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Addis Ababa University Libraries Electronic Thesis and Dissertations: AAU-ETD! >
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http://hdl.handle.net/123456789/28
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| Title: | Assessment of Benthic-Macroinvertebrate structures in relation to Environmental Degradation in some Ethiopian Rivers |
| Authors: | Baye, Sitotaw |
| Date Added: | 31-Aug-2007 |
| Abstract: | Surface water monitoring programs rely on biological, chemical, and habitat
information to make science-based judgments on aquatic life use-support
designations. Urbanization and extensive agriculture within and adjacent to stream
corridors can seriously impact aquatic species and their habitats. This study
assessed biological impairment to macroinvertebrate communities in some rivers/
streams primarily disturbed by extensive agricultural activities, industrial and urban
land use in Ethiopia. These primary land uses are considered to be the most
important threatening factors to aquatic ecosystem. A total of 15 sites were sampled
for macroinvertebrates and environmental parameters. These data were collected
between August 2005 and June 2006. Sites were categorized a priori into three
groups (reference, rural, and urban) based on the predominant land use upstream of
the sampling reach. Macroinvertebrate sampling was conducted in accordance with
Rapid Bioassessment Protocol. Physicochemical parameters (by using standard
methods) were collected and habitat features were scored with the EPA Rapid
Bioassessment Protocol (RBP) Habitat Assessment procedures. Streams data were
compared to reference conditions. Sites were assessed with the Benthic Index of
Biotic Integrity (B-IBI), an aggregate index that incorporates 14 metrics. Exploratory
box plots and scatter plots were viewed along with Pearson correlation coefficients
and linear regression to evaluate relationships between environmental and biological
data. Multivariate techniques such as principal components analysis (PCA),
correspondence analysis (CA) and cluster analysis were used. Significance tests
were performed on environmental and biological Parameters with the student t- test.
There were significant differences in most of the environmental variables (p<0.05)
between most categories, but reference and residential sites were not significantly
different in some parameters. The dispersion of disturbed sites in PCA ordination
space clearly demonstrated that environmental factors deviated from the reference
condition. Taxonomically, visual inspection of the CA ordination suggested that
reference communities were highly similar to each other. However, substantial
departure of urban sites from the reference site array indicated very different
community makeup. This analysis also demonstrated distinct separation of
assemblages from rural versus urban sites. Streams from the urban categories had
significantly lower B-IBI and positive metrics scores, and significantly higher negative
metrics scores than reference sites (p<0.05). The B-IBI and its associated metrics
were significantly correlated (p<0.05) to most physiochemical parameters and RBP
total habitat scores. The dramatic decrease of EPT taxa at urban sites indicated that
these organisms are especially sensitive to excessive nutrient and organic loading.
Overall, the B-IBI indicated that nearly all urban sites were impaired. The data
presented here indicated that macroinvertebrate communities are sensitive and
vulnerable to urban/industrial land uses. To best characterize and monitor ecological
conditions of these rivers, regular sampling of all variables and development of a
single mutlimetric index developed from biological and environmental variables is
suggested. |
| Description: | I wish to express my deepest gratitude and thanks to my adviser Dr. Seyoum
Mengistou; without his initiative to this work would not have been undertaken. I
also recall and appreciate his invaluable financial and moral support to start my
study earlier and to complete it on time. His encourage ment and appreciation
throughout my study at the University and while I was working for my thesis have
been very indispensable.
I am also very grateful to Dr. Abebe Getahun for his invaluable advice and
financial support. I would like to extend my thanks to the Biology Department of
Addis Ababa University, for the supply of necessary chemicals and equipment to
conduct Laboratory analysis.
My thanks also goes to Prof. Zerihun Woldu for his credited support in the
statistical analysis, Ato Solomon Akalu for his unreserved co-operation during
field and laboratory work; and Ato Ayalew Wondie and Ato Taddesse Fetahi for
their continuous advice in my study.
I am highly indebted and grateful to my brother, Tilahun Zewdu, my sister Tsigie
Sitotaw, as well as, my friends Ato Fekade Asmamaw and Ato Mekashaw Yimer
for their encouragement during my study. I am also indebted to Ato Asnake
Mekuriaw for his invaluable advice to continue my education and to join Addis
Ababa University.
Last but not least, I would like to thank all my classmates for their co-operative
and enjoyable friendship during my stay in the University.
Above all, thanks to the Almighty God; without His will, nothing could have
happened. |
| URI: | http://hdl.handle.net/123456789/28 |
| Appears in: | Thesis - Biology
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