SOCIO-ECONOMIC STATUS AND BIOASSESSMENT OF THE ECOLOGICAL INTEGRITY OF KING’WAL WETLAND, NANDI COUNTY, KENYA

Abstract

Wetlands play a vital role in maintaining ecological balance, providing valuable ecosystem services, and supporting socio-economic activities for local communities. However, wetlands worldwide, including the King‘wal wetland under current study, are under threat from anthropogenic activities. Understanding the extent and implications of these changes forms the backdrop of this study. This study aimed to assess the impacts of anthropogenic activities on the King‘wal wetland by assessing the water quality variation, macrophytes and macroinvertebrate assemblages, indices of monitoring ecological integrity and examining the socio-economic status, wetland utilization and management, of King'wal wetland. The research was conducted from January to December 2011, with data collected monthly from four sites each having three subsites. Dissolved oxygen (DO), conductivity and pH were measured in situ using a yellow spring instrument (YSI) multiprobe meter, and aliquots of 500ml each were collected in acid washed high density poly ethylene (HDPE) bottles at each site for laboratory analysis. Macroinvertebrate metrics for the Index of Biological Integrity and Human Disturbance Score (HDS) were also assessed. The plant species diversity was determined by conducting random belt transects across the area, while macroinvertebrates were collected using a semi-quantitative kick-net sampling method. There were significant differences in the biodiversity of wetland flora in the study area (χ2 = 65.121, df = 8, p = < 0.001). Significant spatial variations were observed in all physico-chemical water quality variables (pH, dissolved oxygen, conductivity, total nitrogen, and total phosphorus) (p < 0.05). Water pH was highest at Kingwal Bridge, followed by Kiptenden, and lowest at Kesses. The concentration of dissolved oxygen (DO) decreased downstream from Kesses (the upstream site) to Kimondi (the downstream site) (F = 7.9732, p = 0.0002). Conductivity (EC) was highest at Kingwal Bridge, while total nitrogen (TN) and total phosphorus (TP) were highest at Kesses, followed by the Kiptenden sampling site. Total Nitrogen (TN) in water was significantly different (F = 34.5343, P = < 0.001) between the sites and Total Phosphorus (TP) in water differed significantly (F = 11.2321, p = 0.0001) during the sampling periods. The study identified a low macrophyte diversity of approximately 20 species, with 10 species occurring across all sites. The macroinvertebrate species diversity index (Shannon) was higher (2.84) at Kesses, while Kiptenden recorded the lowest diversity (2.65). % oligochaetes /chironomids (OC) relative to the total macroinvertebrate; Kesses had the highest value (6.1%), followed by Kingwal (4.5%), and Kiptenden had the lowest (1.9%). Kruskall-wallis test revealed significant differences in the abundance of the macroinvertebrate assemblages among the sampling sites (H = 7.987, df = 3, p = 0.0193). The percentage of EPT (Ephemeroptera, Plecoptera, and Trichoptera) taxa, an indicator of stream health, was highest at Kesses and lowest at Kingwal Bridge. These abundances were significantly different across the study sites (H = 5.1322, df = 3, p = 0.002). The upstream Kesses site had the highest Index of Biological Integrity (IBI) score and the lowest Human Disturbance Index (HDI) score. The analysis revealed a significant negative relationship (p < 0.05) between the Macroinvertebrate Index of Biotic Integrity (M-IBI) and Human Disturbance Index (HDI, indicating that anthropogenic activities degraded water quality, macrophytes, and macroinvertebrates diversity among the sites. Socio-economic data was collected using a household survey. The findings revealed a ranking order of decreasing importance: grains (98.4%), vegetables (88.9%), papyrus (85.7%), grass (82.7%), water (77.8%), and fodder (77.8%). Social services provided by the wetland included water recharge (75.3%), cultural practices (54.6%), flood control (53.5%), and erosion protection (43.4%). The dominant plant species were Aeschynomene abyssinica (48.8%), Carex pendula (45.8%), Cyperus papyrus (44.5%), and Lemna minor (32.3. The most commonly reported animal species by the majority of respondents were sitatunga (Tragelaphus spekei) (80.2%), and cranes (65.3%). Management and conservation strategies, implemented in time, should be embraced.