Heavy metal contamination and ecological risk assessments in the sediments and zoobenthos of selected mangrove ecosystems, South China

• Vegetation types significantly influenced the levels of heavy metal in zoobenthos.
• Regional human activities influenced heavy metal levels in mangrove sediments.
• Mangrove sediments posed considerable ecological risk of heavy metal contamination.

Mangrove ecosystems provide ideal habitats for many marine organisms, but few studies have been conducted on the possible impact of heavy metals on these fragile inter-tidal estuarine wetlands. This study aimed to investigate heavy metal contamination in the sediments and zoobenthos in different mangrove ecosystems of southern China and to evaluate potential ecology risks of heavy metals in the sediment of mangrove ecosystems. Significant differences among different geographical regions were observed for the contents of Cu, Zn, As, Cd, and Pb in the sediment, while no significant differences were found among different vegetations. Except for Pb, the heavy metal contents in two species of crabs (Perisesarma bidens and Parasesarma plicata) in the Aegiceras corniculatum forest were lower than those in Bruguiera gymnorrhiza forest or Pagatpat forest. The sediment in the most mangrove ecosystems of China posed considerable or moderate ecological risk. Correlation analysis and principal component analysis (PCA) revealed that Cr, Cu, Zn and Pb were mainly derived from anthropogenic activities such as industrial effluents and domestic sewage.