Estimations of anthropogenic nutrient flows at the coral reef island Ko Sak, Thailand : A simplified source flow analysis

Sammanfattning: High levels of nutrients in tropical coastal areas is a big problem and poses large threats to coral reefs. Therefore this study will focus on nutrient flows from a source perspective. The aim of this study is to identify and quantify the phosphorus and nitrogen emissions from human activities at the island Ko Sak, Thailand. We also investigated possibilities regarding reduction of these emissions. The study was conducted by first identifying the major nutrient emitting human activities during two separate days and then quantifying them one by one. Data was acquired through a combination of personal field observations and literature studies. The following four sources were identified as the most interesting in terms of nutrient emissions: toilet waste on the island, boat sewage, littering (fruit and coconut leftovers) and liquid restaurant waste. The result shows that the sources to the largest phosphorus emissions were littering and toilet waste, while the phosphorus from boat sewage and liquid restaurant waste was lower in comparison. The largest source of nitrogen emissions was toilet waste. In combination with boat sewage they accounted for about 80 % - 90 % of the total nitrogen emissions. The liquid restaurant waste was also in this case very small in comparison and littering completely negligible. The total phosphorus emissions were 514 g/day on April 13 and 438 g/day on May 8 and the total nitrogen emissions were 1750 g/day on April 13 and 1990 g/day on May 8. The two areas identified with largest potential in terms of reducing nutrient emissions were toilet waste and littering due to their relatively large emissions combined with relatively simple flows. Examples of solutions presented is a more controlled toilet waste management system and substituting certain food sold.