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Pumice stones deliver a lesson from the depths of the sea
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.
2022-07-24
