Tag Archives: Great

Great Lakes sediments show high levels of microplastic contamination

New research from the University of Western Ontario reports that the sediment lining the bottom of the Great Lakes is chock-full of microplastics.

Image credits Bruno Glätsch.

Plastics are one of the most widespread contaminants on Earth — and every bit of it was made by humans. A particular subset of them, that of plastic particles under five millimeters in size (known as microplastics), are particularly problematic.

Microplastics are tiny enough to evade most natural and man-made filtration systems, they’re easily mistaken for food and swallowed by wildlife (but aren’t digestible), and they can also be produced by the degradation of plastic masses dumped into the ocean.

And there’s a lot of it

As microplastics build up in the world’s waterways, they are also getting lodged in sediment layers. A new paper looked at the Great Lakes as a case study for microplastic pollution and its place in geologic processes.

The team, comprised of sedimentary petrologist Patricia Corcoran and her students at the University of Western Ontario, looked at the main sources of microplastics in sediment samples recovered from the Great Lakes. They also analyzed the distribution of these contaminants, looked for areas with particularly high levels of microplastics, and estimated which animals are placed at risk by exposure to these particles. Towards this goal, they retrieved sediment samples (both offshore and nearshore) from Lakes Huron, Ontario, Erie, St. Clair, and their tributaries.

Lab analyses revealed that microplastic concentrations in these samples reached as high as 4.270 microplastic particles per kilogram of (dry) sediment in the lakes, and up to 2.444 microplastic particles per kilogram of (dry) river sediment.

The team reports that microplastic content shows a strong link to the levels of organic debris in a given sample: the more organic material, the more microplastics were found. They add that benthic (lake bottom) microplastics were more abundant near areas with large human populations (these areas are further associated with plastic use and plastic production facilities).

One particularly important finding was that, although a large number of man-made particles were found in the samples, only around one-third were actual plastic.

“When we chemically analyzed fibers only 33% were plastic — the others, materials like dyed cotton or cellulose,” Corcoran says. “So we can’t assume that every fiber we see under the microscope is plastic.”

The team also looked at pellets (bigger microplastic particles, around the size of an individual lentil) in samples taken from 66 beaches across all five Great Lakes. They report finding 12.974 pellets over 660 square meters (7.104 sq ft) of investigated beach area. Two of the beaches that contained most pellets were close to population or industrial centers, but, apart from them, the team didn’t find any significant association between pellet number and areas of human activity. The pellets, they explain, were mostly concentrated around tributaries.

“In other words,” she says, “rivers and creeks are the main pathways used by pellets to reach the lakes.”

Corcoran has previously studied anthropogenic stones in Hawaii, a very in your face example of how plastics are imprinting themselves into the Earth’s geological record. She and her team at the time named these rocks “plastiglomerates” to showcase just how much plastic they contained — and she says the present study finds the early stages of a similar process underway in the Great Lakes.

The paper “Anthropogenic Grains: Microplastics in Benthic Compartments of the Great Lakes Watershed” will be presented by Sara Belontz of the University of Western Ontario at the GSA Annual Meeting in Phoenix, Arizona (Tuesday, 24 Sept. 2:30 p.m., in the North Building of the Phoenix Convention Center, Room 224A).

Great tits.

Different personalities help species face and adapt to threats, environmental changes

Personality may be adaptability’s trump card.

Great tits.

A pair of great tits (the bird).
Image via Pixabay.

Researchers at LMU Munich say that differences in personality could be a kind of insurance policy on the part of evolution. Different personalities, they report in a new paper, help maintain the level of biological variation needed to keep whole populations healthy and thriving.

Birds of a feather

The team focused their study on great tits (Parus major). The birds show some level of adaptability to environmental change, most notably through flexibility in choosing when to rear their chicks. High temperatures tend to make them build their nests and lay eggs earlier in the year, while colder temperatures make them put the whole matter off until the weather improves.

Natural selection favors such behavioral adaptability, the team explains, as long as the genetic variation is available — i.e. as long as the right genetic variants encoding reproductive behavior are present in the population, the birds will decide for themselves when is best to lay eggs, since that increases the chances their chicks will survive.

Personality is, at least in part, the source of this behavioral adaptability, the team reports. LMU behavioral biologist Niels Dingemanse and his doctoral student Robin Abbey-Lee have shown that the bolder among these birds lay their eggs earlier, when conditions allow it, while the shy ones wait for safe conditions, the team reports. In essence, their personalities allow them to interact with a threat (in this case, shifting weather) in different ways, which ensure that at least some members successfully rear their chicks.

The level of predation also has an influence on the timing and particularities of nesting behavior. The European sparrowhawk (Accipiter nisus) is a major predator of great tits, the team explains, with fledglings and young tits being the most vulnerable.

Sparrowhawks brood at a time when new generations of tits reach the fledgling stage, to make sure there will be plenty of pickings to feed baby sparrowhawks with. Some great tits, according to the team, react by deferring breeding, to give their offspring a higher chance of survival. They will also become markedly more alert and sing less often as they hear the call of a hunting sparrowhawk.

“In previous studies, however, we found that not all birds display this reaction to the same degree,” says Dingemanse. “Different individuals exhibit different personalities, and some are more explorative, daring and more aggressive than others.”

The team looked into whether these personality differences actually translate into a meaningful variation in the timing of breeding at the population level. During the breeding season – from April to June – the researchers exposed birds in a total of 12 tit populations to either the recorded call of the sparrowhawk or the song of the harmless blackbird.

Under these two conditions, the team explains, character differences did have an impact on the timing of breeding. More daring birds generally tend to explore their local environments more eagerly and thus breed later. The ones spooked by the team, however, began breeding earlier than what’s usual for great tits. Shier birds behaved exactly the opposite way.

It’s interesting to note that in the end, both personality types achieved essentially the same level of breeding success, according to the authors. This suggests that variation in personality does contribute to keeping a population’s genetic variability at healthy levels.

“In this way, populations can also become more resilient in the face of anthropogenic alterations of their environments, such as climate change,” Dingemanse points out.

The paper “Adaptive individual variation in phenological responses to perceived predation levels” has been published in the journal Nature Communications.

Neptune.

Hubble captured the first evidence of a Great Dark Spot storm forming on Neptune

NASA has spotted one of Neptune’s Great Dark Spots as it was forming, a new study reports. This is the first time humanity has witnessed such an event.

Neptune.

“Does this picture make my spot look dark?”
Image credits NASA / JPL / Voyager 2.

By peering through the lens of the Hubble Space Telescope, NASA researchers have captured one of Neptune’s storms at is was brewing. While six such dark spots have been observed on Neptune in the past, this is the first time we’ve seen one during formation.

The findings will help us better understand our neighboring planets, as well as those far away — exoplanets — in general, as well as the weather patterns and nature of gas giants in particular.

There be a storm a’brewin!

“If you study the exoplanets and you want to understand how they work, you really need to understand our planets first,” said Amy Simon, a planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland and lead author of the new study.

“We have so little information on Uranus and Neptune.”

Jupiter’s Great Red Spot is perhaps the best-known alien storm — but it’s far from the only one. Neptune, as well as our other gaseous-if-somewhat-unfortunately-named neighbor Uranus also boast their own storms in the form of Great Spots.

Neptune’s storms take the shape of Great Dark Spots. Researchers have, so far, spotted six such Spots on Neptune since 1989, when Voyager 2 identified the first two. Hubble has spotted four more since its launch in 1990. The authors of this study have analyzed images Hubble has taken of Uranus over the past several years to chronicle the growth of a new Great Dark Spot that became visible in 2018. The wealth of data recorded by Hubble helped the team understand how often Neptune develops dark spots and how long they last, and gain a bit of insight into the inner workings of ice giant planets.

Voyager 2 saw two storms on Neptune, the (Earth-sized) Great Dark Spot and the Dark Spot 2, in 1989. Images taken by Hubble five years later revealed that both spots had vanished.

“It was certainly a surprise,” Simon said. “We were used to looking at Jupiter’s Great Red Spot, which presumably had been there for more than a hundred years.”

However, a new Dark Spot reared its head on the face of Neptune in 2015. While Simon’s team was busy analyzing Hubble images of this spot, they found some mysteriously-white clouds in the area where the Great Dark Spot used to be. Then, in 2018, a new Great Dark Spot splashed across its surface; it was nearly identical in size, shape, and position as the one seen in 1989, the team reports, right where those clouds used to be.

“We were so busy tracking this smaller storm from 2015, that we weren’t necessarily expecting to see another big one so soon,” Simon said.

These high-altitude white clouds, the team says, are made up of methane ice crystals. The team suspected they somehow accompany the storms that form dark spots, likely hovering above them the same way that lenticular clouds cap tall mountains here on Earth.

Lenticular cloud.

A lenticular cloud spotted over a mountain in the Snæfellsjökull National Park, Iceland.
Image credits joiseyshowaa / Flickr.

So the team set out to track these clouds from 2016 (when they were first spotted) to 2018 (when the Spot gobbled them up). They were brightest in 2016 and 2017, the team found, just before the new Great Dark Spot emerged. The team turned to computer models of Neptune’s atmosphere to understand what they were seeing. According to the results, these companion clouds are brighter over deep storms. The fact that they appeared two years before the Great Dark Spot and then lost some brightness when it became visible suggests dark spots may originate much deeper in Neptune’s atmosphere than previously thought, the team explains.

They also used data from Voyager 2 and Hubble to measure how long these storms last, and how frequently they occur, on which they report in a second study. Each storm can last up to six years, though most only survive for two, the paper reads, and the team suspects new storms appear on Neptune every four to six years or so. This last tidbit would make the Great Dark Spots of Neptune different from those on Jupiter, whose Great Red Spot is at least 350 years old (it was first seen in 1830).

Jupiter’s storms endure as they’re caged in by thin jet streams, which keep them from changing latitude (north-south) and hold them together. Neptunian winds flow in much wider bands, and instead push storms like the Great Dark Spot slowly across latitudes. They can generally survive the planet’s westward equatorial winds, and eastward-blowing currents close to the equator, before getting ripped apart in higher latitudes.

“We have never directly measured winds within Neptune’s dark vortices, but we estimate the wind speeds are in the ballpark of 328 feet (100 meters) per second, quite similar to wind speeds within Jupiter’s Great Red Spot,” said Wong.

Simon, Wong and Hsu also used images from Hubble and Voyager 2 to pinpoint how long these storms last and how frequently they occur. They report in a second study published today in the Astronomical Journal that they suspect new storms crop up on Neptune every four to six years. Each storm may last up to six years, though two-year lifespans are more likely, according to the findings.

The paper “Formation of a New Great Dark Spot on Neptune in 2018” has been published in the journal Geophysical Research Letters.

Great Ideas.

Book review: ‘Ten Great Ideas about Chance’

If life is a game a chance, knowing how to weigh your odds makes all the difference.Great Ideas.

“Ten Great Ideas about Chance”
By Persi Diaconis, Brian Skyrms.
Princeton University Press, 272pp. | Buy on Amazon

Throughout the sixteenth and seventeenth centuries, gamblers and mathematicians set the stage for a new line of thinking that would shape nearly every field today, from economics and finance to physics and computer science: they transformed chance from something that happens to you into a well-ordered discipline, something you can calculate and quantify. This book traces ten great ideas that shaped the field, exploring the mathematical, historical, philosophical, even psychological aspects of probability and statistics.

Accessible, yet meticulous in its math, Persi Diaconis and Brian Skyrms‘ Ten Great Ideas about Chance is an instructive but fun lecture.

Roll the dice

The book was borne of an interdisciplinary course the two authors — one a mathematician and one a philosopher — taught at Stanford University. As such, it’s built on the assumption that you’ve had some prior experience with either statistics or probability. In case you haven’t, the authors included an Appendix with a brief rundown of the basic elements of probability.

Each of the ten great ideas discussed in the book gets its own chapter. The first will take you through a brief tour of the early days of probability theory, starting with the 1500s, and introduce the concept that chance is, in fact, something we can measure. Chapter 2 also deals with measurement, showcasing how probabilities can be measured in more complex situations that lack a finite collection of equally-probable outcomes.

The third great idea is that, as humans, we’re inherently bad at dealing with probabilistic concepts. One simple example that shows how much wording influences our perception is the operating room scenario: telling a patient that they have a 90% chance of surviving an operation, for example, is more likely to induce him to agree to the procedure than telling him he has a 10% chance of dying — despite that both statements mean the exact same thing.

The fourth and fifth chapter explores the connection between probability and frequency, followed by two chapters dedicated to Bayesian analysis. Chapter 7, titled “Unification”, binds all these together and cements the links between chance, probability, and frequency.

The following two chapters impart context to probability theory, showing how it relates to other disciplines. Chapter 8 deals with algorithmic randomness, the use of computers for random number generation, while chapter 9 looks at probability in the context of physics. The final chapter deals with Hume’s assertion that, in the authors’ words, “there is a problem of understanding and validating inductive reasoning.”

Should I read it?

Ten Great Ideas about Chance treats the topic from an unusual angle, and it will help any faculty members teaching probability by providing a fresh take. The book uses calculus quite freely, and a solid understanding of integral signs and limit arguments will come in very handy while navigating its pages.

But don’t get discouraged by the technical talk — the book packs this stuffy topic in a pleasant, easy to read format. As someone with only a summary education in the field, I can attest that even those of us who are newcomers to probability will find quite a lot of interesting information here, peppered with “aha” moments. Even if math wasn’t ever your cup of tea, Ten Great Ideas about Chance remains accessible — despite some chapters being quite challenging and likely to give non-specialists some hard times, most of the book (especially its earliest chapters) do a great job of conversing with a wide audience.

One feature I’ve especially appreciated is the inclusion of end-of-chapter summaries, as it really helped wrap my brain around some of the topics I’ve had difficulty with. Ten Great Ideas about Chance also features an annotated bibliography and appendices in many chapters, which treat topics the authors deemed too tangential or technical for the main body of the work.

All in all, it’s a great book for anyone who wants to understand some of the central tenets of probability, how they were discovered, and how they can be tamed in our day-to-day lives.