Patella spp. as an alternative to Mytilus spp. in Marine Pollution Studies

The species more widely used for marine pollution studies is mussel, Mytilus spp., as it is a filter feeder, sessile, easy to get and present in most worldwide coasts. However, sometimes it is necessary to have an alternative for areas where mussels are scarce or even absent. Patella spp. could be a useful substitute to Mytilus as these organisms have already been used in some pollution studies (Bartolomé, 2011) and both groups have similar characteristics except for the feeding strategy that in limpets is based on grazing on the small algae that grow on the rocks where they live. For this study, four sampling sites where selected: two in Galicia (Ría de Arousa and Ría de Ferrol) and two in the Bay of Biscay (Suances and Fuenterrabía). In the four sampling sites both mussels and limpets were collected and 12 parent PAHs were analysed by means of HPLC and fluorescence detector with programmable wavelength (Viñas 2002). The method is subject to a strict quality control that guarantees the quality of the data. Mussels always present a higher PAH content that limpets sampled in the same area. When comparing the value for the sum of PAHs it is shown that the maximum value measured in limpets (26.0 µg/kg d.w. in Arousa) is less than the minimum value measured in mussels (63.7 µg/kg d.w. in Fuenterrabía). However, the sites pointed as more polluted using limpets coincide with the ones that are pointed out using mussels and the other way around. The individual PAH distribution pattern also presents some differences in both species mainly due to the phenathrene proportion that is higher in limpets than in mussels and this is clearer in the Bay of Biscay area. The main conclusion of the study is that there is no direct conversion factor between the PAH burden in both species but it could be possible to estimate the pollution status of an area using limpets. To compare levels between species it would be necessary to do some more work including more sampling sites where both organisms are sampled.