Benthic assemblages for ecological evaluation of Lake Borollus, Mediterranean Sea, ‎Egypt.‎

Abstract

Lake Borollus is one of the largest and oldest Egyptian lakes, whereas it is located in the ‎far north of the Delta and mediates between the two branches of Rosetta and Damietta. ‎It is connected to the Mediterranean Sea through Boghaz El Borollus and to the Nile ‎through the Bermbal Canal, which was established in 1926 to feed the lake with ‎abundant quantities of Nile water and Nile fish. Central coordinates: latitude 31°30' N ‎and longitude 30°49' E with an area has decreased from 160,000 acres to 108,000 acres. ‎The present work provides an ecological study on the regional and temporal distribution ‎of benthic communities in particular along the wetlands lakes waters. Indicated that, the ‎effective sediment and water variables which significantly correlated with the distribution ‎and abundance of the identified benthos assemblages of vegetation and animal’s groups ‎include sediments structure, water quality (pH, S%, DO, BOD, temperature. Overall, 10 ‎taxa and 27 species of macroinvertebrates were identified. They were exclusively ‎associated with submerged vascular plants Potamogeton pectinatus while only 10 were ‎alive forms and the rest were represented by calcareous shells of molluscs. The benthic ‎flora and fauna were estimated in the Lake Botollus, Egypt is subjected to the influx of ‎sewage effluents, agriculture drainages and industrial wastes. Also considerable amounts ‎of drain water are constantly discharged along the southern drains. Quantitative hauls ‎were performed at the different habitats during winter and summer, 2017 covering 12 ‎sampling sites and 9 drains discharged directly to the lake which bottom sampling was ‎collected by grab sampler were selected to represent the covering the different ‎environments. The dredged area per each station was 225 cm2 per haul. Results ‎illustrated that the distribution of benthos in the estimated area is greatly affected by the ‎degree of pollution as well as the prevailing hydrological conditions. The aquatic ‎submerged vascular plants Potamogeton pectinatus appeared as the most common ‎species in the lake in addition the bottom animals appeared more- sensitive to pollution ‎than submerged vascular; thus, their lowest counts were recorded at the most sites and ‎the fauna was mainly represented by the Nematoda, Oligochaeta, Polychaeta, Insects ‎larvae, Ostracoda, Amphipoda, Barnacles, and juvenile larvae of Mollusca. Sediments in ‎some areas consist of organic materials (sludge) is composed of waste sewage and ‎agricultural and industrial and others of sandy silt (silt), calcareous shells are mainly of ‎molluscs’ and therefore it can determine some environments prevailing in the lake. ‎Results indicated for examining configuration qualitative benthic macro during the study ‎period were recorded 27 species, including 9 species of living benthic macro organisms ‎include one type of aquatic submerged vascular plants of species Potamogeton ‎pectinatus. Although higher values of taxonomic richness, the Shannon and index (H`) ‎and evenness (J`) were obtained with the water Potamogeton pectinatus habitat as well ‎as Ostracoda Sclerochilus contortus were most abundant.‎