EFEITOS DO ÓLEO DIESEL NA GERMINAÇÃO E CRESCIMENTO DE PROPÁGULOS DE Rhizophora mangle L., Avicennia germinans (L.) L. e Laguncularia racemosa C.F. Gaertn

Abstract

After being released into the environment, diesel oil tends to cause negative impacts with acute and chronic effects on the different species of mangroves. There are several examples of accidents with oil spills and leaks that affected aquatic, coastal and terrestrial ecosystems, including the mangrove ecosystem that has high ecological, economic and social relevance. Research carried out with mangrove propagules and seedlings in a controlled environment tends to help the understanding of how the effects of tensors act in the processes of germination and growth of mangrove species. The propagules and seedlings of this research were submitted to different treatments with diesel oil, and, three replications, in laboratory environments and seedling nursery. For the germination studies of Laguncularia racemosa and Avicennia germinans, the experiments were separated into a control batch (without the addition of diesel oil) and six treatments with different percentages of diesel oil (0.5%; 1%; 1.5%; 2 %; 3% and 4%) emulsified in 500ml of estuarine water each. The tests performed included germinability (G%), mean germination time (AMT), mean germination velocity (VMG), germination velocity index (IVG) and mortality rate. For the study of growth and development of Rhizophora mangle, the seedlings were distributed in a control experiment (without the addition of diesel oil) and six treatments with different volumes of diesel oil (7.5ml, 10ml, 15ml, 20ml, 30ml and 50ml) applied directly in the seedling sediment. Tests included granulometric analysis, seedling height and diameter analysis, root biomass analysis (below-ground biomass), anatomical analysis and mortality rate analysis. The results showed that each species studied suffered a different effect on the components of diesel oil. Laguncularia racemosa was more sensitive to diesel oil in the germination process with a significant mortality rate, while Avicennia germinans suffered more external anomalies and Rhizophora mangle had as a result negative effects on its structural development such as significantly altered height and diameter, as well as other significant effects. The present study aimed to analyze the effects of diesel oil on the germination of Laguncularia racemosa and Avicennia germinans and on the growth and development of seedlings of Rhizophora mangle, in order to contribute to the knowledge of the response of the propagules in areas degraded by the presence of diesel oil. In addition to contributing to the understanding of procedures and actions to improve public policies and management of the Brazilian coastal zone, with regard to mangrove ecosystems.