Dynamics of Macroalgae at Two Different Ecological Sites in Alexandria Coastal Waters

A year cycle investigation of the macroalgae dynamics in Alexandria coastal waters was conducted at two selected stations that maximize possible differences in seawater characteristics. Eleven genera, including seventeen species were identified at the Eastern Harbour (EH) and Abou Talat (AT). The total species richness was higher at EH, but the algal species composition was highly similar at the two sites. The floristic ratio at EH indicates a mixed flora of warm temperate nature. The prevalence of red and brown algae was detected at relatively high salinities, and green opportunistic algae at lower salinities, and with nutrient pulses indicate its importance as ecological factors regulate the structure of the macroalgae communities in Alexandria waters. The changes in algal proportion reflected the anthropogenic influence and/or improvement in environmental quality at times. Incidents of massive green macroalgae proliferation occurred at a wide range of environmental variations, and with the sharing of other red species. Ulva fasciata represented a perennial species and the spring warming and nutrient enrichment seem to interact with its massive growth. The study is yet the first attempt to measure the algal biomass of different species under different physical and chemical ecological stresses.