الفهرس 
Seasonal study on phytoplankton and phytobenthos in Qarun LakeOnly 14 pages are availabe for public view
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Abstract
The present investigation deals mainly with the study of the algal flora of Qarun Lake and Wadi El Rayan Lakes. Phytoplankton and phytobenthos materials were collected seasonally from these lakes during the period from September 2007 to May 2008. Physical and chemical characters of waters at the investigated lakes were also studied, in an attempt to find out the relationships between these environmental factors, algal assemblages and species composition.
As regards to the phytoplankton, phytobenthos and periphytic algae grown on sediments, a total of 90 algal taxa from 51genera related to 6 algal divisions were identified from Qarun Lake. The total number of phytoplankton recorded was 34 species. The maximum number of individuals was recorded at the eastern side and the minimum value was found at the western side of the lake. The blooming of Prorocentrum micans was observed in Qarun Lake. Examination of epilithic and epiphytic algal growth revealed the identification of 67 algal taxa belonging to five algal divisions. The highest phytoplankton biomass in Lake Qarun was obtained in summer season which is confirmed by the maximum value of chlorophyll a during the same season. from the available literature, it was found that 16 algal taxa were newly recorded in Qarun Lake
With regard to the salinity level in the upper and the lower lake of Wadi El Rayan it was noted that the 2nd lake was more saline than the 1st lake as the salinity values detected in water of the lower lake of an average 8.79 %o were higher than those values that recorded in the water samples of the first lake of an average 1.38 %o. Therefore, water of the upper lake was found to be in the range of freshwater while the water of the lower lake was brackish - marine tendency.
A total of 63 genera were recorded from the upper and lower lakes where the highest number of genera was observed at the upper lake of 54 algal genera and the lowest value was found at the lower lake by 33 genera. It was found that 93 taxa were recorded at the upper lake and 55 taxa were observed at the lower lake. A remarkable algal bloom of Microcystis aeruginosa, Microcystis flos – aquae was found during winter season in the upper lake. This algal bloom cause many problems in the water due to the potential toxicity of Microcystis spp. Concerning the phytobenthos recorded at the upper lake and lower lake of Wadi El Rayan, 154 algal taxa were recorded where the highest number was found at the second lake of 118 taxa and the lowest one were found at the first lake of 109 taxa. According to the available literature on Wadi El Rayan Lakes, 50 new algal taxa were recorded in the two lakes.
In conclusion, the results obtained from this investigation indicate deterioration in the physicochemical characters of the studied lakes due to the substantial input of fertilizers and nutrient salts which show an exacerbated problem of eutrophication. Also Qarun Lake and the lower lake of Wadi El Rayan suffered from progressive increase of salinity results in altering the ecosystem of these lakes by the time. Such changes lead to the decrease in the inhabiting biota. As a result of algal bloom, potential toxicity of the water was increased leading to many problems.
Then it is recommended that, continuous studies must be done to pursuit the different changes in the physicochemical characters and the effect of its higher accumulation on the productivity of the lakes and also reducing the pollutants loaded into the lakes by the treatment of this water before gushing into the lakes in order to decrease the algal bloom and potential toxicity.
Keywords: Qarun Lake, Wadi El Rayan Lakes, Inland Lake, water quality, eutrophication, algal bloom.