Accumulation of metals and metalloids in marine invertebrates and macroalgae in False Bay (Cape Town, South Africa)

Abstract

The concentrations of 18 metal(loid)s were measured in five marine invertebrate species (Oxystele tigrine and sinensis, Marthasterias glacialis, Cymbula oculus and granatina, Parechinus angulosus, and Mytilus galloprovincialis) and five macroalgae/seaweed species (Aeodes orbitosa, Gelidium pristoides, Caulerpa filiformis, Ulva sp., and Bifurcaria brassicac formis) collected from eight sites within the marine environment of False Bay, Cape Town, South Africa. To assess the potential human health hazards associated with consumption, samples were acid digestion and analysed using inductively coupled plasma optical emission spectrometry (ICP-OES). The analysed elements included trace metals (Fe, Mn, Zn) toxic metals (Pb, Cd, As), transition metals (Ta, Ti), alkali metals (Li), and metalloid (Se, As). Metal concentration varied widely among species and locations, with values ranging from Zn: not detected (nd)—3836.04 mg/kg dry weight (dw); As: nd—77.98 mg/kg dw; Pb: nd—301.15 mg/kg dw; Li: nd—97.28 mg/kg dw, indicating diverse metal accumulation patterns. Human health risk was evaluated using the target hazard quotient (THQ) and hazard index (HI). Arsenic consistently exceeded the THQ threshold of one across all sites, and all the HI values were greater than one for all edible species, suggesting potential non-carcinogenic health risks associated with the consumption, except for M. glacialis, which is not commonly consumed. The HI metrics demonstrate the adverse impacts of metal concentration in marine biota. The observed spatial and biological variability in metal accumulation highlights the limitations of relying solely on metal concentrations for assessing health risks, food safety or anthropogenic contamination, and therefore more frequent and comprehensive monitoring is recommended.