Invasive species and those normally found in the Atlantic and polar regions have been spotted in the deep seas of the eastern Mediterranean. The unexpected visitors were seen by a remotely operated vehicle descending to depths of up to 1Ìękilometre in waters off Lebanon.

The team, led by marine conservation agency Oceana, were left speechless by the discovery of an Atlantic Lantern Shark during their recent month-long expedition. Measuring 20 centimetres and glowing bright blue along its spine and belly, this particular species of Lantern is a shark generally associated with the chilly waters of the Atlantic. Why it’s here, no one knows.

It was just one of a number of surprises, says Oceana’s senior research director Ricardo Aguilar: “This is an area that is almost completely unexplored. A lot of what we are finding is brand new. It’s very exciting.”

With over 200 species collected, the task now is to ascertain what they are, and how and why they got there.

Hitching a ride

“We simply do not yet know why some of these polar species, like the scarlet-red starfish Leptasterias, are settling here,” says Aguilar. It could be that the deep sea area is poorer in biodiversity, which means less competition for the newcomers.

“Or it could also be that they settled here in the past, without us knowing,” he says. “We have no frame of reference to judge these findings against.”

The team found that the cold-water Atlantic and polar species are found in much deeper areas of the Mediterranean – possibly because water is colder further down.

The projects’ submarine also revealed a previously unknown and large belt of brightly coloured coralligenous gardens 80 meters down. More commonly found in the western Mediterranean, these reef-like structures are mainly formed of red algae, which form new habitats by making calcium carbonate substrate.

The team also saw invasive lionfish and rabbitfish, originally from the Red Sea, whose presence here can be explained more easily. They may have been carried in the ballast water of ships coming through the Suez Canal, says Aguilar.

These species are pushing out native species and destroying the habitat by overgrazing.

“Some rocks have now been stripped bare of algae,” says Aguilar. “Rabbit Fish for example eat tonnes and tonnes of the stuff, forcing the disappearance of resident species,” Aguilar says. “They just cannot compete and it’s a problem that is increasing.”

Findings from the expedition will be used to help identify sties suitable for designation as marine protection areas by the Lebanese government.

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Prolonged din

Turn tail

Long-lived species like sharks, rays and skates are declining at an alarming rate in sites across the North Sea.

So says Ricardo Aguilar, senior research director of marine conservation organisation Oceana whose European headquarters are in Madrid, Spain. His team has just returned from a two-month expedition surveying waters around the UK, Netherlands, Norway and Denmark.

“It’s scary how quickly they seem to be disappearing, and it’s not just the sharks. Big molluscs, quahog and the horse mussels are also getting harder and harder to find.”

The team visited 13 sites, chosen for their diverse range of habitats and ecosystems. “We wanted to visit a really good cross-section of marine environments. Places where the seabed was made up of mud and clay, coastal areas, coral gardens, even kelp forests off the coast of Norway.”

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Working alongside a variety of organisations including the Marine Conservation Society and the North East Atlantic Fisheries Commission, Oceana will use information gleaned from the survey to help strengthen potential future proposals for a network of marine protection areas across the region.

“Parts of the North Sea are still very much alive, and there are hotspots which are very bio-diverse,” says Aguilar. “In general though, it has been impacted very heavily by industrialisation and dredging,” Aguilar says.

The team travelled over 2000 nautical miles and documented nearly 700 species with the help of a team of divers and a submerged remotely operated vehicle equipped with two cameras.

Data from the expedition will now be shared with national authorities, scientists, and other organisations, to support broader efforts to protect the North Sea. Oceana is promoting the establishment of a coherent network of North Sea protection areas to preserve biodiversity and help to restore depleted fish stocks.

Ice-free normality

It was one of the biggest and deadliest tsunamis in recorded history. The Boxing Day tsunami of 2004 killed a quarter of million people with waves reaching 15 metres.

Now, a drilling expedition under way in the Indian Ocean hopes to uncover the secrets of large underwater earthquakes that can trigger such tsunamis.

A multinational team on board the research vessel Joides Resolution, a “floating laboratory”, is about to collect sediment samples from 1.5 kilometres beneath the ocean floor.

“We want to find out more about how specific sediments control the size and type of earthquakes in this kind of environment,” says of the University of Southampton.

The team will focus on the Sunda subduction zone, where the Indo-Australian plate goes beneath the Sunda plate. The fault that forms between them is where many large-scale earthquakes have , including the one that caused the Boxing Day tsunami.

The team is drilling some 4900 metres below the sea surface, on a section of the seabed that lies to the west of Indonesia, before the Indo-Australian plate reaches the subduction zone.

They will take samples of the sediment and rock thatÌęwas scraped off from the downgoing tectonic plate.

One of the primary questions they hope to answer is whether the pressures and temperatures experienced at depth here lead to the unusual properties of this subduction zone fault, and if that in turn leads to larger and more powerful earthquakes.

Sediments tend to become denser at high temperatures and pressures, and eventually turn into rock. In some cases though, fluids become trapped and the sedimentary materials are then weakened.

“We think the former is dominating here, and that the strengthening of the material leads to the earthquake rupture taking place at shallower depths within the subduction zone than normal,” says McNeill. “If the materials are stronger at shallower depths and over a wider area of the subduction zone, this can make the earthquake rupture wider, causing a larger magnitude earthquake.”

“We can’t predict earthquakes, but we can learn more about what happens below the Earth’s surface, why rocks break and cause earthquakes that ultimately trigger tsunamis,” says of the Colorado School of Mines.

As well as analysing what the sediments are made of, the team will identify fossils to tell when and where the sediments formed, and work out how they deform at the high pressures and temperatures deeper down in the subduction zone.

In addition to finding out what they call the “recipe for disaster”, they hope to learn about Earth’s past climate and the history of the Himalayas.

The expedition is part of theÌę and runsÌęuntil 6 October. You can .

Read more: Seabed core reveals how lush Antarctica changed to icy desert

The deep sea is about to yield more of its secrets. The alliance, launched this week, brings together more than 30 international organisations from the fields of science, technology and business to try to learn more about Earth’s final frontier.

“We know more about the surface of Mars and the moon than we do about our own seabed,” says principal scientist at the University ofÌęOxford.

The alliance’s XL Catlin Deep Ocean Survey will kick off with dives in Bermuda this month, using both manned and autonomous submersibles.

Rogers says such increasingly sophisticated craft are giving us unprecedented access to the deep sea. “We see a great need to learn, and we now have the technology to do it.”

Nekton’s ultimate aim is to diagnose the health of waters below 200 metres, to better inform policy decisions on protecting these habitats.

Read more: “Better world: End the pillaging of the high seas” and “Deep sea special: The undiscovered oceans”

This article will appear in print under the headline “Deeper exploration”

Robot helper

Even to the untrained eye, it’s easy to see that the Great Barrier Reef is in more than a little hot water.

As I board my charter flight from Cairns bound for the remote scientific research station on Lizard Island, I mentally prepare myself for devastating scenes.

Climbing steeply, we bank sharply to the right – and soon the tropical green of Queensland’s northern coast is replaced by a startlingly bright turquoise sea.

It doesn’t take long for my fears to be realised. I look down at an opalescent sea awash with white. Reefs that were once among the world’s most unspoiled now languish under a baking sky, every one seemingly bleached.

My pilot turns and gives me a thumbs down, shaking his head sombrely.

Worst on record

This is the worst bleaching event the Great Barrier Reef has ever seen, according to , director at the ARC Centre of Excellence for Coral Reef Studies in Townsville, Queensland.

Bleaching happens when corals become stressed and expel algae called zooxanthellae living inside them. These colourful algae provide up to 90 per cent of the energy needs of corals through photosynthesis. Corals can survive bleaching, but will die if they stay in that condition for long enough.

This year’s bleaching has been linked to the strongest El Niño event on record and climate change, both of which are driving up ocean temperatures here.

“One of the impacts of El Niño here in Australia is a weaker monsoon,” says , manager of climate-change prediction services at the Australian Bureau of Meteorology. “For the reef, that means less cloud and more sunny days.”

This puts more heat stress on corals, leading to bleaching, which has been getting progressively worse.

“It’s already very clear that what we are seeing here is much greater than back in 2002, which in turn was greater than 1998,” says Hughes.

He lays the blame firmly at the door of climate change. “The baseline of sea temperature is going up decade by decade due to global warming. When an El Niño event comes along, it adds an extra spike to that rising baseline. We’ve always had those spikes, but before global warming they didn’t cause the damage that they do now.”

Bad signs

This is my first visit to the reef, and it’s not looking good
 at all.

Home to of fish, 411 types of hard coral and a third of the world’s soft coral, the reef is the largest living structure on the planet.

Its sheer magnitude makes the reality of surveying it neither quick nor simple: it covers an area bigger than the UK, the Netherlands and Switzerland combined.

Hughes first focused his aerial surveys on the reef’s northernmost section, which was the hardest-hit area. He concluded recently that 95 per cent of it had been “severely bleached”.

“It was the saddest research trip of my life,” says Hughes, who is yet to find a southern boundary to the bleaching.

“Initially I thought we’d only have to survey the most northern part,” he says. “It’s clear though that this bleaching is much more extensive than we thought.”

In 2002, just 18 per cent of reefs in the Great Barrier Reef – 120 in total – were severely bleached. This year, well over 500 reefs have been affected so far. “This is much more severe than anything we have seen before,” says Hughes.

It could be another six to eight weeks before we get a full picture of how much coral has been lost.

Researchers are keen to find out how multiple bleaching events are affecting the corals.

It takes around 10 years for faster-growing corals to recover from bad bleaching, says of the University of Queensland in Brisbane. “We could be getting close to a scenario where the return time for bleaching is actually shorter than the recovery period, and that would be a recipe for ever-declining coral cover.”

Among the corals

On Lizard Island, the research station lies a stone’s throw from the shortest landing strip I’ve ever seen. I’m picked up in a classic 1990s white land cruiser and 10 minutes later, after bumping along a short sandy track, I arrive at the research station, which provides accommodation, dive boats, laboratories, a full aquarium and scuba equipment.

“The amount of coral being affected by this year’s bleaching is mind-boggling,” says Lyle Vail, one of the station directors. “You see corals that you’re familiar with, have swum with and that you know individually, and now they are dying.”

And he says that with soft corals, which lack the skeleton of hard corals, only bare rock is left once they’re gone. “You’d never even know they were there. It’s devastating,” he says.

I dive alongside a team of documentary film-makers, among once-pristine coral that’s now dying before our eyes. A single word is enough to describe our emotions as we head back to base: heartbreak.

It’s hard to imagine how the reef – held up as a bastion for those around the world – can fully bounce back. The hope for many of the scientists is that this event will at least communicate to a global audience the reality of climate change and the effects it’s having on the natural world.

“Coral cover on the Great Barrier Reef could look very different 10 years from now,” says Hoegh-Guldberg. He highlights that 50 per cent of its coral cover has been lost in the past 30 years and predicts a further decline of 20 per cent if we continue on this path.

“If we don’t take aggressive action on climate change over the next decade, it will essentially mean the end of coral-dominated paradises like the Great Barrier Reef and intact coral reefs across the world,” he says.

Read more: Coral comeback: Reefs have secret weapon against climate change; Mission implausible: Extreme schemes to save the reefs

A little stress can help corals

More heat, more stress

Survival strategies

Not too late