Bivalve molluscs are traditionally used in gastronomy, and their harvesting represents a critical socioeconomic activity to coastal communities. However, due to their filter-feeding behavior that facilitates the ingesting of bioavailable contaminants, regular monitoring is needed to ensure food safety. Specifically, these organisms may act as vectors for transferring metals to higher trophic levels, including humans. Arsenic (As), cadmium (Cd), lead (Pb) and mercury (Hg) are listed in the Priority Pollutant List from the Clean Water Act by EPA, as these metals require particular attention due to their high toxicity, persistence and bioaccumulation. Although the recent efforts to reduce anthropogenic emissions worldwide, historical contamination leads to considerable burdens of metals in the sediments of aquatic systems. Therefore, anthropogenic activities, seasonal storms, and tides are expected to resuspend bottom sediments, making metals available to the biota. Therefore, monitoring metals’ presence along the Portuguese coast is extremely relevant to environmental and food safety issues. This study aimed to assess As, Cd, Pb and Hg concentrations in clams (Ruditapes decussatus and/or Ruditapes philippinarum) collected monthly in aquaculture areas of three coastal lagoons (Ria de Aveiro, Ria Formosa and Óbidos Lagoon, April 2019 – January 2020). Metals quantification in the edible tissues of clams was carried out through: i) DMA-80 Evo Direct Mercury Analysis System for Hg quantification; ii) inductively coupled plasma mass spectrometry (ICP-MS), using the Agilent Technologies-7700Series equipment, for As, Cd and Pb. None of the studied metals was found above the legal limits regarding human consumption of bivalves. Clams proved to be good bioindicators of metal presence. Arsenic increased in both clams from Óbidos lagoon in the summer period, and its levels only decreased in R. philippinarum in the following months. As expected, clams from Ria Formosa and Ria de Aveiro presented higher levels of Hg than Óbidos lagoon throughout the year (Figure 1). Further fluctuations in As, Cd, Pb, and Hg accumulation due to seasonality will be discussed.
This work is part of the project DepurD (MAR-01.03.01-FEAMP-0046), supported by Portugal and the European Union through MAR2020, Portugal2020 and FEAMP