Abstract
The Brazilian northeastern coast suffered in 2019 the greatest acute impact of oil in the country’s history, with all states in the region being affected by extra-heavy oil. Holothuria (Halodeima) grisea is a detritivorous holoturoid, which ingests sediment to feed, and can passively ingest oil from spills existing in the sediment. To investigate the occurrence of oil in the intestinal content of H. (H.) grisea, a N of 20 individuals was collected on the Salvador coast (BA) in October 2019 between the coordinates 12°57 ‘S / 38°20’ W. Of this total, 10 individuals were found dead in the environment and 10 collected alive, for comparison purposes. Of the individuals found dead, 40% were eviscerated (without intestines) and it was not possible to carry out content analysis. Of the 6 remaining dead individuals, 67% had oil in their intestinal contents. For the 10 live sea cucumbers collected, none was eviscerated and all had a full intestine, with oil being observed in the intestinal content of 1 specimen (10%). The χ2 test confirmed with α of 0.025 the possible relationship between oil and the mortality of H. (H.) grisea, demonstrating that the acute oil spill probably was lethal for this species on the northeastern coast of Brazil.
 Keywords: sea cucumber, hydrocarbons, PAHs.
Highlights
Petroleum activity in the marine environment can cause several types of environmental impacts such as habitat degradation, which is one of the main factors that cause the reduction of the planet’s biodiversity (Gomes; Palma & Silva, 2000; Martins et al, 2015)
Crude oil is a mix of polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), hydrogen sulfide and several metals trace, which can poison the organisms in an acute and chronic way, mainly the toxic fractions of oil associated with the aromatics compounds, which can kill by intoxication (Blackburn et al, 2014; Lourenço et al, 2020; Pena et al, 2020)
Studies carried out on the northwest coast of the Atlantic Ocean considered extremely high concentrations of oil in marine sediment ranging between 11,3 and 2,900 mg/kg (Tong et al, 1999), values that in proportional terms would be less than 1% of oil per kilo of sediment. Comparing this result to the oil percentages that were found in the sea cucumber intestinal tract sediment in the stretch between Pedra do Sal and Itapuã in Salvador, it is observed that the oil percentages in relation to the sediment were higher than the concentrations considered extremely high of oil for sediment in the environment described in the literature, which would have a direct relationship with the acute impact of the spill and with the mortality of individuals, considering that sea cucumbers are organisms sensitive to any contaminants accumulated in marine sediments (Kamyab et al, 2016)
Summary
Petroleum activity in the marine environment can cause several types of environmental impacts such as habitat degradation, which is one of the main factors that cause the reduction of the planet’s biodiversity (Gomes; Palma & Silva, 2000; Martins et al, 2015). In relation to PAHs pollution in aquatic environments, accidents with oil spills are among the most severe for benthic invertebrates, causing toxic effects such as embryonic abnormalities and immunotoxicity (Honda & Suzuki, 2020), mechanical effects such as asphyxiation by clogging respiratory structures, and bioecological effects such as impacts on growth, food and disturbances in the food web (Blackburn et al, 2014). The sea cucumber Holothuria (Halodeima) grisea is a deposit-eating species and can act in the marine environment as a mitigating agent for environmental damage due to its consuming character of organic material and recycling the sediment contributing to the textural and geo-environmental characteristics of the areas where it occurs, among them the base and cracks of the intertidal region rocks (Costa, 2010; Sousa, 2014). There is no information in the scientific literature on this subject for H. (H.) grisea or other species of sea cucumbers
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