Ocean Warming Is Causing Deep-Sea Creatures to Rapidly Migrate Toward Poles
By Tim Radford
Scientists have taken the temperature of the deep seas and found alarming signs of change: ocean warming is prompting many creatures to migrate fast.
The species that live in the deep and the dark are moving towards the poles at twice to almost four times the speed of surface creatures.
The implication is that – even though conditions in the abyssal plain are far more stable than surface currents – the creatures of the abyss are feeling the heat.
The oceans of the world cover almost three-fourths of the globe and, from surface to seafloor, provide at least 90% of the planet's living space.
And although there has been repeated attention to the health of the waters that define the Blue Planet, it remains immensely difficult to arrive at a consistent, global figure for rates of change in temperature of the planet's largest habitat.
Oceanographers are fond of complaining that humankind knows more about the surface of Mars and Venus than it does about the bedrock and marine sediments at depth.
This may still be true, but repeated studies have confirmed that the ocean floor ecosystem is surprisingly rich, varied and potentially at risk.
Now researchers from Australia, Europe, Japan, South Africa and the Philippines report in the journal Nature Climate Change that although they could not deliver thermometer readings, they had found an indirect measure: the rate at which marine creatures move on because they don't care for their local temperature shifts.
They call this "climate velocity." They had data for 20,000 marine species. And they found that overall, at depths greater than 1000 meters, marine creatures have been on the move much faster than their fellow citizens near the surface, over the second half of the 20th century.
Computer simulations tell an even more alarming story: by the end of this century, creatures in the mesopelagic layer – from 200 meters down to 1000 meters – will be moving away between four and 11 times faster than those at the surface do now.
The finding is indirectly supported by a second and unrelated study on the same day in the journal Nature Ecology & Evolution. French scientists looked at studies of more than 12,000 kinds of the migrations of bacteria, plant, fungus and animal to find that sea creatures are already floating, swimming or crawling towards the poles six times faster than those on land, as a response to global heating driven by profligate human use of fossil fuels.
So shifts in range can be interpreted as an indicator of the stress on the ocean habitats. This creates complications for conservationists arguing for internationally protected zones – protected from fishing trawl nets, and from submarine mining operations – because, if for no other reason, not only are ocean creatures moving at different speeds at different depths; some of the shifts are in different directions.
"Significantly reducing carbon emissions is vital to control warming and help take control of climate velocities in the surface layers of the ocean by 2100," said Anthony Richardson of the University of Queensland in Australia, one of the authors.
"But because of the immense size and depth of the ocean, warming already observed at the ocean surface will mix into deeper waters. This means that marine life in the deep ocean will face escalating threats from ocean warming until the end of the century, no matter what we do now.
"This leaves only one option – act urgently to alleviate other human-generated threats to deep sea life, including seabed mining and deep-sea bottom-fishing."
Reposted with permission from Climate News Network.
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The ghoulishly named ogre-faced spider can "hear" with its legs and use that ability to catch insects flying behind it, the study published in Current Biology Thursday concluded.
"Spiders are sensitive to airborne sound," Cornell professor emeritus Dr. Charles Walcott, who was not involved with the study, told the Cornell Chronicle. "That's the big message really."
The net-casting, ogre-faced spider (Deinopis spinosa) has a unique hunting strategy, as study coauthor Cornell University postdoctoral researcher Jay Stafstrom explained in a video.
They hunt only at night using a special kind of web: an A-shaped frame made from non-sticky silk that supports a fuzzy rectangle that they hold with their front forelegs and use to trap prey.
They do this in two ways. In a maneuver called a "forward strike," they pounce down on prey moving beneath them on the ground. This is enabled by their large eyes — the biggest of any spider. These eyes give them 2,000 times the night vision that we have, Science explained.
But the spiders can also perform a move called the "backward strike," Stafstrom explained, in which they reach their legs behind them and catch insects flying through the air.
"So here comes a flying bug and somehow the spider gets information on the sound direction and its distance. The spiders time the 200-millisecond leap if the fly is within its capture zone – much like an over-the-shoulder catch. The spider gets its prey. They're accurate," coauthor Ronald Hoy, the D & D Joslovitz Merksamer Professor in the Department of Neurobiology and Behavior in the College of Arts and Sciences, told the Cornell Chronicle.
What the researchers wanted to understand was how the spiders could tell what was moving behind them when they have no ears.
It isn't a question of peripheral vision. In a 2016 study, the same team blindfolded the spiders and sent them out to hunt, Science explained. This prevented the spiders from making their forward strikes, but they were still able to catch prey using the backwards strike. The researchers thought the spiders were "hearing" their prey with the sensors on the tips of their legs. All spiders have these sensors, but scientists had previously thought they were only able to detect vibrations through surfaces, not sounds in the air.
To test how well the ogre-faced spiders could actually hear, the researchers conducted a two-part experiment.
First, they inserted electrodes into removed spider legs and into the brains of intact spiders. They put the spiders and the legs into a vibration-proof booth and played sounds from two meters (approximately 6.5 feet) away. The spiders and the legs responded to sounds from 100 hertz to 10,000 hertz.
Next, they played the five sounds that had triggered the biggest response to 25 spiders in the wild and 51 spiders in the lab. More than half the spiders did the "backward strike" move when they heard sounds that have a lower frequency similar to insect wing beats. When the higher frequency sounds were played, the spiders did not move. This suggests the higher frequencies may mimic the sounds of predators like birds.
University of Cincinnati spider behavioral ecologist George Uetz told Science that the results were a "surprise" that indicated science has much to learn about spiders as a whole. Because all spiders have these receptors on their legs, it is possible that all spiders can hear. This theory was first put forward by Walcott 60 years ago, but was dismissed at the time, according to the Cornell Chronicle. But studies of other spiders have turned up further evidence since. A 2016 study found that a kind of jumping spider can pick up sonic vibrations in the air.
"We don't know diddly about spiders," Uetz told Science. "They are much more complex than people ever thought they were."
Learning more provides scientists with an opportunity to study their sensory abilities in order to improve technology like bio-sensors, directional microphones and visual processing algorithms, Stafstrom told CNN.
"The point is any understudied, underappreciated group has fascinating lives, even a yucky spider, and we can learn something from it," he told CNN.
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In 'Road Map for a More Sustainable Future,' NY Regulator Tells Banks to Consider Climate Risks in Planning
By Brett Wilkins
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