الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
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SUMMARY
This study was carried out at. Abbassc National
Aquaculture Research Center to get some clue information
about the seasonal changes of phytoplankton~ with the
relationships of seasonal changes of aqua ervironrnental
factors under fish ponds ecosystem. This study ~~s started
from April 1988 till March 1989. Monthly, ~amples were
collected to determine water physical and chemical propert.es as well as
the communities of the prevailing phytoplankton (diffel’ent algae) in
three depths, i.e. 30, 60 and 90 em from the upper surface. The
following results could be summarized as follows:
I). Aqua factors:
A). Physical properties:
a). It was found a thermal stratifications, cs the first
wormer one on the upper water layer (the first 3C cm depth),
followed by the intermediate one which lie at the depth of
60 cm from the water surface, while the third lcyer occupy
the 90 cm from water surface, the cooler one.
b). It was found that thermal stratification is varied from
month to another. The hiahest value of stratification was
gained during Septe.ber, while the lowest onE was gained
durina May. The rate of ther.al stratification increased in
the third water layer than the second one with different
months.
c). Water teaperature is considered as the tcp of main
factors which affected all of the water properties either
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physical, chemical or biological factors.
2. Changes in dissolved oxygem (D, 02):
a), It was found that the thermal stratificatioJlassociated
with D. 02 stratification, as the D. 02 ducrease with
increasing the water depth. The upper water la~’er contain
the highest D. 02 followed by the second layer, while the
third layer contain the lowest D. O2•
b). It was found that the highest values of ). 02 were
gained during winter season (Nov” Dec” and Jan,), while,
the lowest values gained during autumn (Aug., Sept. and
Oct.). Accordingly, the deepest 02 depletion occ1Jrredduring
September (the middle of autumn).
c), There are complete relationship between p1ytoplankton
density and D. 02 concentration in water. The c)ncentration
of 0, ~ may be depended on the rate of ph)tosynthetic
activity.
3. Cbanles in water pH:
a). It was found that the pH values over 7,
reaction of water was basic. This finding is
expected as the sedement in Abbassa was basic.
i.e. the
naturally
b). It was found that very low fluctuations in pH with the
depth of water, as the values were seemed to be Dore or less
constant within the different studies depths,
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c). The seasonal changes in pH values were very low and no
clear trend was gained.
4). Changes in electric conductivity (E.C.) and i:otal
soluble salts (T.S.S.):
a). The variable changes in E.C. of water Unde1” fish ponds
habitate may be related to many factors sllch as the
applications of fertilizations, the source o~ irrigated
water, the pond sedements. the addition of fi;h diets and
decaying of organic matters. It was found that the fluctLationin E.C.
from month to another reflected its effects on T.S.S.
b). The changes of E.e. and T.S.S. seemed to be without no
clear trend with regards to the changes of water depth. But,
in some months the deepest water layer (90 em) seemed to
contain higher E.C. and T.S.S. than upper two ones.
e). The deep fluctuation (increase or decrease) in E.C. and
T.S.S., from month to another, may be resulted from many
factors which mentioned before. The sudden inctease in E.e.
and T.S.S. having a direct role on the type of ~hytoplankton
abundance which possessed the high ability to tolerate the
high levels of T.S.S.
d). It must be recommended to added more fre!:h Nile water
during the months in which the T.S.S. increasecl to dilute
the T.S.S. under Abbassa habitate to get or I1inimized the
sudden changes in T.S.S.
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5). Changes in total hardness (T.H.) and total alkalinity T.A.):
a). The T.H. values were greater than T.A .• this occurred
during the first four months of the season fronlApril till
August. On the other hand, T.H. values were lowE~rthan T.A.
from September till March.
b). It was found a high value of T.H. and T.A under the
cultivation of fishes in ponds of Abbassa habita”:eover the
desirable levels which ranging from 20 to 300 mglL.
c). The great fluctuation of seasonal changes ”f T.A. was
also noticed. but in many cases with negative correlations. It could be
revealed that no clear trends were gained with water deptt.
6). Changes in turbidity (as for.azine units):
a). It was found a continuous increase in turbidity units
during the first four months, then a deep decrease was
observed during August. However, during the other months the
fluctuation increases in turbidity were gained.
b). There are turbid stratifications under fish pond
conditions, as the third water layer was more turbid than
the other two ones. Accordinsly, the hi.her t~rbidity the
lower of photosynthetic rate was gained.
B). Chemical properties:
1). Seasonal changes in nitrogen in the forlLof nitrate,
ammonia. a••onium and total nitrogen.
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a). It was found that the nitrogen in the form of nitrate
was the domenant fraction, followed by nitrogen in the form
of ammonium (the ionized form), while ammonia ranked the
third in this respect.
b). It was found nitrate stratification phenomenon, as the
upper water layer (30 crn depth) showed the highe!lt N levels.
followed by the second depth, while the third depth ranked
the third in this respect.
c). The seasonal changes in N as the form of nitrate began
with the lowest value during April then increasE~ gradually
till it reached into the maximum during August, then decline
during September and increased during October ard November,
then decline during December and January anc increased
during February and March.
d). It was found no clear trends with N in the two forms of
ammonia and ammonium. with regards to seasonal changes and
stratification phenomenon.
2). Seasonal changes in phosphorys:
a). No clear phosphorus stratification was gainej.
b). The seasonal changes in the levels of phosph,rus seemed
to be more or less stable during the first thr~e months •
.then declined greatly from July till the end of the season.
The decline was greater during August and Septemb!r.
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3). Seasonal changes in potassium:
The level of potassium was low during
spring season and it was found in
the
high
Donths of
relatively
concentrations during the months of summer and autumn seasons.
4). Seasonal changes in calcium:
a). The seasonal change in Ca·· was not great, as this
divalent cation was found in higher amounts undEr our aqua
ecosystem.
b). Calcium stratification was not clear under our aqua
ecosystem, however, in most months the lower wa’:ersurface
(90 cm depth) contain some higher Ca·· concentration than
the upper ones.
5). Seasonal changes in sodium:
a). Na. increased during April, March and Jun, but it
decrease and fluctuated during other months. The fluctuation
in sodium levels aay be related to the ion Exchangeable
ability under our aqua ecosystem habitate.
6). Seasonal changes in iron and zinc:
a). The available and soluble iron and zinc in water were
low during different periods. The lowest iron was found
during July, September and Harch, but the higheBt value was
gained during OCtober. The higher levels of zi nc was found
during the First six months.
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b). Iron and zinc stratification showed no clear trend with
different water depths.
7). Seasonal changes in manganese:
a). The concentration of Mn·· under fish ponds of Abbassa
is relativelY high and exceed both of iron and zinc. Also,
the stratification of Mn·· was found under aqua ecosystem
habitate, as the concentration decreased gradually from the
upper surface into the lower one.
b). The seasonal changes in Mn·· was increasE:d gradually
during May, Jun, July, and August, then dec ..ine during
September, October and November.
8). Seasonal changes in sulfate:
a). It was found that sulfate seemed to be stratified under
fish pond, as the lower water layer contained higher
concentration of sulfate than the other two ones.
b). Low level of sulfate was gained during April, then
increased gradually till it reached the ma>:imum during
September, then decreased slightly during Decemt~r, January,
February and Harch.
9). Seasonal changes in chloride:
It was found higher a.ounts of chloride dlTing April,
May and June, then decline after that. In addition, there is
no clear stratification of chloride under our ecosystem.
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II. Phytoplankton population list in the study fish pond:
During the study season, it was found 29 genera of
phytoplankton which collected from fresh water of fish ponds
under this work and were classified under four phyla (or
division), i.e. Chlorophyta, pyrrhophyta, chrysophyta and cvanophyta.
A. It was found under Chlorophyta, 13 genera, classified
under 9 families and 4 orders.
B. Under Pyrrhophyta only 2 genera under 2 families and 1
order.
c. Under Chrysophyta 5 genera classified under 5 faimilies
and 2 orders.
D. Under cyanophyta 9 genera classified under
, .+ faimilies
and 3 orders.
Every genus was descriped in details in this
dissertation.
III. Veeetation analysis of phytoplankton:
A). Seasonal chances io yarious phytoplaoktoDJ\umber pet
a). The upper water layer possessed higher phytoplankton
QO •• 1:
than the lower two depths, followed by the second layer, but
the third one ranked the third in this respect.
-_. ----- ---
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b). It could be revealed that the number of phytoplankton
increased gradually during summer and the beginning of
Autumn in the upper two water layers, but the fluctuation
was gained during October till the end of the season.
c). The maximum yield of phytoplal’lktons biomass populations
were gained during December in the upper two depths.
d). There were complete correlations between the different
studied environmental factors and the biomass populations of
phytoplankton.
e). It was found a sudden increase in Chlamydomonas during
December t thus it was suggested that this genus ]’equired low
temperature, also it was presented in great amounts during
autuan and winter and disappeared coapletely during the summer season.
f). The most domenant communities under Abbassa, aqua was the
phylum of Chlorophyta, followed by phylum Cyanaphyta,
chrysophyta, while phylum Pyrrhophyta ranked the fourth in
this respect. Thus, the .ain co••unity was Chlorophyta (green algae),
g). The seasonal changes in the different members of the
four phyla were discussed in details with di’~ferent water
layers depths.
h). The correlation and the relationships analysis between
different phyla and aqua factors was discussed in details.