Sediment–leaf trace metal relationships across four mangrove species in subtropical Australia

Abstract Aims Mangrove ecosystems regulate trace metal dynamics in coastal sediments; however, differences in trace metal accumulation in different mangrove species within the same site remain poorly understood. Understanding species-specific trace metal accumulation can lead to a better understanding of the biological controls on trace metal bioavailability, trophic transfer capacity, and metal sequestration in mangrove ecosystems. Methods We evaluated sediment–leaf trace metal relationships, species-specific accumulation patterns, and the influence of sediment geochemistry and metal bioavailability on trace metal accumulation across four mangrove species ( Avicennia marina, Aegiceras corniculatum , Rhizophora stylosa , and Bruguiera gymnorrhiza ) at four sites in Queensland, Australia. Results Leaf trace metal concentrations differed significantly among species for 10 of the 11 analysable elements. A. marina exhibited the highest concentrations of most non-essential elements, whereas Mn and Mo were highest in B. gymnorrhiza and R. stylosa . No significant species-specific sediment–leaf relationships remained significant after false discovery rate correction, though statistical power was limited. Median bioconcentration factors were below one for all species–element combinations, indicating limited transfer of trace metals from sediments to leaves. Sediment bioavailability was consistently low (ΣSEM/AVS = 0.02–0.08), and sediment geochemistry was dominated by gradients in organic matter, fine sediments and sulphides. Conclusions Species, rather than sediment trace metal concentrations, was the primary determinant of leaf trace metal accumulation. Low bioconcetration factors and low predicted sediment metal bioavailability indicate that these mangrove species may function as phytostabilisers, limiting trace metal transfer to above-ground tissues. Consequently, sediment chemistry provides a more reliable indicator of trace metal contamination than leaf tissues in mangroves.