(Image: Dale Edwin Murray)
With the expansion of the Suez Canal, the relentless stream of invaders from the Red Sea will turn into a raging torrent – but there is a way to stop them
IN 2011, workers struggled to unclog the cooling system of a power plant in Hadera, Israel. Thousands of what looked like wet plastic bags were desperately scraped out of the plant’s water intake. But still they kept pouring in – breaking up into gelatinous slime and threatening to cut off the electricity supply of millions of people.
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The culprit was a large stinging jellyfish called Rhopilema nomadica. It often forms massive swarms, some as much as 100 kilometres long. “When these blooms appear, tourists have to stay on the beach, and fishermen have to stay on the shore,” says marine biologist Bella Galil of the National Institute of Oceanography in Israel.
Yet until the mid-1970s, this species wasn’t found in the Mediterranean. It arrived via the Suez Canal. For most of the year, the current in the canal flows from the Red Sea northwards in the direction of the slightly lower Mediterranean. “It’s like one of those travelators at the airport,” says Galil. “You get on it and whoosh, you’re in the Mediterranean.”
As a result, hundreds of species from the Red Sea have invaded the Mediterranean. And things are about to get even worse: the invader travelator is getting an upgrade. Last year, Egypt announced a $4 billion project to widen the existing canal and add another lane, doubling its capacity by the end of 2015, to the alarm of biologists. But this doesn’t have to be bad news, they say: the canal can be expanded and the flow of invaders slashed at the same time.
Invasive marine species can arrive by many routes, from hitching a ride in the ballast water of ships to being released from aquariums. But the 190-kilometre-long Suez Canal is undoubtedly the main invasion route into the Mediterranean. In , Galil estimated that of the 700 or so invasive species recorded in the Mediterranean, half had arrived via the Suez Canal. put the number of invaders at 1000, with 420 coming via the canal.
Med turning Red
To put this in perspective, there are about 17,000 species in the Mediterranean, of which 1000 are found only in that sea. So the number of invasive species could soon outstrip the number of endemic species, if it hasn’t already. “Bioinvasions occur all over the world. But here it is much worse,” says Galil. “Now we are facing a doubling of that system.”
Global warming is aiding the invaders, too, by making it easier for tropical Red Sea species to survive in the cooler Mediterranean (see map). “The Mediterranean is warming, meaning it is becoming much more hospitable to invasive Red Sea species,” says Galil. “The practical border of the Red Sea is now somewhere off the coast of Italy – Sicily, Malta, even as far as Gibraltar.”
Does it matter? The invasion isn’t all bad news. There are some benefits for the fishing industry: the soaring populations of some invasive species have increased catches in some places, and the large Japanese tiger prawn is particularly prized. The invaders are also increasing biodiversity at a time when it is declining almost everywhere else in the world, says Daniel Golani, a biologist at the Hebrew University of Jerusalem.FIG-mg30100801.jpg
But some of the newcomers are outcompeting and displacing native species, not increasing diversity by living alongside them. And others are making a nuisance of themselves. The R. nomadica jellyfish costs the fishing industry dear. During swarms, it is not unusual for boats to have to discard their entire catch because their nets become clogged with jellyfish. “It’s not good news economically,” says Galil.
What’s more, at least after eating the toxic silver-cheeked pufferfish, Lagocephalus sceleratus, another Suez migrant which has spread across the eastern Mediterranean over the past decade. People were initially unaware of the danger.
Golani argues that it is subjective to say invading species “damage” ecosystems. But in at least some cases, the term damage seems justified. Take the two species of Red Sea rabbitfish, first recorded in the eastern Mediterranean in 1924. In the warm regions where these fish thrive, there has been a fall of 65 per cent in the abundance of large seaweed and 40 per cent in overall species richness, . The problem, it concluded, is that while native herbivores eat only adult seaweed, the invading rabbitfish nibble at the rocks too, eating very young seaweed and preventing regeneration of the seaweed forests that many other species depend on.
The overall impact of this massive bioinvasion into the Mediterranean is poorly understood, though. Much of the sea isn’t well monitored, so we don’t know what’s happening. It’s also hard to disentangle the effects of invaders from those of pollution, overfishing and climate change.
What’s more, it will be many decades, or even centuries, before the full impact of existing invaders becomes clear. Many invasive species do not seem to be a problem at first, only to start running riot after a few decades, perhaps because it takes them time to adapt to local conditions. And invasion via the Suez only began in earnest in the 1970s.
When the canal opened in 1869, large salty lakes along its path and freshwater from the neighbouring Nile acted as natural barriers. The sudden changes in salinity killed most organisms as they were travelling through. But by the 1970s the salt deposits in the lakes were washed away by the ever-widening waterway and the fresh water was cut off by the damming of the Nile.
In , Galil and signatories representing 14 marine biology organisations called on the Egyptian government to prevent even more invaders arriving, arguing that “the potential reach and magnitude of the cumulative impacts are enormous”. The number of signatories has grown to 278 scientists from 33 countries.
They say reintroducing salinity barriers by installing locks could be a way of mitigating the impact of the canal expansion. “We are not against the development of the Suez Canal,” says Galil. “That is important to stress. We just want it to be done in an environmentally sensitive way.”
Neither the Egyptian government nor the Suez Canal Authority responded to New Scientist‘s requests for comment. Even the UN’s Mediterranean Action Plan, an organisation tasked with protecting the sea, admits it is only now contacting the Egyptian authorities about whether the canal expansion will contravene the Barcelona Convention – an agreement to minimise pollution and species invasions in the Med.
In the meantime, the invasion continues.
This article appeared in print under the headline “The great invasion”
