The continued discharge of untreated sewage into the waters off Kenting National Park is responsible for the deterioration of the coral reefs in the area, an academic said on Monday.
Lin Hsing-juh (林幸助), a professor at National Chung Hsing University’s Department of Life Sciences, came to the conclusion after monitoring and studying coral reef ecosystems off the nation’s southernmost tip for more than a decade.
His findings were published recently in the journal Limnology and Oceanography.
Lin said for coral reefs to thrive, they must grow in clean shallow water with a low density of anthropogenic nutrients, a stable density of salt, moderate temperature and bright sunshine.
Human encroachment in the form of excessive development and the arrival of 4 million tourists a year in the Kenting area has led to an increase in the amount of sewage in Kenting’s coastal regions, Lin said.
Lin found that Kenting’s Nanwan (南灣) and Wanlitung (萬里桐), which boast the largest concentration of tourists, have suffered the most serious entrophication, or nutrient pollution.
To facilitate his study, Lin established a mesocosm — a controlled ecosystem approximating natural conditions — to conduct extensive observations and experiments and to verify his findings.
“Outdoor field surveys can only observe the results of coral reef deterioration; they provide no clues as to the processes and causes of the degeneration,” Lin said.
With the assistance of the National Museum of Marine Biology and Aquarium in Pingtung County, Lin built a mesocosm — the first of its kind in the world — that replicated the coral reef ecosystem in Nanwan 20 years ago when there was less human activity. After 10 years of observation, simulations and experiments, Lin reached the conclusion that untreated sewage was to blame for the deterioration of the Kenting coral reef ecosystem.
To replicate the pollution in the area, Lin introduced sewage or anthropogenic (human-made) nutrients into the mesocosm at a rate of 5.5mmol per square meter. Mmol, or a millimole, is a unit measuring the amount of a substance.
“It turned out that algae grew rapidly and completely covered the coral, resulting in their death,” Lin said.
He also observed that normally passive sea anemones also began to attack the coral following the introduction of the sewage.
Overfishing, particularly of fish species that can stem the growth of algae and sea anemones, has led to a further imbalance in Kenting’s ecosystem, Lin said.
Coral reefs are natural habitats for more than 25 percent of marine life and fish output from the reefs accounts for 12 percent of the global fish catch, Lin said, adding that conservation of natural coral reef ecosystems was therefore essential.
Coral reefs are also important because they help protect the coastline, minimize beach erosion caused by big waves and tsunamis, and nurture coastal fishery resources, he said.
Lin said the most urgent task was to prevent the excessive flow of sewage or anthropogenic contaminants into the ocean and to step up efforts to conserve coral reefs and fish species.