BENTHIC ASSEMBLAGES FOR ECOLOGICAL EVALUATION OF BARDAWIL LAGOON, MEDITERRANEAN SEA, EGYPT

Abstract

Bardawil Lagoon is the only highly saline oligotrophic lagoon in Egypt, has an area of ca. 650 km2 with water depths ranged 0.3m to 3m and economically important in terms of fish production. It is the optimum zone getting migratory birds in winter. It is separated from the Mediterranean Sea by a narrow sandy shelf (90 km length, and 22 km width). Ecological evaluation of benthic communities in Bardawil Lagoon to follow-up study of the distribution of benthic study at 12 selected sampling sites representing different environmental habitats for long periods through the project of Environmental Study Wetlands OF North Egyptians Lakes where samples were collected seasonally (2010-2015) and semi-annually (2015 - 2019). The results and data analysis indicated that the distribution, composition and dominance of macro benthic organisms in Lake Bardawil were composed mainly of Ostracoda, Polychaeta, Sea grasses, Bivalvia, Insecta larvae communities and dominated the constituent of bottom fauna. The variations in the benthic biomass were the heaviest at sites elRaodh and meddle elRaodh representing 1354 and 1105 g/m2 which corresponding respectively to 18.2 % and 14.9% of the annual average of benthic biomass (619 g/m2). Regional variations abundance of the benthic structure was highest at sites elTelol and elRaodh representing 3486 ind/m2 and 3635 ind/m2 which corresponding respectively to 14.8% and 15.3% of the annual average of benthic density (1978 ind/m2). Sites of sampling study were evenly spread (J’ > 0.8) at most sites except at elTelol and elRaodh also, high diversity (H’ > 3.00) was at the most sites and show lower value at sites elTelol, elGals, Boughaz I, elNaser, and Raba`a while, Swartz Dominance indexes of number of 5 species over 75% showed low values at sites elGals, Boughaz I, elNaser, and Raba`a. The abiotic environmental effects in the Bardawil Lagoon are general to those generally observed in other areas influenced by organic wastes, namely, changed in the physic-chemical properties of the sediments and low oxygen concentrations in the bottom water due to decomposition of organic materials.