Integrative assessment of coastal pollution in a Ría coastal system (Galicia, NW Spain): Correspondence between sediment chemistry and toxicity

Elutriate embryo-larval bioassays with sea-urchins (Paracentrotus lividus) and ascidians (Ciona intestinalis) were conducted concurrently with trace metal analyses as part of an integrative assessment of sediment pollution at Ría de Pontevedra (Galicia, NW Spain). High metal contents in sediments were found in localised areas from the inner part of the estuary indicating a clear anthropogenic influence. In particular, very high Cu, Zn and Pb levels were found at sites P2 and P3, which were also the most toxic to the embryo-larval bioassays. Sediment quality guidelines were used to help in the ecological interpretation of sediment chemistry data and to identify pollutants of concern. Cu and Zn in P3 were consistently above the effects range median (ERM) values, which seem to be good predictors of toxicity to sea-urchin and ascidian embryos. A toxic unit approach, based on published EC50 values and metal levels in elutriates, was used to assess the harmful ecological effects associated to sediment chemistry. Toxicity detected in P3 may be explained on the basis of the toxic unit model; however, the high toxicity detected at P2 may be attributable not only to the metals quantified in the analyses but also to unmeasured organic pollutants. Multidimensional scaling applied independently to the toxicology and chemistry data resulted in a good agreement between both types of configurations. Moreover, the Mantel test revealed a significant correlation (rM = 0.481; p = 0.019) between metal concentrations and toxicity data profiles, supporting the correspondence between configurations.