## 3 Results  
A five-year survey of intertidal _Mya arenaria_ clams was undertaken to follow changes in clam health status based on morphological parameters such as condition factor (clam mass/longitudinal shell length), age and growth index (longitudinal shell length/age). Moreover, the air survival time and dehydration rate were also analyzed, in keeping withthe study by [PERSON] et al. [10]. First, the sites were characterized by measuring water pH, salinity, dissolved oxygen contents and granularity (results not shown). Over the 5-year sampling period, the water pH and oxygen saturation levels varied from 7.8 to 8.3 and 95-99%, respectively, regardless of the sites. Water salinity ranged between 28 and 34 g/L at BAU, BSC and TAD sites located in the SLE but dropped to between 21 and 24 g/L at the BSM site, which was located downstream of the Saguenay Fjord (Figure 1). The sediment mud flat was composed of sandy material containing 10-30% gravel (0.1-10 cm size) at the SLE sites but was mostly sand at the BSM site. The tissue-elemental loadings were also determined in clam tissues over the first 3 years of the survey to determine potential contamination problems (Table 1). Elemental analysis revealed that 30 elements revealed changes between the reference site with either the polluted or BSM sites. With respect to the polluted sites, the following elements were significantly increased (>2-fold are in **bold**): **Ag (2.4-fold)**, Ca (1.16-fold), Cd (1.2-fold), Cr (1.6-fold), **Mn (2.5-fold)**, Mo (1.6-fold), Nb (1.6-fold), Nd (1.7-fold), K (0.9-fold), Sm (1.2-fold) and **V (6.3-fold)**. The following elements were found at higher levels at the BSM compared to reference sites: Al (1.7-fold of reference site), Ba (1.7-fold), Be (1.4-fold), Ce (2.5-fold), Co (2-fold), Cu (1.3-fold), **Ga (2-fold)**, Gd (1.8-fold), Fe (1.7-fold), **La (2.75-fold)**, Pb (1.7-fold), Mg (0.7-fold), **Hg (2.5-fold)**, **Ni (2.2-fold)**, **Sm (2-fold)**, Sn (1.7-fold), U (1.3-fold), **V (20-fold)**, Zn (1.9-fold) and Zr (1.3-fold). The following elements were significantly higher at BSM compared to the polluted sites: Cd (1.25-fold of polluted sites), Ce (2.5-fold), Mn (1.1-fold), Nd (1.2-fold), Sm (1.6-fold), and V (3.2-fold). Thus, these elements are considered the main elemental contaminants by either polluted (marina, harbors) or the BSM. The threshold concentration for each element could be calculated based on two approaches: the 95 th percentile and the geometric means. The 95 th percentile value of the reference site was considered a threshold to expect possible toxicological impacts. The geometric mean (squared product of the concentration of the natural and polluted sites) could be another approach to identify concentration limits in clams (Table 1). These values should be considered hypothetical because they are not uniquely present in clam tissues, i.e., mixture effects are unknown. For example, if we take the most important ones above and those correlated with at least one of four physiological biomarkers (CF, GI, LT, WL), the threshold concentration of V (0.1 \(\upmu\)g/g), La (0.7 \(\upmu\)g/g), Ag (0.12 \(\upmu\)g/g), Mn (3.8 \(\upmu\)g/g), Cd (0.08 \(\upmu\)g/g), Cr (5 \(\upmu\)g/g) and Mo (0.67 \(\upmu\)g/g) could serve as a flag system to identify potential sites at risk provided impacts are observed with the three morphological biomarkers (CF, GI and LT) explained below.