الفهرس 
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Abstract
The present study investigated the impact of three freshwater
bivalves; namely, Caelatura aegyptiaca, Corbicula fluminea
and Unio teretiusculus on the quality of fresh water. The
investigations have been done through two categories:
First; to evaluate the condition of water quality of the study
area – Al-wasta Island on the River Nile – Assiut, Egypt,
samples of water and sediment from the field have been taken
and analyzed. Environmental parameters (Temperature of
water, pH, Conductivity, total dissolved salts and dissolved
oxygen) were measured in the Rive Nile before the beginning
of the experiment. Some chemical parameters(The parameters
included measures nutrients {(ammonia (NH4), nitrate (NO3),
nitrite (NO2), and Ortho-phosphorus (O-Po4)} total organic
carbon (TOC), total suspended solids (TSS), chemical oxygen
demand (COD), Fluoride (F), sulfate (SO4), sulfide (S),
alkalinity and phenol were measured in water of river Nile
before the beginning of the experiments. Seven heavy metals
(Pb, Cd, Fe, Cu, Mn, Zn and Cr) were determined in the water
and sediment from the study area on the river Nile.
Also samples of the three species studied have been collected
from the River Nile and let to excrete their fecal pellets in
Petri dishes in the laboratory for bacteriological test. Also seven heavy metals (Pb, Cd, Fe, Cu, Mn, Zn and Cr) were
determined in the faces of these freshwater bivalves.
The second category was the analysis of samples of water in
which the three freshwater bivalves are living (aquaria) to
determine the impact of these bivalves on water quality.
Environmental parameters (temperature, pH, Conductivity,
total dissolved salts, dissolved oxygen and salinity) were
measured daily in the water in the all aquaria. Chemical
parameters were measured daily in these water as ammonia
and some of them measured weekly as {bromide (Br), chloride
(CL), fluoride (F) nitrate (NO3), nitrite (NO2), phosphate
(PO4) and sulfate (SO4). Also seven heavy metals (Pb, Cd, Fe,
Cu, Mn, Zn and Cr) were detemiened in the tissues of the three
freshwater bivalve studied; Caelatura aegyptiaca, Corbicula
fluminea and Unio teretiusculus.
The bioconcentration factors (BCF) of heavy metals in the
tissues of the three freshwater bivalves studied; Caelatura
aegyptiaca, Corbicula fluminea and Unio teretiusculus were
determined. For most metals, a BCF value of less than 1.00 is
considered normal. from the results obtained for the
freshwater bivalve; Caelatura aegyptiaca it was observed that
Pb, Cd, Fe, Cu and Zn have BCF values ranging from 0.23 to
0.68, which are considered normal since they are less than
1.00. Mn has BCF value of 1.88 and Cr has a 1.47 BCF value.
All these values were considered too high when compared
with the highest value of 1.00 expected for any metal Falusi et al., (2007). The high BCF values obtained for Pb, Cd, Fe, Cu
and Zn therefore indicated that the metals were highly
bioaccumulated and bio-magnified in the tissues.
For the heavy metals in the tissues of Corbicula fluminea
species it was observed that Cd, Fe, Mn, Cu and Zn have BCF
values ranging from 0.08 to 0.64, which are considered normal
since they are less than 1.00. Pb has BCF value of 1.37 and Cr
has 1.56 BCF value.
In the case of the freshwater species Unio teretiusculus, it was
noticed that Pb, Cd, Fe, Cu and Zn have BCF values ranging
from 0.17 to 0.32, which are considered normal since they are
less than 1.00. Mn has BCF value of 1.72 and Cr has 1.25 BCF
value. The high BCF values obtained for Pb, Cd, Fe, Cu and
Zn therefore indicated that the metals were highly
bioaccumulated and bio-magnified in the tissues. Cr has the
highest BCF and was therefore, the most bio-magnified of all
the metals studied in the tissues of the three freshwater species
studied.
The present study showed that the freshwater bivalve species,
Corbicula fluminea was the most highly species among the
other studied species in releasing anions such as (Nitrate,
sulfate, phosphate and chloride) and ammonia around water.
The same species also had the highest impact in changing the pH and salinity. The freshwater bivalves species; Corbicula
fluminea also had the highest BCF value for heavy metals;
(Pb, Fe and Cr). The freshwater bivalve species; Caelatura
aegyptiaca had the highest impact in increasing some anions
such as (Nitrite, bromide, fluoride). It should keep in mind that
these adverse impacts of the above mentioned bivalve species
on the water were noticed in the closed habitat in the
laboratory, but in the Nile where these organisms are present,
no such effect were recorded. This is due to the dilution effect
of water.