Seasonal variability of phytoplankton along some of the Red Sea harbors during 2019-2021.

Surface seawater and phytoplankton samples were collected from different stations covering the areas of six harbors in the Egyptian Red Sea during 2019-2021. The obtained results revealed 119 phytoplankton species, including 80 species of diatoms, 27 species of dinoflagellates, and six species of both cyanophytes and chlorophytes. Diatoms such as Proboscia alata var. gracillima, Chaetoceros curvisetus, Asterionellopsis glacialis, and Licmophora flabellata produced the highest phytoplankton peak in most harbors. A relatively high phytoplankton population density was recorded at stations near Port Tawfiq Harbor, followed by Zaytiyat. This could be due to the relatively high impacts from various petroleum factories as well as the Sewage Treatment Company, which reflect the area's eutrophic conditions. In general, the highest phytoplankton population density was observed in February 2021, with average counts of 7112 units/L. This is primarily due to the diatom Licmophora flabellata, which accounted for approximately 44% of all phytoplankton in Safaga Harbor waters. However, most of the phytoplankton species in the current study were unique to the Egyptian Red Sea region. On the other hand, several of the harmful species, such as the dinoflagellates Prorocentrum, Goniaulax, and Dinophysis spp., as well as the Cyanobacterium Oscillatoria sp., were found in low counts at some sites of the Egyptian harbors. The statistical analysis of the data indicated that dissolved nitrate (0.81-18.45µM) and ammonium (0.47-5.01µM) were the most effective factors controlling phytoplankton abundance. The multiple regression analysis was calculated to show the relationship between phytoplankton abundance and the most effective environmental factors. A regression equation was obtained and could be applied in the future to predict the total phytoplankton abundance in the coastal waters of the investigated Red Sea harbors. [ABSTRACT FROM AUTHOR]