Organotins in marine mussels from three Mediterranean islands

Abstract

Mytilus gallnpmvindalis mussels (Bivalvia: Mytilidae) were caged in 11 locations spread in the coastal waters of the three central Mediterranean islands of Malta, Lampedusa and Linosa, for 12 weeks during the summer of either 2006 or 2007. This bivalve filters voluminous amounts of seawater to feed on phytoplankton and suspended organic matter, and in this process takes up organotin compounds present in the water column, most often attached to particulate matter. Tributyltin (TBT) is an important organotin that has biocidal properties and was until recently widely applied in marine antifouling paints. M. galloprovincialis is capable of bioaccumulating organotin compounds within its body, and since it has a low capability of degrading TBT to its lower derivatives, the animal was used as a bioindicator to assess the quantities of organotin species in coastal areas of interest. Organotin contents in bivalve samples were determined using an in situ simultaneous derivatisation and extraction with sodium tetraethylborate. The method was optimised to eliminate the most common matrix effect problems associated with biological samples. Mechanical agitation was coupled with stirring in a warm ultrasonic bath so as to obtain a high sample dissolution. The technique was validated using the mussel tissue Certified Reference Material ERM® - CE 4 77. Compared to other studies, the sites analysed in this work were found to contain a relatively low total organotin concentration, most of which did not exceed 50 ngSn/g wet weight. More polluted areas such as Punta Maccaterri outside Lampedusa' s main port and Qammieh sewage outlet area in Malta featured a higher organotin concentration than the other sites. The most abundant organotin compound was monobutyltin (MBT) and high MBT/TBT and DBT/TBT ratios were observed, indicating a low TBT input into the marine environment and a quick degradation of any introduced TBT. The very little TBT detected was mostly confined to the more polluted regions. Based on these findings it may be concluded that the organotin concentrations in the sampled islands' coastal waters are relatively low and due to the total organotin prohibition enforced from January 2008, lower concentrations of these toxic compounds are to be expected from future similar studies.