CRISPR Corals: Should we genetically modify corals to help them survive?
Although coral has been resilient enough to survive mass extinction events, humans have ramped up the pressure on marine ecosystems in an evolutionary millisecond, which doesn't give them enough time to adapt. Some scientists think that we should genetically modify corals through a process known as assisted evolution in order to help them catch up with the acceleration of climate change. However, these ‘super-corals’ could pose a new threat to the environment and there are safer conservation methods that have yet to be exhausted.
Coral Colonies are made up of individual polyps that contain algae. Colony image via https://scubadiverlife.com/coral-biology-part/ Polyp image via https://ocean.si.edu/ocean-life/invertebrates/close-coral-polyp.
Assisted evolution is a conservation method where humans intervene to help a species evolve faster than they could naturally. The main threat to corals is the warming ocean, which causes the single-celled algae that live in their tissues to leave. This is known as coral bleaching, and it usually leads to coral death because the algae are their source of food. As a result, scientists are trying to use assisted evolution on corals and their algae to help them tolerate warming conditions.
Methods used to assist coral evolution can vary. Scientists are using the new CRISPR-Cas9 gene-editing tools on coral, which can directly change their DNA in order to study which genes are important for heat-tolerance. They are trying to make genetically modified corals that can survive climate change. Another technique is to breed the algae that can stand hotter conditions, just like you would breed dogs to select for a certain fur colour. You pick out the algae that can survive in warm water and let them reproduce to pass on their genes.
There are also more moderate methods being developed where researchers can train corals by exposing them to bleaching conditions and letting them recover. These methods don't change the genetic code, so they are considered to be a safer alternative to genetic engineering. Check out the video below to see an example of these methods being used!
How to train your coral. In this video by the Gates Coral Lab of the Hawaii Institute of Marine Biology, Dr. Ruth Gates gives an excellent explanation of the pressures corals face and how we can help them respond to bleaching events using epigenetic changes.
Assisted evolution is not without its risks and limitations. Critics fear that populations that are bred to be resistant to climate change may have too little genetic diversity, which is known to increase the risk of disease. It is also possible that these genetically altered organisms could take over because of their advantages and lead to even more destruction in the environment. This is especially true because there is so much that is unknown about ocean ecosystems, so deciding which corals to save is tricky. Furthermore, it is not clear whether this technology could be scaled up enough to make a large difference in the state of the ocean, especially considering that the process can be expensive. Overall, it seems that there are many hurdles to overcome if assisted evolution is to be implemented.
Which reef looks more natural? What if the corals on the right were genetically engineered to survive? Assisted evolution blurs the lines between nature and human creation. Damaged reef via https://www.britannica.com/science/plastic-pollution/Plastic-pollution-in-oceans-and-on-land. Pristine reef via https://blog.nationalgeographic.org/2016/04/06/so-you-live-near-a-coral-reef-why-experts-say-thats-not-good-news-for-reef-conservation/.
Is it necessary?
While traditional conservation efforts have been working towards the preservation of natural ecosystems, assisted evolution is focused on designing organisms to survive in the world we have created. This raises the question: is it okay to mould the world around our destructive habits and can we really preserve nature if it is engineered by humans? It seems that assisted evolution could enable us to perpetuate our resource-hungry approach, leading us to require extreme biotechnical advancements just to meet our needs.
In the ethical debate about assisted evolution, I am tentatively against its implementation. I believe that we should urge policymakers to take action on conservation methods that are already proven to work. Implementing marine protected areas, reducing carbon emissions, and banning destructive fishing practices are all ways that we can help save coral reefs. However, if we are not willing to sacrifice some amount of short-term economic gain to protect our ecosystems and the services they provide us, we may come to a point where we have no choice but to resort to assisted evolution strategies. In short, I think we should research these technologies but focus on more tangible conservation practices.
1. Filbee-Dexter, K. & Smajdor, A. Ethics of assisted evolution in marine conservation. Front. Mar. Sci. 6, (2019).
2. Anthony, K. et al. New interventions are needed to save coral reefs. Nature Ecology and Evolution vol. 1 1420–1422 (2017).
3. Van Oppen, M. J. H., Oliver, J. K., Putnam, H. M. & Gates, R. D. Building coral reef resilience through assisted evolution. Proceedings of the National Academy of Sciences of the United States of America vol. 112 2307–2313 (2015).
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