Oil Spill Effect on Macrobenthic Community and Their Activities

Almost all the mistakes we make harm the environment and the species on the planet in one way or another. Some effects on nature are slow and invisible whilst others affect immediately on site. Our seas and oceans were devastated in a short period of time from the contamination of liquid petroleum hydrocarbon and damaged to the environment for decades to come. In addition to killing fish, marine mammals and birds, oil spills affects benthic organisms. When oil is deposited at the sediment-water interface, it interferes inhabiting benthic organisms. Benthic organisms play a major role in sediment biogeochemical processes such as organic matter degradation and nutrient cycling (Aller, 1982).

In anoxic marine sediments, oxygen transport into the sediments transform elements and compound in the sediment (e.g. denitrification). Bioturbation and irrigation by benthic animals’ activities supply oxygen for microbial respiration which degrades organic matter and fuels nutrient cycling (Kristensen et al., 2012). As the seafloor is their habitat, deteriorated conditions of water and/or sediment quality make them difficult to survive (Dauer 1993). In this literature review, I will investigate the oil spill effect on benthic community and their activities, reviewing the case study of Caleta Valdés, Patagonia, Argentina. I will then conclude how oil spill pollution can be managed.

The Patagonian coast is regarded as a pristine environment. A single large overflow of crude oil or petroleum may alter the environmental status (Dalton and Jin 2010). With over more than 3000 km of the coastline, oil production is the most important economy in Patagonia. Petroleum is produced from two oil basins. Crude oil loading in ports and maritime transport from exploitation sites to the refineries are the major threats to Patagonian marine ecosystems . Although some zones were polluted with hydrocarbon (Commendatore et al. 2012), certain areas such as Caleta Valdés have never been affected yet. The response of the benthic communities to the petroleum contamination in this sensitive environment was assessed by Ferrando et al. (2014) and their results showed that macrobenthic community were low resistance capacities to the oil contamination. Both the density (mainly at the surface layers of 0-0.5 cm) and specific richness decreased with the increasing oil contamination.

Sensitive species disappeared, but other species like Oligochaeta sp. 1, Paranebalia sp., and Ostracoda sp. 1 species had a higher resistance to oil contamination. Oligochaetes gradually recovered in 2 days after the spill, behaving as tolerant or resilient species to the impact. Paranebalia sp. (Crustacea: Phyllocarida: Leptostraca) was dominant in the most contaminated sediments and behaved as a tolerant species. Ostracoda sp. 2 was also dominant at the end. Castège et al. (2013) studied benthic community from Guéthary (Bay of Biscay, France), affected by the Prestige oil spill in 2002, and found perturbation signs and slow recovery until 5 years after the spill. According to Sell et al. (1995), the cleanup disturbed the re-establishment of the biota and also the recovery process.

The values of the biodiffusion (Db) and bioadvection (r) coefficients showed a decrease of sediment reworking intensity with an increase of oil concentration. This means that the bioturbation activity was suppressed across the sediment column, even in deeper sediments where the community was not severely affected. Similarly, Nereis diversicolor reworking was reduced in the presence of Arabian Light crude oil (Gilbert et al. 1994). Contrastingly, Stauffert et al. 2013 found that Hediste diversicolor reworking activity may be boosted.

Overall, the different responses to oil pollution depend on the resistance capacity of the species based on their biological traits, physiological status, and stage of development. Indeed, the severity of oil impacts depends on many factors: oil amount, chemical composition, form (weathered or not), occurrence (solubilized or in suspension), exposure time, life stage (juvenile or adult), season and type of affected environment. As benthic biota and their activity (bioturbation) have an important role in microbial aerobic biodegradation of hydrocarbons (Cuny et al. 2011), in sediments affected by oil spill, the microbial bioremediation of hydrocarbons would be significantly reduced. This shows that the absence of benthic community and their activity had a large impact on the ecosystem.

Regarding with the global energy demands, transporting or drilling oil cannot be stopped. Oil spill disasters have been occurred throughout the world from vessels crashing and problems with oil drilling. Oil spill waste is considered a hazardous waste and therefore response strategies should be prepared. A hierarchy of waste management operations orders source reduction as the preferred option and disposal as the least desirable. First, temporary storage sites must be designated directly adjacent to oiled areas which can facilitate the initial collection of waste for transport. Then, intermediate and long-run storage sites must be established for supplemental processing or treatment. Long-run storage sites may be final disposal, or treatment sites.

During cleanup operations, segregation and secondary contamination should keep in mind. The collected waste (oily liquid, solid, debris, etc) are separate and delivered to temporary storage that lead to the ultimate treatment, or disposal location. Corresponding departments and staff should be trained for sorting and educated the consequences and costs of poor segregation. Moreover, secondary contamination should be avoided. The spread of oil to unpolluted areas via response activities associated with people, transport and equipment can be occurred.

Oil spill compensation should be charged for the cost of response actions and waste management. Finally, oil usage must be reduced, and renewable energy should be replaced.