Sulphate reduction associated with roots and rhizomes of the marine macrophyte Zostera marina

The activity, the location and the oxygen sensitivity of sulphate reducers associated with sediment-free roots and rhizomes of the seagrass Zostera marina were investigated. Sulphate reduction rates were determined after treatment of roots and rhizomes with hypochlorite or exposure to air. Untreated roots and rhizomes served as controls, In general, root-as well as rhizome-associated sulphate reduction rates were high (20 to 50 mu mol SO42- gdw(-1) d(-1)). After surface sterilisation, the sulphate reduction rates decreased by about 90 %, indicating that most of the sulphate reducers were associated with the surface of the roots and rhizomes. Pre-incubation of roots for 8 h in the presence of 0 to 20% oxygen (in steps of 2 %) did not affect the sulphate reduction rates determined posterior under anoxic conditions. This demonstrates a high tolerance of root surface-associated sulphate reducers towards oxygen.