Author(s): Howayda H. Abd El-Hady, Nehad Khalifa

Abstract: Zooplankton community and biochemical contents of phytoplankton were compared between nonvegetated and vegetated regions among two plants communities, Halophila stipulacea (Forsskål) Ascherson and Cymodocea nodosa (Ucria) Ascherson, in Bardawil Lagoon. There were slight differences in water properties between the three studied sectors in Bardawil Lagoon. The results illustrated a strong allelopathic effect of H. stipulacea plant on the protein contents of phytoplankton. Non- vegetated area of the lake recorded the maximum contents of carbohydrate, thus the two plants had negative chemical interference on phytoplankton carbohydrates. Halophila stipulacea had a slight stimulating effect on phytoplankton lipid contents. While there was no variation in lipids at the area covered with C. nodosa and non-vegetated area. The three studied sectors were characterized by a similar taxonomic compositionrnof zooplankton communities and considerable variations in densities of various zooplankton groups. All classes were collected in greater numbers in vegetation, Copepoda and Pteropoda are highly associated with H. stipulacea, while C. nodosa gathering rotifer, protozoa and meroplankton, which could indicate there was a stimulating allelopathic effect of macrophytes on their density.

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