Browsing by Author "Orwa, Patrick"
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Publication Diversity, composition and abundance of macroinvertebrates associated with water hyacinth mats in Lake Victoria, Kenya(African Journal of Education,Science and Technology, 2015-03-30) Orwa, Patrick; Omondi, Reuben; William, Ojwang; Josephat, MwanchiThis study is set to investigate the macroinvertebrate community structure within water hyacinth in the Kenyan waters of Lake Victoria. This is helpful in determining the relationship between water hyacinth and macroinvertebrates. A total of four replicates were taken from 18 sampling stations within the lake using a Ponar grab and a 500 µm scoop net. The samples were washed through a 300 µm sieve and sorted alive in the field. The organisms were then identified to genus level and further categorized into functional feeding guilds using available keys and literature. The vertical position of the organisms at a water hyacinth mat was also examined. The data was then analyzed for diversity and abundance. One way ANOVA was further done to test any significant variation in community attributes between stations within the lake. All the physic-chemical parameters measured varied significantly though pairwise comparison revealed that most stations were in same sub set. A total of 14 orders and 34 genera were identified during the study. Out of which, 13 genera which include Chironomus, Lymneae, Hirudo, Tubifex, Platycnemis, Sympetrum, Trithemis, Melanoides, Biomphalaria, Ilybius, Elmis, Leptocerus, and Hexagenia were found at every sampling station. Most of the taxa found were predators probably feeding on mosquito larvae which could explain their absence. There was no significant difference in the diversity between stations though they varied in abundance. It is thus concluded that water hyacinth influences the distribution of macroinvertebrates and can thus be used to predict their presence. The feeding guilds were however assigned using existing literature. It is therefore recommended that a further study be done to confirm the feeding habits and the presence of mosquito larvae. Key words: Macroinvertebrates, hyacinth, Lake VictoriaPublication Diversity, composition and abundance of macroinvertebrates associated with water hyacinth mats in Lake Victoria, Kenya(Academic Journals, 2015-03-30) Orwa, Patrick; Omondi, Reuben; William, Ojwang; Josephat, MwanchiThis study is set to investigate the macroinvertebrate community structure within water hyacinth in the Kenyan waters of Lake Victoria. This is helpful in determining the relationship between water hyacinth and macroinvertebrates. A total of four replicates were taken from 18 sampling stations within the lake using a Ponar grab and a 500 µm scoop net. The samples were washed through a 300 µm sieve and sorted alive in the field. The organisms were then identified to genus level and further categorized into functional feeding guilds using available keys and literature. The vertical position of the organisms at a water hyacinth mat was also examined. The data was then analyzed for diversity and abundance. One way ANOVA was further done to test any significant variation in community attributes between stations within the lake. All the physic-chemical parameters measured varied significantly though pairwise comparison revealed that most stations were in same sub set. A total of 14 orders and 34 genera were identified during the study. Out of which, 13 genera which include Chironomus, Lymneae, Hirudo, Tubifex, Platycnemis, Sympetrum, Trithemis, Melanoides, Biomphalaria, Ilybius, Elmis, Leptocerus, and Hexagenia were found at every sampling station. Most of the taxa found were predators probably feeding on mosquito larvae which could explain their absence. There was no significant difference in the diversity between stations though they varied in abundance. It is thus concluded that water hyacinth influences the distribution of macroinvertebrates and can thus be used to predict their presence. The feeding guilds were however assigned using existing literature. It is therefore recommended that a further study be done to confirm the feeding habits and the presence of mosquito larvae. Key words: Macroinvertebrates, hyacinth, Lake VictoriaPublication Effect of Eichhornia crassipes on coliforms load in small water bodies within Lake Victoria basin, Kenya(Academic Journals, 2015-03-11) Veronica, Ombwa; Orwa, Patrick; Alice, Mutie; Omondi, Reuben; Kenneth, Werimo; Ouko, JohnThe study investigates the effects of Eichhornia crassipes (water hyacinth) infestation based on coliform loads which are pollution indicator organisms. These dams have fish and the waters are commonly used for domestic purposes without any treatment hence it is necessary to check their status. Sampling was done on 25 small water bodies and from which water samples were taken for microbial determination. Membrane filtration method was used to enumerate fecal coliforms by use lauryl sulphate broth and incubated at 44 ± 0.5°C for 18 to 24 h. The results show that water bodies infested by water hyacinth harbored higher levels of fecal coliforms compared to those devoid of the weed. The high fecal coliform levels have negative impacts on the lives of communities using these water bodies. In addition, it reduces native species and disrupts food chains and nutrient cycle. The small water bodies within the Lake Victoria basin need frequent monitoring in order to give the relevant authorities concrete information for proper sensitization to the communities. Water hyacinth should also be properly managed so that it does not chock dams that are used for domestic and fishing activities.Publication Spatial variation in diversity, distribution, and abundance of macroinvertebrates and their response to physicochemical param- eters in River Nyakomisaro, kisii-Kenya(IJTHF, 2020-02-20) Jomo, Boston; Omondi, Reuben; Getabu, Albert; Orwa, PatrickAquatic animal and plant diversity of tropical aquatic ecosystems are severely threatened by frequent anthropogenic activities. The study investigated spatial variation in macroinvertebrate community and physicochemical parameters of River Nyakomisaro from July to December 2016. Five sampling sites were selected and a pool, a rie and a run identied in each site for sampling. Kick sampling was employed in collecting macroinvertebrate samples while selected physicochemical parameters were determined in situ using a water quality multi-parameter meter model 85–15 ft YS1. A total of 6,104 macroinvertebrates belonging to 30 genera, 22 families and 10 orders were recorded. The highest diversity (2.719 ± 0.018) was recorded in station 1 while station 5 had the lowest diversity (1.229 ± 0.026). The highest abundance was recorded in station 5 with 1,948 macroinvertebrates dominated by Chironomids which are highly tolerant to perturbations while station 1 recorded the lowest abundance of 473 macroinvertebrates and dominated by macroinvertebrate communities that are sensitive to environmental pollution. Analysis of variance (ANOVA) showed signicant dierences (p<0.05) in diversity, abundance, and distribution of macroinvertebrates of River Nyakomisaro. Headwater stations had taxa that thrive in undisturbed waters with a reduction of genera that are sensitive to perturbations such as Ephemeroptera, Plecoptera, and Trichoptera in downstream stations. This was a clear indication of pollution of the waters downstream. This response makes macroinvertebrate communities in River Nyakomisaro good bio-indicators of water quality. Therefore, the ndings of the current study can form a basis for the establishment of strategies for conservation, protection, and restoration of macroinvertebrates and the integrity of river Nyakomisar