Assessing the use of the edible sea urchin (Paracentrotus lividus) as a bioindicator of local pollution by heavy metals

Abstract

Living organisms represent the most appropriate indicator for monitoring the environmental quality of a water body, as they integrate biotic and abiotic components through their adaptive responses. The present study assessed the feasibility of using the sea urchin Paracentrotus lividus (Lamarck, 1816) as a bioindicator of heavy metal pollution in Malta. The project involved analysing the levels of the heavy metals zinc, copper, lead and cadmium in the different body compartments of the sea urchin (coelomic fluid, internal tissue, skeleton, Aristotle's Lantern, male and female gonads) and in superficial marine sediment samples collected from Wied iz-Zurrieq, Qalet Marku, Maghtab, Xghajra and Cirkewwa. All heavy metal analyses were carried out using voltammetry. Heavy metals have a known tendency to accumulate in sediments; the results in sediments indicate that the sampled locations of Wied iz-Zurrieq, Xghajra and Maghtab are to a certain extent hot spots of local pollution in the coastal marine environment. P.lividus has been confirmed as a suitable bioindicator to be used in local field biomonitoring studies; the recorded heavy metals were observed to be influenced by the reproductive state and by gender. The local results have been compared to the regional available data on P.lividus and the similarity in metal concentrations as measured by these different studies implies that homeostatic processes are in control in the sea urchins, allowing metal regulation to take place. Such studies, as also confirmed locally indicate that P.lividus concentrates metals most efficiently in the internal tissue and in the gonads. In conclusion, through comparison with the regional available data on metal content in the body compartments of P.lividus, it has been identified that local P.lividus gonads seem to be concentrated with elevated levels of lead. Similarly, the lead concentrations in the gonads were found to exceed the maximum allowable limit for lead in seafood.