Heat-Adapted Corals in the Arabian Gulf Offer Hope for Reef Conservation

Bethany Smith
Nov 4 · 4 min read

Coral reefs are hugely important ecosystems, both for biodiversity and in the ecosystem services they provide. They cover just 0.1% of the ocean floor and yet support over a quarter of all marine fish species, as well as being worth over $1 trillion dollars via their capabilities as coastal defences, their attraction for tourism and their support of local fisheries.

It is their incredible structure which allows them to do this. The complex interweaving metropolis of the reef dissipates energy from waves to reduce coastal erosion and the impact of storm surges, as well as drawing in tourists and sheltering a diverse array of fish species that can help feed local communities.

Corals are small polyp animals which form a symbiotic relationship with algae. These algae photosynthesise and provide the polyp with up to 90% of its energy, energy it uses to construct the astonishing calcium carbonate skeletons which make up the reef. When temperatures get too high, as a stress response the polyps expel their algae, turning the once bright reef to a blank white, hence the term “coral bleaching”.

If the temperatures remain too high, and the algae do not return to their polyps soon enough, the polyps can starve and die. They are unable to maintain their skeletons and the reef can undergo erosion, losing much of the benefits mentioned above.

As global warming proceeds, corals undergo bleaching events more regularly, with the IPCC predicting large-scale damage to coral ecosystems based on our current emissions trajectory. But what if there were corals already adapted to what our future warm waters will be like? The hottest sea with significant amounts of coral is the Arabian/ Persian Gulf and the species here are able to survive temperatures that would ordinarily kill most other species.

Temperatures across the tropics are predicted to increase by 1–3°C, meaning that the current conditions of the Gulf could be a good representation of what conditions will be like more generally in areas occupied by corals. The Gulf corals have had thousands of years to adapt to these conditions, but other corals will have only 100 years to do so.

A potential way in which coral reefs could be helped in the fight against climate change is by assisted migration of the Gulf species to different areas in the Indo-Pacific region. In these cooler areas we know the Gulf species would have a higher likelihood of survival than the non-Gulf species, as a result of their existing adaptations.

It might be worried that moving a species from one area to another could have adverse consequences for the community being moved into, as a result of disruptions in the interactions between the species currently existing there. But there used to be species similar to those found in the Gulf in other areas, which have been lost, so translocation represents a re-introduction, which is less likely to have any negative side-effects.

The temperatures in the Gulf will increase like anywhere else in the world, reaching highs that might be too great for those adapted species present there. Therefore moving species to cooler areas offers hopes of preserving these species whilst also saving non-adapted reefs from the brink.

Bibliography

Heron et al. 2017. Impacts of Climate Change on World Heritage Coral Reefs : A First Global Scientific Assessment. Paris, UNESCO World Heritage Centre.

WWF. 2018. Living Planet Report — 2018: Aiming Higher. Grooten, M. and Almond, R.E.A.(Eds). WWF, Gland, Switzerland.

Saving the World’s Coral Reefs, Coral Reef Alliance, URL: https://coral.org/coral-reefs-101/why-care-about-reefs/food/ last accessed: 03.11.19

Purkis, S.J., Renegar, D.A. & Riegl, B.M. (2010) The most temperature adapted corals have an Achille’s Heel Marine Pollution Bulletin, 2011 pp 246–250

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