Intl. J. of Mol. Evol. and Biodivers. 2015, Vol. 5, No. 5, 1-9
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Climate
Zambia being divided into three ecological zones or
regions namely I, II and III. The climatic condition of
the study area falls under climate zone III. The area
experiences average temperatures ranging from 15ºC
to as high as 36ºC and receives rainfall ranging from
800mm to over 1 000 mm.
Experimental design
In this study, a systematic sampling design was employed.
The initial sampling site was selected randomly.
Sampling sites were spaced at uniform intervals
throughout the 1 km section of the stream sampled.
Each sampling site of 10 m x 10 m was established
every after 100 m from the initial sampling site.
Sampling
This study was conducted in the dry season of 2014.
Samples for both physico-chemical parameters and
invertebrates were collected in July and August 2014.
Ten sampling sites along the longitudinal stream
gradient were selected and the sites were designated
as S1-S10.
Invertebrates
Sampling took place from 31 July 2014 to 4 August
2014. Invertebrate samples were always collected by
the same operator with a standard hand net consisting
of a metal frame holding a conical net (20 cm×30 cm,
150µm mesh size). In the field, the collected material
was sieved through 500 mm and 250 mm mesh sieves
and put into collection bottles. The sampling effort at
each site was 30 min. Within a site two riffles and two
pools were sampled. All samples were preserved with
4% formalin until counting. All the organisms in the
sample were counted and identified to the lowest
possible taxonomic level (family level) using a
mini-SASS identification key (Appendix 4). There are
no current keys available to the Zambian fauna, but
the mini-SASS key used made it possible to classify
the fauna specimens to the family level without loss of
accuracy.
Physicals-chemical parameters
Samples for physico-chemical parameters were taken
at the same location and almost simultaneously with
the samples for invertebrates. Water temperature, pH,
conductivity and redox were measured
in situ
using
electronic measure equipment.
Data analysis
Descriptive statistics were used to analyze physico-ch
emical data. For the invertebrate communities one
index was calculated for each site. The Shannon-
Wiener Diversity Index (Hʹ) a diversity index that
incorporates richness and evenness was used to
calculate diversity. Hʹ was calculated as follows:Hʹ = -
∑ (P
¡
In [P¡])Where P¡ is the relative abundance (n¡/N)
of family ¡, n¡= number of individuals in family ¡and
N = total number of individuals in all families. H¡
ranges from 0 for a community with a single family, to
over 7 for a very diverse community. The statistical
software package (Analyse it) was used for statistical
analysis. Simple regression was used to determine the
level of significance of the relationship between
invertebrates and physico-chemical parameters.
The water quality of the Mwekera stream was
assessed using the South African Scoring System
version 5 (SASS5) (Dickens and Graham, 2002), in
which invertebrates are identified to family level and
each family is assigned a tolerance level, from 1-10 to
indicate their resistance to pollution. Tolerant taxa are
given low scores and sensitive ones high scores. The
total score for each site was calculated by summing
the individual taxon scores. The Average Score per
Taxon (ASPT) was calculated by dividing the total
SASS5 score by the number of taxa in the sample.
The higher the SASS5 score and/or the ASPT value,
the better the water quality is deemed to be (assuming
that habitat availability is not limiting.
From the results, the water quality of Mwekera stream
varied from excellent to fair in the upstream direction
due to increase in land erosion as evidenced by low
species richness, abundance and diversity of the
invertebrate fauna. This was as a result of natural
forces and an increase in charcoal burning activities.
The abundance of invertebrates were highest at sit S1
and lowest at S5. Sampling site S1 had an excellent
water quality while site S5 had poor water quality, and
the rest of the sites had fair water quality. The results
indicated the existence of a significant relationship
between water quality parameters of Mwekera stream
with the invertebrate community. Therefore, this
