Dependence of Phenanthrene Dissipation in Mangrove Sediment on the Distance to Root Surface of Kandelia Obovata L

Abstract

We explored the relationship between the distance from roots and rhizosphere-mediated phenanthrene (PHE) dissipation in planted mangrove sediment. A compartmentalized device (rhizobox) was used that separated root surface and four consecutive rhizosphere layers that extended 0–2, 2–4, 4–6, and >6 mm away from the root surface. Kandelia obovata L. Druce seedlings were grown for 4 months in sediment spiked with 10 mg·kg⁻¹ PHE. PHE dissipation, microbial community structure and enzymatic activities at millimeter scale in the vicinity of plant roots were analyzed. Results indicated significant differences in PHE dissipation through the various layers in the planted rhizobox. PHE dissipation exhibited the most rapid loss in the 0–2 mm near-rhizosphere layer, the lowest in far-rhizosphere (>6 mm) layer. Microbial community structure as indicated by denaturing gradient gel electrophoresis (DGGE) profiles showed that special bacterial species and larger bacterial numbers were observed in near-rhizosphere layers. Depending on the distance to root surface, near-rhizosphere bacterial species and enzymatic activities were more abundant than root compartment and far-rhizosphere, resulting in rapid dissipation of PHE.

KEY WORDS::

• polycyclic aromatic hydrocarbons (PAHs)
• rhizoremediation
• mangrove plant
• denaturing gradient gel electrophoresis (DGGE)
• sediment enzymes

ACKNOWLEDGMENTS

We extend our thanks to the National Natural Science Foundation of China (No. 30970527-30710103908) for financial support of this study. Todd A. Anderson and Darcy Chase, Department of Environmental Toxicology, Texas Tech University; Donminik Weiss, Department of Earth Science and Engineering, Imperial College London, UK, are gratefully acknowledged for their careful revising of this manuscript.