Invasion Biology

Wednesday, January 24, 2007

WATER HYACINTHS THREATENS SOUTH AFRICAN MARINE SPECIES

Water hyacinth (Eichhornia crassipes) is native species in the Amazon Basin. Water hyacinth was introduced in South Africa as an ornamental plant. Now the plant has grown out of control causing havoc in South African water systems and killing marine plants. The water hyacinth is regarded as the world’s worst water weed by the IUNC (World Conservation Union), GISP (Global Invasive Species Programme) and Ramsar Convention on Wetlands of International Impotence [1].

When water hyacinth has found suitable grow conditions it can multiply its population every 12 days. Water hyacinth grows best in warm and humid conditions and water with high nutrients levels (especially from animals and human waste and agricultural fertilisers). Water hyacinth flourishes in still water particularly in shallow water because in open rivers it is washed away by floods. Water hyacinth can get rooted in the soil, flower and produce seeds. Its seeds can last up to 15 years and germinate when the conditions becomes favourable. Most of the indigenous plants are found in shallow water [1].

Water hyacinth forms floating mats on top of the water which obstruct the flow of water and shipping. The water hyacinth forms dense colonies at the edge of lakes, rivers and they smother indigenous species. Water hyacinth clogs the waterways and kills indigenous species by cutting off the sunlight and oxygen [1]. Water hyacinth also makes it for rural people to fetch water and fishing in the rivers.

Scientists discovered five different types of tiny bugs also from the Amazon so that they can kill the water hyacinth since the bugs feed on the water hyacinth in the Amazon. The bugs included the two beetles (Neochetina eichhorniae and Neochetina bruchi) which eat the leaves and crown of the water hyacinth and a mite (Orthogalumna terebrantis) which extract feeding galleries between the leaf veins. A moth’s (Niphograpta albiguttalis) larvae feed on the leaf surface and burrow into the crown of the plant. Lastly is the mirid (Eccritotarsus catarinensis) which extract chlorophyll from the leaves which causes water hyacinth to be brown [2]. Then the plant dies.

The bugs do not kill all the water hyacinth but it reduces the number of the plants from being invasive so that they can be controllable. The bugs are effective but consume a lot of time. The chemical method was also applied but the problem with it is that chemicals kill the bugs, indigenous species without killing the water hyacinth.

Although the scientists have found a way to end this problem but we are still facing yet another problem because the water hyacinth are exotic also the bugs are exotic. What will happen when all the water hyacinth has been depleted? The bugs will start eating the indigenous species or start being invasive.

REFERENCES

1. Griffith, M. Center for Aquatic and Invasive Plants. Geological Survey and University of Florida. [Internet]. Available from: http://news.nationalgeographic.com/news/2003/03/0303_030303_hyacinth_2.html

2. Langeland, K. Wetlands & Waterways. [Internet]. Available from: https://www.denix.osd.mil/denix/Public/ES-Programs/Conservation/Invasive/wetlands.html


Lethabo Mosomane
CSIR
Pretoria
0001
Tel: 27 12 841 2133
Fax: 27 12 842 3676
mail: lmosomane@csir.co.za
http://lmosomane.blogspot.com/

2 Comments:

  • Nicely structured, good coverage...just watch your grammar sometimes, okay?

    Also, I like the fact that you're concerned that the insects may become invasive, but what makes you so certain that they will do (as you say in your last sentence)?

    By Blogger NcK, at January 24, 2007 2:46 PM  

  • You mentioned it was introduced as an ornamental - a little more detail, it was I think, the aquaculture industry that introduced it. People are still advocating its introduction since it can take up excess nutrients from the water especially heavy metals. Definately some structure to your article.

    By Blogger Rich Knight, at January 24, 2007 3:03 PM  

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