Freshwater environments are especially susceptible to microplastic contamination due to their proximity to urbanised and industrial areas. Also, there is a lack of information about the effects of this pollutant on freshwaters making it difficult the conservation of these environments. Benthic species, such as the freshwater amphipod Hyalella azteca, have been superficially studied so far for evaluation of microplastic pollution. In the present study, we analyzed whether polyethylene terephthalate (PET) microplastics could lead to reduced survival of H. azteca or changes in biochemical markers (SOD, CAT, MDA, and GST) at environmentally relevant concentrations (60 and 600 particles) after 7 d of exposure. The results showed that there was no significant mortality at any of the concentrations tested. The enzyme CAT showed no variation compared to the control group at any of the concentrations. SOD, MDA, and GST were statistically different (p < 0.05). Our study demonstrated that PET MP did not affect the survival of H. azteca at environmentally relevant concentrations. However, changes in biomarkers of oxidative stress may be detected at low level of exposure (60 particles). Although survival is not affected, the macrobenthic invertebrate community may be under threat in environments where there is PET microplastic pollution.

Fipronil is an insecticide widely used in the agricultural and veterinary sectors for its efficacy in pest control. The presence of fipronil in the environment is mainly due to agricultural and domestic practices and is frequently found in different types of environmental matrices in concentrations ranging from µg/L to mg/L and can be hazardous to non-target organisms due to its high toxicity. This study was carried out to obtain and characterize microorganisms from soil which are capable of biodegrading fipronil that could be of great biotechnological interest. For this purpose, bioprospecting was carried out using fipronil (0.6 g/L) as the main source of carbon and nitrogen for growth. Once obtained, the strain was identified by sequencing the 16S ribosomal RNA (rRNA) gene and the capacity to degrade fipronil was monitored by GC-MS. Our study showed a presence in soil samples of the strain identified as Enterobacter chengduensis, which was able to metabolize fipronil and its metabolites during the mineralization process. Enterobacter chengduensis was able to biodegrade fipronil (96%) and its metabolites fipronil-sulfone (92%) and fipronil-sulfide (79%) in 14 days. Overall, the results of this study provided a bacterium with great potential that could contribute to the degradation of fipronil in the environment.