ASSESSING TROPHIC STATE AND WATER QUALITY OF SMALL LAKES AND PONDS IN PERAK

There are thousands of ponds and small lakes in Perak created naturally or as a result of past mining activities in the 1800s and 1900s. Some of these small water bodies have been converted to lake park to provide other ecosystem services such as recreation besides having potential to be used as alternative water supply. Most of these lakes were not monitored nor evaluated in terms of their water quality or trophic conditions to enable better understanding of their safe application for recreation. Water quality sampling was performed at sixteen lakes and ponds in Perak involving in situ and ex-situ measurements of ten environmental parameters. About six lakes have very low dissolved oxygen (DO) levels needed to sustain aquatic life and few lakes have very low transparency levels (<0.3 m) to be compatible for primary contact recreational use. More than 75% of the study lakes and ponds were nutrient rich. Trophic state analyses using different indices developed for temperate and tropical environments showed one lake in oligotrophic condition, five lakes in mesotrophic to eutrophic conditions and 10 lakes in eutrophic to hypereutrophic conditions. Hypereutrophic lakes were characterised as having low DO, high nutrient, turbidity, and chlorophyll a. This study found some deviations among the trophic classification of lakes between temperate and tropical indices and suggests the use of a suitable trophic index to provide better understanding of the trophic conditions of waterbodies in Perak. Continuous monitoring using the specific water quality criteria and standards for lakes will support preservation of lake ecosystem health.