User:Ljfaith/sandbox

The release of massive amounts of untreated wastewater (sewage), agricultural and industrial runoff directly into Lake Victoria over the past 30 years, has greatly increased the nutrient levels of nitrogen and phosphorus in the lake “triggering massive growth of exotic water hyacinth, which colonised the lake in the late 1990’s”. This invasive weed creates anoxic (total depletion of oxygen levels) conditions in the lake inhibiting decomposing plant material, raising toxicity and disease levels to both fish and people. At the same time the plant’s mat or “web” creates a barrier for boats and ferries to maneuver, impedes access to the shoreline, interferes with hydroelectric power generation, and blocks the intake of water for industries. On the flip side, water hyacinth mats can potentially have a positive effect on fish life in that they create a barrier to overfishing and allow for fish growth, there has even been the reappearance of some fish species thought to have been extinct in recent years. However, the overall effects of the water hyacinth are still unknown.

Growth of the water hyacinth in Lake Victoria has been tracked since 1993, reaching its maxima biomass in 1997 and then declining again by the end of 2001. Greater growth was observed in the northern part of the lake, in relatively protected areas, which may be linked to current and weather patterns and could also be due to the climate and water conditions, which are more suitable to the plants growth (as there are large urban areas to the north end of the lake, in Uganda).

The weed was first attempted to be controlled by hand, removed manually from the lake, however, re-growth occurred quickly. Public awareness exercises were also conducted. More recently, measures have been used such as the introduction of natural insect predators, including two different water hyacinth weevils and large harvesting and chopping boats, which seem to be much more effective in eliminating the water hyacinth.