Abstract:
Wetlands are ecosystems of immense value to humans due to the fact that they provide construction materials, food, medicine, pasture. In addition, they provide ecosystem services such as pollution mitigation due to the fact that they absorb pollutants and nutrients from the effluents flowing through them and also act as carbon storage (sequestration). Globally, wetlands are under threat due to anthropogenic activities and climate change. Humans have resorted to converting wetlands to farmlands, institutions and other infrastructure destroying aquatic flora and fauna. This study aimed at assessing the effects of anthropogenic activity on diversity of macrophytes and water quality of Sironga and Kapkatet wetlands. The study was carried for six months from February – July 2019. Physico-chemical parameters were measured in situ using a multi parameter meter model number YSI 15B. Samples for nutrients were collected in triplicates and analyzed using standard methods as described in APHA 2014. Significant differences of the physico-chemical parameters among different sampling sites were analyzed using ANOVA and Tukey pairwise test. Biodiversity indices, species richness and evenness were calculated. Macrophytes distribution and abundance were studied on 20 randomly distributed sampling sites in each wetland using 5m2 quadrat and 20m long line transects. Relationship between physico-chemical parameters, nutrients and macrophytes density were studied using Pearson’s correlation. Analysis revealed that water quality was poor and in particular dissolved oxygen concentrations were anoxic at several sampling sites and below recommended WHO and NEMA standards. Anthropogenic damages for Sironga and Kapkatet wetlands were estimated at 90.5 % and 75.1% respectively. Consequently, there has been unprecedented loss of wetland macrophytes together with their ecosystem functions, goods and services in both wetlands. Due to nutrient influxes from farming activities in the wetland catchments the TP:TN ratios were found to be 1:4.2 and 1:3.2 respectively indicting that the two ecosystems were eutrophic. Macrophytes diversity and species composition were high in both wetlands. The most dominant macrophytes were Centella asiatica, Digitaria abyssinica, Poa annua and Cyperus helferi, Cyperus rotundus for Sironga and Kapkatet wetlands respectively. The poor ecosystem integrity of the wetlands is due to the anthropogenic activities in their catchments and the changing climatic conditions. There should be maintenance of a buffer strip of native vegetation along the wetlands to prevent erosion and improve the health of the wetlands. Current land use approaches in the wetlands are unsustainable and expensive, the wetlands should be conserved and largely restored in to their original state in this way their touristic potential will be realized in terms of revenue collection, self- employment and a sustainable supply of goods and services to humans. Sironga wetland which is substantially large should be developed into a game park together with tourist hotel establishments. Information presented in this thesis will be of use in informing policy on the conservation and management of wetlands.
