Fig. 5.

Conceptual summary of the influence of radial oxygen loss (ROL) on defence against sulphide intrusion in Halophila ovalis and Zostera muelleri. Seagrasses enhance sulphide production in bulk sediments owing to release of exudates and decomposition of underground tissue (blue text in box). On the microscale (white text in box), growing roots lose oxygen from root tips, which works to defend against sulphide intrusion into vulnerable young roots by both abiotically oxidising sulphides in the rhizosphere, as well as promoting the colonisation of sulphide-oxidising cable bacteria (shown in purple) and decreasing the colonisation of sulphate-reducing bacteria (shown in yellow)