Responses of Phytoplankton and Zooplankton Communities to Water Quality in Suez Gulf of the Red Sea, Egypt

Marine plankton in the Red Sea are continuously exposed to various environmental pressures. This study provides a comprehensive analysis of both biological and environmental parameters across five distinct locations along the western coast of the Suez Gulf, Red Sea, Egypt (2021–2022). Our findings highlighted significant seasonal variations in total suspended solids (TSS), chemical oxygen demand (COD), nitrate, and phosphate concentrations, with notable differences observed during autumn. Additionally, the counts of total coliform and fecal coliform ranged from 2.0×10² to 4×10⁵ and 3.0×10² to 7×10² MPN/100 mL in locations 1, 2, 3, and 4, respectively. The density of total coliform was consistently detected in all seasons in location 5. Sediment samples revealed metal concentrations ranging from 9 to 3,579 mg/kg for manganese (Mn), 0.25 to 6.5mg/ kg for arsenic, 2.6 to 4,543mg/ kg for iron, 0.03 to 14mg/ kg for chromium, 0.03 to 81mg/ kg for copper, 0.5 to 8.75mg/ kg for nickel, 0.03 to 176.5mg/ kg for lead, 0.03 to 4.25mg/ kg for cadmium, and 4.0 to 336mg/ kg for zinc. The dominant algal groups observed were diatoms, blue-green algae, and dinoflagellates. Maximum algal counts were recorded during autumn (411 org./mL) and spring (381 org./mL). The zooplankton community consisted of five groups: Protozoa, Rotatoria (Rotifera), Arthropoda (Crustacea), and larval stages of both Nematoda and Insecta, with crustaceans being the most prevalent, followed by rotifers. These findings suggest that human activities may significantly influence water quality in certain areas of the Suez Gulf.