ผลของทองแดงและสังกะสีต่อสรีรวิทยาของสาหร่ายสีเขียวชนิด Chlorella vulgaris Beyerinck

Abstract

Microalgae are common model organisms used in ecotoxicological investigations. The present study assessed the physiological responses of Chlorella vulgaris to copper (CuSO4*5H2O) and zinc (ZnCl2) exposure at different concentrations (control 125 250 500 and 1,000 μM) for five days. Heavy metals were introduced into the growing media during the exponential phase. Heavy metal accumulation was measured at the end of the experiment. Photosynthetic efficiency and proline content were measured after 0, 6,12 hours and 3, 5 days after treatment. Chlorophyll a, total reactive oxygen species (ROS) and lipid peroxidation (LPO) were measured at the beginning and at the end of the experiment. Both heavy metals showed dose-dependent cellular accumulation. Decreased maximum quantum efficiency of photosystem II (Fv/Fm) and effective quantum efficiency of photosystem II (OPSII) were influenced by both heavy metal concentration and time of exposure and showed a reduction from day 3 of exposure. Other toxicity symptoms included chlorophyll degradation and an increase in reactive oxygen species (ROS). Exposure to both heavy metals resulted in a decrease in chlorophyll a content to a similar extent. While an increase in ROS was detected only for 1,000 μM copper, an increase in lipid peroxidation was detected in 250-1,000 μM copper and 500-1,000 μM zinc. Proline, an amino acid with various putative protective functions against stress, exhibited a rapid increase with increases in heavy metal concentration and time of exposure. These results provide a suite of effective biomarkers for heavy metal exposure using C. vulgaris as a bioindicator.