7 Dec 2016
Leveraging Microbes When Responding to a Spill
Credit: Getty Images.
Microbes play a key role in the response to an oil spill. Approximately half of the oil released during the Deepwater Horizon spill has been or will be degraded by naturally occurring microbes that live in the Gulf of Mexico. Because microbes play such a large role in the degradation of spilled oil, an effective spill response requires an understanding of the microbial response to the spill. Microbial ecology experiments, which measure this response, can provide spill responders with four key types of information.
Natural Biodegradation Rate—If a spill occurs, how quickly will the indigenous microbes degrade the spilled oil? The effectiveness of a spill-response strategy should be measured against that baseline. An intervention might do nothing (or, worse, it might slow down natural degradation), and it would be impossible to know this without having measured the baseline degradation rate.
Recalcitrance of Spilled Fractions—Which fractions of the oil are broken down quickly, and which will persist? Responders should focus on interventions that degrade or contain the fractions that are most toxic or least likely to be broken down naturally.
Limiting Nutrients—In some environments, the absence of a nutrient (e.g., iron or phosphorous) limits microbes’ ability to break down oil. It may be possible to add that nutrient into the environment to relieve that limitation.
Effect of Dispersants—Do dispersants increase the rate at which the naturally occurring microbes degrade the oil, or do the microbes preferentially consume the dispersant instead of the oil?
The results of microbial experiments can have an immediate and substantial effect on spill-response strategy. For example, if applying a chemical dispersant is expected to increase the baseline degradation rate by some amount, this improved removal of oil from the environment can be rationally and quantitatively weighed against the effects of releasing a potentially toxic dispersant. In the long term, these experiments can provide evidence that the optimal, scientifically informed spill-response strategy was used. We expect that the enormous benefits from these experiments will outweigh the cost and inconvenience of having them performed.
Unfortunately, there is no single, worldwide answer to all those questions. In a study supported by BP, we found that microbial degradation of oil is different in different areas around the world. Just as there are different kinds of oil in different places, there are different kinds of microbes, too. Different kinds of microbes will respond to different kinds of oil in ways that can be measured but not accurately predicted.
Because microbial behavior varies from place to place—and probably from year to year in the same place—we recommend that, in the event of a spill, responders measure microbial behavior in that place at that time and use that data to inform their response strategy. Fortunately, experiments to gather the kind of information we listed can be performed in a matter of days or weeks.
Because spill responses are emergencies, we recommend flexible data collection decision-making rather than a rigid procedure. Spill-response strategists should develop relationships with trained microbiologists and microbial ecologists who, in the event of a spill, will perform experiments directly at the spill site. This relationship can be productive before a spill occurs; spill-response strategies should be formulated initially on the basis of baseline microbiological surveys. In theory, anyone with the right equipment and protocols could perform these experiments, but we expect that, in practice, many ad hoc decisions will need to be made by experimenters during the spill-response emergency. Microbial ecologists and environmental microbiologists are the best qualified to make the flexible decisions that are most likely to produce useful data in an uncertain situation. A decision that appears innocuous to a layperson might lead to a completely failed experiment.
We recommend the following timeline for a data-driven response:
During Normal Operations—Contact and develop informal relationships with microbiologists and microbial ecologists who study the exploited basin. Determine their willingness to be members of an ad hoc spill-response team. Discuss the recommended experiments.
Just After the Spill—Contact ad hoc team members. Develop plans for sampling the microbial community and performing the experiments. Conduct or support baseline measurements of microbial behavior and use that data to inform the prepared spill-response strategy.
Days After the Spill—Conduct or support microbial community sampling.
Two Weeks After the Spill—Initial experiments should have concluded. Interpret experimental results and incorporate that data dynamically into the spill response. Plan the next round of short-term experiments to improve on relevant knowledge gained in the first round.
Beyond 2 Weeks—Continue operations that provide information that guides the spill response. Begin research into the effect of the spill using the ad hoc team or by recruiting new members.
In general, academics would be intellectually eager to have access to samples from an oil spill, and they probably are also motivated to provide information that would lead to a more effective spill response.
The material requirements for these experiments are modest:
- Tens of liters of water or tens of grams of sediment from the affected area
- Milliliters of the spilled oil
- Milliliters of dispersant
- Thousands or tens of thousands of dollars in technical and personnel costs
For experimenters, we emphasize that initial experiments should answer practical questions about spill-response strategies such as the ones outlined here. In each experiment, water (or water and sediment) is placed in a bottle and amended with oil, dispersant, or nutrients. Respirometry can measure the carbon dioxide evolved by the microbes and, thus, the amount of oil or dispersant they broke down. Mass spectrometry and chromatography can measure the fractions of oil broken down by the microbes. Every experiment should be paired with a relevant control inoculated with artificial seawater or authentic seawater sterilized by autoclaving.
We hope that this information can help spill-response practitioners understand how to make spill-response decisions that are informed by the behavior of the microbes that will always be a major partner in cleaning up spilled oil.