(Dissolved Oxygen and 5-day Biochemical Oxygen Demand in marine waters)
Dissolved Oxygen (DO) and 5-day Biochemical Oxygen Demand (BOD5) are two important parameters indicating the general conditions of the water.
Dissolved Oxygen indicates the total amount of oxygen dissolved in the water. Most marine organisms need oxygen for respiration and maintenance of life. Dissolved Oxygen content in water can also be affected by natural factors including weather, temperature, water turbulence, hydrological conditions, algal blooms, etc. Lower DO levels may occasionally occur due to natural water column stratification phenomenon.
5-day Biochemical Oxygen Demand measures the amount of oxygen consumed by microorganisms in decomposing organic matters in water. It is generally used to reflect the level of organic pollution of environmental water.
Marine waters with BOD5 levels lower than 3 mg/L are considered of good quality.
The recent DO and BOD5 data at selected stations in 10 Water Control Zones are available on this web page.
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Remark : No monitoring was conducted at marine monitoring station MM15 in October 2008 due to adverse weather.
