Wildlife

New estimate on coral age hints at recovery hope

The symbiotic relationship between corals and micro-algae is much older and more robust than previously thought – a finding that implies the world’s reefs might be more resilient to global warming than predicted.

Coral cells rely on long-term mutually beneficial relationships with algae known as zooxanthellae. These live inside the cells and facilitate the capture and exploitation of sunlight that powers the creation of reefs. It is the death of these plant-like micro-organisms in response to warming temperatures that catalyses coral bleaching.

Research into the evolutionary history of the symbiosis, however, raises at least a faint hope that over longer time periods resilience and recovery may be possible.

Originally held to be a single species, classified in its own genus, Symbiodium, by the turn of the century researchers were noting considerable diversity among the zooxanthellae, and classifying lineages accordingly. However, available sequencing techniques provided only relatively crude results for the age and divergence dates of the newly identified species, together with a rough estimate suggesting the symbiosis with coral began around 60 million years ago.

Past estimates placed the initiation of these symbiotic relationships at 50 to 65 million years ago. The research indicates that modern corals and their algal partners have been entwined with each other for much longer – since the time of the dinosaurs, approximately 160 million years ago.

The relationship between the algae and the coral, thus, began during the Jurassic period – a finding with potentially optimistic implications. During their long existence, they have faced severe episodes of environmental change, but have managed to bounce back after each one.

Heat-resistant Coral Reefs Found in Indonesia

A recent scientific survey off the coast of Sulawesi Island in Indonesia suggests that some shallow water corals may be less vulnerable to global warming than previously thought.

Between 2014 and 2017, the world’s reefs endured the worst coral bleaching event in history, as the cyclical El Niño climate event combined with anthropogenic warming to cause unprecedented increases in water temperature.

But the June survey found the Sulawesi reefs were surprisingly healthy. In fact they were in better condition than when they were originally surveyed in 2014 - a surprise for British scientist Dr Emma Kennedy, who led the research team.

Indonesia is situated in the heart of the Coral Triangle - home to the greatest levels of marine biodiversity on the planet. There are reefs here that contain more species than the entire Caribbean, which is why the bioregion is of particular interest to scientists looking into reef resilience.

The hope is that if key reefs can be protected from other stressors such as plastic pollution and overfishing, they can ride out the worst impacts of climate change and replenish adversely affected reefs once ocean temperatures stabilise.

The findings of the Sulawesi survey will help scientists and conservationists target coral conservation programmes elsewhere in the world. With perhaps three decades left to rescue a vital global ecosystem from extinction, it is progress that’s sorely needed.