Great Barrier Reef suffers severe coral bleaching yet again

10 Apr 2017

The Great Barrier Reef. Image: Benedikt Juerges/Shutterstock

Only weeks after the damage of 2016 was fully assessed in the Great Barrier Reef, 2017’s bleaching event has devastated the delicate ecosystem.

Bleached corals are not dead, but they are certainly distressed and, given the delicate nature of these ecosystems, it’s a visible warning that coral loss is imminent.

With that in mind, what’s happening to the Great Barrier Reef just off Australia is deeply troubling.

Prof Terry Hughes of James Cook University (JCU) in Australia is back in the news just four weeks after his 2016 findings painted a worrying picture.

Last year was devastating for the region, with mass bleaching hitting two-thirds of the reef. What was even more concerning was how little a role El Niño temperatures played in the event.

At the time, Hughes hoped that 2016 would be followed by years of stability and, perhaps, recovery. Those hopes have now been dashed.

A massive aerial reconnaissance mission above the reef found that the bleaching effect has caused devastation, stretching beyond the limits of 2016’s extensive reach.

Coupled with the 2017 mass bleaching event, Cyclone Debbie struck a corridor of the Great Barrier Reef at the end of March.

The intense, slow-moving cyclone was likely to have caused varying levels of damage along a path up to 100km in width, according to JCU.

Any cooling effects are likely to be negligible in relation to the destruction that was caused, unfortunately damaging a section of the reef that had largely escaped the worst of the bleaching last year.

“Clearly, the reef is struggling with multiple impacts,” said Hughes. “Without a doubt, the most pressing of these is global warming. As temperatures continue to rise, the corals will experience more and more of these events: 1 degrees Celsius of warming so far has already caused four events in the past 19 years.”

Bleaching evidence at Mission Beach reefs. Image: Bette Willis

Bleaching evidence at Mission Beach reefs. Image: Bette Willis

Cairns Townsville bleaching. Image: Ed Roberts

Cairns Townsville bleaching. Image: Ed Roberts

1998, 2002, 2016 and 2017 now mark the four toughest years on record for the Great Barrier Reef, with mere pockets remaining untouched by the warming damage.

“The combined impact of this back-to-back bleaching stretches for 1,500km, leaving only the southern third unscathed,” said Hughes.

Worryingly, there is very little that local authorities can do to help out. A study last month in Nature claimed that water quality and fishing pressure “had minimal effect” on the bleaching, with local efforts affording “little or no resistance to extreme heat”.

“Consequently, immediate global action to curb future warming is essential to secure a future for coral reefs.”

Coral bleaching is caused by rising water temperatures that are exacerbated by man-made climate change – oceans absorb the vast majority of the increase in the Earth’s heat.

The effect we’re having on the oceans is becoming clearer and clearer with every worrying report. For example, earlier this year, it emerged that human-made pollutants that were banned in the 1970s have emerged deep within the food chain of our oceans’ darkest depths.

These pollutions included polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers – pollutants commonly used as electrical insulators and flame retardants.

The former was banned in the 1970s in many parts of the world, which means that during its four-decade run, enough PCB was produced – estimated at 1.3m tonnes – to have a potentially damaging impact 40 years later.

Reefs are under threat everywhere. This time last year, the surprising discovery of a new, large coral reef in the murky waters of the Amazon was immediately tempered with the realisation that it was under threat.

Red, green and brown algae. 34 species of seaweed. 61 different types of sponge. Cnidaria and 73 species of reef fish. Despite the life that exists there, it appears that the coral reef discovery, measuring 9,500 sq km in total, was more of a warning than a rejoice.

Gordon Hunt was a journalist with Silicon Republic