During mining activitie historically developed at Sierra Minera (Cartagena-La Unión, Spain), high amounts of trace elements were discharged to the Mar Menor coastal lagoon through different wadis, mainly the Beal wadi. The objective of this study is to establish the role played by the Cymodocea nodosa on the coastal-marine dynamic of trace elments at the Mar Menor lagoon (Spain). To this end, the content of nine trace elements in different marine environmental compartments at two different locations were determined by means inductively coupled plasma atomic emission spectometry. The results obtained showed a ver high concentration levels of trace elements in all the enviromental compartments tested at the exit of the Beal wadi. In addition, the behaior observed for each marine environmental compartment analysed showed that the seagrass Cymodocea nodosa could mobilise most of the trace elements present in marine sediments and water causing the re-accumulation of them in the coastal sediments due to the Cymodocea nodosa beach cast litter, which is mainly constitued by the detached leaves of that seagrass.