Let’s talk about Water Hyacinth today, which is a big problem for China’s ecosystem. Water Hyacinth (Eichhornia crassipes), which originated in South America, was introduced into China in 1930s due to extremely limited food supply during war times. Then it was used to supplement the feed for stock raising in 1960-70s. So far, so good.
Then the evil side turned up. We abandoned using it because of limited nutritive value and it becomes wild. The rampant overgrowth occupies the reservoirs and lakes, and blocks the river ways and the irrigation channels, causing irreversible destroys to the ecosystem, reducing biodiversity, and obstructing agricultural development and water transport. We suffered a lot from the uncontrollable propagation, including enormous death of aquatic organism, and increased frequency of eco-disasters. The loss is up to billions of dollar each year due to the invasion of foreign species.
So how does it kill others? The mass propagation of water hyacinth could cover the whole surface of rivers or lakes. It reduces the air exchange between atmosphere and the water, and blocks the penetration of sunshine, suppressing the growth of plankton and depriving lives of other aquatic creatures. Moreover it could change pH value of water, decrease the dissolved oxygen, and destroy the underwater food supply chain. In some severely afflicted areas, the biodiversity declines rapidly, and some local species (including aquatic animals and plants) are almost extinct. For instance, the Dianchi Lake, in Yunnan, China, used to have 16 species of aquatic plants and 68 animals before 1960s. Then the lake was occupied by water hyacinth by up to 1000 hectares. As a result, most aquatic plants died out and only 30+ species of animals survived in 1980s.
It is not totally useless, however. Some may think water hyacinth causes the eutrophication plankton. In fact, it can suppress plankton propagating and cleanse the water with eutrophication. As competing species, the water hyacinth would absorb the sunshine and minerals also as needed by plankton. Besides, some chemical compounds secreted by the root of water hyacinth can kill the cells of plankton by damaging the intracellular ion balance.
The water hyacinth is also good at absorbing pollutant and therefore purifies the wastewater. But attention should be paid as the water hyacinth itself can become concentrative in heavy metal irons and other poisonous chemicals, so we should keep it away from other wildlife and dispose carefully by landfill as explosive gas could result from the process. Due to concentration of pollutant, we have to avoid eating the fish and other underwater animals in polluted areas because they feed on water hyacinth.
To help mitigate the problem of overgrowth of water hyacinth, China Science Academy introduced two kinds of insects (Neochetina eichhorniae and N. bruchi hustache) from US and Argentina, which eat water hyacinth only. The insects have already suppressed the propagation of water hyacinth in designated areas and will provide long term and robust balance compared with manual and chemical control. Story continues.
Jiang, H. and Zhang, H 2003, Research review of control of water hyacinth (Eichhornia crassipes). China agricultural technological herald.
Ding, J. and Fu, W 1996, Biological control: using biodiversity to protect biodiversity. 4, (4), pp 222-227.
Jianqing, D., Ren, W., Weidong, F., & Guoliang, Z 2001, Water hyacinth in China: Its distribution, problems and control status. Biological and integrated control of water hyacinth, Eichhornia crassipes, 102.
By Lin (u4616660)