Monitoring of Marine Water

The EPD's marine monitoring programme is designed to assess the water quality of Hong Kong's marine waters. It does this by testing samples taken from different locations for over 20 parameters, and assessing the extent to which these samples comply with the key parameters of the WQOs (i.e. those that can be clearly measured). These key parameters include:

Taking water sampling using an electronic crane

• Of the physical and chemical aggregate properties: dissolved oxygen (bottom and depth-averaged);
• Of the nutrients and inorganic constituents: total inorganic nitrogen and unionised ammonia;
• Of the biological and microbiological features: chlorophyll-a (for the Tolo Harbour and Channel WCZ only), and E. coli (for all subzones of WCZs that are classified as being for 'secondary contact recreation' or 'fish culture').

The EPD's marine monitoring programme was developed in the 1980s and has since been further refined and augmented. The EPD was first founded in 1986, when one of its tasks was to take over the monitoring activities being run by different Government departments, including the Marine Department and the (former) Agriculture and Fisheries Department. The newly-established EPD consolidated the various programmes into a single comprehensive monitoring programme, which now includes monitoring of marine water, sediment and phytoplankton. The programme is currently run by the Monitoring Section of the EPD's Waste and Water Science Group, and is used to indicate the health of Hong Kong's bodies of water, reveal long-term changes, assess the effectiveness of pollution control measures, and plan further water policies and strategies.

Monitoring of Marine Sediment

Measuring electrochemical potential of marine sediment collected by a grab sampler

In addition to water testing, the quality of the marine environment can be assessed by the monitoring and testing of sediment. Sediment is the ultimate resting place of all pollutants in the sea. Marine pollutants occurring at levels that are too low to measure in water can be identified in sediment. Such toxic contaminants not only affect a variety of organisms living within or on the surface of the sediment, they can also build up in the food chain, for example in fish or shellfish, and be harmful to humans or animals.

The EPD tests sediment in different parts of Hong Kong for over 60 physical, chemical and biological parameters. Using detailed Government guidelines ('Environment, Transport and Work Bureau Technical Circular ETWB(W) No. 34/2002 - Management of Dredged / Excavated Sediment'), the EPD compares any contaminants in sediment against a 'Lower Chemical Exceedance Level' and an 'Upper Chemical Exceedance Level'. Based on these two levels, sediment is categorised into three types ranging from 'not contaminated', through 'slightly contaminated', to 'heavily contaminated'. This categorisation is important when it comes to activities like sediment dredging or removal, because it affects how those involved in such activities must handle and dispose of the sediment. Sediments are sampled twice a year, and data is usually based on mean five-year values.

Monitoring of Phytoplankton

Phytoplankton analysis using an inverted microscope

Phytoplankton monitoring is designed to track changes in phytoplankton populations at certain key locations. Phytoplankton is the first biological component to respond to nutrient enrichment of marine water, so monitoring them provides the EPD with essential information for addressing the problem of nutrient enrichment. The EPD's monitoring of phytoplankton has been a longstanding part of its marine monitoring programme since the 1980s. Its scope was reviewed and expanded in 1993 and 1994 to become more systematic and comprehensive. It has been particularly important in providing data that has helped respond to and control the adverse effects of excessive algal bloom and red tides on Hong Kong's marine ecosystem.