## 3 Results  
### Mercury Bioaccumulation and Tissue Partitioning  
In the beginning of the experiment (day 0), significantly lower THg concentration (\(p<0.012\)) was detected in brain (\(0.04\pm 0.01\) mg\(\cdot\)kg\({}^{-1}\) ww) than those found in liver (\(0.07\pm 0.01\) mg\(\cdot\)kg\({}^{-1}\) ww; \(p=0.012\)) and muscle (\(0.09\pm 0.01\) mg\(\cdot\)kg\({}^{-1}\) ww; \(p=0.002\)) (Table S1, Supplementary Materials). After 28 days, fish from the non-contaminated (non-CONT) treatment exhibited significantly higher THg concentrations in the muscle (\(0.12\pm 0.01\) mg\(\cdot\)kg\({}^{-1}\) ww; \(p=0.003\)), compared to the initial day (Table S1, Supplementary Materials). THg concentrations in \(S\). _senegalensis_ tissues in CONT treatments throughout the experiment are presented in Figure 1.  
Figure 1: \(Cont\). In general, the liver exhibited higher Hg concentrations (ranging from 2.52 to 4.29 mg\(\cdot\)kg\({}^{-1}\) ww), followed by brain (ranging from 0.97 to 1.57 mg\(\cdot\)kg\({}^{-1}\) ww) and muscle (ranging from 0.83 to 2.14 mg\(\cdot\)kg\({}^{-1}\) ww), regardless of treatment (Figure 1). Acidification (i.e., CONT + A treatment) significantly decreased Hg concentrations in muscle (47% decrease; \(p\) = 0.0001), liver (29% decrease; \(p\) = 0.0001), and brain (16% decrease; \(p\) = 0.03) compared to Hg exposure alone (i.e., CONT treatment). In opposition, warming (i.e., treatment CONT + W) significantly increased Hg concentrations in all fish tissues (\(p\) < 0.001; 36%, 19%, and 35% in muscle, liver, and brain, respectively; see Figure 1). Matching these results, Hg net accumulation rate (NAR) significantly varied among tissues and treatments (Table 1). Liver presented the highest Hg NARs, regardless of treatment (ranging between 87.6 and 150.6 mg\(\cdot\)day\({}^{-1}\)), whereas lower NARs were found in the muscle (26.5 mg\(\cdot\)day\({}^{-1}\)) and brain (73.3 mg\(\cdot\)day\({}^{-1}\); Table 1). In fish muscle, Hg NARs were significantly enhanced by the combination of warming and acidification (treatment CONT + A + W; \(p\) < 0.05), as well as by warming, but they significantly decreased with acidification. In contrast, NARs in fish brain and liver were significantly affected by warming or acidification alone (i.e., in liver, CONT treatment significantly increased upon warming, \(p\) = 0.0002, and decreased upon acidification, \(p\) = 0.001), but not by the combination of warming and acidification (i.e., in brain, CONT treatment significantly increased upon warming alone, \(p\) = 0.0003, but not upon the interaction between these two abiotic stressors or acidification alone). Figure 1: Total mercury (THg) concentrations (mg\(\cdot\)kg\({}^{-1}\) wet weight (ww)) in muscle (**a**), liver (**b**), and brain (**c**) of juvenile _Solea senegalensis_ (mean \(\pm\) standard deviation) fed with Hg-enriched diet in each treatment during the exposure (on days 0, 14, and 28) and elimination (day 35) periods. Abbreviations: CONT—animals fed with Hg-contaminated diet, seawater temperature set at 19 \({}^{\circ}\)C, and pH set at 8.0 units. ; CONT + A—animals fed with Hg-contaminated diet, seawater temperature set at 19 \({}^{\circ}\)C, and pH set at 7.6 units; CONT + W—animals fed with Hg-contaminated diet, seawater temperature set at 23 \({}^{\circ}\)C, and pH set at 8.0 units; CONT + A + W—animals fed with Hg-contaminated diet, seawater temperature set at 23 \({}^{\circ}\)C, and pH set at 7.6 units. Gray lines indicate temperature set at 23 \({}^{\circ}\)C (warming (W)), whereas continuous lines indicate pH set at 8.0 units, and discontinuous lines indicate pH set at 7.6 units (acidification (A)). Different letters for each sampling day represent significant differences (\(p\) < 0.05) between treatments. During the seven days of the Hg clearance period (i.e., day 35), different elimination patterns were observed in the three tissues (Figure 1).