18 September 2009 culture period ranged between nine and 18 months. The farms were completely drained after each culture period but a portion of the water was frequently renewed during the culture period. Fertilization and nutrition were used at sites II and III, while they was not in use at site I, even though that site had the highest fish production. Bacteriological Analysis For bacteriological studies, water and sediment samples were taken from each source and one representative growout pond on each farm. Sterile glass bottles and plastic bags were used for the samples. Cultured fish samples (Oreochromis niloticus) were collected from each farm and packed immediately in sterile polyethylene bags. Samples were analyzed immediately following Standard Methods for Examination of Water and Wastewater (APHA 1992). Total viable bacteria (TVB) and Aeromonas species (Aero.), known to be opportunistic human pathogens, were quantified in addition to three indicators of fecal contamination: total coliforms (TC), fecal coliforms (FC) and fecal Streptococci (FS). Three replicates of plate count agar, Endo Agar Base and Azide Agar Base culture media were adopted from the Oxoid Manual (1985) and Ampicillin – dextrin agar (ADA) medium for the enumeration of Aeromonas spp. in water by membrane filtration (Havelaar et al. 1987). For enumeration, isolation and preliminary identification of bacteria in the samples, serial dilution up to 10-4, spread plate method, micro-filtration method (Micro Filtration Systems Comp. Ca. No. A045-Do 47y, pore size 0.45 µm), were used (APHA 1992). Identification of well-isolated pure colonies proceeded to the generic level based on biochemical tests according to Bergey’s Manual (1994). Heavy Metals Analysis Triplicate water and sediment samples were taken from each source and one representative growout pond on each farm using Nansen bottle and the grab samplers. Representative samples of cultured species were collected with small nets. All the samples were analyzed for detection of the trace metals cadmium, copper, zinc and lead (Cd, Cu, Pb and Zn) with a Perkin Elmer atomic absorption Analyst 100 spectrophotometer equipped with a hydride system and graphite furnace according to APHA (1995). Results Bacteriological Analyses The mean counts of bacteria in the water at the three study sites are shown in Figure 2. The highest mean counts Fig. 1. Map showing Suez Canal and the location of the study sites. of TVB, Aeromonas spp., TC and FC were found in the water of site I (sewage water supply), while relatively low numbers were found at sites II and III, (agriculture and treated sewage water supply. The mean count of TVBs in the growout ponds were 886x102, 510 and 18x102 cfu/ mL for sites I, II and III, respectively, while the corresponding figures in their water source were 26x103, 2360 and 40 cfu /mL. Aeromonas spp. mean counts were 42x102 and 29 x102 cfu/ml for the growout pond and its water supply of site I, while Aeromonas spp. was very low in the growout pond and the water supply of sites II and III, ranging from 0-10 cfu/mL. Total coliform levels in the growout ponds were 82x103, 6x102 and 7 x102, cfu/mL and in the water supplies were 36x103, 660 and 20 cfu /mL for sites I, II and III, respectively. Fecal coliform was recorded only at site I with mean count of 82x103 and 40x103 cfu/ mL for the pond and water supply. Also, FS was recorded only in the pond of site I (4x102 cfu/mL) and the water supply of site II (8 x102 cfu/mL). The mean counts of bacteria in the sediment of the three studied sites is shown in Figure 3. A similar pattern for the mean counts of bacteria in the water was observed for the sediment at the three sites. The mean count of TVB in the sediment of growout ponds was 250, 760 and 360 cfu/g for sites I, II and III, respectively, while the corresponding figures in the sediments of their water sources were 320, 470 and 130 cfu/g. Aeromonas spp. was recorded in low numbers at site II (110 and 50 cfu/g in the growout pond and its water supply), with the lowest numbers occurring in the sediment of the water source of site I (10 cfu/g). Coliforms were recorded only at site I (5x103 and 4970 cfu/g in the growout pond and its water supply. Fecal coliform was also recorded only at site I (3760 and 41x102 cfu/g in the growout pond and its water supply). Fecal Streptococci was almost absent in all the sediment samples except for the sediment of the water supply for site I (20 cfu/g.). The mean counts of bacteria in the farmed fish at the three studied sites are shown in Figure 4. The highest contamination was recorded in the farmed fish at site I. The mean counts of TVB in muscles of O. niloticus were 225x102, 10 and 23 cfu/g for sites I, II and III, respectively. Aeromonas spp. were recorded only in low numbers in the O. niloticus of site II (10 cfu/gm). Total coliform counts were 178x102, 300 and 300 cfu/g and FC counts were 16x103, 100 and 190 cfu/g for O. niloticus at sites I, II and III, respectively. Fecal Streptococci were completely absent in the fish samples. Heavy Metal Analyses The mean concentrations of cadmium, copper, zinc and lead in water at the three study sites are presented in Table 1. The mean concentrations of heavy metals studied were (Continued from page 16)
RkJQdWJsaXNoZXIy MjExNDY=