by Dr.Avantika Bhaskar
This beautiful purple flowered plant is believed to be one of the world’s worst water weed. Invasive species like this reduce native species abundance and richness, decrease genetic diversity and alter ecosystem services and processes. Eichhornia crassipes (Mart.) Solms (Pontederiaceae), commonly known as Water Hyacinth is a native of Amazon basin, South America from where it has spread to more than 50 countries in five continents over the past 150 years because of human activities. The weed has been reported to have reached India in 1902. It appeared initially in Bengal and has now spread throughout the country. It has invaded variety of wetlands like lakes, ponds, tanks, estuaries, marshes, slow flowing rivers, etc.
Water hyacinth is a free-floating perennial aquatic plant with broad, thick, glossy, and ovate leaves. The leaves have long, spongy and bulbous stalks. The plant bears a spike of 8-15 flowers with six petals. The plant flowers throughout the year producing up to 3000 seeds which can live up to 20 years. It also vegetatively propagates horizontally through growing stolons.
The species exhibits rapid growth rate and extensive seed dispersal capabilities. It also shows broad environmental tolerance and grows profusely in nutrient rich water contaminated with urban and agricultural runoffs. Owing to these characteristics it successfully competes with other aquatic plants leading to drastic changes in plant and animal communities. It also impacts physico-chemical properties of water like causing decline in temperature, pH, Biological oxygen demand and nutrient levels. In some cases a decline in dissolved oxygen has been observed resulting in fish mortality.
All these changes subsequently result in reduced water quality, affect water storage capacity and irrigation hampering agriculture, impact fisheries, block waterways and hydropower generation, etc. It also increases the breeding habitat for mosquitoes, snails and other harmful microorganisms.
Though difficult the weed can be controlled through physical, chemical and biological means. Physical methods include drainage of water body followed by manual or mechanical removal using weed harvesters, crusher boats, etc. Chemical method involves use of herbicides. Biological control of water hyacinth uses native enemies of water hyacinth like some weevil beetles, moth species and some fungal pathogens. A new strategy developed for controlling the spread of water hyacinth is through its utilization for various purposes like waste water treatment, as a substrate for bioethanol and biogas production, as livestock feed, medicines, fibre, etc. It can also be processed for making paper, baskets, ropes, mats, etc.
Tamil Name: Aagaya Thamarai, Kula Vaazhai
- Jafari, N. Ecological and socio-economic utilization of water hyacinth (Eichhornia crassipes Mart Solms). (2010). J. Appl. Sci. Environ. Manage., Vol. 14(2):43 – 49.
- Lancar, L. and Krake, K. Aquatic Weeds & their Management. International Commission on Irrigation and Drainage, March 2002.
- Téllez, T., López, E., Granado, G., Pérez, E., López, R., and Guzmán, J., 2008. The water hyacinth, Eichhornia crassipes: an invasive plant in the Guadiana River Basin (Spain). Aquatic Invasions 3: 42-53.
- UNEP Global Environment Alert Service. Water hyacinth – Can its aggressive invasion be controlled? April, 2013. unep.org/pdf/UNEP_GEAS_APRIL_2013.pdf
- Zhang, Y. Y., Zhang, D. Y., and Barrett, S. C. (2010). Genetic uniformity characterizes the invasive spread of water hyacinth (Eichhornia crassipes), a clonal aquatic plant. Molecular ecology, 19(9), 1774-1786.