Seid Tiku Mereta

Analysis of environmental factors determining the abundance and diversity of macroinvertebrate taxa in natural wetlands of Southwest Ethiopia

Abstract In Ethiopia, wetland resources play a vital role in the lives of adjacent communities by helping them to achieve food security and livelihoods. However, many wetlands throughout the country are facing degradation as high population growth rate increases the need for more fertile agricultural land. Lack of awareness and logistic constraints are important reasons for the weak consideration of wetland ecosystems by the countrys development planners. In this paper, we set out to develop methods for predicting species–environment relationships. Decision tree models and Canonical Correspondence Analysis (CCA) were used to identify factors influencing macroinvertebrate community structure in natural wetlands of Southwest Ethiopia. The models were based on a dataset of 109 samples collected from 57 sites located in eight different wetlands. Sixteen macroinvertebrate taxa were selected based on their frequency of occurrence to determine the status of the wetlands. It was found that Corixidae, Baetidae and Hydrophilidae had the highest predictive model performance. This indicates that these taxa have clear requirements regarding their environmental conditions. The low Kappa value combined with the high number of Correctly Classified Instances of Chironomidae may be related to their high frequency of occurrence, so that their presence is of little predictive power. This was also further illustrated by the Canonical Correspondence Analysis (CCA) where the family of Chironomidae, common at nearly every sampling station in the wetlands, was plotted in the centre of the CCA axis. Vegetation cover, water depth, and conductivity were the most important variables determining the presence or absence of macroinvertebrate taxa. These variables were selected in more than 80% of the classification tree models and played a critical role in the ordination analyses. The sensitivity analysis, based on the regression tree models, also showed that vegetation cover and conductivity were affecting the abundance of some macroinvertebrate taxa. Information on habitat quality and environmental factors preserving a high diversity are essential to develop conservation and management programs for wetlands and their related ecosystem services in Ethiopia, where wetland resources are being lost at a high rate, and continue to be at high risk due to expansion of agricultural and other development activities.

Physico-chemical and biological characterization of anopheline mosquito larval habitats (Diptera: Culicidae): implications for malaria control.

BackgroundA fundamental understanding of the spatial distribution and ecology of mosquito larvae is essential for effective vector control intervention strategies. In this study, data-driven decision tree models, generalized linear models and ordination analysis were used to identify the most important biotic and abiotic factors that affect the occurrence and abundance of mosquito larvae in Southwest Ethiopia.MethodsIn total, 220 samples were taken at 180 sampling locations during the years 2010 and 2012. Sampling sites were characterized based on physical, chemical and biological attributes. The predictive performance of decision tree models was evaluated based on correctly classified instances (CCI), Cohen’s kappa statistic (κ) and the determination coefficient (R2). A conditional analysis was performed on the regression tree models to test the relation between key environmental and biological parameters and the abundance of mosquito larvae.ResultsThe decision tree model developed for anopheline larvae showed a good model performance (CCI = 84 ± 2%, and κ = 0.66 ± 0.04), indicating that the genus has clear habitat requirements. Anopheline mosquito larvae showed a widespread distribution and especially occurred in small human-made aquatic habitats. Water temperature, canopy cover, emergent vegetation cover, and presence of predators and competitors were found to be the main variables determining the abundance and distribution of anopheline larvae. In contrast, anopheline mosquito larvae were found to be less prominently present in permanent larval habitats. This could be attributed to the high abundance and diversity of natural predators and competitors suppressing the mosquito population densities.ConclusionsThe findings of this study suggest that targeting smaller human-made aquatic habitats could result in effective larval control of anopheline mosquitoes in the study area. Controlling the occurrence of mosquito larvae via drainage of permanent wetlands may not be a good management strategy as it negatively affects the occurrence and abundance of mosquito predators and competitors and promotes an increase in anopheline population densities.

Comparison of the Abiotic Preferences of Macroinvertebrates in Tropical River Basins

We assessed and compared abiotic preferences of aquatic macroinvertebrates in three river basins located in Ecuador, Ethiopia and Vietnam. Upon using logistic regression models we analyzed the relationship between the probability of occurrence of five macroinvertebrate families, ranging from pollution tolerant to pollution sensitive, (Chironomidae, Baetidae, Hydroptilidae, Libellulidae and Leptophlebiidae) and physical-chemical water quality conditions. Within the investigated physical-chemical ranges, nine out of twenty-five interaction effects were significant. Our analyses suggested river basin dependent associations between the macroinvertebrate families and the corresponding physical-chemical conditions. It was found that pollution tolerant families showed no clear abiotic preference and occurred at most sampling locations, i.e. Chironomidae were present in 91%, 84% and 93% of the samples taken in Ecuador, Ethiopia and Vietnam. Pollution sensitive families were strongly associated with dissolved oxygen and stream velocity, e.g. Leptophlebiidae were only present in 48%, 2% and 18% of the samples in Ecuador, Ethiopia and Vietnam. Despite some limitations in the study design, we concluded that associations between macroinvertebrates and abiotic conditions can be river basin-specific and hence are not automatically transferable across river basins in the tropics.

Analysing the effects of water quality on the occurrence of freshwater macroinvertebrate taxa among tropical river basins from different continents

Macroinvertebrates are globally used in environmental monitoring and assessment. However, due to environmental and biological evolution, local adaptations of species might occur. This can contribute to uncertainties in the extrapolation of familyspecific ecological models developed from one region to another. Thus, we aimed to determine if models can be extrapolated to other regions with similar climatic conditions and if a reliable model can be developed from a pooled dataset (consisting of data from different regions). The occurrence of five families was modelled based on physical-chemical water quality variables with classification trees using the data from three tropical river basins (Chaguana in Ecuador, Gilgel Gibe in Ethiopia and Cau in Vietnam). The relevance of each model was tested on complementary data from both the same and other river basins, to test specificity and universality. Furthermore, models with a pooled dataset were developed and tested. Model reliability was assessed based on chance-corrected agreement (Cohens kappa, kappa) and percent agreement (correctly classified instances, CCI). Values of higher than 0.4 (kappa) and 70% (CCI) were used to classify models as good. Only the pollution sensitive taxon (Leptophlebiidae) resulted in reliable models for most cases. In general, responses of macroinvertebrates towards pollution were different among countries except for the pollution sensitive taxa. Thus, extrapolation of ecological models for sensitive taxa to another river basin with similar climatic and environmental conditions is possible. Nevertheless, this type of systematic analyses for all families is necessary to determine and minimize uncertainty in ecological assessment.

Using Macroinvertebrates and Birds to Assess the Environmental Status of Wetlands across Different Climatic Zones in Southwestern Ethiopia

We investigated the variation in macroinvertebrate and bird fauna of 12 different freshwater wetlands located in three different climatic zones of southwestern Ethiopia. Data on macroinvertebrates, birds, physico-chemical water quality variables, human disturbance and vegetation cover were collected from 62 sampling sites during the dry and wet season of 2015. Generalized linear mixed models (GLMMs) were used to identify the most important variables explaining the variation in macroinvertebrates and birds. Twenty four percent of the variation in macroinvertebrate richness was explained by a combination of vegetation cover and dissolved oxygen, whereas 34% of the variation in macroinvertebrate abundance was explained by a combination of dissolved oxygen saturation, electric conductivity, total phosphorus and vegetation cover. A combination of water depth, dissolved oxygen, human disturbance and macroinvertebrate abundance explained about 34% and 31% of variation in bird species richness and abundance, respectively. Richness and abundance of macroinvertebrate and wetland dependent birds were significantly (P < 0.05) different between wetlands. When investigating the ecological status of wetlands, local environmental conditions of wetland should be taken into account for the development of wetland conservation strategies.

Effect of Human-Induced Environmental Changes on Bird Diversity and Abundance in Natural Wetlands of Southwest Ethiopia

Abstract. The diversity and abundance of wetland birds have been threatened by increasing anthropogenic activities during recent decades. The objective of this study was to determine the effect of human-induced disturbance on bird species richness and abundance of natural wetlands in southwest Ethiopia. Bird surveys were performed at 56 locations during both the wet and dry seasons in 2010 and 2011. Generalized linear modeling (G) was used to correlate species richness with environmental variables. It was found that wetlands with low human disturbance were characterized by a higher richness (n > 10) of wetland dependent specialist birds (depending completely on wetlands for food and nesting) than the highly disturbed wetlands. However, for wetland-associated birds (those able to nest and feed in wetlands as well as in other habitats), there was no significant difference (P = 0.31) in species richness between disturbed and non-disturbed wetlands. The abundance of wetland dependent specialist birds was significantly affected (P < 0.001) by human disturbance, whereas the abundance of wetland associated birds was not (P = 0.39). Fifty-three percent of the variation in species richness of wetland dependent birds was explained by a combination of water depth, sludge depth, conductivity, chlorophyll a, total phosphorus, human disturbance and vegetation cover. It is recommended that anthropogenic activities should be minimized and controlled in and around these wetlands to conserve biodiversity.

Climate Resilience Index as a tool to explore households\' resilience to climate change-induced shocks in Dinki watershed, central highlands of Ethiopia

This study assessed households’ resilience to climate change-induced shocks in Dinki watershed, northcentral highlands of Ethiopia. The data were collected through cross-sectional survey conducted on 288 households, six focus group discussions and 15 key informant interviews. The Climate Resilience Index (CRI) and the Livelihood Resilience Index (LRI) based on the three-resilience capacities (3Ds) frame, using absorptive, adaptive and transformative, were used to measure households’ resilience to climate change-induced shocks on agro-ecological unit of analysis. Findings indicate that the CRI and the resilience capacities based on the indexed scores of major components clearly differentiated the study communities in terms of their agro-ecological zones. Specifically, the LRI score showed that absorptive capacity (0.495) was the leading contributing factor to resilience followed by adaptive (0.449) and transformative (0.387) capacities. Likewise, the midland was relatively more resilient with a mean index value of 0.461. The study showed that access to and use of livelihood resources, such as farmlands and livestock holdings, diversity of income sources, infrastructure and social capital were determinants of households’ resilience. In general, it might be due to their exposure to recurrent shocks coupled with limited adaptive capacities including underdeveloped public services, poor livelihood diversification practices, among others, the study communities showed minimal resilience capacity with a mean score of 0.44. Thus, in addition to short-term buffering strategies, intervention priority focusing on both adaptive and transformative capacities, particularly focusing on most vulnerable localities and constrained livelihood strategies, would contribute to ensure long-term resilience in the study communities.

Efficacy of Achyranthes aspera (L.) as a Molluscicidal Bait Formulation against Fresh Water Snail Biomphalaria pfeifferi

Molluscicidal plant products have interesting attributes of environmental friendliness and accessibility to local communities. Their bait formulations are more economical and target specific as they are applied only to the snail-infested sections of the water habitat. Their active ingestion by target snails could also increase gastric concentrations and enhance effectiveness. This study aimed to evaluate the comparative effectiveness of Achyranthes aspera (A. aspera) leaf hydroethanolic extract in bait and immersion applications. Serial dilutions of the extract in water for immersion, and in snail food pellets for bait test, were set. Adult Biomphalaria pfeifferi snails exposed to the bioassays for 24 hours and data were analyzed using probit model. The plant showed molluscicidal activity in both methods. The respective LC50 and LC90 doses were 20.37 and 46.84 ppm in the immersion and 3.10 and 11.08 ppm in the bait. The more efficient bait method reduced the LC50 by 6.57 and the LC90 by 4.23 times. This finding provides a strong foundation for the molluscicidal potential of A. aspera. It is applicable and possibly more effective if formulated into those commercially available snail food pellets or flakes. However, selection and optimization of suitable baits is a crucial step for maximum output.

Seasonal and spatial variation of reservoir water quality in the southwest of Ethiopia

This research investigated the spatiotemporal variation of water quality in the Gilgel Gibe reservoir, Ethiopia, using physicochemical water quality parameters. Nonparametric tests and multivariate statistical techniques were used to evaluate data sets measured during dry and rainy seasons. Electrical conductivity (EC), pH, biochemical oxygen demand (BOD5), total phosphorus (TP), total nitrogen (TN), nitrate (NO3−), total dissolved solids (TDSs), and total suspended solids (TSSs) were all significantly different among seasons (Mann-Whitney U test, p < 0.01). In addition, principal component analysis distinguished dry season samples from wet season samples. The dry season was positively associated with EC, pH, TP, TN, NO3−, TDS, and TSS and negatively associated with BOD5. The wet season was in contrast associated with high values of turbidity, soluble reactive phosphorus (SRP), water temperature, and dissolved oxygen (DO). Within the reservoir, spatial variation was observed for some of the water quality parameters, with significant difference at p = < 0.05. Overall, high nutrient concentrations suggest eutrophic conditions, likely due to high nutrient loading from the watershed. Levels of TSS, attributed to inputs from tributaries, have been excessive enough to inhibit light penetration and thus have a considerable impact on the aquatic food web. Our findings indicate that the reservoir is at high risk of eutrophication and siltation, and hence, urgent action should target the planning and implementation of integrated watershed management for this and similar reservoirs in the region.

Habitat suitability modelling for predicting potential habitats of freshwater snail intermediate hosts in Omo-Gibe river basin, Southwest Ethiopia

Abstract In spite of considerable progress made in the prevention and control of schistosomiasis and other snail-borne diseases, transmission has intensified in some endemic areas as a result of land-use and climate changes. We used decision tree models and multivariate analysis to identify factors affecting the occurrence and abundance of medically important freshwater snail intermediate hosts in the Omo-Gibe river basin, Ethiopia. The models were based on a dataset of 140 samples collected from lakes, wetlands, rivers, dam reservoir shores and irrigation canals. A total of 1866 freshwater snails belonging to four genera and seven species were collected. Biomphalaria pfeifferi, Lymnaea natalensis and Bulinus globosus had fair to moderate predictive performance based on Kappa statistics (ĸ > 0.2), indicating that these species have clear environmental requirements within the habitat gradient studied. The most important variables influencing the abundance and occurrence of snail species were the presence of predator and competitor, canopy cover, type of water body, waste dumping and water pH. In conclusion, snail species occurred less frequently and in smaller numbers in water bodies with minimal human disturbances. Therefore, preventing human disturbance in water bodies may enhance aquatic biodiversity, thereby increasing the abundance of snail predators and competitors. Preventing the pollution of these ecosystems is essential to maintain their ecological integrity and sustain the ecosystem services they provide to local communities.