The impact of duckweed growth on water quality in sub-tropical ponds

Field experiments on duckweeds, Lemna aequinoctialis, were carried out to determine the effect of plant characteristics on water-quality variables in ponds. In view of their rapid growth rates and ability to cover water surfaces very quickly, such studies are necessary, especially in sub-tropical countries, in order to develop viable management strategies. Morphological parameters like leaf length, leaf width, and root length of individual plants along with cover percent of Lemna were studied in each pond along with important water-quality parameters. The plant parameters were related to the studied water-quality variables using regression analysis. Equations showed that changes in root length and cover, both easily measurable growth responses of duckweeds, could be used to reflect changes in two important water-quality variables like DO and phosphorus (both total and soluble reactive) concentrations in pond waters and hence be used effectively for routine monitoring. This study also gives an indication that ponds with low cover of duckweeds could possibly be more effective for prediction purposes.