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Microplastics in the soil point to another potential ecosystem collapse

When these particles are eaten by earthworms, the results are not good.

Photo by: Andia/ Universal Images Group via Getty Images
  • New research from Anglia Ruskin University states that microplastics in soil are causing earthworms to lose weight.
  • Soil affected by microplastics produces less crop yield due to less productive earthworms and lower pH levels.
  • If this trend continues, our entire agricultural system could be compromised.

In the last installment of "How Plastic is Destroying Us," we discussed the billions of microplastic particles being leeched from tea bags into your mug. It turns out such particles are turning up in the darndest places. A new study, published in Environmental Science & Technology, reveals another unfortunate locale: the digestive tract of earthworms.

Outside of fishing and post-rainy day sidewalks, most of us pay little attention to endogeic worms, the class of worms that live in the top soil. That doesn't mean they lack importance for our survival. By feeding on soil, these wiggly critters—Aporrectodea rosea, rosy-tipped earthworms—mix minerals and air into the soil, which helps, among other things, plants to sprout. Worms are an essential component of our agricultural system.

A team at Anglia Ruskin University in Cambridge wanted to know if the introduction of microplastics into the soil would stunt plant growth. Short answer: yes. After placing different microplastic fibers—biodegradable polylactic acid (PLA), conventional high-density polyethylene (HDPE), and microplastic clothing fibers—into the soil, they planted perennial ryegrass (Lolium perenne). Fewer seeds germinated.

Microplastic contamination is a growing concern for soil health, yet, as the team writes, it has not been well-studied. Fertilizer made from sewage sludge, rain, and airborne fallout are all means for these particles to settle into the earth. The long-term impact could include stunted soil biodiversity.

Microplastics are everywhere | Sarah Dudas | TEDxBinghamtonUniversity

We often mistake broad names for processes as "extra." For example, dark matter, which represents 85 percent of all matter in the universe, is believed to non-baryonic, yet physicists recognize that it could be comprised of subatomic particles we haven't yet discovered. The universe isn't know for creating filler; usually, our own ignorance is the culprit.

"Dirt" and "soil," to non-farmers at least, are often treated as an earth layer; referencing it is often in the negative, as when a parent scolds a child for "playing in the dirt." But soil is a process, living and organic, dependent on decaying and dead matter constantly being churned through (by earthworms, for example) and recycled.

Soil is one of the major reasons that America has become a global power. Our fields supply an incredible amount of food for the planet. By contrast, China, with its billion-plus population to feed, struggles to produce adequate amounts of nutrition due to less fertile soil. This is, in fact, one of the undiscussed underpinnings of the current "trade war."

Damaged soil destroys not only ecosystems, but societies as well. When famers try to increase crop yield by introducing plastic mulches and irrigation, they're unknowingly polluting the soil with tons of microplastic particles. These particles are then ingested by earthworms (among other animals), causing them to lose weight.

The research team chose the most important grass grown in temperate regions; in grassland ecosystems ryegrass is abundant. A variety of ecosystems were used, some with added microplastics, one control without. Earthworms were most affected by HDPE microplastics, though any of the added particles made life worse for the worms.

Beach covered in microplastics

A view of the Schiavonea beach with microplastics, transported by the Ionian sea during the last sea storm.

Photo by Alfonso Di Vincenzo/KONTROLAB /LightRocket via Getty Images

Soil is generally low in nutrient value, meaning that worms have to eat and pass a lot of it for their existence. The team compares the results to aquatic environments, in which the digestive tracts of fish, like worms, are obstructed and worn away. The consumption of microplastic particles stunts their growth while compromising the survival of the organism.

Beyond worms, the particles (especially HDPE) decrease soil pH. This directly affects the diversity of organisms living there. As with the human microbiome, in which a diverse population of bacteria is healthiest, soil pays a steep price when diversity drops.

These particles don't remain in the soil; they end up, in some cases, on your plate. The team writes,

"In agricultural settings, such effects may have implications for the production and quality of crop plants, by directly affecting plant development and altering the soil environment in which they are produced as well as having potential implications for human health through the accumulation of microplastics and harmful compounds in the tissues of plants."

All plastics are biodegradable. The problem is, some take weeks to mineralize while others hang around for millions of years. Until we implement broad solutions that implement a shelf life for plastics, these particles aren't going anywhere—except inside of our digestive tracts, eventually. As with worms, such news doesn't look good for the health of our species.

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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."

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