The effect of water Hyacinth, Eichhornia Crassipes, infestation on phytoplankton productivity in Lake Naivasha and the status of control

Abstract

The paper presents data collected in an assessment of effects of water hyacinth infestation on phytoplankton productivity in Lake Naivasha. A summary of the status of control and strategies for the future is given. The ecological effects of water hyacinth, Eichhornia crassipes, on Lake Naivasha have received little attention compared to the large body of work available on the weed’s socioeconomic impact on the country’s water ways and methods for its removal. This study was conducted to determine if water hyacinth infestation in Lake Naivasha affects phytoplankton productivity. Several sampling stations were set up in the lake at sites where the floating mats of the weed were present and sites where the weed was absent. Phytoplankton chlorophyll-a concentration and dissolved oxygen were measured at each station and used as proxies for phytoplankton productivity. The study findings show that phytoplankton productivity is reduced when water hyacinth is present, suggesting that the water hyacinth is not only a nuisance but that it can also alter the ecology within a lake by changing species composition and biodiversity. Although water hyacinth has continued posing serious ecological consequences, there is hope that the control strategies already adopted will continue to reduce deleterious impacts and allow sustained development in the Lake Naivasha Basin. There is, however, a great need to undertake research to quantify the levels of damage, and the costs of control, loss of livelihood, disease, and disruption of normal operations caused by water hyacinth.