Can a 16th Century Shipwreck Be Considered a Mercury Source in the 21st Century?—A Case Study in the Azores Archipelago (Portugal)

During the Spanish colonial era, ships frequently transported mercury across the Atlantic to the New World to be used in gold mining. As many of those eventually sank, shipwrecks may represent a local source of mercury contamination in the marine environment. In this context, evaluating mercury contamination in coastal sediments and mercury magnification in marine food webs is crucial for understanding mercury dynamics and estimating exposure to marine life in locations where shipwrecks occurred. This study investigated mercury concentration present in coastal sediments and biota from three distinct groups: macroalgae (Asparagopsis armata and Ulva lactuca), gastropods (Littorina striata and Patella candei gomesii) and crustaceans (Palaemon elegans and Pachygrapsus marmoratus) collected in the Azores Archipelago, Portugal (one site near a 16th-century shipwreck and others in locations further away). Mercury analyses indicated that the sediments and species from the shipwreck area had significantly higher mercury levels than the other areas. Fine sediments showed values above those established in sediment quality guidelines; however, considering the mercury concentration of the total sediment fraction, adverse biological effects are not expected to occur. Moreover, increased mercury concentration from primary producers to consumers reinforced the biomagnification potential of this metal.