Habitat characteristics for different freshwater snail species as determined biologically through macroinvertebrate information.

Macro-invertebrates including freshwater snails collected from 643 sites over 8 successive seasons among the River Nile, branches, main canals and certain drains in eight Egyptian Governorates. Thirteen snail species and one bivalve species were identified. The most distributed were Lanistus carinatus and Physa acuta while the most abundant were Cleopatra bulimoides and Physa acuta during the whole study. The sites that harbored each snail species in all the examined water-courses were grouped seasonally and their biological assessment was determined by their minimum and maximum total point similarity percentage to that of the corresponded reference site and mean of the total points. Habitats for most snail species attained minimum total point's similarity percentage less than 21% (very poor habitat) during autumn and winter then spring while during summer very poor habitat was harbored by only few snail species. P. acuta was the only survived snails in habitat which attained 0 as a minimum total point's similarity percentage during two seasons and L. carinatus and Succinea cleopatra during one season. With respect to medically important snails very poor sites constituted 23% of Biomphalaria alexandrina sites, 14% of Lymnaea natalensis and 9.4% of Bulinus truncatus sites. The studied macroinvertebrate matrices, total number of organisms, taxa richness, the Ephemeroptera, Plecoptera, and Trichoptera (EPT) index, ratio of EPT index to chironomidae, ratio of scraper to filtering collector, contribution of dominant macroinvertebrate major group, comparison revealed descending tolerances from B. alexanrina followed by L. natalensis then B. truncates, but Hilsenhoff Biotic Index (HBI) showed the same tolerance to organic pollution.

Chemical and biological assessment for Egyptian surface freshwater environment with reference to human activities.

The Egyptian freshwater was assessed in the River Nile, branches, main canals and certain drainages in eight Governorates, over eight successive seasons starting from spring 2008. Chemical assessment was made through ten parameters and the biological one was made through macro-invertebrates information. Results showed that means of Cd, Pb, Cu, Hg, Mn, Fe, Ni, Na, K & Ca varied in watercourses seasonally within somewhat narrow ranges, which may exceed the level of concern but with some elevations in branches, Rayahs and canals during certain seasons. Sites showed chemical levels over the permissible one or those gain total points < or = 6.3 according to the biological assessment indicate that very poor habitat or those of Hilsenhoff Biotic Index (HBI) equal to 7-10 indicate that organic pollution were observed in all the studied watercourses reflecting hazard non point source pollution. Damietta branch in the region of Damietta city characterized with elevations in the concentration of most chemicals examined. The percentages of sites that showed chemical level over the permissible one were 70.56% for K, 54.08% for Cu, 50.08% for Na, 22.08% for Cd, 11.36% for Fe, 5.6% for Pb, 1.92% for Ni, 1.12% for Mn, 0.16% for Ca and at last 0.0736% for Hg. The biological assessment was more able to define more polluted sites than did the chemical one. Human activity data revealed that each of the drains, Giza and Qalyubia canals showed the highest item conduction (animal or plant waste, macroscopic pollution and presence of bridges or barriers) and this was co parallel with their highest pollution recordation.