Spatial and species-specific variation in trace metal contamination in beach bivalves unveils complex environmental...

Trace metal (As, Cd, Cr, Cu, Ni, Zn, Pb and Hg) concentrations were assessed in bivalves Tivela mactroides and Donax hanleyanus, from 35 beaches along the Northern Coast of São Paulo State, Brazil. Arsenic and lead exceeded the maximum limits permitted in seafood in 100 % and 14 % of the samples, respectively, raising concerns on the risks to ecosystem and human health. We observed a clear distinction in metal composition between species, but hotspots varied between trace metals and no clear spatial patterns were reported. Overall, variations were not explained by urbanization or beach morphodynamics. Species-specific physiological responses to contaminants, varied sources of trace metals and the highly dynamic environment increase the complexity and pose challenges for beach biomonitoring. Thus, using both bivalves as complementary biomonitors for broader spatial assessments is not recommended. Further research is needed to understand species-specific responses in clams and other taxa, ensuring more reliable biomonitoring strategies in beach environments.