Abstract:
Research was conducted to investigate the potential of Wolffia globosa (Roxb.) Hartog
& Plas as bioindicator of copper and zinc contamination in natural water resources. The
investigation was carried out under laboratory conditions containing different amounts of zinc
and copper. The impact of build up of metal concentration on some metabolic parameters such
as visible symptoms, relative growth, biomass productivity, and chlorophyll determination
were also studied. W. globosa was cultured in 1% Hoagland’ s nutrient solution with copper
and zinc separately at concentrations of 0.07, 0.83, 1.66, 3.31, and 6.62 mg/L, respectively.
After 3, 6, 9, 12, and 14 days of exposure, W. globosa was separately harvested to determine
the effects of copper and zinc on plant morphology, relative growth, biomass productivity, and
chlorophyll content. The results revealed the concentrations of copper at ≥ 0.83 mg/L showed
inhibitory effects on morphology, relative growth, biomass productivity of W. globosa since
the first three days of exposure and became more apparent when the exposure time was
increased. At the same concentrations, zinc tended to have less effect on morphology, relative
growth and biomass productivity than Cu. The morphological damage of plants treated with
zinc could not be observed by the naked eye. The recent research suggested that W. globosa
has a potential to be used as a bioindicator for copper contamination.
The ability of W. globosa to accumulate copper and zinc was investigated. The results
revealed that W. globosa has less capacity to remove zinc and copper. The highest amount of
copper accumulated by W. globosa was 16.07 mg/kg dried weight (at the first 3 days of
exposure) while the highest amount of zinc was 131.23 mg/kg (at 6 days of exposure).
Furthermore, copper and zinc showed the inhibitory effect to the accumulation rate of each
other when they were mixed together at the ratio of 1:1 (v/v).