Quantcast
Environmental News for a Healthier Planet and Life

Bleaching Has Struck the Southernmost Coral Reef in the World

Oceans
Bleaching Has Struck the Southernmost Coral Reef in the World
Lord Howe Island lagoon in New South Wales, Australia. Peter Unger / Lonely Planet Images / Getty Images

By Tess Moriarty, Bill Leggat, C. Mark Eakin, Rosie Steinberg, Scott Heron and Tracy Ainsworth

This month corals in Lord Howe Island Marine Park began showing signs of bleaching. The 145,000 hectare marine park contains the most southerly coral reef in the world, in one of the most isolated ecosystems on the planet.


Following early reports of bleaching in the area, researchers from three Australian universities and two government agencies have worked together throughout March to investigate and document the bleaching.

Sustained heat stress has seen 90 percent of some reefs bleached, although other parts of the marine park have escaped largely unscathed.

Bleaching is Uneven

Coral bleaching observed at Lord Howe in March 2019.


Author Provided

Lord Howe Island was named a UNESCO World Heritage site in 1982. It is the coral reef closest to a pole, and contains many species found nowhere else in the world.

Two of us (Tess Moriarty and Rosie Steinberg) have surveyed reefs across Lord Howe Island Marine Park to determine the extent of bleaching in the populations of hard coral, soft coral and anemones. This research found severe bleaching on the inshore lagoon reefs, where up to 95 percent of corals are showing signs of extensive bleaching.

However, bleaching is highly variable across Lord Howe Island. Some areas within the Lord Howe Island lagoon coral reef are not showing signs of bleaching and have remained healthy and vibrant throughout the summer. There are also corals on the outer reef and at deeper reef sites that have remained healthy, with minimal or no bleaching.

One surveyed reef location in Lord Howe Island Marine Park is severely impacted, with more than 90 percent of corals bleached; at the next most affected reef site roughly 50 percent of corals are bleached, and the remaining sites are less than 30 percent bleached. At least three sites have less than 5 percent bleached corals.

Healthy coral photographed at Lord Howe marine park in March 2019.


Author Provided

Over the past week heat stress has continued in this area, and return visits to these sites revealed that the coral condition has worsened. There is evidence that some corals are now dying on the most severely affected reefs.

Forecasts for the coming week indicate that water temperatures are likely to cool below the bleaching threshold, which will hopefully provide timely relief for corals in this valuable reef ecosystem. In the coming days, weeks and months we will continue to monitor the affected reefs and determine the impact of this event to the reef system, and investigate coral recovery.

What’s Causing the Bleaching?

The bleaching was caused by high seawater temperature from a persistent summer marine heatwave off southeastern Australia. Temperature in January was a full degree Celsius warmer than usual, and from the end of January to mid-February temperatures remained above the local bleaching threshold.

Sustained heat stressed the Lord Howe Island reefs, and put them at risk. They had a temporary reprieve with cooler temperatures in late February, but by March another increase put the ocean temperature well above safe levels. This is now the third recorded bleaching event to have occurred on this remote reef system.

Satellite monitoring of sea-surface temperature (SST) revealed three periods in excess of the Bleaching Threshold during which heat stress accumulated (measured as Degree Heating Weeks, DHW). Since January 2019, SST (purple) exceeded expected monthly average values (blue +) by as much as 2°C. The grey line and envelope indicate the predicted range of SST in the near future.


NOAA Coral Reef Watch

However, this heatwave has not equally affected the whole reef system. In parts of the lagoon areas the water can be cooler, due to factors like ocean currents and fresh groundwater intrusion, protecting some areas from bleaching. Some coral varieties are also more heat-resistant, and a particular reef that has been exposed to high temperatures in the past may better cope with the current conditions. For a complex variety of reasons, the bleaching is unevenly affecting the whole marine park.

Coral bleaching is the greatest threat to the sustainability of coral reefs worldwide and is now clearly one of the greatest challenges we face in responding to the impact of global climate change. UNESCO World Heritage regions, such as the Lord Howe Island Group, require urgent action to address the cause and impact of a changing climate, coupled with continued management to ensure these systems remain intact for future generations.

The authors thank ProDive Lord Howe Island and Lord Howe Island Environmental Tours for assistance during fieldwork.

Reposted with permission from our media associate The Conversation.

The Bulletin of the Atomic Scientists' "Doomsday Clock" — an estimate of how close humanity is to the apocalypse — remains at 100 seconds to zero for 2021. Eva Hambach / AFP / Getty Images

By Brett Wilkins

One hundred seconds to midnight. That's how close humanity is to the apocalypse, and it's as close as the world has ever been, according to Wednesday's annual announcement from the Bulletin of the Atomic Scientists, a group that has been running its "Doomsday Clock" since the early years of the nuclear age in 1947.

Read More Show Less

EcoWatch Daily Newsletter

The 13th North Atlantic right whale calf with their mother off Wassaw Island, Georgia on Jan. 19, 2010. @GeorgiaWild, under NOAA permit #20556

North Atlantic right whales are in serious trouble, but there is hope. A total of 14 new calves of the extremely endangered species have been spotted this winter between Florida and North Carolina.

Read More Show Less

Trending

There are new lifestyle "medicines" that are free that doctors could be prescribing for all their patients. Marko Geber / Getty Images

By Yoram Vodovotz and Michael Parkinson

The majority of Americans are stressed, sleep-deprived and overweight and suffer from largely preventable lifestyle diseases such as heart disease, cancer, stroke and diabetes. Being overweight or obese contributes to the 50% of adults who suffer high blood pressure, 10% with diabetes and additional 35% with pre-diabetes. And the costs are unaffordable and growing. About 90% of the nearly $4 trillion Americans spend annually for health care in the U.S. is for chronic diseases and mental health conditions. But there are new lifestyle "medicines" that are free that doctors could be prescribing for all their patients.

Read More Show Less
Candles spell out, "Fight for 1 point 5" in front of the Brandenburg Gate in Berlin, Germany on Dec. 11, 2020, in reference to 1.5°C of Earth's warming. The event was organized by the Fridays for Future climate movement. Sean Gallup / Getty Images

Taking an unconventional approach to conduct the largest-ever poll on climate change, the United Nations' Development Program and the University of Oxford surveyed 1.2 million people across 50 countries from October to December of 2020 through ads distributed in mobile gaming apps.

Read More Show Less
A monarch butterfly is perched next to an adult caterpillar on a milkweed plant, the only plant the monarch will lay eggs on and the caterpillar will eat. Cathy Keifer / Getty Images

By Tara Lohan

Fall used to be the time when millions of monarch butterflies in North America would journey upwards of 2,000 miles to warmer winter habitat.

Read More Show Less