David Billett (Deep Seas Environmental Solutions Ltd, UK)
Joye et al (2016) have provided an overview of the environmental effects of the Macondo (Deepwater Horizon) oil well blowout in the Gulf Mexico six years after the event (Deep-Sea Research II129, 4-19). The paper is part of a 400-page Special Volume on research in the Gulf of Mexico following the incident. Detailed research findings are provided in 37 papers, ranging from responses of deep-water corals to oil and chemical dispersants (De Leo et al. 2016) to the presence of both pulsed blooms and of persistent populations of oil-degrading microbial communities (Yang et al. 2016).
Joye et al. (2016) describe the natural seepage of hydrocarbons which occurs extensively in the Gulf of Mexico. Approximately 22,000 natural seeps have been identified (http://1.usa.gov/1aKybyq) in the region. Gulf of Mexico ecosystems, therefore, are regularly and perhaps frequently exposed to diffuse and variable hydrocarbon exposures. In contrast the Deepwater Horizon event was ‘an intense [and] focused’ hydrocarbon release. Rapid changes in microbial populations and activity were noted. Cold adapted microorganisms responded within hours to days (Hazen et al. 2010). Previously rare microorganisms bloomed altering the microbial community structure. The authors concluded that microbial communities degraded both the hydrocarbons and the dispersant chemicals relatively quickly. However, laboratory experiments indicated that dispersants limited and altered the microbial response (Hamden and Fulmar, 2011; Kleindienst et al. 2015). Similarly ecotoxicological experiments on corals showed rapid declines in corals in 1) dispersant and 2) oil plus dispersant treatments, but minimal responses to just oil exposure (De Leo et al. 2016).
MERCES considers that results have important implications for the management of oil spills both in the deep sea and in shallow water. Greater knowledge is required on the potential effects of dispersants, especially on the longer term effects on the rate of recovery of marine ecosystems following an accidental release of hydrocarbons. The time taken to restore the biodiversity, functioning and services of marine ecosystems may depend on the methods used to manage the oil release, yet these considerations do not appear to be taken into account by oil spill response teams. Greater testing and assessments of alternative methods may be required.
This is reflected in the final conclusion of Joye et al. (2016) highlighting that understanding the impacts of the Deepwater Horizon oil well blowout was severely compromised by the lack of baseline data on the deep-water Gulf of Mexico ecosystem. Without sufficient baseline data [of the right quality and standardisation] it was extremely difficult to assess large anthropogenic impacts in the deep sea.
The work reported on the Gulf of Mexico oil well blow out is important in the management of other deep-sea commercial activities, most notably fishing and deep-sea mining.
DeLeo, D.M., Ruiz-Ramos, D.V., Baums, I.B., and Cordes, E.E. (2016) Response of deep-water corals to oil and chemical dispersant exposure. Deep-Sea Research II 129, 137-147.
Joye, S.B., Bracco, A., Ozgokmen, T.M., Chanton, J.P., Grosell, M., MacDonald, I.R., Cordes, E.E., Montoya, J.P. and Passow, U (2016) The Gulf of Mexico ecosystem, six years after the Macondo oil well blowout. Deep-Sea Research II 129, 4-19.
Yang, T., Nigro, L.M., Gutierrez, T., D’Ambrosio, L., Joye, S.B., Highsmith, R. and Teske, A.P. (2016) Pulsed blooms and persistent oil-degrading bacteria in the water column during and after the Deepwater Horizon blowout. Deep-Sea Research II 129, 282-291.
