Environmental impacts of phenol pollution on phytoplankton biodiversity at Assiut region, Egypt

Abstract

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...