What causes starfish plagues?



Since 2005, Li Yuanchao and other researchers at the Hainan Institute of Oceans and Fisheries have been monitoring the coral reef ecosystems of the Xisha (Paracel) Islands. Field studies and archival research have identified two crown of thorns outbreaks there. The first began in 2004 and its impact on coral reefs continued until 2019. Then a new epidemic occurred, also in 2019.

Based on these findings and the Australian research, Li’s team published an article in 2019 indicating that crown of thorns outbreaks in Xisha occur approximately every 15 years.

Other species appear in regular cycles due to inherent biological traits. For example, the eastern United States is currently experiencing an epidemic of a sort of “periodic cicada,” which emerges in the hundreds of millions in the spring of every 17th year, to mate, give birth, and die within weeks.

But there is no scientific consensus yet on what causes periodic outbreaks of thorn-crowned starfish, according to information from the Great Barrier Reef Marine Park Authority. A number of factors are likely at play. Biological factors could be part of the answer, such as: decreasing the number of natural enemies; increased nutrition of rivers and upwelling; the propagation of larvae by ocean currents; and the availability of coral prey.

Li Yuanchao’s team attributes crown of thorns outbreaks to typhoons, reduced predatory fish populations on coral reefs, global warming, and human activity. Typhoons add nutrients to the water by disrupting the seabed, which means more starfish larvae survive. Warmer temperatures and fewer fish increase the chances of starfish hatching and survival. Monitoring data from Li’s team shows that warmer temperatures increase survival rates. Average temperatures in the waters around Xisha exceeded 30 ° C in 2006-2007 and 2014-2018, and the number of starfish increases during these periods.

Although there are no conclusions on the causes of the outbreaks, Zeng Xiaoqi, a professor at the China Ocean University who studies echinoderms, says there is a lot of surveillance data available on the crown of thorns. , as many countries have started to research them, the damage they cause to coral reefs. But there is still not enough research on the North Pacific starfish, he added.

“There were epidemics in 2006 and 2007, but we don’t know what happened before, or what will happen after,†Zeng said. He points out that the crown of thorns and the North Pacific starfish belong to the Asteroid class, but are different species with different characteristics. They live in different environments, and the causes and timing of their outbreaks should not be confused.

More research needed

The North Pacific starfish is becoming an ecological disaster across the North Pacific. In China and Japan alone, there have been 10 major epidemics since 1953, according to a 2019 article by researchers at the Yantai Coastal Zone Research Institute of the Chinese Academy of Sciences and other institutions. Meanwhile, a review of academic research found that few studies on the species had been conducted, without any quantitative work on how it is affected by acidification and warming caused by climate change or by human activity such as shellfish farming.

When asked about the causes of the latest outbreak in Jiaozhou Bay, researchers who studied the North Pacific starfish told China Dialogue that they had only done limited research and could not provide answers. final.

Discussions about the cause of the crown-of-thorns starfish outbreaks are also still ongoing. Given the destruction they cause to coral reefs, long-term monitoring should begin as soon as possible, according to Lian Jiansheng, a coral researcher at the Chinese Academy’s Institute of South China Sea Oceanology. Sciences.

Lack of funding is a factor holding back research. In his article, Li Yuanchao wrote that although central and local government allocates money to fight crown of thorns outbreaks, it is emergency funding, not designed to help research the mechanisms and causes of epidemics, the animal’s life cycle or possible prevention mechanisms.

Speaking to China Dialogue, the researchers repeatedly stressed the importance of tracking and monitoring starfish. Zeng Xiaoqi believes that the North Pacific starfish should be covered by regular monitoring of the environment and coastal organisms, in order to better understand its distribution, reproduction and population changes in key areas. Zhang Guangtao added that it is especially necessary to monitor the number of larvae and their movement, so that the risk of an outbreak can be identified and controlled. He also suggested appropriate releases of starfish larval predators, such as croaker, perch, and plaice.



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