I recently came across a study, conducted in the wake of the 2010 Gulf of Mexico Oil spill. This particular research discovered that crude oil was causing heart defects in juvenile fish in the Gulf.  Particularly in species that are commercially important, such as tuna and amberjack. As a budding biologist and keen conservationist this topic captured my mind and kept me reading.

To create a bit of context, there was an oil spill off the oil rig Deep Horizon between April and July 2010.It resulted in the release of 4 million barrels of crude oil into the Gulf of Mexico. The outcry was huge, the environmental impact incomprehensible and vast. What wasn’t realised at the time was how vast the scope and far-reaching the consequences would be.

bp-rig Oil-Rig-Explosion-in-Gulf-of-Mexico-10 gulf-oil-spill-615-500x332

Every season, huge spawning (when sperm and eggs are released into the water to be externally fertilised) events occur in the Gulf (in the upper layer, or ‘pelagic’ region) and it quickly becomes a nursery ground for many fish. This study explained how the developing fish heart is very sensitive to the effects of some of the compounds in crude oil, specifically to a family known as the polycyclic aromatic hydrocarbons (PAHs). This compound has a particularly negative effect on heart development.


By recreating the oceanic conditions of the Gulf at the time of the oil spill and exposing newly fertilised fish embryos (an unhatched developing fish egg) to the oil, the effects on the development of the heart became apparent. The scientist who conducted this study used yellowfin tuna, bluefin tuna and amberjack to run these tests, as these are commercially important pelagic fish that are found in the Gulf. Getting to this point of choosing species was quite hard though and required many considerations. For example, embryos are very sensitive to physical contact and are therefore hard to handle in a laboratory environment. Also, getting access to embryos of these species is not a simple task. The results however, were quite clear.

Fish that had been exposed to the oily water suffered from two particular defects which were outwardly visible in a variety of malformations. The next bit, the defects, have some complicated words, but it’s quite simple really, so don’t freak out :)

The first defect is Pericaridal Edema. This is the build-up of fluid in the sac around the heart (pericardial fluid) and it happens because the circulatory system is failing. All species exposed to the oil showed signs of this defect. The other is a more general decrease in heart rate and increase in irregular arrhythmias (when the heart beats in an abnormal rhythm). Visibly, one can see that an embryo is suffering from these defects if the eye and tail aren’t properly developing and if the body axis is curved upward.


There were many conclusions that were drawn from this particular study. It was shown that the amount of oil the embryos were exposed to is not as important as the size of the egg, a small egg resulting in the faster draw up of oil. It was also shown that the response of embryos to the oil is pretty uniform and doesn’t change between species or with the way in which the embryo was exposed.

This study is the first to analyse the effects of the oil spill on these commercially important fish. It therefore opens up many opportunities for future research to occur and more questions to be asked. This also means that this is the first time these methods have been applied. It is possible that future work might find better ways of overcoming the difficulties that were faced during this research, such as working with embryos in lab environments.

I found this an interesting study to read as I can see how it might be applied to other places where oil exploration and extraction is ongoing or increasing, such as the North Arctic. It is also incredibly relevant because it is looking at aspects of two very important industries: Oil and Commercial fishing. When events like this oil spill occur, we are dealing not only with a huge environmental disaster, but with possible food crises from a lack of fish in the affected area. Job losses in the fishing industry and slowing economies are also concerns that arise in coastal towns and cities reliant on the Gulf for food, jobs and trade. Exposing these far-reaching effects of this oil spill puts pressure on oil companies, too. It means that their “mistakes” and “slip ups” have consequences that are long-lasting and influence the quality of life of many people.

These consequences - defective fish stocks, trade, food availability - are not the charismatic and disastrous corollaries one thinks of when discussing oil spills, yet these are issues that have the greatest consequence. It is sobering, yet important to realise just how far-reaching the harmful human hand can be and for us to be constantly aware of how a single action can have a ripple effect of results.

Photo credits: National Geographic

This blog piece was based upon the following paper: Incardona J.P. et al. 2014. Deepwater Horizon crude oil impacts the developing hearts of large predatory pelagic fish,Proceedings of the National Academy of Sciences.



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