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The whitening of Jeju's seasInvasive coralline algae raise alarm among scientists
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승인 2011.06.24  16:35:10
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▲ A scientist for the Subtropic Fisheries Research Center collects samples of marine life. Photo courtesy Subtropic Fisheries Research Center

Jeju is defined by its ocean. Much of its history, culture and leisure activities have been formed and occur specifically near its rocky shore, but within the last 30 years its coastline has been increasingly threatened by a natural phenomenon known as the whitening of the sea.

Due to climate change and the discharge of waste into the ocean, within the last three decades the sea around Jeju has risen in temperature by .7 degrees. Though this may seem like a marginal increase, in shallow waters this can drastically alter the ecosystem. The rise in temperature has made it more difficult for indigenous species to survive while also creating a more suitable environment for tropical fish and plants, specifically invasive species, which then fight for the limited habitat.

“This is kind of an ecological problem,” said Jeju National University Applied Marine Science Professor Choi Kwang Sik. “For the past two decades the shallow water here has become deforested. There used to be a lot of big macro algae but they are all gone because as temperatures go up they cannot really survive well.”

With the decrease of macro algae, which is used for food and nurseries by fish, “the shallow waters have become really dominated by coralline algae,” which is an invasive species from more tropical climates that is often mistaken for coral, said Choi.

This red skeletal algae has a life span of one to two years “and once it dies off, once they loss all their pigment it becomes white, that is what we can the whitening.” The whitening of the sea is specifically attributed to a lack of marine life in the water.

The coralline algae is aggressive and adheres to the rocky shore and sea bed, preventing seaweed and macro algae from rooting itself and consequently from growing. Fish and aquatic plants in Jeju’s coastline are now facing a lack of food and habitat.

▲ Left, Dr. Hong Seong Wan and right, Professor Choi Kwang Sik. Photos by Darryl Coote

According to Dr. Hong Seong Wan, researcher for the Jeju Special Self-Governing Province Ocean and Fisheries Research Institute, 31.4 percent of all fishery areas on Jeju’s coastline are being affected by this phenomenon.

Starting last year Hong and his research institute have been addressing this problem by trying to replenish the coastline’s macro algae and seaweed populations through two methods. The first method is by building a 10 meter by five meter rope grid and attaching 20 kg of young algae to it (within two years it will grow to 100 kg of algae). This rope mat, as Hong called it, is placed on the ocean bed four to five meters deep. Though, he explained, the coastline is technically anything up to 30 meters in depth, there is no need to place the mats further down because it is not being affected by this whitening. The water there is still cold enough to prevent the changes that are occurring closer to the shore.

“Last year as a trial we planted 10 [rope mats] in Hallim. This year 20 in each place and we plan to expand [the project], but because of lack of money it is very difficult to do that,” said Hong.

Currently Hong and his team have plans to lay these rope mats at some of the most affected areas in Jeju; Daepyeong, Aewol, Gwideok, and Hangwon. He said that of the 31.4 percent affected by this phenomenon the southern and western coasts are where the majority of the whitening is occurring due to being buffeted by the warm Kuroshio’s current from the south.

Since they are at the first stage of this initiative, Hong can not say for certain if it will curb the whiting of Jeju’s coastline.

The other method Hong is employing is to attack the coralline algae head-on by spraying it off the rocks with high pressure water, or turning the rock over hoping to give macro algae and seaweed a place to adhere to.

Both Hong and Choi said that the lack of research is a great hindrance to improving the current state of Jeju’s coastline. Dr. Koo Jun Ho of the National Fisheries Research & Development Institutes’ Subtropical Fisheries Research Center attributed the lack of research to unpredictable weather that prevents proper field studies. Also, due to the scale of the area in question, a lack of funding and the need for expensive equipment like ships and diving apparatuses makes it quite difficult especially when compared to conducting research on land.

Koo has recently completed field research on Jeju’s coastal areas, which admittedly was not as comprehensive as he would have liked due to funding, but his work “can be complemented by future research,” he said.

First begun in 2008, Koo’s research, funded by the Jeju government with 90 million won annually, is to examine the affects of climate change by using the island as a litmus test since it is “the most southern part of Korea so it signals the first changes,” he said. The second purpose is to create policy concerning Jeju’s coastline for the provincial government to implement.

Their field research last month was to observe what was actually occurring in Jeju’s ocean and compare it to previous expeditions.

His team selected eight locations to study because “one area is at least 50 hectares, and we have limited resources,” preventing them from surveying the entire coastal area. This was a common situation mentioned by all interviewees, that research has suffered due to a lack of funding.

Currently Koo and his team are analysing the raw data, but he told The Weekly that programs like Hong’s are necessary.

Koo did agree that the whitening of the sea is a massive force and at times these initiatives and polices feels like pushing a boulder up a hill, but even so it is necessary since without it those who depend upon the coastline “may lose their way of life.”

(Interpretation by Kim Jung Lim and Kim Soo Yang)

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