Deep-dive into healthy coral reefs

A Durban PhD graduate has explored the coral reef system off the coast of South Africa and investigated why it was healthy and functioning compared with coral reefs globally.

Calvin Wells, 31, from Durban North earned his PhD in Civil Engineering from the University of KwaZulu-Natal for research that used the principles of environmental fluid mechanics to show how the interaction between global ocean circulation and the continent of Africa protects the Sodwana reef system from high ocean temperatures.

His thesis was titled “On the Cold Water Temperature Anomalies Along the Coral Reefs at Sodwana Bay, South Africa”.

He said he was working in the coastal engineering field when his former professor contacted him with a research opportunity to study the Sodwana coral reefs.

“I jumped at the opportunity. We have an amazing coral reef system off the coast of South Africa that rivals anywhere around the world. I started with the question of why is it so healthy and functions so well, not from a biological view point, but an oceanographic view point.”

Wells is passionate about the ocean and the environment.

He said with the rising ocean temperatures caused by climate change, coral reefs globally were undergoing a phenomenon called coral bleaching.

“When the ocean temperatures rise too high, above a certain threshold for a certain period, it stresses out the corals and effectively they die. Coral reef ecosystems around the world are really important because they hold 95% of all ocean species. They are the centre-point for ocean biodiversity. With coral bleaching, we are losing a lot of species and creating a massive environmental knock-on effect.

“Our reefs at Sodwana Bay have resilience to coral bleaching. My thesis looked into the physical oceanographic reasons why these coral reefs don’t bleach. It is obviously linked to temperature and temperature is linked to ocean dynamics. Looking at long-term temperature records we found we get cold water temperature anomalies. During summer when all the ocean temperatures are rising we get these rapid drops in temperature in Sodwana, so we get cold water flushing the reefs during our hot summer months. It is linked to the regional global ocean current in the south Indian oceans and strong intermittent current interacting with the complex coastline along South Africa, specifically up north near Mozambique,” he said.

He said the cold water temperature anomalies were driven by the ocean currents on a regional scale interacting with the complex African coastline.

Wells said by understanding why the Sodwana corals were spared they would gain valuable insight into how marginal reefs would respond to constant changes in the global climate and where to focus their efforts in the future to save the corals as ocean temperatures continued to rise.

Wells is a director of a coastal engineering and environmental consultancy.

He said one of the perks of doing the research, which took four years, was getting to scuba dive.

Wells’ thesis has been published in international journals. His insights can be used to promote the sustainable management of coral reefs, locally and globally.