changes in the condition index (Cravo et al 2012) and eventually in the gametogenesis cycle (Breitwieser et al 2016, Gauthier-Clerc et al 2002. According to Mantel and Farmer (1983), metal exposure may alter the fluid ion level in clams, causing the decrease of Na + , Cl -and K + contents as a compensatory process in the internal osmolarity regulation.…”