Wastewater discharge degrades coastal waters and reef communities in southern Thailand.

Runoff and sewage discharge from land developments can cause significant changes in water quality of coastal waters, resulting in coral degradation. Coastal waters around Phuket, Thailand are influenced by numerous sewage outfalls associated with rapid tourism development. Water quality and biological monitoring around the Phuket region was undertaken to quantify water quality and biotic characteristics at various distances from sewage outfalls. The surveys revealed strong gradients in water quality and biotic characteristics associated with tourism concentration levels as well as seasonal variability. Water and reef quality tended to decrease with increasing tourist intensity, but improved with increasing distance from sewage discharge within each of the three study locations. In addition, the effect of wastewater discharge was not localised around the source of pollution, but appeared to be transported to non-developed sites by currents, and exacerbated in the wet season.