The Effect of Anthracene and Phenanthrene on the Growth,Photosynthesis, andSOD Activity of the Green Alga Scenedesmus armatus Depends on the PARIrradiance and CO2 Level

Short-term (24-h) experiments were performed toexamine the effect of phenanthrene (PHE) and anthracene(ANT) on algae grown in a batch culture system at irradiancesof 12, 33, 48, and 64 W m^–2 of the PAR range. Cultures wereaerated (0.1 or 2% CO₂) or nonaerated. As a result of aerationthe concentration of ANT dropped from 0.45 mg L^–1 at thebeginning of the experiment (t₀) to an undetectable value after10 h. The PHE concentration dropped from 9.36 mg L^–1 at t0to 0.17 mg L^–1 after 24 h. ANT at nominal concentrationsexceeding 0.05 mg L^–1 inhibited the growth of the algae in aconcentration- and irradiance-dependent manner. The algistaticeffect of ANT observed at 64 and 48 W m^–2 was independentof the CO₂ level, whereas the growth inhibition at 33 and 12 Wm^–2 was much greater in cultures aerated with 2% than with0.1% CO₂. PHE inhibited the growth only at a concentration of10 mg L^–1 (about 50% of the control) regardless of the irradianceor the CO₂ concentration. The toxicity of both PHE andANT was similar in aerated (0.1% CO₂) and nonaerated cultures.ANT and PHE had a distinct effect on the photosynthesis.At 0.1% CO₂, the irradiance-dependent inhibition (ANT)and stimulation (PHE) of the photosynthesis was observed. Theinhibitory effect of ANT was enhanced when algae were grownat 2% CO₂, but at the same CO₂ concentration PHE did notaffect the photosynthesis. ANT stimulated the total superoxidedismutase (SOD) activity in the cells, this effect being generallymore pronounced at elevated CO₂ levels and increasingwith the irradiance. The total SOD activity was 250–300%higher in cells treated with PHE aerated with 0.1% CO₂. At 2%CO₂ no effect of PHE on the enzymes activity was noted. Theresults obtained indicate that ANT acts as a photosensitizercausing an oxidative damage of cells, while PHE seems toaffect the macromolecular synthesis.