Fig. 1.

Spatial structure and physicochemical environment experienced by microbes within the coral skeleton. The close-up depicts a typical skeletal pore populated by a range of autotrophic (green) and heterotrophic microbes (other colours). These organisms typically experience daily fluctuations in pH (from 7.5–8.5) [41], oxygen (10–210% air saturation) [15] and light (0–10% of PAR and 0–80% of NIR) [29]. In addition, they are exposed to enriched levels of dissolved inorganic phosphorus (DIP) and to concentrations of dissolved inorganic nitrogen (DIN) 10 times higher than in reef water [31, 40]. Outline of the coral from [54]