Could mangrove plants tolerate and remove BDE-209 in contaminated sediments upon long-term exposure?

Highlights: • Constructed mangrove wetland removed > 40% of BDE-209 in sediment within two years. • Mangrove plants could take up and accumulate BDE-209 and debrominated congeners. • Aegiceras (Ac) had more uptake of PBDEs than Avicennia (Am) and Kandelia (Ko). • Ko had higher translocation of BDE-209 and debrominated congeners than Ac and Am. • Am was more tolerant to BDE-209 than Ac and Ko was more sensitive mangrove species. -- Abstract: Polybrominated diphenyl ethers (PBDEs) such as BDE-209, the commonest congener, are known to be toxic. A 24-months study using mangrove mesocosms with mixed mangrove species, namely Avicennia marina (Am), Aegiceras corniculatum (Ac) and Kandelia obovata (Ko), or without any plant was conducted to examine toxicity, removal, translocation and uptake of BDE-209. At month 24, BDE-209 stimulated the production of root superoxide radical (O₂^−*), and leaf and root malondialdehyde (MDA) of Ko, enhanced leaf O₂^−* of Ac, but did not affect the production of O₂^−* and MDA in Am. These findings indicated that the tolerance to BDE-209 was species-specific, with Am being the most tolerant and Ko the most sensitive species. In leaf and root, BDE-209 stimulated peroxidase (POD) activity in both Ac and Ko, and superoxide dismutase (SOD) in Am. After 24-months, more than 60% and 40% of BDE-209 in contaminated sediments were removed in planted and unplanted groups, respectively, with more PBDEs in upper than bottom sediment layers. This study demonstrates that planting tolerant species such as Avicennia marina with high uptake could remedy PBDEs in contaminated sediments.