The effect of organic solvents in photosynthetic corals

• Autor(a) principal: Silva, Davide Augusto Machado
• 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/10773/27958
• topic: Coral; Organic solvents; Ecotoxicology; Oxidative stress; Fotobiology

Tropical coral reefs provide important ecosystem services and goods in the tropical and subtropical regions of the planet. However, the increase of anthropogenic pressures, such as marine pollution or the escalating coral biomass demand for several different economic applications, as well as the damage caused by climate change, have contributed to the degradation of this ecosystem at an alarming rate. Consequently, the international scientific community has been intensifying coral research, aiming to study and acknowledge the effects of existing stress factors and to identify possible mitigation strategies. Thus, ecotoxicology studies, targeting the effect of emergent or persistent pollutants in these organisms can contribute to the state of the art. However, there are no standardized methodologies to test tropical photosynthetic corals, and their response to organic solvents, recurrently required in toxicological appraisals, remains unknown. In this context, the present study aimed to assess the oxidative stress profiles and photochemical response of photosynthetic corals exposed to different organic solvents (ethanol, methanol and dimethyl sulfoxide – DMSO), commonly used in ecotoxicological studies, expecting to contribute to the standardization and optimization of protocols. The results from the first study, with the species Zoanthus sociatus (Hexacorallia: Zoantharia), suggested that this species is more sensitive to DMSO than to ethanol or methanol. DMSO lowest observed effect concentration (LOEC) was 0.01 mL L-1, while for ethanol and methanol LOEC were 0.1 mL L-1, even though the highest concentration of ethanol (2.9 mL L-1) was the only treatment causing mortality to Z. sociatus. Nevertheless, the distinctive response of this species evidenced the need to perform further similar studies with other coral species, given the diversity of these organisms. In this sense, a second trial was performed in order to assess the effect of the same organic solvents in two different species, Montipora digitata (Hexacorallia: Scleractinia) and Sarcophyton glaucum (Octocorallia: Alcyonaria). The species M. digitata, able to produce its own calcium carbonate skeleton, and therefore important to reef build, was more sensitive to ethanol than to methanol or DMSO. Ethanol lowest observed effect concentration (LOEC) was 0.01 mL L-1, for methanol LOEC was 0.3 mL L-1, and for DMSO LOEC was 0.1 mL L-1. Notwithstanding, the highest concentration of ethanol and DMSO (2.9 mL L-1) caused mortality in M. digitata. The species S. glaucum, unable to segregate a calcium carbonate skeleton, was more sensitive to methanol than to ethanol or DMSO. Ethanol LOEC was 2.9 mL L-1, for methanol LOEC was 0.01 mL L-1, and for DMSO LOEC was 0.3 mL L-1. Considering this, a baseline for the use of organic solvents with tropical corals was set. Nevertheless, it is important to stress out that a major knowledge gap regarding coral physiology still exists.