Nature: The number of coral larvae on the Great Barrier Reef declined by 89%, and coral whitening or normalization occurred.

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Nature: The number of coral larvae on the Great Barrier Reef declined by 89%, and coral whitening or normalization occurred.

2019-04-07 08:03:44 629 ℃

"We used to think that the Great Barrier Reef was big but not collapsed." Morgan Pratchett, chief investigator of the Coral Reef Excellence Research Center of the Australian Research Council, said in a statement issued on April 3. A new study co-authored by Plachette shows that coral albinism caused by two consecutive ocean heatwaves in 2016 and 2017 not only resulted in large-scale death of adult corals at that time, but also led to an 89% decline in the number of coral larvae, which directly affected the recovery of coral populations in the Great Barrier Reef. The study was published in the April 3 issue of Nature. Great Barrier Reef is the largest and longest coral reef group in the world. It lies on the northeast coast of Australia in the South Pacific Ocean. It runs through the Coral Sea outside Queensland, northeast Australia. It stretches about 2600 kilometers from Torres Strait to the north and 161 kilometers to the south of the Tropic of South Regression. There are about 2,900 separate reefs and 900 small islands. Coral bleaching refers to the phenomenon of coral whitening. The coral itself is white, but the corals we see are colorful, because the symbiotic algae in the corals have different colors, and these algae provide energy to the corals through photosynthesis. If symbiotic algae leave or die, the coral will turn white and eventually die of loss of nutrient supply. Studies have shown that corals are more susceptible to algae whitening due to the decrease in algae dependence due to rising ocean temperatures.

Over the past 100 years, global ocean heat waves have become more frequent and lasting, which has seriously threatened coral reefs. According to the study, for 100 coral reefs in the tropics, albinism occurred on average every 25 years in the 1980s and every 6 years in 2010 or so. In the past 20 years, the Great Barrier Reef has experienced four large-scale albino disasters, which occurred in 1998, 2002, 2016 and 2017 respectively.

According to climate model, coral albinism will occur every five years on average by 2035. If there is no substantial change in global warming, coral albinism will occur every year after 2044. The

< p> study also showed that the death of large-scale adult corals after albinism disaster was directly related to the large-scale failure of coral larvae reproduction, and the composition of coral groups also changed, which means that the prospects for the restoration of the Great Barrier Reef may not be clear. The data of

show that the level of coral reproduction has dropped to 11.3% of the average level in the past two decades in the whole Great Barrier Reef. The level of coral reproduction in sexual reproduction has dropped to 6.9% of the historical average, compared with 36.5% in asexual reproduction. 。 The reproduction of

corals can be divided into two types: asexual reproduction and sexual reproduction. The asexually reproduced corals usually produce formed coral larvae in one day, while the sexually reproduced corals release eggs and sperm into vitro, which usually takes 4-7 days to form coral larvae. Therefore, from the perspective of germ cell transmission and gene flow, it is generally believed that asexual coral reproduction is more limited. Moreover, because asexual reproduction comes from the proliferation of the same coral population, it does not increase the diversity of coral reef areas and gene pools. This makes coral reefs stable in a few species and weakens the gene in the population.

Researchers believe that the level of restoration of the Great Barrier Reef ecosystem in the future will largely depend on the increase in diversity of young coral and the level of resistance of asexually reproduced coral to albinism.

Researchers also compared the degree of restoration of coral populations in different regions of the Great Barrier Reef, and found that the life span of adult coral populations in central and Northern coral reefs was more affected by global warming and other factors, so the ecological resilience of these regions was worse. In the future, even the fastest-growing species would need at least 10 years to restore their populations. In response, Terry Hughes, director of the Coral Reef Excellence Research Center of the Australian Research Council, said, "There is only one way to solve this problem: to'cure the root cause'- to change the status of global warming by reducing net greenhouse gas emissions."