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This month, the corals of the Lord Howe Island Marine Park in Australia have begun to show signs of bleaching. The 145,000-hectare Marine Park contains the world's southernmost coral reef, in one of the most isolated ecosystems on the planet.
Following initial reports of money laundering in the region, researchers from three Australian universities and two government agencies worked together throughout the month of March to study and document bleaching.
Prolonged heat stress caused 90% discolouration of some reefs, although other parts of the marine park escaped almost unscathed.
Bleaching is unequal
Lord Howe Island was named a World Heritage Site by UNESCO in 1982. It is the coral reef closest to a pole and contains many species that the l we do not find anywhere else.
Two of us (Tess Moriarty and Rosie Steinberg) have been studying the reefs of the Lord Howe Island Marine Park to determine the extent of bleaching in hard coral, soft coral and seaweed populations. anemones. This research revealed severe bleaching on the reefs of the coastal lagoon, where nearly 95% of the corals show signs of significant bleaching.
However, bleaching is very variable on Lord Howe Island. Some areas of the coral reef of the Lord Howe Island lagoon show no signs of whitening and have remained healthy and vibrant throughout the summer. Corals on the outer reef and deeper reef sites also remained healthy, with little or no bleaching.
A reef site studied in the Marine Park of Lord Howe Island is severely affected, with over 90% of the coral bleached; At the second most affected reef site, about 50% of the corals are bleached and the remaining sites are less than 30% bleached. At least three sites have less than 5% bleached corals.
During the past week, heat stress has persisted in this area and return visits to these sites revealed that the condition of the corals had worsened. There is evidence that some corals are now dying on the most severely damaged reefs.
Forecasts for the coming week indicate that the water temperature should cool below the bleaching threshold, which hopefully will quickly relieve corals from this valuable reef ecosystem. In the coming days, weeks, and months, we will continue to monitor affected reefs, determine the impact of this event on the reef system, and investigate coral re-establishment.
What is the cause of money laundering?
The bleaching was caused by the high temperature of seawater caused by a persistent summer heat wave off southeast Australia. In January, the temperature was 0 ° C higher than usual and, from the end of January to mid-February, it was above the local bleaching threshold.
Sustained heat has stressed and threatened the reefs of Lord Howe Island. By the end of February, they were enjoying a temporary respite with cooler temperatures, but by March, a further increase was making the ocean temperature well above safe levels. It is now the third recorded whitening event to be produced on this remote reef system.
However, this heat wave did not affect the entire reef system equally. In some parts of the lagoon, the water can be colder due to factors such as ocean currents and the intrusion of fresh water into the groundwater, thus protecting certain areas of the bleaching. Some coral varieties are also more heat resistant, and a particular reef that has been exposed to high temperatures in the past may be better able to cope with current conditions. For a complex variety of reasons, bleaching unevenly affects the entire marine park.
Coral bleaching is the biggest threat to the sustainability of coral reefs around the world and is now clearly one of the biggest challenges we face in dealing with the impact of global climate change. UNESCO World Heritage regions, such as the Lord Howe Group of Islands, need urgent action to tackle the causes and impact of a disaster. climate change, as well as continued management to ensure that these systems remain intact for future generations.
The authors thank ProDive Lord Howe Island and Lord Howe Island Environmental Tours for their help during the fieldwork.
Tess Moriarty, Ph.D. candidate at the University of Newcastle; Bill Leggat, Associate Professor at the University of Newcastle; C. Mark Eakin, Coordinator of Coral Reef Watch, National Oceans and Atmospheric Administration; Rosie Steinberg, doctoral student, UNSW; Scott Heron, Lecturer, James Cook University; and Tracy Ainsworth, Associate Professor, UNSW.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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