Intl. J. of Mol. Evol. and Biodivers. 2015, Vol. 5, No. 5, 1-9
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depends on the relative quantities of calcium, carbonate
and bicarbonate ions in the water (Sivakumar and
Karuppasamy, 2008).
Redox
Redox potential is a measure for the presence of
oxygen. Its values are used much like pH values to
determine water quality. Just as pH values indicate a
system’s relative state for receiving or donating
hydrogen ions, redox values characterize a system’s
relative state for gaining or losing electrons. it is one
of the most important abiotic factor affecting invertebrate
abundance and diversity (Davies and Day, 1998).
Redox of natural lakes and streams is relatively
insensitive to changes in dissolved oxygen concentration
except under very low oxygen concentrations. The
more oxygen levels, the higher the redox values.
Conductivity
Conductivity is a measure of the water’s ability to
conduct an electric current. It is also useful for
estimating the concentration of total dissolved solids
(TDS) in the water. Because the measurement is made
using two electrodes placed one centimeter apart,
conductivity is generally reported as microsiemen’s
per centimeter (μS/cm). The streams with high
alkalinity often have high conductivity (Bronmark and
Hansson, 1998).
Temperature
Water temperature is a critical physical property of
rivers and streams. Temperature has a major influence
on the biological productivity and development of
freshwater organisms. It defines suitable habitat
ranges, and controls chemical characteristics and
processes of stream ecosystems (Brown and Krygier,
1967). Stream temperature has been studied by many
researchers due to its essential role in defining stream
ecosystems. Stream temperatures can be affected by
environmental factors including atmospheric and
climatic conditions, physical characteristics of the
watershed and stream, and hydrologic inputs (Brown
and Krygier, 1967). In addition, human activity has an
increasingly important effect on stream ecosystems
and on stream temperature Stream temperature
changes as a result of heat fluxes between the stream
and surrounding environment. Changes in stream
temperature are dependent on net heat fluxes and
stream discharge, and are directly proportional to the
stream surface area and inversely proportional to
discharge (Webb, 1996). The exchange of heat
between the environment and the stream occurs
primarily across the air-water boundary and the
streambed-stream water interface through short- and
long-wave radiation inputs, evaporation, convective
heat transfer between the stream and atmosphere,
conductive transfer between the steam water and bed,
and advective energy transfer between water sources
(Brown and Krygier, 1967). The thermal regime of
small streams varies widely depending on atmospheric
and physical conditions. For example, shallow streams
with low flows react to heat flux changes more
dramatically than do larger rivers (Brown, 1969).
Water in headwater streams is generally close to a
baseline temperature, which can be the temperature of
groundwater, and increases as the water flows
downstream towards equilibrium with atmospheric
temperature. Atmospheric conditions can include air
temperature, vapor pressure, solar radiation, wind
speed, cloud cover, and relative humidity (Erickson
and Stefan, 2000). Most aquatic organisms have
adapted to survive within a range of water temperature.
Organisms like stoneflies and mayflies prefer cooler
water, while others like dragonflies need warmer
condition. As the temperature of water increases, cool
water species will be replaced by warm water
organisms. Temperature also affects aquatic life
sensitivity to toxic wastes and disease, either due to
rising water temperature or the resulting decrease in
dissolved oxygen. Water temperature influences
aquatic weeds, algal blooms and surrounding air
temperature (Kalyoncu et al., 2009). The metabolic
and physiological activity and life process such as
feeding, reproduction, movements and distribution of
aquatic organisms are greatly influenced by water
temperature.
The overall objective of the study was to assess the
impact of water quality on invertebrate species
abundance and richness in Mwekera stream with
specific objectives, which were; to assess the effect of
water quality (temperature, conductivity, pH, and
redox) on invertebrate species abundance and richness
