The concentration of OA in seagrass epiphytic material varied significantly between the seagrass species from which they were collected, with H. spinulosa found to have significantly more OA present in epiphytic material per wet weight of seagrass ( Fig. 3, 1). In addition, this species of seagrass was only found at Rous Channel, the site found to have significantly higher concentrations of OA when only Z.