A miniaturized bismuth-based sensor to evaluate the marine organism Styela plicata bioremediation capacity toward heavy metal polluted seawater.

Cadmium and lead are highly toxic heavy metals which cause a severe worldwide pollution. In addition to the toxic effect produced by the direct exposure, they can be bioconcentrated and accumulated in living organisms, including humans. Herein, a miniaturized and disposable electrochemical sensor was improved for the simultaneous detection of cadmium and lead ions to study the bioremediation of polluted seawater in presence of the filter-feeding marine organism Styela plicata. A screen-printed electrode modified in situ with a bismuth film was selected using the anodic stripping analysis as detection technique. This sensor was coupled with a portable potentiostat and the detection of cadmium and lead ions was carried out by Square Wave Anodic Stripping Voltammetry, allowing the simultaneous detection of both heavy metals at ppb level (LOD=0.3ppb for lead, 1.5ppb for cadmium). This analytical tool was then applied to assess the bioremediation capacity of S. plicata through a bioremediation experiment, in which the organism has been exposed to seawater artificially polluted with 1000ppb of Cd ²⁺ and Pb ²⁺ . The matrix effect of both seawater and acid digested biological samples was evaluated. A bioconcentration phenomenon was observed for both heavy metals through the analysis of S. plicata tissues. In details, Pb ²⁺ resulted to be about 2.5 times more bioconcentrated than Cd ²⁺ , giving an effective bioremediation level in seawater of 13% and 40% for Cd ²⁺ and Pb ²⁺ , respectively. Thus, our results demonstrate the capability of S. plicata to bioremediate Cd ²⁺ and Pb ²⁺ polluted seawater as well as the suitability of the electrochemical sensor for contaminated marine environment monitoring and bioremediation evaluation.
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