Ceratophyllum demersum as an indicator of mercury contamination in Thailand and Finland

Ceratophyllum demersum L. is a submerged plant commonly occurring in freshwater in Thailand and in many other countries. Shoots of this plant collected near a caustic soda factory in Thailand contained from 0.67 to 4.62 ppm (mean 1.72 ppm) of mercury (dry weight), while those from the control area had only 0.03 to 0.08 ppm (mean 0.04 ppm) of mercury. Some samples of the plant collected from polluted areas in Finland also had elevated mercury contents, 0.21 to 1.10 ppm as compared with 0.05 ppm in a sample from an unpolluted area. Thus, this plant is suitable as an indicator species for monitoring mercury contamination.