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Phenol is a common organic pollutant in the aquatic habitats. However, its adverse effects on the composition and diversity of phytoplankton are still poorly understood. Phenol can cause toxic effects to different living organisms even at low concentrations. The present study investigated the effect of phenol on phytoplankton diversity and community structure in samples collected from ten polluted sites. The concentration of phenol in the investigated sites were generally higher than 0.05 mg L −1 which is over the allowable limit. The spatial complexity of the microalgal community was investigated using different alpha (α) diversity measures for the largest microalgal groups (Cyanobacteria, Chlorophyta, Bacillariophyta). Distancebased redundancy analysis (dbRDA) indicated that phenol pollution had adverse effects on both phytoplankton diversity and taxonomic structure. Accordingly, the algal pollution index (API) was negatively correlated with richness and diversity of the main phytoplankton groups. The most tolerant species to phenol stress belong to Chlorophyta and Cyanobacteria. In addition, the total phytoplankton community was grouped into 19 functional groups (FGs) which associated with the preference of a certain environmental conditions. A laboratory toxicity experiment was also performed to identify the negative effects of short-term exposure to phenol on different microalgal species. Thus, the most sensitive taxa were disappeared in response to the phenol treatment. Overall, this study is valuable in indicating the adverse effects of phenol pollution to the natural phytoplankton community.Environmental impacts of phenol pollution on phytoplankton biodiversity at Assiut region, Egypt 334 Determination of sodium and potassiumSodium and potassium ion concentrations were determined using flame photometer (Flame Photometer M 71 D type Nr/ LPG075) [7]. Determination of calcium and magnesiumThe complexometric titration method [8] was employed for both calcium and magnesium determinations. For calcium determination, freshwater sample (1 mL) was diluted by 5 mL of distilled water and KOH solution (2 mL, 10% w/v). The mixture was titrated against Na 2 -EDTA (0.005 N) in the presence of muroxide as an indicator until a purple end point. The 0.005 N EDTA is equivalent to 0.1 mg of calcium. Similarly, for the determination of magnesium, freshwater sample (1 mL) was diluted by distilled water (5 mL) and titrated with Na 2 -EDTA (0.005 N) in the presence of Erichrome Black T as an indicator until a blue end point. The amount of EDTA consumed is equivalent to Ca 2+ plus Mg 2+ . The 0.005 N of EDTA is equivalent to 0.06 mg of magnesium. Determination of water chlorinityChlorinity was analyzed by the method of [9]. Water sample (1 mL) was mixed with 10 mL distilled water followed by adding 1 mL of K 2 Cr 2 O 7 (5% w/v) as indicator. The solution was titrated against AgNO 3 (0.05 N) until orange color appeared. Determination of nitrateNitrate was spectrophotometrically determined by chromotropic acid (1,8dihydroxynaphthal...

The present study investigated the effects of different phenol concentrations (200 – 1000 mg L−1) towards Chlorella sp. under different culture conditions (light vs. dark) and NaNO3 concentrations (0 – 0.1 g L−1) using central composite design. Phenol induced hormesis effects on the algal growth and cellular metabolites. Nitrate was identified as a crucial factor for promoting the uptake of phenol by Chlorella cells, while light was a limiting factor for growth, but the phyco-toxicity of phenol was decreased in the dark. The pigment contents were generally increased in the treated cells to protect against the oxidative phenol stress. The incorporation of 200 mg L−1 phenol and 0.05 g L−1 NaNO3 to the illuminated cells markedly promoted biomass and lipid contents to 0.22 g L−1 and 26.26% w/w, which was 44 and 112% higher than the phenol-less control, respectively. Under the same conditions, the increase of phenol concentration to 600 mg L−1, the protein contents were increased to 18.59% w/w. Conversely, the algal cells were able to accumulate more than 60% w/w of soluble carbohydrates under dark conditions at 600 mg L−1 of phenol. Nitrate replete conditions stimulated lipid accumulation at the expense of protein biosynthesis. Furthermore, most of the treatments showed an increase of H2O2 and malonaldehyde contents, especially for the illuminated cells. However, catalase activity tended to increase under dark conditions, especially at low phenol and nitrate concentrations. This study is valuable in indicating the effects of phenol on microalgae by exploiting response surface methodology, which can be applied as a powerful tool in growth monitoring and toxicity assessment.