When I learned I would be going on exchange in Barbados, I was elated. The tropical weather, learning about sustainability, and especially the brilliant coral reefs really drew me to the country. I couldn’t wait to jump in the water, see the giant fans and tabletops, dive among the fishes, and be blown away by all the tropical colours. Of course, it never lives up to the pictures.
Caribbean Coral is Dying
Coral all over the world is dying. Rising sea surface temperatures force them to expel a special kind of algae called zooxanthellae which would naturally live symbiotically inside the coral, providing it with energy by performing photosynthesis. This is called coral bleaching, and while it is not actual coral death, it reduces coral health enough that they become extremely vulnerable to perturbations such as hurricanes, the stress of tourism, and disease.
Most sunscreens are also damaging to corals. 80% of chemical sunscreens use a chemical called oxybenzone, which is toxic to humans, but also causes deformities in all life stages of coral. When swimmers enter the water with sunscreen on, oxybenzone gets into the water and damages coral. Overfishing also takes its toll on reefs, as fish play a vital role in maintaining the ecosystem balance corals need to survive. Finally, coral disease is spreading through the Caribbean, killing off large swaths of coral, especially those most important in building reefs.
Why does it Matter?
Coral reefs host the greatest biodiversity in the ocean, and the Caribbean reefs are the second most diverse, after the Indo-Pacific. Biodiversity is particularly important in combating climate change, as it is the basis for adaptability and resilience to change. The more diversity you have, both between and within species, the more different genes there are. Among those genes, there are more that can survive in a changed or weakened environment. So, in short, biodiversity is creating species that are resilient to climate change by genetic brute force. In addition, biodiversity allows humans to search for new medicines and cures in the natural world, as was the case with the discovery of penicillin.
Coral also provides lots of economic opportunities to the local population. This is especially important given that 60% of coral reefs are located in developing nations. Reefs attract tourists looking to snorkel and dive among colourful fish and corals. The reefs also support the fishing industry by housing large herbivores such as parrotfish and surgeonfish.
The New Regime
The fact that is particularly scary about coral die-off is that reefs will soon reach a point where even if humans were to suddenly clean up their act and allow them to return to their natural state, they would never be the same. In fact, for corals to return to their previous abundance once they reach this point, humans would need to actively support their recovery.
This is because there is another type of life ready to take over reefs in the absence of coral: algae. Algae grows faster than algae, and if it gets a foothold, can outcompete coral for space as well as shading out the sun, which corals need to benefit from their symbiotic zooxanthellae. Once algae start to outcompete coral, fewer corals are reproducing, meaning fewer corals for the next generation, and the whole reef will eventually shift to algal domination.
This is called a tipping point, and it means if we want to keep coral reefs, we need to act now to protect them. But how can this be done?
Parrotfish – The Heroes
While in Barbados, my class actually did some research on coral-parrotfish dynamics. We took data from a protected area and a non-protected area, looking at how many parrotfish were found in each and how the coral cover differed between the two.
Our results showed that, surprise surprise, there are significantly more parrotfish in marine protected areas than in uncontrolled reefs. This is because they face less fishing pressure, so there are more fish. This becomes an interesting finding when you consider the fact that parrotfish are quite beneficial to coral. This is because they eat algae and keep regime shift to algal domination in check. As algae becomes more dominant, parrotfish have more to eat, and reproduce more, and the larger population eats more of the algae. Parrotfish and other large herbivores are extremely important in opposing regime shifts, making them particularly important to long-term coral reef sustainability.
This is why marine protected areas are so important. If overfishing continues to destroy stocks of herbivorous fish, as it has done in the past, then our parrotfish heroes will not be able to keep protecting the corals from their algal competitors, and the coral reefs will fall to regime shift. Algal reefs cannot support the level of biodiversity and local income that coral reefs can, as they do not provide as much benefit to other organisms as corals do.
So, our study, and many others, showed the importance of marine protected areas to Barbados and the Caribbean. First, there needs to be more of them. Less than 1% of Barbados’ coral is protected and in the Caribbean, the number is around 20%. If more marine protected areas are put in place, then the populations of large herbivorous fish could recover and push reefs farther from regime shift. But just setting up protected areas is not enough, they must also be sufficiently patrolled and enforced, as well as safe from corruption. There are many barriers to this, such as protests from fishers and financial issues for the local governments, but if we want to protect coral, we need to figure these issues out as soon as possible.
Luckily, we still have time. Thanks to our herbivorous heroes that remain, we are not yet at the point of regime shift. But, that tipping point is getting close, so governments must act now to protect one of the most beautiful and complex ecosystems in the world.
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Coral World Ocean Park. (2023, June 15). Coral Disease – Coral World Ocean Park. Coralworldvi. https://coralworldvi.com/coral-disease
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Morrow, K. (2020, November 24). Scuba diving Barbados: Best spots & what to expect | SANDALS. Hello Paradise – the Official Sandals Resorts Travel & Lifestyle Blog. https://www.sandals.com/blog/scuba-diving-barbados/
Science Museum UK. (2021, February 23). How was penicillin developed? Science Museum. https://www.sciencemuseum.org.uk/objects-and-stories/how-was-penicillin-developed
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