Dynamics of phytoplankton community in the Eastern Harbor and Qaitbay Bay, Alexandria, Egypt: Seasonal abundance and ecological insights

This year-long study—from June 2021 to May 2022—in the Eastern Harbor (EH) and Qaitbay (QB) Bay regions, Alexandria, Egypt, revealed a diverse phytoplankton community. Sampling from both locations recorded 54 genera and 6 phyla, with Bacillariophyceae being the dominant phylum (31 genera, 71 taxa). Throughout all seasons and stations, Bacillariophyceae prevailed, reaching its highest abundance of 2.62 × 104 ind./L in summer. Key species included Skeletonema costatum, Asterionella japonica, Pseudo-nitzschia seriata, and Gyrosigma macrum. The annual average phytoplankton abundance in EH and QB was 2.22 × 106 ind./L. The Canonical Correspondence Analysis (CCA) highlighted pH, nitrate, and dissolved oxygen as influential factors, with nitrate having the strongest impact. Diversity peaked in summer at S3 (2.12) and decreased in winter at S6 (0.91), indicating uneven phytoplankton distribution. Therefore, this study provides valuable insights into phytoplankton dynamics and distribution in the EH and QB regions across different seasons and locations.