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Spatio-temporal variation of microphytoplankton communities in Obhur Creek, the central Red Sea

El-Sherbiny Mohsen M., Al-Harbi Mamdouh A., Kumar Anand J.

Oceanological and Hydrobiological Studies

2021

Vol. 50, No. 1

98--114

The abundance and distribution of microphyto-plankton and related physicochemical factors were assessed monthly in Obhur Creek, the central Red Sea. Sampling was carried out near the entrance, the middle and end parts of the creek. During the course of the present study, the Red Sea was characterized by predominantly oligotrophic conditions. Nutrient concentrations were relatively higher in the end part of the creek compared to the two other study sites. Chlorophyll a was also low throughout the year (average: 0.35 ± 0.32 mg m−3), except in May when it showed clear peaks at open-water and middle sites of the creek (1.85 and 1.04 mg m−3, respectively). Phytoplankton abundance followed a similar pattern to that of chlorophyll a with considerably higher abundance at these sites in May (3063.27 × 103 and 1082.34 × 103 individuals m−3, respectively). This unusually higher abundance was mostly due to the proliferation of the diatom Pseudo-nitzschia cf. delicatissima (Cleve) Heiden. Silicate concentrations were statistically significantly correlated with total phytoplankton. A total of 220 phytoplankton species were recorded during the study period (117 diatoms, 99 dinoflagellates and four cyanophytes). Diatoms dominated in the phytoplankton abundance (75%) and were followed by dinoflagellates (20%), while cyanophytes accounted for a minimal proportion. Of all phytoplankton species observed during the study, 21 diatom and four dinoflagellate species were considered as new records for the Red Sea, and two diatom and 14 dinoflagellate species were listed as harmful algal species worldwide.

Distribution and community structure of microphytoplankton in relation to increasing anthropogenic impact along coastal waters of Jeddah, the central Red Sea

Al-Amri Aisha A., Qari Huda A., El-Sherbiny Mohsen M.

Oceanological and Hydrobiological Studies

2020

Vol. 49, No. 2

193--205

Seasonal distribution and diversity of surface phytoplankton have been studied in relation to anthropogenic activities at seven locations along the coastal waters of Jeddah, Saudi Arabia in 2017. The concentration of nitrite, nitrate, ammonia, phosphate and silicate varied over wide ranges: 0.04–20.27, 0.05–29.3, 0.22–78.16, 0.02–25.90 and 43–24.50 μmol l-1, respectively. Inorganic nutrients, phytoplankton biomass and density were at eutrophic levels at two lagoon locations (4 and 5), while other coastal locations showed oligotrophic characteristics of the Red Sea. Phytoplankton biomass was positively correlated with all measured inorganic nutrients. The total phytoplankton density varied between 52.4 × 103 and 40800 × 103 cells m-3 (average 6249.9×103 ± 10797×103 cells m-3). A total of 174 species of phytoplankton (95 diatoms, 75 dinoflagellates, 3 cyanophytes and 1 silicoflagellates) were recorded in this study, with the dominance of diatoms (95.1%). Higher densities observed at lagoon locations were mainly due to the proliferation of the diatom species Skeletonema costatum and Chaetoceros decipiens. In terms of diversity, dinoflagellates were more numerous than diatoms in July, otherwise mostly diatoms dominated. On the other hand, cyanophytes were more abundant in November. Based on the present study, anthropogenic activities (especially sewage effluent) in Jeddah coastal waters had a significant impact on the phytoplankton densities and diversity.