Habitat characteristics for different freshwater snail species as determined biologically through macroin- vertebrate 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 watercourses 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 and 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

association between fresh water snails, macrophytes and water quality in different water courses in Egypt

The pattern of association between freshwater snails and macrophytes in relation to some water quality parameters were studied in 258 sites representing the Nile River. main branches, canals and drainages in Menia. Giza. Helwan, Cairo. Qalyubiya, Esmailia. Behaira and Damietta Governorates during May 2008 - March 2009. The survey study collects 15 aquatic plant species and 13 snail species. Statistical analysis showed high significant correlation between snails and plants [r = 0.462]. The examined sites were divided into four categories, sites with plant only [20%], sites with snails only [7%], sites free from both plants and snails [9%] and the biggest category which include sites with both plants and snails [64%]. Results showed that free sites characterized by the highest concentrations of cadmium, lead, mercury, sodium and potassium. Plant sites were characterized with the highest concentration of dissolved oxygen. Snail sites characterized with highest concentration in calcium. Sites in which snails associated with plants were characterized with higher ranges of chemicals, dissolved oxygen and conductivity than that observed in sites with snails only and this indicates the helpful role of plants for increasing snail tolerance to unfavorable conditions