Trace-element bioaccumulation in Mytilus sp. from the Mallorquín swamp, Colombia: Association with water physicochemical conditions.

BACKGROUND: Heavy metal exposure remains an important concern for environmental public health. AIM: This study assessed the associations between water physicochemical conditions and trace-element concentrations in Mytilus sp. from the Mallorquín swamp in Barranquilla, Colombia. METHODOLOGY: Water and mussel samples were collected during two sampling periods (S1 and S2), and physicochemical parameters, including pH, temperature, salinity, dissolved oxygen, and redox potential, were measured in situ. Samples underwent standardized cleaning and acid digestion procedures, and concentrations of cadmium (Cd), mercury (Hg), arsenic (As), lead (Pb), and copper (Cu) were quantified using ICP-OES, with total Hg determined using an online vapor-generation system coupled to ICP-OES. Descriptive statistics, correlation analyses, and linear regression models were used to evaluate associations between physicochemical conditions and tissue metal concentrations. We also analyzed data at the station-monitoring-event level. RESULTS: Surface-water concentrations decreased from S1 to S2, including As from 53.9 to 11.8 µg/L and Cu from 2.09 to 0.25 µg/L. In Mytilus sp. tissues, mean As and Cu concentrations increased from 8343 to 12,951 ng/g and from 3144 to 11,574 ng/g, respectively, whereas Hg and Pb decreased from 242 to 95 ng/g and from 1430 to 705 ng/g. Hg and Pb showed the strongest tissue correlation (r = 0.82; p < 0.05). Across both sampling periods, higher salinity was associated with lower Hg concentrations (β = -74.68 ng/g per PSU; 95% CI: -157.63, 8.27; p = 0.07) and lower Pb concentrations (β = -412.01 ng/g per PSU; 95% CI: -866.29, 42.27; p = 0.07). Redox potential showed positive associations with Hg (β = 4.88 ng/g per mV; 95% CI: -1.94, 11.70; p = 0.14) and Pb (β = 27.33 ng/g per mV; 95% CI: -10.30, 64.96; p = 0.14), although these estimates were imprecise. Higher dissolved oxygen was associated with higher Cu concentrations (β = 7107.28 ng/g per mg O₂/L; 95% CI: 1744.43, 12,470.13; p = 0.011). CONCLUSION: Overall, the results showed short-term, metal-specific differences and modest associations between physicochemical conditions and tissue concentrations. These findings support the use of resident mussels for environmental biomonitoring but do not establish causal mechanisms or quantify dietary or human-health risk.