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Pumice stones deliver a lesson from the depths of the sea

Pumice stones deliver a lesson from the depths of the sea

2022-07-24

Last August in Japan’’s Bonin island chain, an underwater volcano erupted, spewing out vast amounts of pumice stones. Carried by the ocean, these floating rocks eventually reached Taiwan, after traveling some 2,000 kilometers, and covered the coast in a blanket of yellow-gray. While the pebbles on the shore make quite a sight, they’’ve been a disaster for fishermen. How has the pumice harmed the fishing industry, and how has it affected the local ecology? We find out today in our Sunday special report.

Lin Chun lives in New Taipei’s Aodi village. At the start of the year, he made a troubling discovery.

This beach looks ordinary enough, but it’s the source of Lin’s worries.

Lin Chun
Marine association head
Previously, this terrain was a reef. Here you’ll mainly find shellfish, sea snails and the like, and hermit crabs.

Today, we see few creatures besides the odd shellfish here and there. Where a reef had once stood, there is now a “beach” covered in a thick layer of pebbles.

A closer look reveals fine pores on the surface of each pebble. These pebbles are actually volcanic pumice stones. Lin, who loves the ocean and its wildlife, fears that the stones are disturbing the local ecosystem.

Voice of Lin Chun
Marine association head
It’s likely that this hole was used by crabs to enter and exit the rock. There are probably many holes and cracks in this rock that have been plugged by the pumice stones, and now the crabs can’t get out.

This scene is not exclusive to New Taipei’s Aodi village, but can be seen all along the coast of Taiwan proper. Where did the pumice come from, and what impact has it brought?

In August 2021, the Fukutoku-Okanoba undersea volcano near the Bonin Islands had its largest eruption in a century. A vast quantity of pumice spewed into the sea and followed the ocean currents to the west.

The Bonin Islands are located in the southeast of Japan. When the Fukutoku-Okanoba volcano erupted in August 2021, it spewed out pumice composed of silicon dioxide, aluminum oxide, and iron oxide. By October, the pumice had drifted to Okinawa, paralyzing the local fishing ports. By early December, it had also arrived in Taiwan.

Chiu Yung-fang
National Academy of Marine Research president
It basically followed the ocean current. There is a current on the west side of the Pacific Ocean basin, and its eddies flow partly north and partly south. The part that goes south enters the South China Sea, passes through the Kuroshio Current, and then heads north to reach Taiwan.

No part of Taiwan’s coastline was spared by the pumice, although some areas were hit worse than others.

Chiu Yung-fang
National Academy of Marine Research president
Because the Kuroshio Current flows farther out, a considerable amount of pumice washed up here, but not too much. Once the pumice had drifted to this area, the northeasterly monsoons brought them in, so a lot of pumice washed up here. Then once it came around to Taoyuan, a lot of pumice was deposited there.

According to data from the National Academy of Marine Research, the worst-hit areas were Northern Taiwan, Pingtung, Taitung, and Penghu. When a large volume of pumice accumulates on a shore, what happens to the local water quality and marine wildlife?

Sung Hsin-chen
Ocean Conservation Administration deputy head
In December 2021, we drew samples of water near Taitung’s Miramar and Green Island, as well as near Wushibi in Yilan. The water quality of the samples was not abnormal. Pumice is the product of a natural geological activity. I think that throughout the course of the Earth’s evolution, over these tens of millions or hundreds of millions of years, similar situations have occurred and are not unfamiliar to living organisms. For example, sea turtles evolved over 1 or 2 hundred million years, and I think that they instinctively know how to avoid danger.

Turtles and cetaceans that roam the sea have the ability to flee danger. But what about the marine creatures that can’t swim far?

In Japan’s Okinawa, pumice accumulation caused water along the shore to turn pitch black. What impact does that have?

To understand the impact of pumice on reef ecology, we hire Lin – a seasoned diver who collects marine trash – to capture undersea footage in the waters off Aodi village.

As soon as he jumps in, pumice stones large and small start to fly his way. We’d thought that all the stones were on the surface of the ocean, but a good amount of them are underwater. Off the coast of Aodi village, there isn’t enough pumice to block sunlight from reaching the ocean floor. But there is a much thicker layer just some 10 kilometers away in the Nanya area.

Lin Chun
Marine association head
Because corals and many microorganisms rely on photosynthesis for food production, the absence of light can wipe out the bottom of the food chain. That would have a massive impact. Small fish eat the microorganisms, medium fish eat the small fish, and big fish eat the medium fish. When the microorganisms die off, that affects the predators next in the sequence.

Here in Aodi, Lin’s main concern is the tiny pumice pebbles that flow under the sea.

Lin Chun
Marine association head
The area within a meter of the ocean surface is filled with volcanic pumice. I think that sea turtles and fish are mistakenly eating the debris, because that debris looks like plankton.

In Okinawa, fish farmers did indeed find pumice stones in the stomachs of dead fish. Without a doubt, volcanic pumice is posing a severe test to coastal ecology.

But there is also another group of victims: fishermen.

These fishermen have a laugh despite their predicament. The fishing port in front of them is swamped by volcanic pumice. It’s the first time these men have seen such a thing, and the boats in the harbor have suffered to no small degree. While a fishing boat is running, it must continuously pump seawater to cool its engine. But when the seawater is full of pumice stones, the boat’s cooling system becomes clogged, causing the engine to overheat.

Chang Yuan-tang
Waimushan sustainable fishing association head
If pumice stones get sucked into the cooling system, you can get a professional to clear it out. That might cost around NT$10,000. But the problem is, if you don’t pay attention, the entire engine can overheat. Once that happens, if the engine burns out, you’ve got a considerable expense on your hands. It could be several hundred thousand New Taiwan dollars.

As he speaks, the owner of a damaged boat arrives on the scene.

Recently, Yen Chu-sheng’s boat broke down when its cooling system sucked up too much pumice. Besides having to pay for repairs, he was unable to fish for a whole week, which meant he had no income. To prevent another accident, he made his own three-stage pumice filter.

Seawater is filtered once before entering the cabin, and filtered again as it enters the cooling system. Before it enters the engine, the water is filtered a third time. On top of that, pumice is fished out from the water tank with the help of a net. Yen spends his day catching fish and fishing pumice, rushing from one task to the other.

He laments his plight, overcome by a sense of helplessness. With so much pumice in the port and beyond, he faces a dilemma when deciding whether to go out to sea.

Chang Yuan-tang
Waimushan sustainable fishing association head
Each year, just before and after the Spring Festival, there’s a lot of squid that can be caught. But we’re afraid to move these boats out. If you don’t go out when the weather is good, you have no chance with the squid. But once you’re out there, you’re afraid your engine will get clogged. I hope the government can better look out for our fishermen. If a fisherman suffers damages or sees an impact from this, we hope the government will give him a hand.

In the meantime, local fisheries groups are working to make life easier for those in the trade.

The Ruifang District Fishermen’’s Association has jurisdiction over four fishing ports: Shen’ao Shuinandong, Nanya, and Bitou, areas that are thick with pumice. These boats are mired in a sand-colored sea. If you didn’t know about the pumice, it would be easy to think the boats were stranded on a beach.

The president of the fisheries group, Huang Chih-ming, has waged a fierce battle against pumice. This past month, he bought more durable skimming nets for clearing out floating stones.

Huang Chih-ming
Ruifang District Fishermen’’s Association head
This one cost NT$3,000.

He also made the switch from black garbage bags to permeable sandbags.

These are lessons learned through trial and error, through months of struggling against the pumice in the port.

Huang Chih-ming
Ruifang District Fishermen’’s Association head
Our fishermen have been extremely troubled by this. The northeasterly winds blow in that pumice, filling the entire port with it. You have no choice but to try to skim it out.

If they don’t skim the port with nets, the fishing boats can’t venture out to sea. But manual labor can only go so far.

Huang says that machines would be able to clear out pumice more efficiently.

Huang Chih-ming
Ruifang District Fishermen’’s Association head
As for the pumice at sea – I do have an idea. The government can hire some deck barges and deal with the pumice using backhoes. This would prevent the pumice from drifting into our fishing ports.

After being fished out from the sea, the pumice stones sit in bags stacked high beside the port. One big question is where to send them.

Huang Chih-ming
Ruifang District Fishermen’’s Association head
We have a tremendous amount of pumice stones. We’ve got more than 10,000 bags at this point, and they have nowhere to go.

An even bigger question is whether this vast amount of waste can be converted into something valuable.

Lee Tzung-han
Taoyuan agricultural research station assistant researcher
When volcanic pumice floats over, there’s a lot of marine debris mixed in. So our first step is to get rid of the larger pieces of debris.

Here at the Taoyuan District Agricultural Research and Extension Station, these researchers are working on unlocking the value of pumice stones.

Lee Tzung-han
Taoyuan agricultural research station assistant researcher
Because there’s a great deal of sea salt in there, we need to give it a rinse to remove the salt.

Before pumice stones can be used in agriculture, the first order of business is to remove their sodium content, so that they don’t harm crop growth.

Tang Hsueh-jung
Taoyuan agricultural research station assistant researcher
When you’re making cold side dishes or pickled sauerkraut, you use a lot of salt. When salt comes into contact with a plant, it has a dehydrating effect, making it difficult for the plant to absorb water. The plant can’t draw up nutrients through the water, either.

Once all their sodium is removed, volcanic pumice becomes very similar to a commercially available medium used for plant cultivation: expanded clay aggregate.

Hsu Ya-ting
Taoyuan agricultural research station assistant researcher
This is expanded clay aggregate. It is very light and its pores are very large, so it allows soil to maintain very good drainage and air circulation.

Tang Hsueh-jung
Taoyuan agricultural research station assistant researcher
Growing mediums for plants – mediums that have relatively large pores can be used to adjust the soil, to reduce the likelihood of root rot due to the accumulation of water.

Through soaking and rinsing, volcanic pumice is given a new lease on life.

Tang Hsueh-jung
Taoyuan agricultural research station assistant researcher
The salinity of untreated pumice is around 2.0. Pumice that’s treated, as you can see, has a fairly low level of salinity. This is now about 0.15.

Experiments show that treated pumice meets agricultural regulations on salinity content, and that it can be used successfully as a growing medium. Researchers say that pumice stones are better suited for use in potted plants and should not be scattered in fields, as they can wash away in rain and cause problems.

Lin Chun
Marine association head
When the sun goes down, these little crabs come out. What we can gather from their presence is, perhaps the impact of the pumice has been very great, or perhaps it’s been very small. But at any rate, these crabs are among the few survivors we see.

Arising from the depths of the ocean floor, volcanic pumice reminds us of the beauty and fragility of the natural world.

Lin Chun
Marine association head
If this natural occurrence is already bringing harm, we human beings should not make that harm even worse. I hope that through this volcanic pumice, we can deepen our understanding of the natural world and become better at cherishing it, to ensure its continued survival.



來自海底的一堂課

2022-07-24

日本小笠原群島海底火山去年八月大噴發之後,今年三月底再度噴發,讓台灣漁業和海洋相關單位再度繃緊了神經。因為去年大噴發之後,大量火山浮石隨著洋流漂了兩千公里,漂到台灣,台灣四周海面和各地海岸,幾乎都布滿一大片灰灰黃黃的小石子。從地球科學的角度來看,這些火山浮石是難得一見的自然景觀,但對漁民來說卻是一場災難,到底這些火山浮石,是如何漂流千里來到台灣,對於漁民造成了什麼樣的影響,又會不會影響水質和生態呢?

住在新北澳底的林群,今年初開始,有個令他煩惱不已的新發現。

這厚厚一層「沙灘」,看似平凡無奇,為何會是個煩惱呢。

[[林群 台灣海洋基金會董事]]
“(原本這邊是) 礁岩地形,這邊最多的是貝類,海蝸牛之類的,還有寄居蟹”

眼前除了零星幾顆貝,其他生物一時都沒見著,而這一層厚「沙」,將原本礁岩硬生生變成了沙灘。

仔細一看這些沙布滿細孔,它其實是「火山浮石」,關心生態的林群,擔心地貌改變也將影響生物。

[[聲音來源: 林 群 台灣海洋基金會董事]]
“這個洞比較可能是有螃蟹成功進出的,也許有很多石縫、石洞,牠已經被大大小小浮石卡到,牠出不來”

這景象不只發生在新北澳底,而是全台海岸的共同問題,到底浮石從哪裡來,又會造成什麼影響。

2021年8月時,位於小笠原群島一帶的福德岡之場海底火山,發生近百年來最大規模噴發,隨之迸出的大量浮石,就這樣順著洋流往西。

小笠原群島位在日本東南方,2021年8月海底火山爆發,噴出了大量以二氧化矽、氧化鋁、氧化鐵組成的輕質浮石,10月它漂抵沖繩,癱瘓了漁港,12月初也抵達台灣。

[[邱永芳 院長 國家海洋研究院]]
“它基本上是跟著洋流在走,因為有西太平洋洋流,它渦流在跑,一部分往北,一部分往南,往南的部分會進到南海,經過黑潮再往北帶,就碰到台灣”

全台沿海一帶無一倖免,只是多與少的差別。

[[邱永芳 院長 國家海洋研究院]]
“這邊因為有的黑潮是靠近外面一點,進到裡面的量不少,但是還不是那麼多,漂到這邊以後,因為東北季風又把它帶進來,這邊反而就比較多,繞到桃園這邊來,是比較多”

國海院資料顯示,北台灣、屏東、台東、澎湖都屬重災區,那麼浮石大量累積,對水質、對生物會造成什麼衝擊。

[[宋欣真副署長 海洋保育署]]
“我們2021年12月,在台東美麗灣、綠島,宜蘭烏石鼻海域,也有去做採水,採樣結果水質沒有異常,這是大自然地質活動的產物,我想在演化過程當中,這幾千萬、幾億年以來,類似這樣狀態對生物來講,應該是不陌生,比如說像海龜是一兩億年的演化,我想牠的本能會知道要去躲避”

徜游於大海的海龜、鯨豚,有能力游走,趨吉避凶,但跑不遠的生物呢。

沖繩的案例顯示,大量浮石累積岸邊,會導致水下漆黑一片,這又會有什麼影響。

為了了解浮石對珊瑚礁生態有無影響,我們特別商請,常下海清海底垃圾的林群幫忙,拍攝澳底水下景象。

一跳入水中,大大小小的浮石就迎面而來,我們原以為浮石只會漂浮在水面,沒想到也會捲入了海下翻滾,所幸澳底海面浮石不多,水下光線不受影響,但距離十多公里外的南雅一帶,厚厚的浮石就沒這麼樂觀。

[[林 群 台灣海洋基金會董事]]
“因為珊瑚跟很多微生物,是靠光合作用產生食物,(沒有光)食物鏈的底層,會有一段被抽掉,這個影響很大,小魚吃微生物,中魚吃小魚,大魚吃中魚,如果底層微生物生存不良,會影響到接下來的獵食者”

在澳底,林群比較擔心的反而是那些海中翻滾的小浮石。

[[林 群 台灣海洋基金會董事]]
“海上一米以內都漂滿了火山浮石,我認為會有海龜跟魚類誤食漂流物的問題,漂流物看起來就像浮游生物”

就像沖繩的養殖業者,就發現暴斃魚群胃中有大量浮石,無疑地,火山浮石問題,對沿岸生態是場嚴峻的試煉。

除此之外,還有一群浮石受害者,漁民。

這些苦中作樂的漁民,眼前漁港還漂著火山浮石,這景象是他們一輩子首見,還造成不少船因浮石而受損。漁船發動時,需要不斷抽取海水為引擎降溫,然而海水中滿含浮石,會阻塞冷卻系統,導致抽不到水而引擎過熱。

[[張源堂理事長 外木山漁業永續協會]]
“浮石吸進到冷卻系統裡面,就請師傅來清理一下,可能一萬元左右,但是問題,你如果沒有注意,整個引擎發熱,過熱以後,引擎燒掉就可觀了,可能要幾十萬”

說著說著,一名受害船主正好到來。

顏祝盛的船,日前就因浮石塞滿冷卻系統而故障,除了花錢請師傅修,還整整一周無法出海捕魚,沒有收入,為了避免再次受害,乾脆土法煉鋼,DIY三道關卡。

水進入船艙前先過濾一次,需要吸水冷卻時再過濾一次,進入引擎前再過濾第三次,而水艙內還要不時用網籃撈除浮石,以他一人作業船,又要忙著抓魚,又要隨時撈浮石,常常措手不及。

連環的感慨是漁民深沉的無奈,目前港內、外海都還漂著大量浮石,要不要出海打漁,陷入兩難。

[[張源堂 理事長 外木山漁業永續協會]]
“在每年過年的前後,都有一批鎖管可以抓,那些船不敢動,如果好天氣不出去又沒機會,一出去又怕引擎阻塞,希望政府能夠多多照顧我們漁民,只要漁民有損傷,受影響的,希望政府來給我們幫忙一下”

為解決漁民出海問題,各地漁業單位也卯足全力。

新北瑞芳區漁會轄有深澳、水湳洞、南雅、鼻頭四個漁港,正是重災區,眼前漁船旁,黃黃一整片,若非事先知道是浮石塞港,這畫面看起來,還比較像是船隻擱淺沙灘。

漁會總幹事黃志明,為浮石問題焦頭爛額,一個月來,不僅網子換成了耐操的魚網材質。

[[黃志明 總幹事 瑞芳區漁會]]
“這一支也要三千元”

袋子也從大黑塑膠袋,換成了透水沙包袋。

這些學習都來自,與浮石辛苦對抗的血汗經驗。

[[黃志明 總幹事 瑞芳區漁會]]
“漁民非常的困擾,因為火山浮石,如果在東北季風吹過來,整個港內都是浮石,你不撈又不行”

不撈漁民無法出海,但光靠人力一網一網撈,怎麼也撈不完。

除了人力,總幹事建議若能借助機器力,將更有效率。

[[黃志明總幹事 瑞芳區漁會]]
“如果在海上,我是有一個想法說,是不是政府可以請一些平台船,用怪手,再做一個撈網,用怪手撈,把這些浮石處理掉,不要讓這些浮石,漂進我們的漁港內”

漁港撈起來的浮石,全堆積在港內,這些浮石去處是一大難題。

[[黃志明 總幹事 瑞芳區漁會]]
“我們浮石撈得非常多,現在堆積起來快一萬多包,沒有地方放”

大量的浮石有沒有機會逆轉,從廢物變黃金呢?

[[李宗翰 桃園農改場助理研究員]]
“火山浮石漂過來,有夾雜很多海洋垃圾,我們第一個動作就是,先將這些比較大的垃圾剔除掉”

在桃園農改場,這群人肩負著重大任務,就是幫火山浮石找出路。

[[李宗翰 桃園農改場助理研究員]]
“因為它裡面帶有大量海水鹽分,要用淋洗的方式把鹽分去除掉”

如果浮石要運用在農業上,首要任務是去除鹽分,才不會危害作物生長。

[[湯雪溶 桃園農改場助理研究員]]
“平常如果在做涼拌小菜,或是在醃酸菜的時候,我們會用大量的鹽,但是這種鹽分在植物裡面,它本身的一個反應就是脫水出來,會造成植株吸水困難,養分也沒有辦法透過水分,帶到它整個部分”

若能順利去除鹽分,火山浮石其實跟市售農業資材,發泡煉石雷同。

[[許雅婷 桃園農改場助理研究員]]
“這個是發泡煉石,煉石的話,它很輕,它的孔隙很大,所以排水性,還有為土壤製造空氣的流通性的效果很好”

[[湯雪溶 桃園農改場助理研究員]]
“這些栽培介質類的,孔徑比較大的去進行一個調整,它就比較不容易因為水分積聚,導致根系腐爛”

那在經過浸泡、淋洗後,這些浮石找到生機了嗎?

[[湯雪溶 桃園農改場助理研究員]]
“沒有處理過的浮石,它的鹽度範圍還是在2點多左右,已經處理過的,可以看到它已經減得滿低的,現在大概是0.15左右”

實驗結果淋洗過的浮石鹽度符合農業規範,可當裁培介質,但專家也提醒,它們較適合用在盆栽而非撒在田間,否則一場雨,它們又會漂走造成問題。

[[林 群 台灣海洋基金會董事]]
“夕陽西下的時候牠們會跑出來,我們可以從小螃蟹知道說,也許影響很大,也許影響很小,這是碩果僅存”

這來自海底的火山浮石,提醒著我們,環境的脆弱與珍貴。

[[林 群 台灣海洋基金會董事]]
“如果自然的過程中已經有傷害的因素,我們人類不要再添加更多的傷害因素,我希望透過這個火山浮石,我們能夠更了解大自然,更愛惜大自然,生生不息”

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