العربية
العربية
Research Highlights

Red Sea reef growth could point to global trends

Published online 2 November 2018

Studying Red Sea peculiarities could help predict future global trends in coral reef growth.

Louise Sarant

Freshly collected limestone blocks (a, b, c) were recovered after 30 months of deployment. They were bleached and dried (d, e, f). Erosion by endolithic sponges is visible in blocks from near- and midshore reef sites. Blocks from mid- and offshore reefs are covered with carbonate crusts from coralline algae.
Freshly collected limestone blocks (a, b, c) were recovered after 30 months of deployment. They were bleached and dried (d, e, f). Erosion by endolithic sponges is visible in blocks from near- and midshore reef sites. Blocks from mid- and offshore reefs are covered with carbonate crusts from coralline algae.
Anna Roik/Biogeosciences
Data on the bio-erosion and bio-accretion (calcification) of limestone blocks deployed in the central Red Sea has facilitated the establishment of a baseline for understanding reef growth rates in the area. The information could help predict future trends.

A team of researchers at King Abdullah University of Science and Technology in Saudi Arabia deployed the few dozen blocks, which bear strong similarities to coral skeletons, in sites located 3, 10 and 25 kilometres from the coast. The blocks were immersed for six months up to two and a half years, exposing them to eroding organisms and processes, such as parrotfish and daily alkalinity fluctuations, and to calcifiers that flesh out reef frameworks, like coralline algae. 

“We deployed the blocks in the study sites and observed their decomposition or accretion over time,” explains KAUST ecologist Anna Roik.

The analyses showed that the blocks placed nearest the shore, in warm and shallow waters, experienced high levels of erosion. Erosion and accretion offset each other on the blocks located 10km from shore, while those furthest from the coast witnessed positive growth. Since all blocks were recovered and analysed before the dramatic bleaching episode of 2015–2016, Roik stresses that “repeating our protocol for the same reef sites after the bleaching event will be of great insight.” 

The data showed that the erosive forces on coral reefs in the Red Sea are not as pronounced as they are elsewhere, while growth on offshore reefs is comparable to other regions of the world, which perform well below what is considered ‘healthy’.

In the long run, the scientists believe this method could help understand future trajectories of reef framework development. The Red Sea corals are under global scientific scrutiny because they thrive in a particularly warm and saline environment. Since oceans are warming, establishing baseline data for reefs living in conditions that deviate from the global average could help forecast future ocean scenarios.

doi:10.1038/nmiddleeast.2018.137

Roik, A. et al. Coral reef carbonate budgets and ecological drivers in the central Red Sea – a naturally high temperature and high total alkalinity environment. Biogeosciences 15, 6277–6296 (2018).