Effect of lead ions on biochemical behavior of Cladophora glomerata in sterilized and non-sterilized media

Freshwater ecosystems are under peril globally due to anthropogenic influences, most notably metals. The present study aimed to evaluate the morphological and biochemical responses of Cladophora glomerata obtained from a freshwater stream to various lead concentrations (0.0, 7.5, 15, 30, and 60 mg/L Pb²⁺) in sterilized and non-sterilized media. Pigments, proline, malondialdehyde (MDA), total phenolic compounds (TPC), hydrogen peroxide, and protein content of the green alga were determined in response to various growing conditions. Pb²⁺ stress had a detrimental effect not only on biochemical components of C. glomerata but also on the algal cell's shape and surface structure. High Pb²⁺ concentrations significantly decreased chlorophyll-a (from 1350 μg/g in non-sterilized and 1340 μg/g in sterilized media for the control group to 1067 μg/g in non-sterilized and 1049 μg/g in sterile media at 60 mg/L Pb²⁺) and protein contents (from 34.47 mg/g for the sterilized and 35.89 mg/g for non-sterilized of the control to 24.82 mg/g for the sterilized and 26.18 mg/g for the non-sterilized at 60 mg/L Pb²⁺) of algal biomass but increased the concentrations of stress compounds (e.g., MDA, proline, and TPC). Variation in the macroalgal biomass composition was also indicated by FTIR analysis based on interactions between amino, amide, and anionic surface groups on the algal biomass and Pb²⁺ ions. Morphological and biochemical responses of C. glomerata reveal that non-sterile conditions encouraged the proliferation of this macroalga under Pb²⁺ exposure.