ABSTRACT
Qualitative and quantitative estimations of bottom fauna was carried out monthly in the Nozha Hydrodrme [Egypt] during the period October, 1986 September, 1987. As a result of the reduced conditions which prevailed at the botton after prolonged additions of inorganic and nitrate fertilizers and increased eutrophication of water perior to the present investigation, the chironomus larvae and the oligochaete paranais sp. Dominated the community and contributed numerically 59.4% and 34.2% of the total benthos respectively, while gammarus spp. Formed only 6.3%. previous estimations of the benthic fauna before application of these fertilizers revealed the dominance of Corophium spp. Which constituted more than 86% by number of the total benthos while they disappeared totally in the present investigation. Also the biomass of bottom fauna has decreased from 6.3 gm fresh wt/m[2] in 1955 to 2.06 gm fresh wt/m[2]. results emphasize the importance of carrying out parallel quantitative estimations of benthos beside that of the phytoplankton and zooplankton communities during periods of application of fertilizers in order to maintain the optimum concentration levels of these fertilizers which yield the most favourable balance between these 3 components