Abstract

Extensive commercial and residential development over past decades added to the list of anthropogenic disturbances to water quality along the coastal region of Alexandria. Three sites were selected along Alexandria coast to maximize possible differences in seawater types. The floristic analysis has allowed the identification of 29 macroalgal species. Rhodophyta were the richest taxon (13 species), chlorophyta (10 species), and phyophyta (6 species). The algal flora was closer to cold, temperate nature than tropical. Quantitative differences in species richness across the three sites reflect their entity, and dependent upon frequency of abiotic measured parameters and geographic features. Nutrient concentrations introduced significant changes in macroalgal populations. Macroalgae overall growth was often nitrogen limited. The proportion of red species increased with increasing environmental quality, in contrast to green species whereby proportions increase with decreasing quality status. The high percentage of cosmopolitan species denotes a strong character of environmental instability. The different sites might be exclusive holder of some species. The percentage coverage (abundance) indicated Chlorophyta the main constituent (44.23-50.78%), followed by Rhodophyta (41.67–48.37%), and while Phaeophyta (2.46–9.55%) exhibited restricted occurrences to relatively less polluted area.

Key words: Macroalgae dynamics, richness, coverage, Alexandria