An Israeli study found that coral intertidal communities have experienced alarming phase shifts over almost a century as a result of environmental changes, Bar Ilan University (BIU) in central Israel reported on Sunday.

Published in the journal Nature Communications, the research provides an in-depth look at the world’s largest coral reef, Australia’s Great Barrier Reef, over the past 91 years, Xinhua reported.

Coral reefs are of vital environmental importance as they provide habitats and shelter for many marine creatures, protect shores from wave and storm damage, provide nutrients and more.

Unfortunately, coral reefs worldwide under increasing stress due to local and global factors and are highly sensitive to environmental change which may result in the loss of reefs, Xinhua reported. Therefore, long-term investigation became increasingly important to understand ecosystem responses.

Such investigation was conducted by researchers at BIU and the Interuniversity Institute for Marine Sciences (IUI) in southern Israel, along with the University of Queensland in Australia. The researchers used an old highly-accurate mapping of the area, produced in 1928 by a British research expedition to the Australian reef.

This mapping enabled the research team to revisit and sample the exact intertidal and subtidal locations previously explored, Xinhua reported.

Thus, it was found that the number of different species of corals and invertebrates has declined over time, including branching coral species which are the main contributors to reef complexity and serve as home to many creatures. At the same time, soft corals which do not contribute to reef buildup and even deter stony corals are taking over much of the reef area.

The study’s lead author, Maoz Fine, professor at BIU and IUI, said “the long-term implications of the changes highlight the importance of avoiding phase shifts in coral reefs which may take many decades to repair, if at all.”

Bleaching occurs when corals are stressed by unusual environmental changes, such as increased sea temperature. Credit: Karryon.com.au.

The Great Barrier Reef is one of the seven wonders of the world. It is larger than the Great Wall of China and the only living thing on earth visible from space.

The reef contains an abundance of marine life and comprises of over 3,000 individual reef systems and coral cays and literally hundreds of picturesque tropical islands with some of the worlds most beautiful sun-soaked, golden beaches.

However, scientists say global warming has caused such extensive damage to the reef, that scientists say its coral may never recover. According to another recent study published in the journal Nature, baby coral in Australia’s Great Barrier Reef have declined by 89% due to mass bleaching in 2016 and 2017.

The study measured the number of surviving adult corals in the Great Barrier Reef — the world’s largest reef system — following extreme heat stress, as well as how many new corals it was able to replenish in 2018, CBS News reported.

Deadly back-to-back bleaching events devastated the reef, and now its ecosystem is struggling to recover. Not only have ocean heat waves led to a dramatic decrease in new coral, but also a change in the types of coral species being produced.

Researchers studied adult and baby coral from 47 locations in various years from 1996 to 2016, then returned to the reef in 2018 to collect the same data. They found that a majority of the northern region’s coral has not been able to recover following mass bleaching events, leading to a decline in new coral as well.

“Dead corals don’t make babies,” the study’s lead author, Professor Terry Hughes, director of the ARC Centre of Excellence for Coral Reef Studies at James Cook University, said in a press release.

According to the study, the biggest decline in replenishment came from the reef’s dominant species of adult coral, called Acropora, which supports thousands of other species. It experienced a 93% drop compared to previous years.

Scientists expect the coral may recover over the next five to ten years — but only if another mass bleaching event doesn’t occur during that time. That’s unlikely given the current trajectory of climate change.

Bleaching occurs when corals are stressed by unusual environmental changes, such as increased sea temperature. They respond by expelling the symbiotic algae living in their tissues, causing the coral to turn white. Without the algae, the coral loses its major source of food and often can’t survive.

“It’s highly unlikely that we could escape a fifth or sixth event in the coming decade,” said co-author Professor Morgan Pratchett. “We used to think that the Great Barrier Reef was too big to fail – until now.”