When someone plants a water hyacinth to liven up the flora in his garden pond, the idea of initializing the spread of an invasive species is probably not the first thing to come to mind. Not only does water hyacinth impede Lake Victoria fisherman from doing their jobs, but it also blankets the surface of the lake and prevents underwater aquatic species from getting essential sunlight. Efforts have been made to mitigate the spread of the water hyacinth, most notably the introduction of the Neochetina weevil to Lake Victoria. Through these efforts using biocontrol and the effects of El Nino, the water hyacinth population was at a time diminished significantly. However, the population is only recently starting to once again emerge and thrive in Lake Victoria.
According to Wilson et al. (2007), the decline in the water hyacinth population was primarily due to the Neochetina weevil. While evidence certainly points to most of the damage to the population being due to the waves caused by El Nino, Wilson et al. (2007) claims that the weevils are what truly kept the hyacinth in check. The article even goes as far as to say that “the El Nino event may have been a major stress to the plants…[but] the plants were already badly damaged by the weevils” (Wilson et al. (2007)) which just goes to show how the weevils played a major role in water hyacinth reduction.
On the other side of the spectrum, Williams et al. (2007) does not accredit the Neochetina weevil as the chief agent in reducing the water hyacinth in Lake Victoria, but instead the severe weather patterns of El Nino. Through use of graphs and hard scientific data of hyacinth population through time, Williams et al. (2007) claims that hyacinth population did not actually decline until El Nino caused the waves which uprooted most of the population in Lake Victoria.
While both articles present a clear and convincing reason as to the causation of the water hyacinth population decline, I believe that Wilson et al. (2007) is the more legitimate of the two. Aside from being a physically longer article, I like Wilson et al. (2007) because it does not beat around the bush in how it admits that the population decline was primarily caused El Nino, but the only reason the damage was possible was because the plants were weakened by weevils prior to El Nino. Even if El Nino was the main cause for the destruction of the species, it was seen that after the storm the weevil population declined which in turn gave rise to an increase in water hyacinth population. So in summation, I feel that Wilson et al. (2007) is an overall better article. Furthermore, if you ever plan on planting anything, you would be well advised to check if this plant could possibly cause an aquatic invasive epidemic. If anything, do it for the sake of the weevils.
NASA Earth Observatory. 2007. Water Hyacinth Re-invades Lake Victoria. http://earthobservatory.nasa.gov/IOTD/vi…. Viewed 20 Jan 2010.
Williams, A. E., R. E. Hecky, and H. C. Duthie. 2007. Water hyacinth decline across Lake Victoria – Was it caused by climatic perturbation or biological control? A reply. Aquatic Botany 87:94-96.
Wilson, J. R. U., O. Ajuonu, T. D. Center, M. P. Hill, M. H. Julien, F. F. Katagira, P. Neuenschwander, S. W. Njoka, J. Ogwang, R. H. Reeder, and T. Van. 2007. The decline of water hyacinth on Lake Victoria was due to biological control by Neochetina spp. Aquatic Botany 87:90-93.