Efeitos do bisfenol-a na capacidade fotossintética e no crescimento de Egeria densa

Abstract

Bisphenol A (BPA) is an emerging contaminant widely used in the plastics industry; its persistent presence in inland water bodies poses a potential threat to aquatic biota. This study investigated the effects of three BPA concentrations (5 mg L⁻¹ [T1], 15 mg L⁻¹ [T2], and 25 mg L⁻¹ [T3], alongside a control [TC]) on the net photosynthetic rates and growth kinetic parameters of the submerged aquatic macrophyte Egeria densa under controlled laboratory conditions (27 °C and a 12-h photoperiod). Median net photosynthetic rates were 1.75 (TC), 1.00 (T1), 1.25 (T2), and 1.35 mg O₂ g⁻¹ DW h⁻¹ (T3). Although photosynthetic activity decreased, treatment differences were not statistically significant (p > 0.05). In contrast, growth kinetic parameters were highly sensitive to the pollutant, with significant differences (p < 0.05) between the control and the higher-concentration treatments (T2 and T3). The growth coefficient (µ) decreased progressively with increasing contaminant levels: 0.14 day⁻¹ in the TC (doubling time, td = 5 days), 0.07 day⁻¹ in T1, 0.04 day⁻¹ in T2, and 0.02 day⁻¹ in T3; this demonstrates that the control value was seven times higher than that of the treatment with 25 mg BPA L⁻¹. Each 1 mg L⁻¹ increase in BPA reduced the plant growth coefficient by approximately 9%. The half-life of the compound in the experimental media ranged from 6.6 to 8.5 weeks. The results suggest that the growth coefficient of E. densa is a more adequate biometric indicator of BPA contamination than net photosynthetic rate, highlighting the importance of integrated approaches for assessing the toxicity of micropollutants in macrophytes.