الفهرس 
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Abstract
The present work was carried out during the period of November-2004 throughout December-2005 at two sites the first was located near the end of Ismailia freshwater canal while the second located near the entrance of Ismailia Drinking-water Plant on the canal. It was aimed to determine the species composition of phytoplankton and physico-chemical parameters affecting the algal periodicity and growth. A short term study was also conducted to evaluate the ability of the water extracts of two medicinal plants Hordeum vulgare (L) and Artemisia judaica either singly or in combination to inhibit the growth of the bloom-forming cyanobacterium Oscillatoria brevis (Kütz.) which known to produce off-flavor problems and toxins in water supply.
Water parameters
Air temperatures varied from 16ºC in January 2005 to 39ºC in August 2005 with an annual mean of 27.35ºC. Water temperatures were highly correlated to the air temperatures (0.996). It was ranged from 15º to 36ºC with a slight variation (0.5 to 1ºC) among the two sites. The recorded values of pH in the two studied sites were neutral to slightly alkaline (7.4 – 9.5). There was a narrow range of variations (0.2 – 2.1) among the sites and the months (0.1 – 0.9 in site I, and 0.1 – 1.3 in site II).
The highest water conductivity was 1997μmohs.cm-1 during November, while the lowest was 211μmohs.cm-1 during August in site II and the average 574.1 μmohs.cm-1. The total dissolved solids were between 99mg.l-1 during August and 1030mg.l-1 during November, with an average of 375.85mg.l-1. TDS was highly correlated to the water conductivity (r = 0.996).
The oxygen levels were between 2.93 and 7.419mg.l-1 in site I and between 2.77 and 8.645mg.l-1 in site II. The annual mean for the two sites was 5.88mg.l-1. COD showed great variations during seasons; the higher values were obtained in winter and autumn (21.6mg.l-1 at site I and 25.6mg.l-1 at site II), while the lower values were obtained during summer (3.2mg.l-1 at site I and 4mg.l-1 at site II). Chlorophyll a was varied throughout the study period. The maximum was 6.142µg.l-1 during February and the minimum was 0.1903µg.l-1 during January.
Nitrate greatly varied among the months. The maximum was 97.35µg.l-1 in October and the minimum was 6.967µg.l-1 in November, with an annual mean of 35.4µg.l-1. The minimum nitrite was 0.45µg.l-1 during March and the maximum was 5.648µg. l-1 during September at site II. High ammonium content was recorded, 99.3 - 3397.21µg.l-1, with an average of 1178.9µg.l-1 at site I; and 188.15-5168.9µg.l-1, with an average of 1789.35µg.l-1 at site II. Phosphate ranged between obtained as 4.3-79.65µg.l-1 in site I and as 12.19-93.28µg.l-1 in site II. Silicate was 185.84-3115.33 µg.l-1 with average of 1568.65µg.l-1 in site I, and 91.96-4027.32µg.l-1 with average of 1599.98µg.l-1 in site II.
Phytoplankton composition
Sixty–four species of phytoplankton were identified from the two sites, 27 of Bacillariophyta, 21 of Chlorophyta and 16 of Cyanophyta. Bacillariophyta was dominated by the species of Navicula, Cycoltella, Melosira and Nitzchia. Chlorophyta was dominated by 5 species Scenedesmus and 3 species of Pediastrum. During the bloom period, the mates of Oscillatoria brevis and O. princes dominated the Cyanophyta on the water surface. Bacillariophyta such as Cycoltella, Melosira, Navicula, Nitzschia and Synedra dominated the water column in potentially high numbers.
Algal periodicity
Cluster analysis separated the phytoplankton at site I into two major groups on dependence of the monthly co-occurrence of 41 species. The first included 15 species that showed marked seasonal periodicity. The second included 26 species that could be considered as annual species persisting throughout the year. The two major groups can be further subdivided into four sub-groups, two each. At site II, 50 species were separated into two major groups; the first included 22 species that showed marked seasonal periodicity; and the second included 28 species that could be considered as annual species. Each major group can be further subdivided into three sub-groups.
Species abundance:
The abundance of the phytoplankton was low during winter, increased by spring, reached the maximum by fall. The Bacillariohyta dominated the two sites throughout period of the 14 months. Its annual mean was 249cell.l-1 for site I and 832cell.l-1 for site II. The annual mean of Chlorophyta was 110cell.l-1 at site I and 89cell.l-1 at site II. In contrast to Chlorophyta, Cyanophyta dominated site I by 102cell.l-1 and site II by 140cell.l-1.
Site I was dominated by Cosmarium panamense, Pediastrum clathratum and P. obtusum from Chlorophyta; Chroococcus tenax, C. turgidus, Gloeocapsa polydermatica, Microcystis aeruginosa, M. elongate from Cyanophyta; the species of Cycoltella, Navicula, Nitzschia and Synedra from Bacillariophyta. Site II was dominated by Pediastrum clathratum and P. obtusum from Chlorophyta; the species of Melosira, Nitzschia and Synedra from Bacillariophyta.
Cyanobacterial algal bloom:
A bloom of Oscillatoria brevis and O. princes was found at site II and continued for four weeks, from February 1 to March 1, 2005. The two species formed compact algal mates on the surface of the water. The water column below these mates was dominated by many species of Bacillariophyta especially those of the Amphora, Cycoltella, Melosira, Navicula, Nitzschia and Synedra.
Water parameters during algal bloom:
Air temperature reached to 31ºC at the first week, decreased to 19ºC in the second, raised again to 28ºC in the third then decreased to 23ºC by the fourth week. Water temperature rose to 27ºC, decreased 17ºC, rose again to 25ºC, and then decreased to 21ºC.
The pH was narrowly fluctuated (8.5 to 9.2). Dissolved oxygen was first at 9.56mg.l-1, decreased to 3.38mg.l-1, then raised to 6.12mg.l-1 by the fourth week. Chemical oxygen demand was between 3.2 and 12.8 mg.l-1.
Nitrate was measured as 15.67µg.l-1 at the first week and decreased to 5.85µg.l-1 by the end of the blooming. Nitrite was more or less stable during three weeks (2.3, 2.8, and 2.6 µg.l-1, respectively) then increased to 4.5 µg.l-1 by the fourth week. Chlorophyll-a showed a trend parallel to that of nitrate; started at 4.61µg.l-1 and ended at 1.95µg.l-1. Ammonium showed a contrary trend; it started at 329.3µg.l-1 and ended at 1369.0µg.l-1, with an exceptional measure of 135.9µg.l-1 during the third week. Phosphate and silicate showed no clear pattern of variation during algal bloom.
Control of algal bloom by medicinal plants:
A short term study was conducted to evaluate the ability of the water extracts of two medicinal plants Hordeum vulgare (L) and Artemisia judaica either singly or in combination to inhibit the growth of the bloom-forming cyanobacterium Oscillatoria brevis (Kütz.) which known to produce off-flavor problems and toxins in water supply. O. brevis was collected from Ismailia freshwater canal during an algal bloom condition in February 2005 and was grown in BG11 medium under laboratory conditions. Hormogonia number was recorded using Sedgwick rafter cell in a fixed period. The number of hormogonia of the O. brevis was significantly decreased after the treatments with the two investigated plants.
The growth rate of the cultures was gradually suppressed and failed into 59%, 27%, 27% and 22.2% when 50, 100, 150 and 200ppm of Hordeum vulgare were applied, respectively. Artemisia reduced the growth of Oscillatoria brevis within few days from application. It resulted in following growth reduction rates: 16%, 21%, 28% and 5.3% with the application of 50, 100, 150 and 200 ppm, respectively.
A second experiment was carried out for about six weeks to test the inhibitory effect of the lower doses of the two medicinal plants. With the application of 0.2, 0.41, 0.62 and 0.83 ppm of barley straw, the yield suppression ratio (YSR) were 32.6 %, 12 %, 9% and 4.1%, respectively. Artemisia suppressed the growth of O. brevis to 20.5%, 12%, 10% and 8% with the application of 0.2, 0.41, 0.62 and 0.83 ppm, respectively.
Also, a combination of the two plants produced a clear impact in the growth of the cyanobacterium. Growth suppression was 15.2%, 12%, 8% and 8% when Hordeum to Artemisia in a ratio of 1:1 were added by 0.2, 0.41, 0.62 and 0.83 ppm, respectively. The numbers of hormogonia were more affected due to the combinations in 3:1 Hordeum to Artemisia that was proved by a higher reduction ratio as below: 10.6 %, 7.4 %, 8.6 % and 7.2% remained from the initial culture.