Hecky and Bugenyi obtained higher concentrations of phosphorus near the mud surface than the upper photosynthetic zone. Hence the high coverage of S. molesta near the shoreline areas may be linked to the rich organic material usually found at the lake bottoms along the shorelines. This is reflected by the high phosphate levels in Acholi inn landing site though Masindi port, Waitumba and Kayei landing sites had phosphate values contrary to the average S. molesta coverage at those sites . There was accumulation of phosphates at Kayei landing site resulting from less uptake by S. molesta at low coverage. On the other hand, the high coverage of the weed at Waitumba and Masindi port landing sites might have led to the depletion of phosphates in the water at those sites due to increased uptake by the weed. According to Divakaran et al. , the rapid proliferation of S. molesta causes depletion of nutrients. However, S. molesta carriage through attachment on boats increased the weed coverage at Acholi inn landing site which also recorded high phosphates at the same time. The enriched phosphates in Acholi inn could have resulted from the decay of organic matter in the habitat of the weed .
According to Lavelle and Spain , organic matter decomposition is a good source of phosphorus. The high coverage of S. molesta at waste sites and gardens is associated with increased nutrient availability as the pH and temperature ranges at all the study sites were relatively constant and suitable for growth of the weed. According to Cary and Weerts , S. molesta grows optimally in nutrient-rich conditions at pH 6 – 7.5 and water temperatures ranging from 20˚C to 30˚C. However, nutrient availability is more influential to the growth of the weed than pH . The high coverage of S. molesta weed close to the waste sites and gardens is expected as growth of aquatic weeds increases with increase in agricultural productivity . This is due to the fact that agricultural and wastewater runoffs into freshwater ecosystems enrich the nutrient levels in the water bodies . For the case of Lake Kyoga, about 85% of the population in the lake basin is currently engaged in agriculture hence increased cultivation and livestock rearing around the lake. On the other hand, cannabis grow supplies more wastes have also been discharged into the lake from increased human activities and livestock in the lake basin thus elevating phosphate levels in the lake The high coverage of S. molesta at boat docks despite the relatively lower nutrient levels is attributable to the weed getting stuck on boats and then washed off in the boat docks.
Global Invasive Species Database showed that S. molesta can be spread within and between water-bodies by contaminated boats.According to Parsons and Cuthbertson and Gewertz , S. molesta spread between aquatic systems as a hitchhiker on boats, or in shipments of fish is common. For example, the spread of S. molesta into inland waterways of Zimbabwe was associated with the boat movements to and from Lake Kariba . As Lake Kyoga is very much used for fishing and inland water transport , the number of boats on the lake is high hence increased coverage of S. molesta at the boat docks. The coverage of the S. molesta at the different landing sites and anthropogenic activities decreased the concentrations of dissolved oxygen at those sites in line with previous studies which indicated that solid mats of S. molesta reduce the dissolved oxygen concentrations in the water column For instance, dissolved oxygen concentration underneath S. molesta mats in Lake Naivasha only attained 10% saturation as opposed to 64% – 85% in the open water . The relatively high dissolved oxygen concentrations recorded at the boat docks despite the high weed coverage is probably due to the constant breaking of the thick S. molesta mats and mixing of the water at the boat docks as a result of boat movements.
According to Wanda et al. , the brittle stolons of S. molesta are easily broken by the movement of boats. Ongom et al. also reported that mixing of Lake Kyoga water increases the oxygen circulation in the lake. S. molesta weed coverage was the least in the fishing areas associated with low nutrient concentrations and the low weed coverage also resulted into increased dissolved oxygen concentrations at the fishing areas. Water stress or drought is one of the most important abiotic constraints in rice, reducing yield on 23 million ha of area in South and Southeast Asia . In Asia alone, the average loss in rice production in years of drought can exceed one billon US dollars. In water-limited regions, drought risk reduces yield because growers avoid investing money in inputs when they fear crop loss . In irrigated areas, too, water shortage is becoming an increasing problem because of the rising demand for water in urban areas. Water shortage has been historically associated with food shortage, especially in Asia and Africa . By 2025, 13 Mha of irrigated wetland rice in Asia may experience physical water scarcity and 22 Mha of irrigated dry-season rice may suffer from economic water scarcity .