Evaluation of the Impact of Microplastics on Mercury Detoxification Strategies: a Comparison between the Performance of Bacteria and Fungi

• Autor(a) principal: Silva, Laura Tiê Zanchi da
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/158612
• topic: Mercury; Microplastic; Microorganisms; Detoxification; Bioremediation; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia do Ambiente

Estuaries are heavily impacted by anthropogenic contamination, serving as reservoirs of various pollutants such as heavy metals (e.g., mercury (Hg) and microplastics (MP, Ø <5mm). These pollutants can affect water quality and cause toxic effects in aquatic organisms. Mercury, a trace heavy metal, is characterized as neurotoxic, persistent, and bioaccumulative in the food chain. In systems contaminated by Hg, microorganisms are responsible for reducing Hg, contributing to its natural detoxification. However, the effects of the presence of MP in this process are still unknown. The growing concern of microplastics is the chemical additives in their constitution that can be released and their ability to act as vectors of other contaminants, namely Hg. Therefore, the following questions arise 1. The presence of microplastics affects bacterial and fungal-mediated mercury detoxification present in aquatic systems, and how this differs between the two microorganisms, and 2. What are the possible bioremediation strategies. Microbial communities (bacteria and fungi) were isolated from a Hg-contaminated area of the Tagus estuary, and the most resistant strains were selected to assess the effect of the presence of polystyrene (PS) MP (40 mg/L) on the detoxification of Hg. After 24h, 3, and 5 days of incubation for bacterial isolates and 24h, 5 days, and 10 days of incubation for fungal isolates, the following factors were analyzed: Hg detoxification capacity, acute toxicity (Microtox bioassay) of the leachate, and variation of pH. Isolates were identified through the amplification of 16SrRNA and ITS, respectively. The results showed that (i) strains isolated from the Tagus Estuary are resistant to Hg, (ii) fungal isolates are more resistant than bacteria and, consequently, have a greater capacity to detoxify Hg, (ii) the presence of PS MPs affect the availability of Hg and bacteria in the medium. It can be concluded that MPs interact with Hg detoxification processes and, therefore, should be considered in bioremediation strategies.