## 4 Conclusions  
There is a large gap in available environmental data in the coastal area of the Atacama region. Even though the region serves as an excellent natural laboratory because of meteorological and oceanic dynamics (Humboldt Current, flooding, tsunamis, presence of wetlands and protected areas), historical and contemporary anthropogenic impacts have not yet been studied in detail. Waste discharges from mining activities for more than 50 years, through the Salado River, and the influence on the surrounding areas, such as Pan de Azucar National Park (PA) and, to a lesser extent, Flamenco Bay (PB), determines the contamination associated with each area studied. Thus, the results of the current study showed that the coastal sediments within a short stretch of 80 km are polluted by Bi, Ca, As, Ag and Cd. The average As concentration in the sediments (39.88 mg kg\({}^{-1}\)) was above the threshold effect level, with the highest concentrations found in PB (a tourist and benthic management area). The algal biomonitoring revealed a gradient of physiological stress from south to north, with PA (the national park), despite being an exclusive conservation zone, registering the poorest health status (greater Cu bioaccumulation in algae tissue, higher photosynthetic stress in macroalgae and lower biomass of microalgae). Although As concentrations were significantly higher in sediments from PB, an important amount of Cd was found in the leaves of _L. bertoreana_ at this site. A significant concentration of toxic elements, such as As, Zn, Cu, Pb and Fe, were found in PC, but the results showed that these were not responsible for the toxicological effects in algal species. The current study highlights the need for further research, including more marine organisms and sites, as well as the application of national guidelines for the quality of marine sediments. Future research recommendations would also include oceanographic studies to determine marine currents' influence.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app13116360/s1](https://www.mdpi.com/article/10.3390/app13116360/s1)]([https://www.mdpi.com/article/10.3390/app13116360/s1](https://www.mdpi.com/article/10.3390/app13116360/s1)), Figure S1: Granulometry results from accumulated retention per particle size for samples from (a) PA, (b) PB, (c) PC, (d) total; Figure S2: Grain-size sediment distribution of collected sediments samples (PA, PB, PC, \(n=3\)); Table S1: Detection limit (DL) and quantification limit (QL) for water, sediment and algal samples from the current study.  
Conceptualisation, E.B. and E.C.; methodology, all authors; software, E.B., E.C. and Y.R.-L.; validation, all authors; formal analysis, E.B., E.C. and Y.R.-L.; investigation, all authors; resources, all authors; data curation, E.B., E.C., Y.R.-L. and A.G.; writing--original draft preparation, all authors; writing--review and editing, all authors; visualisation, E.B. and E.C.; supervision, E.B.; project administration, E.B.; funding acquisition, E.B. All authors have read and agreed to the published version of the manuscript.  
Not applicable.  
The authors are grateful for the project ATA20992 from MINEDUC. [PERSON] is grateful for ANID/FONDECYT 11180015 and [PERSON] is grateful for the M2616 Project and TSUARA Project M2615, funded by Universidad Rey Juan Carlos (Spain).  
The authors declare no conflict of interest.