The impact of human activities on abundance and distribution of Macro-invertebrates in Walugogo Wetland-Eastern Uganda
The study was conducted in Walugogo wetland (2km on Iganga – Jinja highway) with the objectives identifying the human activities impacting on Walugogo wetland and how these activities influence the abundance and distribution of macro-invertebrates in the wetland. The study involved identification of three (3) study locations namely; 1 (undisturbed), 2 (intermediate) and 3 (disturbed). Three sites were selected in each study location basing on topographical gradient of location to get a representative sample for each location. Data was taken through direct observation, use of pH, electro-conductivity, dissolved oxygen meters and traps. Results regarding human activities, ecological findings at different sites, physic-chemicals parameters and macro-invertebrates are presented. Physico-chemical parameters of conductivity, temperature, pH and dissolved oxygen were determined. The major human activities impacting on Walugogo wetland were agriculture, industrial activities (Tembo steel Rolling and Abottoir) road works and human settlement. The intermediate study location had the highest conductivity of 1366 cm µs-1 followed by undisturbed location (1286 µs cm-1) and lastly the disturbed location (836 µs cm-1’). Statistically significant difference was found for this parameter of conductivity among the locations (p=0.009). The disturbed location had the highest temperature (26OC), followed by intermediate location (250C) and undisturbed location had the lowest temperature (210C). Temperature was significantly different (P=0.00001) among the locations. On dissolved oxygen (mg/1), the intermediate location had the highest value of 1.02, followed by disturbed with 0.95 and lastly the undisturbed location with value 0.89. While in terms of pH the disturbed location had the lowest value (7.10) highest in the intermediate (7.38) and in between value of 7.33 was recorded for the undisturbed location. Significant differences were found in dissolved oxygen and pH (p=0.037, 0.021) respectively. The major taxa of macro-invertebrates identified from Walugogo wetland included the orders of: Coleoptera, Hemiptera, Annelida, Odonata, Diptera, Orthoptera, Gastropoda and Nematoda. Biodiversity indices and weighted biotic indices were used to assess the overall impact of human activities on biodiversity. A total of 404 macro-invertebrates were collected and identified into 34 taxa. Of these, 64 (16%) were collected from disturbed location, 105 (26%) from intermediate location and 234 (58%) from undisturbed location, 105. Of the 34 taxa, 15 (44%) were caught from intermediate location, 12 (35%) from undisturbed location and 07 (21%) from disturbed location. Abundance was highest in undisturbed location (58%) followed by intermediate location (26%) and lowest in disturbed location (16%). Mean total taxa richness was found to be significantly different (P = 0.002) among the undisturbed, intermediate and disturbed locations. The relative abundance (evenness) was higher in the undisturbed location (1.54) and lowest in disturbed location (1.09) according to the Shannon-Weiner biodiversity index. The intermediate and disturbed locations had a higher weighted biotic index of 54 indicated severe impacts from human activities. The lower value of 38.54 recorded for undisturbed location indicated severe eutrophication at Walugogo wetland, as in the Swan coastal plain wetlands (Western Australia). The nature of vegetation to some extent varied across the study locations. The dominant vegetation recorded from the wetland was Phragmites mauritianus (reed swamp). This was interspersed with Typhea domingesis (Sedge). In the undisturbed location, Phragmites mauritianus, Typhea domingesis, Phoenix reclinta, Acacia polycantha and interspersion strata of dense grass (Mimosa pigra, Leersia hexandra) were the main dominant vegetation, Leersia hexandra, polygonum setulosum, sesbania sesban, mimosa pigra and shrubs were the dominant vegetation in the intermediate study location while disturbed location was dominantly covered by crops (Oryza sativa, Culcasia corocosimia, Ipomea batatas, Manihot esculenta, Saccharum officinate, and Phaseous vulgaris) and weeds such as Bidens pilosa and Comelina bengliosis. From calculations of bio-diversity indices, weighted biotic indices, percentage composition and statistical analysis, it was concluded that human activities negatively influence the abundance and distribution of macro-invertebrates. From percentage composition where the undisturbed location had 58%, the intermediate location with 26% and the disturbed location with 16%, comparatively the undisturbed location of the wetland had the highest macro-invertebrate community in terms of abundance and distribution than the disturbed region. In terms of habitant preferences, macro-invertebrates preferred undisturbed location in the wetland. Human activities were found to alter habitats. This was through destruction of vegetation and pollution (Introduction of wastes). Such activities result into alteration of physic-chemical parameters such as temperature, pH, dissolved oxygen and conductivity. The destruction of vegetation and altered physic-chemical parameters undermine the suitability of habitat for organisms. Ecological differences in study locations due to human activities appear to be the major cause of the observed differences in bio-diversity indices of macro-invertebrates. Hence human activities negatively impact on the abundance and distribution of macro-invertebrates in wetlands. Based on the results of the study; it is recommended that sensitize Iganga town council authority and general public on the importance of Walugogo wetland, involve community in planning wetland activities, there is need to regulate industrial discharge (Tembo steel rolling and Abattoir) into the wetland, introduce new technologies like Upland rice and enforce environmental restoration measures.