quality in the inner Gulf of Thailand, into which the Chao Phraya, Tha Chin, Pak Panang, and Rayong Rivers and several canals discharge, revealed high concentrations of domestic pollutants. Very low DO levels (0.3, 1.8, 3.5 mg/L) were found in the areas of Klong 12 Thanwa, Mae Klong, and Tha Chin. Additionally, TCB and heavy metal levels appeared to be higher than allowable standards in the same areas. In Bang Pakong District the level of total suspended solids (TSS) appeared to be high. The western seaboard generally appeared to have "good" water quality. However, TCB levels in some areas where domestic waste water discharged into the sea without treatment exceeded the standard. Water quality in most areas of the eastern seaboard was in "good" condition, except for high levels of total suspended solids and TCB in the areas of Laem Chabang and Map Ta Phut. Despite rapid growth, overall coastal water quality in the Andaman Sea were still in "very good" condition, except for the few areas that revealed concerns of DO and TCB levels. Water pollution has become obvious in many areas. In 1997, hundreds of thousands of fish and other aquatic life in the Nam Phong River died as a result of industrial pollution. Large amounts of arsenic were found in the groundwater in Nakhon Si Thammarat Province, a result of mining in the area. Pollution affects the marine environment. Red tides, caused by excessive algae growth and a result of pollution, oil spills, and invasive species are some of the factors that are affecting Thailand's marine biodiversity. Another major source of pollution are the heavy metals that have seeped into the rivers of Thailand. In the Chao Phraya estuary, mercury levels have far exceeded normal standards, and high concentrations of heavy metals on the river bed pose a serious threat to ecosystems. In March 2017 Associate Professor Thon Thamrongnawasawat, vice dean of the fisheries faculty of Kasetsart University, said, "... there is something terribly wrong with the Thai sea [Gulf of Thailand]." His observation followed on the deaths of two Bruda whales and two whale sharks in the Gulf of Thailand since the beginning of the year. The latest casualty is a 12-metre Bruda whale weighing about two tonnes. It washed ashore in Village Nine of Tambon Thongchai, Bang Saphan District, Prachuap Khiri Khan Province. Earlier, one six-month old Bruda whale was found dead on the beach