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Climate change may bring acidic oceans full of jellyfish

One often-neglected result of climate change is ocean acidification. If this process continues, we may start to see fewer fish and more jellyfish.

PHILIPPE HUGUEN/AFP/Getty Images
  • Since the beginning of the industrial era, humanity has been pumping out unprecedented levels of CO2 into the atmosphere.
  • A significant portion of this CO2 is sucked back into the ocean, where it reacts with water to produce carbonic acid.
  • Most species fair poorly in the newly acidic ocean. Jellyfish, however, seem to resist ocean acidification more than others.

Human beings don't do well when they try to understand things past a certain scale. When you consider the 7.5 billion people on the planet, you don't think of them in the same way as, say, the people who you meet walking your dog or your extended family. People can't conceive of how small the Earth is in comparison with the Sun, and people can't conceive of how broad and ubiquitous climate change really is — which is why some folks scoff at the idea when the Northeast US experiences record snowfall.

Most of us limit our understanding of climate change to the impact that CO2 has on our atmosphere and the resulting warming of the planet. But climate change is a multifaceted phenomenon. As we change our planet's chemistry, all environments experience a subsequent change, not just through the air we breathe but also in the oceans. The oceans of the future won't just be bigger from melting sea ice; they will become acidic seas where the jellyfish reign supreme.

Why the ocean you know and love won’t exist in 50 years

How CO2 turns oceans acidic

CO2 released into the atmosphere traps heat, driving the bulk of climate change's obvious effects. But not all of that CO2 stays in the atmosphere. Since the beginning of the industrial age, the world's oceans have absorbed 525 billion tons of CO2. Today, oceans suck up about 22 million tons per day, roughly a quarter of all the man-made CO2 released into the atmosphere.

In a way, this is helpful. If more CO2 was retained in the atmosphere, the faster the planet would heat up from the greenhouse gas effect. There's no such thing as a free lunch, however. As CO2 mixes with the oceans' H2O, the two molecules combine to form carbonic acid (H2CO3), lowering the oceans' pH and increasing its acidity. Under normal circumstances, natural processes from the dissolved minerals deposited into the oceans by rivers help to keep the oceans' pH levels in balance, but the rate at which oceans are absorbing our CO2 means this process has not been sufficient.

Life under ocean acidification

PHILIPPE LOPEZ/AFP/Getty Images

Nearly all forms of life are extremely sensitive to pH levels. You can imagine how difficult it would be for humanity if all of our air was slightly acidic — such is the case in the oceans. But, like any environmental change, there are losers and winners.

The most obvious loser in this new environment are species that build shells, like oysters, clams, and corals. Any disruption to a food chain puts an ecosystem in danger, but the increased difficulty that corals face when building their shells is particularly worrisome. Corals are a foundation species, meaning that they create and maintain a habitat for other species. Without them, an estimated 4,000 species will be at risk.

While many species of shell-building animals and fish are negatively impacted by ocean acidification, jellyfish don't seem to struggle much at all. One of the ways scientists discovered this was by looking at places in the ocean where CO2 levels are naturally higher, such as nearby volcanic seeps in the Mediterranean. In these locations, jellyfish and other "nuisance" species like dangerous algae exist in much higher numbers than elsewhere. Additional research, too, has demonstrated that as pH levels drop in the ocean, jellyfish numbers rise.

It's unclear how jellyfish will fare as the oceans become even more acidic in the future. So far, it seems they are resistant to acidification, but not immune to it. Some researchers believe that the selectivity of this damage — that ocean acidification seems to affect other species more — is what's leading to the jellyfish's rise. As their competitors and prey becomes less fit, jellyfish capitalize by ramping up their consumption.

As an example, one study looked at how well copepods and jellyfish fared in tanks of normal ocean water and tanks of acidified ocean water. Copepods are small, abundant crustaceans that are critical to ocean ecology, serving as a food source for nearly every species. When box jellyfish were added to the copepod tanks that contained normal ocean water, the jellyfish consumed 37% of the copepods. When added to the acidified tanks, jellyfish ate 83% of the copepods. However, it's not clear whether this occurred because the copepods had been weakened by the acidification, whether the jellyfish became hungrier under the strain of acidification, or some combination of the two.

Jellyfish numbers appear to be on the rise, and it looks like ocean acidification is to blame. Unless we learn to curb our CO2 outputs, it may be that our future oceans may become more gelatinous than we'd like.

How accountability at work can transform your organization

If you don't practice accountability at work you're letting the formula for success slip right through your hands.

Videos
  • What is accountability? It's a tool for improving performance and, once its potential is thoroughly understood, it can be leveraged at scale in any team or organization.
  • In this lesson for leaders, managers, and individuals, Shideh Sedgh Bina, a founding partner of Insigniam and the editor-in-chief of IQ Insigniam Quarterly, explains why it is so crucial to success.
  • Learn to recognize the mindset of accountable versus unaccountable people, then use Shideh's guided exercise as a template for your next post-project accountability analysis—whether that project was a success or it fell short, it's equally important to do the reckoning.

What if Middle-earth was in Pakistan?

Iranian Tolkien scholar finds intriguing parallels between subcontinental geography and famous map of Middle-earth

Could this former river island in the Indus have inspired Tolkien to create Cair Andros, the ship-shaped island in the Anduin river?

Image: Mohammad Reza Kamali, reproduced with kind permission
Strange Maps
  • J.R.R. Tolkien himself hinted that his stories are set in a really ancient version of Europe.
  • But a fantasy realm can be inspired by a variety of places; and perhaps so is Tolkien's world.
  • These intriguing similarities with Asian topography show that it may be time to 'decolonise' Middle-earth.
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Giant whale sharks have teeth on their eyeballs

The ocean's largest shark relies on vision more than previously believed.

An eight-metre-long Whale shark swims with other fish at the Okinawa Churaumi Aquarium on February 26, 2010 in Motobu, Okinawa, Japan.

Photo by Koichi Kamoshida/Getty Images
Surprising Science
  • Japanese researchers discovered that the whale shark has "tiny teeth"—dermal denticles—protecting its eyes from abrasion.
  • They also found the shark is able to retract its eyeball into the eye socket.
  • Their research confirms that this giant fish relies on vision more than previously believed.
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A massive star has mysteriously vanished, confusing astronomers

A gigantic star makes off during an eight-year gap in observations.

Image source: ESO/L. Calçada
Surprising Science
  • The massive star in the Kinsman Dwarf Galaxy seems to have disappeared between 2011 and 2019.
  • It's likely that it erupted, but could it have collapsed into a black hole without a supernova?
  • Maybe it's still there, but much less luminous and/or covered by dust.

A "very massive star" in the Kinman Dwarf galaxy caught the attention of astronomers in the early years of the 2000s: It seemed to be reaching a late-ish chapter in its life story and offered a rare chance to observe the death of a large star in a region low in metallicity. However, by the time scientists had the chance to turn the European Southern Observatory's (ESO) Very Large Telescope (VLT) in Paranal, Chile back around to it in 2019 — it's not a slow-turner, just an in-demand device — it was utterly gone without a trace. But how?

The two leading theories about what happened are that either it's still there, still erupting its way through its death throes, with less luminosity and perhaps obscured by dust, or it just up and collapsed into a black hole without going through a supernova stage. "If true, this would be the first direct detection of such a monster star ending its life in this manner," says Andrew Allan of Trinity College Dublin, Ireland, leader of the observation team whose study is published in Monthly Notices of the Royal Astronomical Society.

So, em...

Between astronomers' last look in 2011 and 2019 is a large enough interval of time for something to happen. Not that 2001 (when it was first observed) or 2019 have much meaning, since we're always watching the past out there and the Kinman Dwarf Galaxy is 75 million light years away. We often think of cosmic events as slow-moving phenomena because so often their follow-on effects are massive and unfold to us over time. But things happen just as fast big as small. The number of things that happened in the first 10 millionth of a trillionth of a trillionth of a trillionth of a second after the Big Bang, for example, is insane.

In any event, the Kinsman Dwarf Galaxy, or PHL 293B, is far way, too far for astronomers to directly observe its stars. Their presence can be inferred from spectroscopic signatures — specifically, PHL 293B between 2001 and 2011 consistently featured strong signatures of hydrogen that indicated the presence of a massive "luminous blue variable" (LBV) star about 2.5 times more brilliant than our Sun. Astronomers suspect that some very large stars may spend their final years as LBVs.

Though LBVs are known to experience radical shifts in spectra and brightness, they reliably leave specific traces that help confirm their ongoing presence. In 2019 the hydrogen signatures, and such traces, were gone. Allan says, "It would be highly unusual for such a massive star to disappear without producing a bright supernova explosion."

The Kinsman Dwarf Galaxy, or PHL 293B, is one of the most metal-poor galaxies known. Explosive, massive, Wolf-Rayet stars are seldom seen in such environments — NASA refers to such stars as those that "live fast, die hard." Red supergiants are also rare to low Z environments. The now-missing star was looked to as a rare opportunity to observe a massive star's late stages in such an environment.

Celestial sleuthing

In August 2019, the team pointed the four eight-meter telescopes of ESO's ESPRESSO array simultaneously toward the LBV's former location: nothing. They also gave the VLT's X-shooter instrument a shot a few months later: also nothing.

Still pursuing the missing star, the scientists acquired access to older data for comparison to what they already felt they knew. "The ESO Science Archive Facility enabled us to find and use data of the same object obtained in 2002 and 2009," says Andrea Mehner, an ESO staff member who worked on the study. "The comparison of the 2002 high-resolution UVES spectra with our observations obtained in 2019 with ESO's newest high-resolution spectrograph ESPRESSO was especially revealing, from both an astronomical and an instrumentation point of view."

Examination of this data suggested that the LBV may have indeed been winding up to a grand final sometime after 2011.

Team member Jose Groh, also of Trinity College, says "We may have detected one of the most massive stars of the local Universe going gently into the night. Our discovery would not have been made without using the powerful ESO 8-meter telescopes, their unique instrumentation, and the prompt access to those capabilities following the recent agreement of Ireland to join ESO."

Combining the 2019 data with contemporaneous Hubble Space Telescope (HST) imagery leaves the authors of the reports with the sense that "the LBV was in an eruptive state at least between 2001 and 2011, which then ended, and may have been followed by a collapse into a massive BH without the production of an SN. This scenario is consistent with the available HST and ground-based photometry."

Or...

A star collapsing into a black hole without a supernova would be a rare event, and that argues against the idea. The paper also notes that we may simply have missed the star's supernova during the eight-year observation gap.

LBVs are known to be highly unstable, so the star dropping to a state of less luminosity or producing a dust cover would be much more in the realm of expected behavior.

Says the paper: "A combination of a slightly reduced luminosity and a thick dusty shell could result in the star being obscured. While the lack of variability between the 2009 and 2019 near-infrared continuum from our X-shooter spectra eliminates the possibility of formation of hot dust (⪆1500 K), mid-infrared observations are necessary to rule out a slowly expanding cooler dust shell."

The authors of the report are pretty confident the star experienced a dramatic eruption after 2011. Beyond that, though:

"Based on our observations and models, we suggest that PHL 293B hosted an LBV with an eruption that ended sometime after 2011. This could have been followed by
(1) a surviving star or
(2) a collapse of the LBV to a BH [black hole] without the production of a bright SN, but possibly with a weak transient."

Future of Learning

Changing the way we grade students could trigger a wave of innovation

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