Int.J.Curr.Microbiol.App.Sci (2014) 3(6) - IJCMAS

15 Pages·2016·0.32 MB·English

Int.J.Curr.Microbiol.App.Sci (2014) 3(6): 230-244
International Journal of Current Microbiology and Applied Sciences
ISSN: 2319-7706 Volume 3 Number 6 (2014) pp. 230-24 4
http://www.ijcmas.com

Original Research Article

Assessment of physicochemical parameters in relation with fish ecology in
Ishasha River and Lake Edward, Albertine Rift Valley, East Africa

Mulongaibalu Mbalassa1, 2*, Jean Jacques Mashingamo Bagalwa1,4,
Muderhwa Nshombo2,3, and Mujugu Eliezer Kateyo1

1Makerere University College of Agricultural and Environmental Sciences; Department of
Environmental Management, Kampala, Uganda
2Université Officielle de Bukavu ; Faculté des Sciences et Sciences Appliquées, Département de
Biologie, Section : Hydrobiologie ; Bukavu, D. R. Congo
3Centre de Recherche en Hydrobiologie, Uvira, D. R. Congo
4Centre de Recherche en Science Naturelles de Lwiro, Bukavu, D. R. Congo
*Corresponding author

A B S T R A C T

The present study was designed to determine the physicochemical parameters

status along lo wer Ishasha River and littoral zone of Lake Edward, East Africa, for
a period of e ight months from July 2011 to May 2012. Water samples were
Keywords
collected on monthly basis in eight sites (river and lake) and analyzed for surface

water temperature, dissolved oxygen, pH, electrical conductivity, total dissolved

Physico- solids, and wa ter transparency. These parameters were compared with water quality

che mical standards to demonstrate their ability to support fish species in selected sites.
para meters, Analysis showed longitudinal differences (p< 0.05) along the river. Water was

water quality, slightly cool, well oxygenated and alkaline at upstream; and contained much more

Isha sha TDS and EC at downstream, indicating the impact of agriculture and deforestation
Riv er, Lake on the river. In the littoral zone, exce pt for DO, all parameters differed (p< 0.05)
from site to site; owing to differences in effluent inputs from respective outlets. In
Edw ard,
overall, the mean values of the parameters remained within the safe limits of water
Alb ertine
quality standards during the study period in all sites; revealing that
Rift Valley
physicochemical parameters in these habitats were permissible for most aquatic

species. But, measures should be taken to regulate agricultural and deforestation

activities upriver to avoid advert conditions.

Introduction

Lakes and rivers are very important part of (Furhan Iqbal et al., 2004; Adakole et al.,
our natural heritage. They have widely 2008). The maintenance of healthy aquatic
been utilized by mankind over the ecosystem is dependent on the
centuries to the extent that very few, if not physicochemical properties and biological
many are now in a natural condition diversity (Venkatesharaju et al., 2010).
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Int.J.Curr.Microbiol.App.Sci (2014) 3(6): 230-244

The interactions of both the physical and predation levels (Serafy and Harrel, 1993;
chemical properties of water play a Scott et al., 2005). These factors are
significant role in composition, responsible for distribution of organisms
distribution, abundance, movements and in different fresh water habitats according
diversity of aquatic organisms (Mustapha to their adaptations, which allow them to
and Omotosho, 2005; Sangpal et al., 2011; survive in a specific habitat (Jeffries and
Murungan and Prabaharn, 2012; Deepak Mills, 1990).
and Singh, 2014). To minimize energy
expended for survival, species typically Lakes and rivers in the Albertine Rift
favor habitat conditions that optimize their Valley, East Africa, are known for their
physiology process (Matthews, 1990). exceptional biodiversity (Lowe-
McConnell, 1987; Kurt and Hecky, 1987;
In particular, fish populations are highly Coulter, 1991; Snoeks, 1991; 1994; Hori
dependent upon the variations of et al., 1993; Nakai et al., 1994; Plumptre
physicochemical characteristics of their et al., 2003, 2004), for example Lake
aquatic habitat which supports their Tanganyika, with unique and many
biological functions (Mushahida-Al-Noor endemic species (Fryer and Iles, 1972;
and Kamruzzaman, 2013, Whitfield 1998; Thys van Audenaerde et al., 1980; Lowe-
Albaret 1999; Blaber, 2000; Jeffries and McConnell, 1987; Kurt and Hecky, 1987;
Mills, 1990; Furhan Iqbal et al., 2004; Ali, Brichard, 1989; Coulter, 1991; Snoeks,
1999; Koloanda and Oladimeji, 2004; 1991; 1994; Hori et al., 1993; Nakai et al.,
Ojutiku and Kolo, 2011). Among the 1994). Although abundant, rivers of the
physicochemical factors, temperature, Albertine Rift valley have received little
Dissolved Oxygen, pH, turbidity, water research attention from ecologists and
transparency and current among others, remain largely unknown in many respects
and their regular or irregular fluctuations, (Lehman, 2002). Many of these rivers are
have been identified as determinants in also believed to provide important
riverine fish ecology (Boyd, 1998; spawning grounds for commercially
Whitfield 1998; Ali, 1999; Albaret, 1999; important lake fishes (Lowe-McConnell,
Blaber, 2000; Thirumala et al., 2011; 1987; ICNC, 1972).
Mushahida-Al-Noor and Kamruzzaman,
2013). Virtually, very little direct measurements
are available (Lehman, 2002; Kasangaki,
Marshall and Elliot (1998), noted 2007; Kasangaki et al., 2008; Mbalassa,
significant correlations between a number 2008; Bagalwa et al., 2014) for the water
of individual fish species and water chemistry of rivers draining into Lake
temperature, salinity, dissolved oxygen Edward in the Albertine Rift valley. Some
and depth. Blaber and Blaber (1980) chemical measurements done in several
reported that turbidity is associated with bays and river deltas (Damas, 1937;
productive feeding areas and provides Marlier, 1951, 1954) showed that, nutrient
cover for fishes. Other studies have concentrations found in Lake Edward over
determined that fish move away from years, were highly influenced by the
alkaline waters when pH levels approach fluvial inputs to the lake (Lehman, 2002).
9.06 – 10.0, unless more important According to Kilham (1984), Lake
survival factors outweigh avoidance, Edward and all of the lakes of the
including food availability or lower Albertine Rift valley are ecologically and
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evolutionary influenced by their affluent (Beadle, 1981). An analysis of the
inputs. physicochemical parameters is necessary
to understand ecological and
Despite their ecological and evolutionary environmental pathways of Lake Edward
roles, the real ecology and chemistry of aquatic resources. The objective of this
the rivers that flow into Lake Edward is study was to determine the
essentially unknown and unmeasured physicochemical parameters in lower
(Kilham, 1984; Lehman, 2002). One such Ishasha River and Lake Edward for their
affluent is Ishasha River at the Republic ability to support aquatic species,
Democratic of Congo - Uganda border in especially fish in the selected sites.
the Bwindi, Virunga and Queen Elizabeth
National Parks. Recent ecological studies Materials and Methods
in some rivers, including Ishasha River
have made a contribution to the Study site
understanding of the ecological aspects
such as fish diversity (Kasangaki, 2007; Lake Edward is a natural border of the
Mbalassa, 2008) and the impacts of Democratic Republic of Congo (DR
exogenous inputs into the riverine benthic Congo) and Uganda in the Albertine Rift
communities (Kasangaki et al., 2008). region (Fig.1). The lake is located at 912
m of altitude, between 29o 15’ and 29o 55’
Ishasha River is of immense significance East and 0o 45’ South (Verbeke, 1957;
in terms of ecological services, fisheries Beadle 1981). Its watershed drains a total
resources and, economic benefits to area of about 2, 250 km2 (Damas, 1937).
communities around Lake Edward Basin. The lake has a maximum length of about
It runs through four protected areas 80 km and the maximum width of about
namely Mgahinga, Bwindi, Queen 40 km, with the maximum depth
Elizabeth and Virunga National Parks, estimated at 117m, while the mean depth
before it pours into Lake Edward (Beadle, is about 40 m, and water volume of
1981). These protected areas are among approximately 90 km3 (Damas, 1937;
the critical world heritage sites and Verbeke, 1957). The climate is tropical
biosphere reserves (IUCN, 1997; 2001; with bimodal rainfall distribution. The dry
2002). Ishasha is believed to provide season spans from December to February
feeding and spawning grounds for and June to August and the rainy season
migratory fish species from Lake Edward from March to May and September to
(ICNC, 1972; Mbalassa, 2008). The river November. The annual rainfall varies from
is also important to the people of the areas; 650 - 900mm (Verbeke, 1957; Beadle,
it is used as source of water and fish, and 1981). The monthly mean maxima of
contributes to livelihood sustenance of the temperature vary from 26.3oC in January
local communities. Because of its role as to 30oC in September, while the minima
spawning grounds for fish, its downstream vary from 15.5oC to 17.8oC. The absolute
habitats are considered sensitive and maximum temperature is of 32oC
should be protected from human generally in February, and the absolute
disturbance (ICNC, 1972). minimum temperature is of 14oC generally
recorded in January, February, June and
There is no doubt that fish are driven by July (Damas, 1937; Verbeke, 1957). The
their physicochemical surroundings to watershed has many tributaries, major
areas that are physiologically optimal ones being Ishasha, Rutshuru, and Rwindi
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Rivers from the Virunga Volcanoes in the measurements were done within a 200
southeast of the lake in the DR Congo side meter sampling-stretch in the middle of
and Ntungwe, Nchwera, Rwampunu, section of the river at surface water. In the
Nyamweru Rivers and Nyamugasani river lake, measurements were done within 500
(from Ruwenzori highlands), and Kazinga meters in the littoral zone from the river
channel in northeast of the lake in the mouths. At this distance, waters from the
Uganda side (Figure 1). Ishasha River runs two ecosystems (river and lake) were
through four protected areas namely assumed to be completely mixed.
Mgahinga, Bwindi, Queen Elizabeth and Physicochemical parameters including
Virunga National Parks before it pours water surface temperature (To), pH,
into the lake (Beadle, 1981). These electrical conductivity (EC), and the total
protected areas are vital components for dissolved solid (TDS) were directly
conserving and managing freshwater measured using the HI 98129 Combo pH
resources, ecosystems and biodiversity of & EC/TDS meter. Water transparency
the Albertine Rift Valley (Plumptre et al., (TRA) was evaluated using a black &
2003, 2004). white Secchi Disc Wildco (P/N 58-B20,
S/N2710). The content of dissolved
Fig.1: Study area and sampling sites (in oxygen (DO) at each site was assessed
red) along Lower Ishasha River and in the with the aid of the DO Meter (YSI55). The
littoral zone of Lake Edward, in Virunga analysis of variance (ANOVA) was run to
and Queen Elizabeth National Parks, compare the variations in physicochemical
Albertine Rift Valley. The sampling sites parameters between sites. The Pearson’s
in the river were established based on their correlation ‘r” was performed to determine
accessibility and the level of human affinities among the physicochemical
impact. Five sites were selected along the parameters using Past3 Software. All the
river; these include Kinyozo (upstream), parameters were compared with water
Lulimbi (middle stretch), Kagezi I, Kagezi quality standards (Boyd and Tucker, 1998;
II and Kagezi III (River mouths). Kagezi I, Ali et al., 2000) in relation to their
II, and III sites form a delta of river suitability to sustain aquatic species in the
mouths of the Ishasha River distant of 3 selected sites.
km in average from each other, pouring
into Lake Edward. In the littoral zone, Results and Discussion
three sites namely Kagezi I-littoral, Kagezi
II-littoral, and Kagezi III-littoral were The mean values of water
selected based on the level of interaction physicochemical parameters in selected
between the river and the lake (Fig. 1). sites along the Lower Ishasha River and
their correlation analysis are presented in
Water Sampling the tables 1and 2, respectively.
Some parameter such as surface
Water sampling was carried out in July – temperature was found relatively
August and September – October 2011 consistent in sampling sites of rivers.
and in February –March and April - May Little, but significant (F = 2.665, p < 0.05)
2012. At each site, sampling was done variations were detected between the sites.
twice a month and each day, Water appeared to be relatively warm
measurements were taken between 6:00 - around Lulimbi (middle stretch), followed
9:00 in the morning, and between 4:00 - by the water around Kagezi III and II river
6:00 in the evening. In the river, months. While, water was found to be cool
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around Kagezi I river mouth compared to the downstream of the river, they receive
other sites. runoff from upriver which brings sediment
loads and organic matter from the heavily
The content of dissolved oxygen (DO) in agricultural lands and deforested areas
the water differed significantly between from adjacent headwaters of the river.
sampling sites (F = 74.96, p < 0.05).
Therefore, the water around Kinyozo Water transparency varied significantly
(upper stretch) and Lulimbi (middle along the river (F = 22.65, p < 0.05).
stretch) contained much more DO than the Therefore, at Kagezi I river, mouth water
rest of the sites. The maximum DO was much clearer than in other sites, this
recorded in these sites was about 6.9 mg/L was followed by the water at Kagezi III
in Lulimbi and the lowest DO was and Kagezi II river mouths, measuring in
recorded in Kagezi II (1.36 mg/L). The average 58.87±3.62 cm, 53.25±5.13 cm,
results show that the upstream sampling and 43.81±1.71 cm, respectively. At
sites, namely Kinyozo and Lulimbi Lulimbi and Kinyozo, water appeared
contained high content of DO than the more turbid, measuring in average
downstream ones, including Kagezi I, II 12.8±0.94 cm and 19.17±1.59 cm,
and III river mouths. respectively.

The water status showed very significant Person’s r correlation in these different
variation in pH values between the sites (F sites about the selected limnological
= 33.28, p < 0.05). However, the water parameters is presented in table 2. The
was found to be alkaline in Kinyozo and Pearson’s r correlation analysis allowed
Lulimbi with 7.33±0.09 and 7.02±0.07 noticing that, some parameters along the
values of pH, respectively. Whereas, in river flow were strongly positively or
Kagezi I, II, and III river mouths water negatively correlated between them. A
was found to be acidic with 6.3 ± 0.03, strong and significant correlation was
6.57±0.08, and 6.60±0.03 values of pH found between the concentration of DO
respectively. and the level pH (r = 0.89, p < 0.05), very
strong positive significant correlation (r =
The content of TDS (F = 20.49, p < 0.05) 0.99, p < 0.05) was found between the
in water and the level of water EC (F = content of TDS and the level of EC along
22.49, p < 0.05) varied significantly the rivers. Positive correlations were also
between the sites. The table shows that found between water transparency and the
among the sites, Kagezi II contained high content of TDS (r = 0.68), and the level of
quantity of TDS (52.87±1.98 mg/l) EC (r = 0.63).
compared to other sites. This was followed
by Kagezi III and Kagezi II with averages However, strong and negative correlations
of about 45.62±2.02 mg/l and 40.75±0.82 were found between the concentration of
mg/l respectively. Water around Lulimbi DO and the content of TDS (r = - 0.86, p <
contained less TDS (31.2±2.24 mg/l) than 0.05), level of EC (r = - 0.83, p < 0.05),
others sites. The results show that, the and between the concentration of DO and
water from the three sites Kagezi I, II, and the level of water transparency (r = - 0.94,
III contained high content of TDS and p < 0.05). Negative correlations were also
high level of EC compared to Kinyozo and found between the variation of To and the
Lulimbi. The three sites, being located at content of TDS (r = - 0.08, p > 0.05), level
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of EC (r = - 0.06, p > 0.05), and between water around Kagezi III-littoral zone
the variation in To and the level of water contained much TDS, measuring in
transparency (r = - 0.43, p > 0.05). average about 361.12±1.47 mg/l; this was
Negative correlations were again found followed by water around Kagezi II-
between the value of pH and the content of littoral zone with 297.25±17.54 mg/l.
TDS (r = - 0.61, p > 0.05), level of EC (r = However, the water around Kagezi I-
- 0.59, p > 0.05), and between the value of littoral zone measured less TDS
pH and the level of water transparency (r = (212.56±44.36 mg/l) compared to the rest
- 0.90, p < 0.05) along the lower Ishasha of sites. The level of water EC varied
River. significantly from site to site (F = 7.049, p
< 0.05). High level of EC was found in
The limnological parameters measured in water around Kagezi III-littoral zone
the littoral sites in the Lake Edward and (718.31±4.15 µm/cm), followed by water
their correlation analysis are presented in around Kagezi II-littoral zone, with
table 3 and 4, respectively. The 589.50±17.54 µm/cm and Kagezi I-littoral
temperature of the surface water in littoral zone with 426.18±88.65 µm/cm.
zone was in general high in all selected
sites, but with significant variation Water transparency varied significantly
between the sites (F = 4.704, p < 0.05). between the sites (F = 7.462, p < 0.05),
The results show that water around Kagezi water around Kagezi III-littoral zone was
III-littoral zone was much warm much more transparent up to
(27.55±0.19 oC); whereas water around 108.56±10.67 cm deep, followed by water
Kagezi I-littoral was slightly cool around Kagezi II-littoral zone (82.56±6.68
(25.59±0.62 oC). The difference in DO cm deep) and Kagezi I-littoral zone at only
concentration was not significant between 64.87±5.95 cm deep. Person’s r
selected sites (F = 2. 273, p > 0.05) in the correlation in the littoral sites is presented
littoral zone. It was noticed that, water in table 4.
around Kagezi III-littoral zone contained
high DO (5.16±0.36 mg/l); followed by In the littoral zone, all the parameters
water around Kagezi I-littoral zone analyzed were found positively strongly
(4.01±0.66 mg/l). Whereas around Kagezi correlated between them. Strong, positive
II-littoral zone contained relatively less and significant correlations were found
DO (3.80±0.36 mg/l). between temperature and DO, pH, TDS,
EC and TRA. pH is also strongly positive
Water was generally alkaline in all the correlated with TDS, EC and TRA, where
selected sites, but the level of pH TDS is strongly correlated with EC and
fluctuated significantly between the sites TRA. There is also a strong positive
(F = 9. 536, p < 0.05). Water around correlation between EC and TRA. For DO
Kagezi III-littoral zone had slightly a high with other parameters there are positive
level of pH (8.88±0.02) than other sites, correlations.
followed by water around Kagezi II-
littoral zone (8.78±0.05), and then by The temperature values recorded in all
water around Kagezi I zone (7.62±0.32). sampling sites in both river and littoral
The quantity of TDS fluctuated zone were generally high, and varied
significantly between the selected sites (F between 22.62±0.16oC - 23.8±0.40°C
= 7. 313, p < 0.05). The results shows that (river) and 25.59±0.62oC - 27.55±0.19oC
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(lake), although little variations were provide some of the best habitats for the
observed between sites, temperatures fitted biological functions of aquatic species in
within the limits standards (Colman et al., these water systems. In the littoral zone,
1992; Boyd, 1998). The present trend has strong correlations were related between
already been acknowledged by Lowe- water temperature and other factors such
McConnell (1987), and pointed out that as DO, pH, TDS and EC. Tassaduqe et al.
tropical regions are characterized by high (2003) also found that the levels of pH and
temperatures with relatively little dissolve solids in the Indus River, Pakistan
variations. For example, the temperatures were directly related to the water
of Lake Victoria were found fluctuating temperature. However, temperature is
between 23°C and 26°C throughout the known by far as the most critical factor
year (Lowe-McConnell, 1992). influencing both aquatic life and other
Temperature is known to have a physicochemical parameters in the water
significant effect not only on the system (Huet, 1986; Colman et al., 1992;
biological functions of the aquatic Boyd, 1998).
organisms, but also on other
physicochemical parameters (Beadle, Among the dissolved gases, the dissolved
1981; Huet, 1986; Lowe-McConnell, oxygen plays the most important role with
1987; Colman et al., 1992; Boyd, 1998). regard to the water quality. It is critical for
However, Kasangaki et al. (2008) found aquatic organisms’ respiration (Colman et
out that, temperature, pH, and water al., 1992). Therefore, the dissolved oxygen
transparency were among the most is among determining factors for the
important factors predicting benthic survival and the growth of aquatic
macro-invertebrate assemblages in the organisms. In the present study, DO
upper Ishasha River. showed high values (> 5 mgl-1) in the
upstream sites, indicating that it was
In most of tropical water systems, species within the permissible limits for aquatic
grow best at temperature between 20 oC lives; whereas DO values were close to the
and 32 oC and water temperatures minimum limit at the downstream sites.
generally remain in this range year-round The content of DO showed an inverse
(Lowe-McConnell, 1987; Boyd, 1998). longitudinal pattern to the river flow
Temperature values recorded during the gradient. This could result from the fact
study period corroborated with the values that, at the upstream sites (Kinyozo and
found by Bagalwa et al. 2014 and those Lulimbi); the river crosses along savannah
reported by Damas (1937), Marlier (1951, grassland area, and receives a direct
1954), Verbeke (1957) and Lehman sunlight which is known to influence the
(2002) in the same areas. The later increase of photosynthesis rate (Boyd,
reported that the monthly mean 1998). The photosynthesis rate combining
fluctuations in temperature values ranged with the water turbulence, could be among
between 20 to 26oC. They further revealed factors contributing to the higher oxygen
that, cloud cover and wind speed were by content recorded upstream. Wootton
far the most influencing climatic factors of (1992) and Maitland and Morgan (1998)
the temperature in the region. In respect to revealed that, the upper stretches of rivers
our findings with regards to the are usually characterized by well-
temperature conditions, lower Ishasha oxygenated water and a current
River and Lake Edward were proved to sufficiently high. The lower content of DO
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recorded at the downstream sites, could One of the major indicators of the water
result from the decomposition of large quality, after the dissolved gases (O and
2
amount of organic matter from high CO ), is the ionic composition of water, of
2
density of aquatic plants covering the river which most important measure is the pH
mouths around these sites. A study by (Colman et al., 1992). The pH is known to
Boyd (1998) found out that, in tropical influence the physiological functions of
waters the rate of DO consumption by fish and other aquatic lives. In upper
decaying organic matter is greater. DO Ishasha River, pH was among the most
showed direct relation with pH along the important factors predicting benthic
river. The reason could be that the macro-invertebrate assemblages
decomposition of organic matter is (Kasangaki et al., 2008). Around a pH 7,
believed to release amounts of humic acids the nutrients are easily assimilated by most
during mineralization that keep water of the plant organisms and the food chain
acidic and thereby decreases the pH. can develop normally (Colman et al.,
Lowe-McConnell (1987) stated that 1992). In turn this allows a good growth of
decomposing vegetal debris generally fish species, among others. The pH of
makes the water acidic. At the same, the water is important because many
DO decreases due to its uptake by biological activities can occur only within
decomposing organisms like bacteria a narrow range (Tassaduqe et al., 2003).
(Boyd, 1998). This could explain the high Thus, pH range for diverse fish production
and significant correlation (r) found is between 6.5 and 9 (Boyd and Tucker,
between the content of DO and the level of 1998; Ali et al., 2000). Any variation
pH along the Lower Ishasha River. beyond acceptable range could be fatal to
many aquatic organisms (Furhan Iqbal et
In the littoral zone, the content of DO was al., 2004).
slightly lower than the safe limits (< 5mgl-
1) at two sites (Kagezi I & II). While at In the present study, upstream sites
Kagezi III, DO was within the safe limits. showed high values of pH than the
In the littoral zone, dissolved oxygen downstream ones. High values of pH at
showed negative relationship with total upstream sites (Kinyozo and Lulimbi) may
dissolved suspensions, water conductivity be caused by the combined effect of low
and transparency. However, water alkalinity and high surface water
turbidity is known among major factors temperature (Marlier, 1954). Whereas, the
decreasing water transparency. The acidic pH recorded at downstream sites
turbidity also affects the penetration of the (Kagezi I, II & III) may be influenced by
sunlight into water (Maitland and Morgan, the presence of humic acids from the
1997) and thereby reduces the decomposition of Papyrus and organic
photosynthetic rate in water, which in turn matters from other macrophytes on the
could reduce the DO content. The results river banks (Lowe-McConnell, 1987).
show that, though water contained DO But, even though, all the values of pH
sufficient to support many aquatic lives in measured along lower Ishasha river
the selected sites, relative variation in its channel set within the limits of standard
content was detected from site to site, ranges, therefore suitable for production of
suggesting that DO is subject to fish and most of aquatic lives. The pH
spatial/local variations within the lower range in the littoral zone varied within the
Ishasha and littoral zone Lake Edward. favourable range, showing the littoral zone
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as suitable for fish production. The present along the river, and to the TDS, Tº, pH
pH values confirm those reported in among others in the littoral zone.
previous studies (Damas 1937; Marlier However, several factors influence the
1951, 1954; Verbeke, 1957; Lehman, conductivity including temperature, ionic
2002; Bagalwa et al. 2014) in the same mobility and ionic valences (Boyd, 1998;
lake. Furhan Iqbal et al., 2004). In turn,
conductivity provides a rapid mean of
Total dissolved solids indicate the total obtaining approximate knowledge of total
amount of inorganic chemicals in solution dissolved solids concentration and salinity
(Colman et al., 1992; Furhan Iqbal et al., of water sample (Odum, 1971). Both, the
2004). A maximum value of 400 mg L-1 of suspended solids and turbidity affect the
total dissolved solids is permissible for penetration of light under water (Maitland
diverse fish population (Boyd and Tucker, and Morgan, 1997; Furhan Iqbal et al.,
1998; Ali et al., 2000). From the results of 2004).
this study, TDS content for both river
channel and the littoral zone of Lake Light penetration varying from 30 cm to
Edward was within the permissible limits, above 60 cm was acknowledged to be
demonstrating that these habitats are favourable for fish production (Boyd and
favorable for aquatic biodiversity. Indeed Tucker, 1998; Ali et al., 2000). However,
many ecologists have revealed a positive in this study the estimated values of water
correlation between total dissolved solids transparency were within the permissible
and turbidity (Chaudhry et al., 1990; limits (43.81±1.71 cm -108.56±10.67 cm),
Salam & Rizvi, 1999; Furhan Iqbal et al., in all downstream and littoral sites. On the
2004). Turbidity is known to have a contrary, water transparency in upstream
negative influence on aquatic diversity, sites was below the limits (12.8±0.94 cm -
distribution and abundance (Cohen et al., 19.17±1.59 cm). Therefore, lower values
1993). of water transparency observed in the
upstream sites could be related to the
The turbidity affects the respiratory intensive agricultural activities along the
capacity of fish and the photosynthetic river catchment, among others.
activities of the plant organisms (Colman
et al., 1992). However, according to Heavy cultivation along with deforestation
Blaber (2000), turbidity can affect fishes was permanently observed on the hills
in three main ways: it may afford greater with steep slopes of the river affluents and
protection for juvenile fish from predators; on the river head waters during the study
it is generally associated with areas where periods. The runoff from the cultivation
there is an abundance of food; and it may and uncovered hill flanks could drain
provide an orientation mechanism for subsequent sediment which in turn
migration to and from the river. Despite its decreases water transparency in the river.
ecological value, excessively high water Maitland and Morgan (1997) stated that
turbidity has been proved to affect fish egg the clearing of forests for agriculture also
survival, hatching success, feeding increases the runoff of surface water and
efficiency (mainly of filter feeders), the rate of soil erosion with subsequent
growth rate and population size (Whitfield silting in the waters draining such areas.
1998). In the present study, the water EC Accordingly, Moss (1988) found out that
was found highly correlated to the TDS Papyrus and other macrophytes inside the
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Int.J.Curr.Microbiol.App.Sci (2014) 3(6): 230-244

river and on the riverbanks, act as huge located in the forest and boundary habitats.
filters for silt and change chemical They also revealed that water transparency
composition of the water passing through. was among the most important factors
Kasangaki et al. (2008) found out that, the predicting benthic macro-invertebrate
agricultural and deforested sites in the assemblages in the upper Ishasha River.
upper Ishasha River generally had low
transparency values compared to the sites

Fig.1 Study area and sampling sites (in red) along Lower Ishasha River and in the littoral zone
of Lake Edward, in Virunga and Queen Elizabeth National Parks, Albertine Rift Valley

Table.1 Mean values (Mean±SE) of water physicochemical parameters in selected sites
along the lower Ishasha River, Albertine Rift region
Sites
Kinyozo Lulimbi Kagezi I Kagezi II Kagezi III
Parameters (RC) (RC) (RM) (RM) (RM) STRDS
Tº (oC) 23.04±0.55 23.8±0.40 22.62±0.16 23.35±0.11 23.60±0.17 20-32
DO (mg/l) 6.64±0.17 6.9±0.54 1.91±0.30 1.36±0.15 1.55±0.03 > 1≥ 5
pH 7.33±0.09 7.02±0.07 6.34±0.03 6.57±0.08 6.60±0.03 6.5 -9
TDS (mg/l) 36.33±1.65 31.2±2.24 40.75±0.82 52.87±1.98 45.62±2.02 ≤ 400
EC µS/cm 73±3.32 62.7±4.56 82.12±1.89 112.5±4.86 91.68±4.15 20-1500
TRA (cm) 19.17±1.59 12.8±0.94 58.87±3.62 43.81±1.71 53.25±5.13 > 30 - 60

Legend: SE: Standard Error, RC: River channel; RM: River mouth; STRDS: Standards of water
quality (Boyd and Tucker, 1998; Ali et al., 2000)

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