الفهرس 
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Abstract
SUMMAR.Y
The nresent investiaation was initiated to make a comprehensive
investiaation of the ~na. tural .o• hv.•. too..lanktonic communities in
fish ponds. that recievinq inorqanic nutrient. especially phosphorus
and nitroqen combination.
On 12 fish ponds filled with fresh water from Gadon canal
(branch of Ismaellia canal) and auqmented with different doses of
superphosphate-P in combination with constant dose of urea-N of
Nile water reveal the following:
1- The appliad P levels had no effect on Chlorophyll ”a” biosynthesis
and fish production which were of no significant differences
between ponds under treatments. So less concentration of
P is enouah for fish production.
2- The applied phosphorus had favourable effects on the qrowth of
Chlorophyta. Bacillariophyta, Cyanophyta. Euglenophyta and total
algal counts showinq significantly different values between ponds
under treatments. However the highest effect was attained in cultures
experimented with 1.67 mq 1-1 P for a period of 5 months
with dominancy of Bacilla~iophyta.
3- The pH values of the Nile water samples were always on the
alkaline side throuqhout the whole period of stUdy.
4- pH. alkalinity. ammonia and orthophosphate-P are siqnificantly
different between ponds under treatments.
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5- Nitrate. total hardness. turbidity, Secchi disk. electric conductivity
and total soluble solids were of no significant differences
between ponds under treatments.
The data obtained from bioassay experiments clearly indicate
that:
1- All the applied N levels had a favourable effect on
Chlorophyll ”a” biosynthesis and algal counts, the maximum yield
was recorded at the highest level of N (5 mq 1-1) after 12~h days
incubation periods.
2- The applied P levels had a favourable effect on Chlorophyll
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”a” biosynthesis and alqal counts. The maximum growth obtained in
cultures supplemented with 0.78 mq 1-1 P after 12th days incubation
periods.
3- Nitroaen and phosphorus in combination enhanced Chlorophyll
”a” biosynthesis and total algal counts. The highest growth
reached at 3 mq 1-1 N + 0.78 rnq 1-1 P with N:P ratio of 4:1.
4- The organic matter (O.M) at 0.5 g 1-lcombined with constant
urea-N and superphosphate-P levels had a favourable effect on . Chlorophyll ”a” biosynthesis and total algal counts. with a
hiqhest qrowth reached on 16th days incubation period.
5- A close correlation was displayed between the Chlorophyll ”a”
accumulation and standing crop of phytoplankton popUlation.
6- With respect to genera composition and their relative proportions
in the enriched water samples. Bacillariophyta was recorded
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to be always dominant over any other group and constituted high
percentaqe of the phytoplankton populations, Chlorophyta shared
the second rank of dominance while Cyanophyta occupied the third
rank while Euqlenophyta was of rare occurrance.
7- The predominance of Bacil1ariophyta was. qenerrally, recorded
for numerous dofferent fresh water systems, when the eutrophic
state of Nile water reached 3.
8- Ammonia and orthophosphate showed a significant positive correlation
with the total phytoplankton crops after 4-days. While a
positive correlation was m~intained between phytoplankton crops &
silicate content at 16th days.
9- There is a negative correlation between total phytoplankton
yield and nitrate content.
10- Oxyqen concentration fluctuated around 5 mg 1-1 and reached
in some cases to 9 mg 1-1.
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11- Orqanic and inorqanic nutrients played the key role in the
qrowth & species composition of planktonic algae.
12- The averaqe water temperature during the present investigation
ranged between 25 to 28 CO. So Nile water samples is of warm
temperature character.
13- Good correlation could be established between algal growth &
water pH level a phenomenon that could be also detected between
the former and Chlorophyll a content of cultures.