Proliferation of <i>Salvinia molesta</i> at Lake Kyoga Landing Sites as a Result of Anthropogenic Influences

Abstract

Salvinia molesta (native of south-eastern Brazil) is a free floating aquatic fern that has spread to several countries around the globe including Uganda. Under optimum growing conditions, the plant is capable of spreading rapidly where it can have immense environmental, economic and human health impacts. Thick mats of the weed have been recorded in some parts of Lake Kyoga, Uganda where it hinders the abstraction of water, docking and boat take-off, bathing and swimming activities. Therefore this study aimed to determine the extent of S. molesta at selected landing sites in Lake Kyoga and the influence of anthropogenic activities on the weed coverage as well as the effect of physico-chemical parameters of the water on the development of the weed. Quadrats were used to ascertain the coverage of S. molesta while the physico-chemical parameters were determined by standard methods. The results showed significant positive correlation of S. molesta weed coverage with phosphates (PO 4 -P) and negative correlations with pH, dissolved oxygen (DO) and water flow rate. Though statistically insignificant waste sites re- ). Salvinia molesta distribution in Lake Kyoga is linked to nutrient (PO 4 -P) supply, proximity to the shoreline and the associated anthropogenic activities. Hence waste sites, gardens and boat docks enhance S. molesta invasion in Lake Kyoga. Therefore, sources of nutrients (phosphates) into Lake Kyoga that favour the proliferation of S. molesta should be minimized through adequate waste treatment and prohibition of How to cite this paper: Andama, M.,

Determination of the Connectedness of Land Use, Land Cover Change to Water Quality Status of a Shallow Lake: A Case of Lake Kyoga Basin, Uganda

“…I has an estimated 9.4 million people [65], which is 22% of the total Ugandan population. Lake Kyoga is one of the major lakes in Uganda, connected to L. Victoria by the Victoria Nile, part of the River Nile that flows up to Egypt [64]. It lies in the country's central part, plays a crucial role in fisheries, water supply, and climate change moderation, and has a vast irrigation potential.…”

“…The flow pattern of the rivers in the lake's catchment, their hydrology, and their contribution to the lake's water guided the choice of the eastern arm as the study area. Few limnological and LULC change studies have been carried on this lake since the 1980s [64,67,[70][71][72][73], hence the paucity of data and information on many aspects.…”

“…Part of the lake's wetlands and satellite lakes, i.e., Bisina and Opeta, are designated Ramsar sites, particularly important for the conservation of birds and ecotourism [74]. Other economic activities in the study area include urbanization, settlements, navigation, and industry [64]. These activities, together with deforestation and wetland degradation, mainly for agricultural purposes, are negatively impacting the water quality of the lake negatively.…”

“…Using a Van Dorn Sampler (2L) at 0.5 m, sampling for laboratory-based parameters was done. This depth was chosen to represent the water column since the lake is shallow, with an average depth of 3 m [64], although the average depth at the study area was 5.4 m attributable to the floods. Unpreserved water samples were taken in triplicates for BOD 5 measurement, using 500 mL glass bottles.…”

“…There are several other studies at the global level that have been carried out to show the nomic activities are the primary drivers of the anthropogenic impacts on land, environ ment, and water resources [22,45,66]. These impacts affect shallow lakes more; hence L Kyoga is facing significant threats which could be responsible for the proliferation of in vasive water weeds, such as Salvinia molesta and Eichhornia crassipes [64,67]. Despite al these threats, detailed studies to link LULC activities in the catchments of L. Kyoga and its water quality have not been carried out.…”