Impact of wildfire ashes on aquatic systems: diatoms

• Autor(a) principal: Pereira, Elsa Patrícia Ribeiro
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/27918
• topic: Wildfires; Ash; Metals; Polycyclic aromatic hydrocarbons; Aqueous extracts of ash; Diatoms; Teratologies

Forest fires are a major environmental problem in countries of southern – Europe, being a recurrent phenomenon, with distant impacts. One of them is their role on the production, mobilization and distribution of contaminants, in particular metals and polycyclic aromatic hydrocarbons (PAHs). Both of them are contaminants of major concern, due to their high environmental persistence, toxicity and tendency to bioaccumulate and biomagnify. Wildfires also have the ability to increase runoff and the consequent transport of sediments and ash with PAHs and metals attached can end up in downstream aquatic habitats. Therefore, the input of surface runoff with different contaminants, could culminate in toxic effects on aquatic species, amidst diatoms. Since these microalgae are a good ecological indicator, ecotoxicological tests were performed on Nitzschia palea (NPAL) and Achnanthidium minutissimum (ADMI) with two aqueous extracts of ash (AEA) made with ashes of low and high severity (LS and HS), from wildfires of low/moderate severity (fist campaign in november), and high severity (second campaign in march), respectively. Whereas diatoms react to the surrounding environment, they responded differently to the different AEA. A significant increment on the growth in the toxicity tests of both species was observed in high severity AEA, while in the LS the opposite occurred, with NPAL presenting an EC50 of 104.98% and ADMI, the most sensitive presented an EC50 of 84.78%. The differences in AEA toxicity may be due to differences in its chemistry. The two species demonstrated similar responses in every concentration in both AEA concerning abnormal cell wall (around 50% of teratological valves). Teratologies also occurred in diatom communities of river Pequeno mainly in Karayevia oblongella (KOBG), more abundant in the first campaign and in Achnanthidium minutissimum (ADMI) more abundant in the second. This may be due to the different sampling season (autumn and spring respectively). All in all, the present study highlights the potential impacts of wildfires on water bodies, compromising the chemical and ecological conditions. In addition, it demonstrates that further research should be done in order to better understand and evaluate the real impact of forest fires in the ecosystems.