Approved Abstracts

Impacts of the mysterious oil spill that covered the Brazilian coast: chronic toxicity of sediments from the states of Pernambuco and Ceará (Brazil)



Author(s): Ueda M.; CASTRO, Í. B.; ALKIMIN, G. D.; Cavalcante, R. M.; SOUZA-SANTOS, L. P.; BURUAEM, L. M.; ABESSA, D. M. S.;
Presenter: Maysa Ueda de Carvalho

In August 2019, tons of crude oil from unknown origin covered the coast of northeast Brazil, spreading residues over 11 coastal states and reaching 55 marine protected areas. This event has been considered the largest environmental incident in extension to affect tropical area, but the early and late environmental and socio-economic impacts are still being assessed. As a consequence, many organisms such as fish, turtles, invertebrates and birds were found covered by oil or presenting traces of oil in their digestive tracts and respiratory systems. Samples of the oil, obtained in different places, evidenced a chemical profile including light aliphatic hydrocarbons (AHs) and polycyclic aromatic hydrocarbons (PAHs), indicating a single origin. Pollution by hydrocarbons is concerning because these chemicals are easily absorbed and bioaccumulated in marine organisms, from producers to top predators and humans. Besides, these contaminants may associate with organic matter and suspended particles, sink to the bottom and accumulate in sediments layers, from which they can be released back to the water column or to the benthic organisms. Toxicity tests have been recommended to evaluate impacts of oil spills. In this study, chronic toxicity tests were conducted using, the estuarine copepod Nitocra sp. and embryos of the sand-dollar Melitta quinquiesperforata, exposed to sediment samples collected in the states of Ceará (sampled between November 2019 and January 2020) and Pernambuco (March 2021). The international protocols for toxicity testing using marine and estuarine species were followed. Ovigerous females of Nitocra sp. were exposed to sediments and elutriates for 10 days and the reproduction rates were evaluated, while eggs of M. quinquiesperforata were exposed for 42h and their embryonic development was observed. The results were checked for normality and homogeneity of variances, and compared with the respective controls by the student-t’test. All the tested samples significantly reduced the reproduction rate of Nitocra sp. (p≤0.05) and induced delay or interruption on the embryonic development of M. quinquiesperfotata. Our results evidence high and persistent impacts on the benthic environment. Based on the results evidenced in experiments using sand-dollars, the recruitment of planktonic larvae may have been affect. This study add complimentary information showing severe effects on the planktonic copepods. Negative effects of oil residues on planktonic and benthic organisms may affect entire marine web chain impacting the functioning and productivity of estuarine and marine ecosystems, which can lead to economic implications as well. Our results also highlight the needs of long-term monitoring in the areas reached by this catastrophic event, in order to subsidize cleaning and restoration plans as well, the appropriate quantification of the negative impacts.
Financial Support: Fundação de Amparo à Pesquisa do Estado de São Paulo - FAPESP (process 2020/04779-6 and 2020/03828-3).


Keywords: soil toxicity; reproduction rate; embryolarval development

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