TITLE:
Proliferation of Salvinia molesta at Lake Kyoga Landing Sites as a Result of Anthropogenic Influences
AUTHORS:
Morgan Andama, Robert Ongom, Ben Lukubye
KEYWORDS:
Freshwater, Human Activities, Invasive Weed, Management, Uganda
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.5 No.11,
November
22,
2017
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
(PO4-P) and negative correlations with pH, dissolved oxygen (DO) and
water flow rate. Though statistically insignificant waste sites recorded the highest
overall S. molesta coverage (82.61 ± 21.12 m2) per 400 m2 quadrat followed by boat docks (82.24 ± 19.45 m2), gardens (50.93 ± 11.82
m2) and finally fishing areas (27.94 ± 5.93 m2) respectively.
The overall weed coverage was highest around the shoreline locations of Acholi inn
landing site (101.72 ± 22.89 m2 per 400 m2) followed by Masindi
port (60.39 ± 15.64 m2), Waitumba (41.89 ± 10.55 m2) and the
least in the offshore location at Kayei landing site (39.71 ± 10.17 m2). Salvinia molesta distribution in Lake Kyoga is linked to nutrient (PO4-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 cultivation close to the lake. Salvinia molesta coverage along the routes of moving boats should also be contained
so as to reduce the spread of the weed in the lake through boat movements. Furthermore,
eradication efforts of S. molesta weed in Lake Kyoga should be heightened
at the shoreline areas of the lake in the various landing sites within the lake
basin.