Scene of more than 150 tons of jellyfish destroying a power plant in China

The sudden swarm of jellyfish overloaded the cooling system, forcing factory workers to work around the clock to clear the blockage and clean up the mess.

For 10 days and nights in September, workers at eastern China's largest coal-fired power plant battled an "unprecedented invader" : a swarm of jellyfish.

At the Zheneng Jiaxing power plant in Zhejiang province, crews work in rotating shifts, urgently clearing millions of jellyfish that have flooded the plant's cooling system, threatening to disrupt operations.

Even after more than 150 tons of jellyfish were cleared from the factory — too much for local sanitation officials to handle — the jellyfish showed no signs of stopping.

The bags of jellyfish continued to pile up, giving off a strong stench. Meanwhile, workers had to remove the jellyfish from the filter by hand, one by one, making the work slow and difficult.

"In the 30-year history of the factory, we have never encountered anything like this," Xi Chao, deputy director of the factory's maintenance department, told state broadcaster CCTV on September 29.

The jellyfish, known as Rhopilema esculentum, has been a delicacy in China since the Tang Dynasty (618-907). This year, the species has seen what domestic media described as 'an unprecedented harvest in decades' along China's coastal areas.

However, for the Zheneng Jiaxing power plant, this increase is not good news.

On September 18, a large swarm of sea jellyfish flooded the plant's circulation pump station, which draws in seawater to cool the generators. The jellyfish latched onto rotating filters, clogging the intake pipes and overloading the filters, eventually shutting down the generators.

The problem is not limited to this plant. In August, two power plants in neighboring Shanghai faced similar jellyfish infestations. And globally, Japan, South Korea, and the United Kingdom have faced similar disruptions over the past three decades.

Experts say the jellyfish surge is a symptom of wider global environmental changes. Factors such as eutrophication – excess nutrients that cause 'algal blooms' and low oxygen conditions that benefit jellyfish – and overfishing, which reduces competition between species, have allowed the creatures to thrive, causing havoc around the world.

"Why don't you eat them?"

News of the jellyfish crisis at the Zheneng Jiaxing Power Plant quickly caused a stir on social media, attracting more than 41.69 million views on the Weibo platform.

'Why not just eat them?' many curious netizens joked, referring to the R. esculentum jellyfish's long history as a popular delicacy in China.

Traditionally, the jellyfish are used in jellyfish salad, a staple in Chinese households for over 1,000 years. Ironically, the amount of jellyfish collected from the power plant could theoretically produce at least 300,000 servings, if not piled up in garbage bags.

Jellyfish attack power plant in Zhejiang, China.

Once considered a symbol of abundance, this jellyfish has now become a symbol of destruction.

'In the past, if we saw an increase in R. esculentum jellyfish, it was not a disaster, but a bumper harvest,' Sun Song, former director of the Institute of Oceanography at the Chinese Academy of Sciences, told Sixth Tone . 'But this time, they clogged the power plant, causing a crisis.'

Jellyfish have long been prized in China for their detoxifying, analgesic, and anti-inflammatory properties. In 1984, faced with a declining jellyfish population due to overfishing, China even took steps to replenish stocks and increase harvests by releasing cultured baby jellyfish.

However, Mr. Xi, the factory's deputy manager, explained to Southern Metropolis Daily that they were not sure whether the jellyfish clogging the factory were completely edible, and thus could not be sold to the public.

According to Sun, besides the edible species, China's coast often sees the proliferation of two other species - Aurelia aurita and Cyanea . Unlike the sought-after jellyfish, these species have no culinary value and are often considered invasive or a nuisance.

destructive species

Over the past few decades, jellyfish blooms have become a global challenge, posing a serious threat to power plants around the world.

'In fact, every power plant in the world has been attacked by jellyfish at some point; it's a global problem ,' explains Sun, who has been studying the species since 2005.

Nuclear power plants are particularly vulnerable, he stressed. Unlike coal plants, which can be shut down quickly, nuclear reactors require a gradual shutdown process. If jellyfish clog the intake pipes and coolant is lost, the reactors risk dangerously overheating, potentially leading to catastrophic explosions.

Because power plants are often built near coastal waters to access cooling water, they are particularly vulnerable to seawater intrusion. This vulnerability has occurred many times.

Jellyfish blooms threaten coastal power plants around the world.

In June 2011, Japan's Shimane nuclear power plant was forced to deal with a jellyfish blockage, followed by Scotland's Torness nuclear power plant, which suffered another major incident in October 2021.

In 2013, one of the world's largest nuclear reactors, Sweden's Oskarshamn nuclear power plant, was shut down due to jellyfish clogging its cooling system, similar to a power plant in Israel in 2019.

In addition to power plants, jellyfish infestations can also significantly disrupt tourism, often ruining picturesque coastlines. Along the famed French Riviera, jellyfish stings have become a regular concern in the summer, even with the installation of $84,500 worth of anti-jellyfish nets. Last summer alone, South Korea recorded about 2,900 jellyfish stings.

A 2023 study found that the risk from jellyfish has steadily increased over the past six decades, from the 1960s to the 2010s. The study found that jellyfish typically breed in bays and semi-enclosed seas.

Other studies suggest that jellyfish populations do not increase continuously but may follow cycles of about 20 years – a theory that needs more data to confirm.

Solution

Jellyfish thrive where other marine life fails due to their unparalleled resilience in harsh environments.

"The biggest competitive advantage of jellyfish lies in their resilience in harsh environments. They are basically opportunistic," said Sun, a former member of the Institute of Oceanography at the Chinese Academy of Sciences, adding that Craspedacusta sowerbii, or peach jellyfish, which has existed for 550 million years and survived several mass extinctions, is a prime example of their adaptability.

Such resilience allows jellyfish to benefit from overfishing and excess nutrients from fertilizers and sewage , according to a 2009 study that first drew global attention to the rise of 'jellyfish blooms.'

Sun told Sixth Tone that both jellyfish and fish rely on plankton for food, but overfishing depletes fish stocks, giving jellyfish an opportunity to dominate the ecosystem. Increased nitrogen and phosphorus levels from eutrophication can lead to algal blooms and oxygen depletion—conditions that hinder fish survival but benefit the more resilient jellyfish.

Solutions to prevent jellyfish outbreaks and attacks on power plants around the world have not been really effective.

'Jellyfish can even eat fish eggs and juvenile fish. When large blooms occur, they take over fishing grounds, making it difficult for other creatures to recover ,' Sun said.

In 2015, an outbreak of Nomura's jellyfish in Japan, each weighing up to 200 kg, caused flatfish catches to drop by 60%.

Jellyfish also have a unique life cycle . Before becoming free-floating jellyfish, they exist as polyps attached to the seafloor. These polyps can lie dormant for years, reproducing asexually until favorable water conditions trigger a sudden population explosion, Sun added.

Sun stressed that jellyfish outbreaks often go undetected until they strike , leaving limited options for intervention when problems arise. 'It's similar to preventing forest fires,' he explained. 'Scientists can tell you why it's happening - it could be dry conditions or a stray spark. But once a fire breaks out, there's not much the experts can do; you need firefighters on the scene.'

Pointing out that awareness of measures to prevent jellyfish from clogging power plant pipelines is still lacking in China, Sun said both domestic and international efforts to manage and mitigate the dangers of jellyfish are constantly growing.

In 2018, the Chinese Academy of Sciences proposed using zooplankton as bait to locate and scrape off the polyps of A. aurita jellyfish. In South Korea, researchers have developed a 'jellyfish killer' — a robot capable of detecting and destroying the creatures.

In the UK, drone technology has become part of a proactive early warning system, using medium-altitude drones to track and signal jellyfish movements towards power stations. And a power plant in Japan has taken a novel approach, installing additional air ducts to create bubbles that lift and divert jellyfish away from water pipes.

For long-term predictions, monitoring jellyfish polyps attached to the seafloor remains an important strategy, Sun said, as their presence indicates the potential size of future outbreaks.

However, he admitted that there is still much work to be done when it comes to observing the seafloor. "In fact, we know less about the seafloor than we do about the surface of the Moon . "