Mighty Mussels Vs Oil


Paper in a nutshell based on the recent publication: Counihan, K (2018) The physiological effects of oil, dispersant and dispersed oil on the bay mussel, Mytilus trossulus, in Arctic/Subarctic conditions. Aquatic Toxicology 199:220-231.


Oil spills have a major impact on coastal environments, and dispersants are used to help speed up oil degradation. The combination of dispersant and oil creates dispersed oil. The small droplets of dispersed oil spread deeper into the water column than untreated oil and may be more harmful to marine species.

There has been limited research on the impact of oil and dispersed oil to marine animals in Subarctic and Arctic conditions, which led Dr. Counihan to conduct a study at the Alaska SeaLife Center on the toxicity of oil, dispersant and dispersed oil.

Fig 1
Flow-through exposure of mussels to oil, dispersant and dispersed oil. Contaminated water was collected in the drums for proper disposal.

Marine mussels are often used in programs to evaluate the health of coastal ecosystems because they are easy to collect and accumulate pollutants as they filter the seawater to feed. The bay mussel (Mytilus trossulus) is a species that lives in the cold northern waters of the Arctic and Subarctic. Therefore, determining how the health of bay mussels is impacted by oil could allow them to be used to monitor the recovery of coastal ecosystems after an oil spill in regions such as Alaska.

Fig 2
Mussels in one of the exposure tanks.

In this study, bay mussels were exposed to oil, dispersant or dispersed oil for 3 weeks. Various tests called biomarkers were conducted to evaluate how the treatments influenced normal mussel function. Most health effects were observed during the first week of exposure. Mussels exposed to oil, dispersant or dispersed oil had elevated stress levels as they tried to detoxify the chemicals. The DNA of the mussels was damaged which could lead to tumor formation or the damage could be inherited by future generations, potentially damaging the population.Mortality was low in all of the exposures, and most physiological functions returned to normal levels after the first week. However, at the end of the 3 week exposure, the mussels in the oil, dispersant and dispersed oil treatments had lost weight. Mussels in poor condition due to weight loss could stop growing, fail to reproduce, or die.

Additional research needs to be conducted to determine how long weight loss and DNA damage persist. This study was an important step in understanding how an oil spill and response activities could influence a sentinel marine species.

Interested in learning more? Use this link to read the full publication.


Written by: Katrina Counihan, PhD

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