Spatial distribution of pollutants along the Galician coast: Insights from starfish bioindicators

Identifying suitable aquatic organisms for biomonitoring of marine waters is crucial for effective environmental management. In this study, for the first time in the region, starfish were used as bioindicator of water quality to evaluate the Galician coast, with rich biodiversity and one of the largest maritime import hubs in Europe. For this purpose, this study focused on two common starfish species in the area: Marthasterias glacialis and Asterias rubens. Samples were collected between January and February 2021 from eight specific locations along the Galician coast, each characterized by unique features and varying levels of anthropogenic pressure. The analysis included 17 organochlorine pesticides (OCPs), as well as 17 trace elements. Notably, and for the first time in this context, saponins and marine toxins (including amnesic, lipophilic and paralytic toxins) were also analyzed in all collected samples. The results revealed that concentrations of inorganic and organic compounds in starfish were comparable to those found in other organisms traditionally used as bioindicators in the same region, such as mussels and oysters. Moreover, the obtention of saponin content at different sampling sites allows for comparisons among areas, making it possible to assess whether significant differences exist. Based on the levels of anthropogenic pressures, interspecies variations and the sensitivity of these organisms to these pollutants, this study concludes that starfish have strong potential as bioindicators for monitoring water quality along the Galician coast. They could be integrated into existing coastal monitoring programs, such as those under the Marine Strategy Framework Directive, providing complementary information alongside traditional bioindicators.