Fatty acid-based index development in estuarine organisms to pinpoint environmental contamination

Estuaries have long been preferred areas of human settlement, where multiple anthropogenic activities take place, which have contributed to a significant decrease in environmental quality of these ecosystems. Accordingly, environmental monitoring and management have long relied on the development of tools that summarize and simplify complex information and provide direct interpretation of quality status. Here, the fatty acid profiles of three abundant estuarine species, namely Hediste diversicolor, Carcinus maenas and Pomatoschistus microps, were used to develop and validate a multimetric index, based on the Euclidean dissimilarities of profiles between sites, in response to contamination gradient in a large urban estuary. Spatial differences were generally related to unsaturated fatty acids (mono- and polyunsaturated, of the n-3 and n-6 series) in all species, albeit more pronounced in P. microps. Multivariate models returned high classification accuracies for the three sampled sites, varying from 73.3% in the invertebrate species to 100.0% in the fish species. Results show the applicability of the developed FA-based index, particularly due to the easy of communication, for managers and the public alike, but also highlight the need for prior validation on species suitability or sensitivity to depict environmental contamination.