米フロリダ沖のサンゴ礁、未知の病気との闘い

【オーランドＡＦＰ＝時事】米フロリダ州中部の研究所にある海水の大きな水槽。人工太陽照明灯の下、生物学者のアーロン・ギャビン氏はその中で生きている７００株以上のサンゴに、小エビを原料とする飼料をピペットで丁寧に与える。（写真は米フロリダ州オーランドにあるフロリダサンゴ救助センターで、救出されたサンゴの世話をするスタッフ）
　ここ「フロリダサンゴ救助センター」での取り組みは、米本土水域にある唯一のサンゴ礁を謎の病気から救う最後の頼みの綱かもしれない。
　ギャビン氏のチームはこの水槽の中に、フロリダ州南端沖のサンゴの生息地を丹念に再現した。潮の流れを人工で起こし、魚も現地から取り寄せた。
　チームはこの海域で、原因不明のイシサンゴ組織喪失病（ＳＣＴＬＤ）という病気に侵されている１８種のサンゴを救おうとしている。
　フロリダキーズ諸島沖の大西洋には、マングローブの林が広がり、魚の群れが素早く泳ぎ回っている。だが、その中に横たわるサンゴは白く脱色し、海底に大きなまだらをつくっている。
　ＳＣＴＬＤは２０１４年、マイアミの近くで初めて確認された。その後、急速に広がり続け、海の生物多様性の要であるイシサンゴの約半分を死滅させた。現在、この海域のイシサンゴ４５種のうち２０種超が絶滅の危機にひんしている。
　この病気はさらにカリブ海を渡り、中米メキシコやベリーズのサンゴにまで被害を及ぼしている。
　ギャビン氏のチームの取り組みは、２０１８年に米海洋大気局（ＮＯＡＡ）とフロリダ魚類野生生物保護委員会が立ち上げた海洋生物保護プロジェクトの一環だ。

■サンゴを海に戻す
　プロジェクトの第１段階は、健康なサンゴの隔離だ。救出された２０００近いサンゴの群体（コロニー）は現在、米国の１４州にある２０か所以上の施設で育っている。
　サンゴを海に戻すのが第２段階だが、サンゴは繁殖が非常に遅いため、実施するまでにはかなり時間がかかりそうだ。
　研究所では救出したサンゴの遺伝的性質を調べている。病気や海水温の上昇、汚染などに抵抗力のある新種を開発するためだ。試みの成否は、この海域に重大な影響をもたらし得る。
　イシサンゴはサンゴ礁として、海洋生物の４分の１の生息地になっている。また外洋と陸地の間で波を和らげてもいる。ハリケーンや暴風雨の際にはとりわけそうだ。
　サンゴ礁が損なわれると、フロリダの観光収入にも響きかねない。ある試算によると、魚釣りやダイビング目的の訪問者を魅了するサンゴ礁は８５億ドル（約９６００億円）の資産価値があるという。
　キーズ諸島最北端の島キーラーゴに住むスティーブ・キャンベルさん（５９）は、今後の成り行きを心配している。小型観光ボートの船長をしているが、商売はすでにサンゴの病気による影響を被っている。
　キャンベルさんは港に立ち、「フロリダキーズでこれまで２０年暮らしてきて、海には毎日出ています」と語った。「見ての通り、この海で生計を立てています。観光客をサンゴ礁に連れて行き、見て楽しんでもらうのです…だから、これは私たちにとっては一大事なのです」【翻訳編集ＡＦＰＢＢＮｅｗｓ】

〔ＡＦＰ＝時事〕（2021/10/13-12:23）

At a laboratory in central Florida, biologist Aaron Gavin uses tiny pipettes to carefully feed shrimp to more than 700 corals living in huge saltwater tanks, with sunlight-mimicking lamps glowing above them.
The work of the scientists here could be the last chance to save the species that make up the only coral reef in the United States' continental waters.
Gavin and his team have diligently recreated the coral reef habitat found in the waters off the southern tip of the state, complete with artificial currents and local fish.
They hope to prevent the 18 species of coral in their care from suffering the same mysterious ailment, called SCTLD (stony coral tissue loss disease), that is afflicting their wild cousins.
Among the sprawling mangroves and darting schools of fish off the Florida Keys, the damaged corals -- normally dark -- now appear as large white patches on the floor of the Atlantic Ocean.
The situation is the same all along the Florida Reef Tract, which stretches 360 miles (580 kilometers) from the Dry Tortugas, which are the westernmost islands in the Florida Keys, all the way to the town of St Lucie, located about 120 miles north of Miami.
It's heartbreaking, and I think the most alarming (thing) about it is that most people don't know it's happening, said Michelle Ashton, the communications director of the Fish and Wildlife Foundation of Florida.
- Rescue -
What Gavin and his colleagues discover at the Florida Coral Rescue Center could change the future of the state's marine ecosystems.
We are holding the corals safely and healthy in our care, explained Justin Zimmerman, the director of the Orlando-based lab, which opened in 2020 and is managed by aquatic theme park company SeaWorld.
If they were still in the wild, up to 90 percent of them would have been dead, Zimmerman said.
The potentially catastrophic SCTLD was first discovered in 2014, near Miami, and has continued to spread rapidly, killing about half of stony coral species, a cornerstone of marine biodiversity.
The disease, whose causes are unknown, is now plaguing the animals further into the Caribbean, all the way in Mexico and Belize.
The rescue lab's work is part of a project created in 2018 by the National Oceanic and Atmospheric Association and the Florida Fish and Wildlife Conservation Commission, and includes dozens of public and private organizations.
The group, faced with the threat of more than 20 of the 45 species of hard corals in the area going extinct, devised the unprecedented plan to extract healthy corals from the region's waters and care for them in these artificially equipped aquariums in the hope they can be returned to their wild habitats in the future.
You are looking at the future of Florida Reef Tract in this room, Aston said of the corals in the Orlando aquariums. And their grandchildren will be what goes back out to the water.
- Return to the sea ?
The first part of the rescue plan has allowed wildlife authorities to save nearly 2,000 colonies of corals, now stored at more than 20 institutions in 14 different states.
The second part of the plan requires researchers to successfully return the corals to the ocean -- though such an operation would likely take place a long time from now, as corals reproduce very slowly.
The scientists are studying the genetics of the rescued animals in an effort to cultivate new specimens that could be more resistant to disease, as well as other threats such as warming water temperatures and pollution.
The success or failure of these endeavors could have huge consequences for the region.
Stony corals, made up of limestone skeletons, are what create coral reefs, which in turn provide a home for a quarter of marine life.
Plus, the structures are natural barriers between the open ocean and land, reducing the strength of waves that hit the coastline, especially during hurricanes and other storms.
And a hit to coral health could mean a hit to Florida tourism revenue, as one study estimated that visitors drawn to the state for fishing and diving along the reef generate $8.5 billion.
Key Largo resident Steve Campbell, 59, is worried about what comes next. He is sitting next to the small tourist boat he captains, currently anchored in the port.
He said the coral disease has already had an impact on his business.
I've been in the Florida Keys now for 20 years, and I'm out on the water every day, he said.
Obviously we make our living out here, so we take people out to the reef for the enjoyment of seeing the reef.
So for us it's extremely important.