Both fragile and tolerant forms of scleractinian corals decreased significantly in percentage cover in more nutrient-rich and turbid waters, while dead corals were significantly more prevalent at locations characterised by poor water quality. In contrast with lower coral cover in the more eutrophic and turbid waters, macro-algae were thriving. The cover of green, brown and red macroalgae increased as water quality became poorer. Structural ecological changes across the water quality gradient were not only evident for the benthos (i.e. cover and composition of corals and algae) but were also manifest for reef fishes. Significantly fewer species and individuals were recorded in sites of poorer water quality
(Reopanichkul et al., 2008; Reopanichkul et al., 2009). The low per-centage cover of coral recorded at Suthep Bay may be attributable to a massive landslide in late 2001 that increased turbidity, fol-lowed by impacts from terrestrial objects (e.g. log, tree branches) drifting into and smashing coral colonies during the 2004 tsunami (Worachananant 2007).