Avaliação dos efeitos do microplástico glitter nas taxas de fotossíntese da Egeria densa (macrófita aquática submersa)

Abstract

The removal of the microplastics glitter by fluxing results in its disposal in sewage treatment plants or deposition directly in aquatic ecosystems, enabling a broad interaction with biota. In this context, this study analyzed the photosynthetic rates (by the light and dark bottle method) of the submerged macrophyte Egeria densa in the presence of three concentrations of glitter: 0.0235 g (T1/T4), 0.0117 g (T2/T5) and 0.0058 g (T3/T6), as well in its absence (control treatment, CT1 and CT2). We tested 800 apical fragments of E. densa distributed in 8 subtreatments (4 under light conditions and 4 in the dark to obtain respiration) with 100 macrophyte fragment in each). The highest net photosynthesis rate (NP = gross photosynthetic (GP) rate subtracted from respiration (RD)) of E. densa was observed in the CT1, showing differences of 13.0%, 32.8% and 59.3% higher compared to T1, T2 and T3, respectively. Only the P N in T1 was not significant (p > 0.05) compared to the other glitter concentrations (T2 and T3). In T1, the highest mean respiration rate (RD) of E. densa was observed, and in T3, the lowest. The presence of glitter may have increased the reflectance, as it is a suspended particle, and resulted in the predominance of regular reflection, common in a well-polished metallic surface. The glitter reflects radiation decreasing the light absorption, altering the utilization of underwater radiation by E. densa. The larger amount of microplastics may result in the continuous reflection of radiation between the suspended glitter particles, allowing them to remain in the bottle, resulting in the higher NP in T1 compared to T3. However, it is considered that Egeria densa has a reduced distribution in places with intense sediment resuspension, and therefore it is assumed that in natural environments the photosynthetic response would be represented by T3. We concluded that the presence of glitter interferes with the absorption of light necessary for photosynthetic processes, reducing it, enabling an imbalance in the metabolism of the ecosystem.