Conservation aquaculture could bring more native oysters to west coast

Saving native oysters

UNIVERSITY OF CALIFORNIA - SANTA BARBARA

Research News

Ten estuaries on the West Coast of North America have been identified as priority locations for expanding the use of conservation aquaculture in a study led by the Native Olympia Oyster Collaborative and funded by the Science for Nature and People Partnership (SNAPP). SNAPP is a research collaboration supported by the National Center for Ecological Analysis & Synthesis (NCEAS) at UC Santa Barbara.

The study, published in Plos One, recommends locations and methods for the strategic expansion of conservation aquaculture to bring back Olympia oyster populations -- both to local estuaries where they have most declined, and into more local restaurants for oyster lovers to dine on. The authors propose using aquaculture in these estuaries -- seven of which are in California -- in a win-win scenario that supports severely declined Olympia oyster populations, while also benefiting people, including local shellfish growers and Tribal communities.

"If you've eaten oysters on the half shell anywhere on the West Coast of North America, chances are good that you've been eating one of a few species introduced to the region for just that purpose," said April Ridlon, SNAPP postdoctoral scholar, collaborative lead of the Native Olympia Oyster Collaborative (NOOC) and lead author of the study. That's partly because the oyster native to this coast, the Olympia oyster (Ostrea lurida), was overfished in the Gold Rush era, and some populations -- faced with other stressors like habitat changes and sedimentation -- never recovered.

Humans have used aquaculture -- growing aquatic animals and plants to produce food -- for millennia." The oysters served at your local oyster bar have likely been grown first in a hatchery in tanks, then put out into a bay or estuary until they reach an appropriate size to be harvested and make it onto your plate," Ridlon said. "This same process can also be used to restore declining wild populations, similar to captive breeding programs for endangered species like California Condors and Hawaiian Monk Seals. Native oysters that are raised in a hatchery can be added to local estuaries permanently to help boost their numbers where populations have severely declined. Using aquaculture techniques to support wild populations of native species is what we call conservation aquaculture."

Restoration of Olympia oyster populations doesn't always require the use of aquaculture; many projects have been implemented across the species' range from British Columbia to Baja California, without using aquaculture at all (see the NOOC Restoration Site Map). Aquaculture techniques can also pose risks, including unintended negative ecological and genetic outcomes resulting from releasing hatchery-raised oysters into wild populations, many of which aren't well understood.

This new study thoroughly evaluates the risks and rewards, and recommends aquaculture only at ten priority estuaries where using it is critical to restore oyster populations, and where the benefits clearly outweigh the risks. Two priority estuaries are in the Puget Sound region of Washington: Northern Puget Sound and Whidbey Basin; one is in Oregon: Netarts Bay. The remaining seven are in California: Humboldt Bay, Tomales Bay, Richardson Bay, Elkhorn Slough, Morro Bay, Carpinteria Marsh, and Mugu Lagoon. Aquaculture can be used to support conservation efforts at all of these sites, without growing native oysters to harvest or sell them.

At some of the priority estuaries with good water quality and a nearby hatchery, commercial aquaculture and harvest also are possible, making this tool a unique way to support both oysters and people. In these estuaries, oyster offspring produced by commercial aquaculture may be swept into the bay and settle in local wild populations, increasing their numbers. Growers may also benefit from adding a new oyster species to those that they grow -- one that is more resilient to the diseases or climate-related events that can wipe out other oyster species entirely.

In Puget Sound, where the Olympia oyster once supported the shellfish industry, many farmers are already growing the native oyster, supported by a niche market of "foodies" looking for a different flavor and the "tide-to-table" experience. "Olys -- the industry nickname for Olympia oysters -- have a unique flavor profile. They're smaller than most other oysters and pack a punch of flavor," said Shina Wysocki, owner of Chelsea Farms Oyster Bar in Olympia, Wash. "They also provide an authentic connection to the traditional foodways of the West Coast." Puget Sound Restoration Fund (PSRF) has thoughtfully engaged with commercial growers to explore conservation aquaculture of Olympia oysters in the region, and hopes to continue this approach at the two priority estuaries identified by the study: Northern Puget Sound and Whidbey basin.

"This model of partnership between growers and restoration organizations could be used in other priority estuaries to expand the toolkit for bringing native oysters back to mudflats and menus in the future," said Betsy Peabody, executive director of PSRF.

And the Olympia oyster isn't the only marine species that can benefit from using aquaculture as a tool to restore its populations. "There is a growing interest in using conservation aquaculture for marine species globally -- to support native populations of everything from kelp to abalone to giant clams," said Tiffany Waters, co-author and global aquaculture manager for The Nature Conservancy. "This kind of collaborative research is so exciting, as it can be used as a model for other species and to provide win-win opportunities for both nature and people."

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A white dwarf living on the edge

Astronomers have identified a white dwarf so massive that it might collapse

W. M. KECK OBSERVATORY

Research News

IMAGE: THIS ILLUSTRATION HIGHLIGHTS A NEWFOUND SMALL WHITE DWARF, DISCOVERED BY ZTF, THAT IS 4,300 KILOMETERS ACROSS, OR ROUGHLY THE SIZE OF EARTH'S MOON, WHICH IS 3,500 KILOMETERS ACROSS. THE TWO... view more 

CREDIT: GIUSEPPE PARISI

Maunakea and Haleakala, Hawai'i - Astronomers have discovered the smallest and most massive white dwarf ever seen. The smoldering cinder, which formed when two less massive white dwarfs merged, is heavy, "packing a mass greater than that of our Sun into a body about the size of our Moon," says Ilaria Caiazzo, the Sherman Fairchild Postdoctoral Scholar Research Associate in Theoretical Astrophysics at Caltech and lead author of the new study appearing in the July 1 issue of the journal Nature. "It may seem counterintuitive, but smaller white dwarfs happen to be more massive. This is due to the fact that white dwarfs lack the nuclear burning that keep up normal stars against their own self gravity, and their size is instead regulated by quantum mechanics."

The discovery was made by the Zwicky Transient Facility, or ZTF, which operates at Caltech's Palomar Observatory; two Hawai'i telescopes - W. M. Keck Observatory on Maunakea, Hawai'i Island and University of Hawai'i Institute for Astronomy's Pan-STARRS (Panoramic Survey Telescope and Rapid Response System) on Haleakala, Maui - helped characterize the dead star, along with the 200-inch Hale Telescope at Palomar, the European Gaia space observatory, and NASA's Neil Gehrels Swift Observatory.

White dwarfs are the collapsed remnants of stars that were once about eight times the mass of our Sun or lighter. Our Sun, for example, after it first puffs up into a red giant in about 5 billion years, will ultimately slough off its outer layers and shrink down into a compact white dwarf. About 97 percent of all stars become white dwarfs.

While our Sun is alone in space without a stellar partner, many stars orbit around each other in pairs. The stars grow old together, and if they are both less than eight solar-masses, they will both evolve into white dwarfs.

The new discovery provides an example of what can happen after this phase. The pair of white dwarfs, which spiral around each other, lose energy in the form of gravitational waves and ultimately merge. If the dead stars are massive enough, they explode in what is called a type Ia supernova. But if they are below a certain mass threshold, they combine together into a new white dwarf that is heavier than either progenitor star. This process of merging boosts the magnetic field of that star and speeds up its rotation compared to that of the progenitors.

Astronomers say that the newfound tiny white dwarf, named ZTF J1901+1458, took the latter route of evolution; its progenitors merged and produced a white dwarf 1.35 times the mass of our Sun. The white dwarf has an extreme magnetic field almost 1 billion times stronger than our Sun's and whips around on its axis at a frenzied pace of one revolution every seven minutes (the zippiest white dwarf known, called EPIC 228939929, rotates every 5.3 minutes).

"We caught this very interesting object that wasn't quite massive enough to explode," says Caiazzo. "We are truly probing how massive a white dwarf can be."

What's more, Caiazzo and her collaborators think that the merged white dwarf may be massive enough to evolve into a neutron-rich dead star, or neutron star, which typically forms when a star much more massive than our Sun explodes in a supernova.

"This is highly speculative, but it's possible that the white dwarf is massive enough to further collapse into a neutron star," says Caiazzo. "It is so massive and dense that, in its core, electrons are being captured by protons in nuclei to form neutrons. Because the pressure from electrons pushes against the force of gravity, keeping the star intact, the core collapses when a large enough number of electrons are removed."

If this neutron star formation hypothesis is correct, it may mean that a significant portion of other neutron stars take shape in this way. The newfound object's close proximity (about 130 light-years away) and its young age (about 100 million years old or less) indicate that similar objects may occur more commonly in our galaxy.

MAGNETIC AND FAST

The white dwarf was first spotted by Caiazzo's colleague Kevin Burdge, a postdoctoral scholar at Caltech, after searching through all-sky images captured by ZTF. This particular white dwarf, when analyzed in combination with data from Gaia, stood out for being very massive and having a rapid rotation.

"No one has systematically been able to explore short-timescale astronomical phenomena on this kind of scale until now. The results of these efforts are stunning," says Burdge, who, in 2019, led the team that discovered a pair of white dwarfs zipping around each other every seven minutes.

The team then analyzed the spectrum of the star using Keck Observatory's Low Resolution Imaging Spectrometer (LRIS), and that is when Caiazzo was struck by the signatures of a very powerful magnetic field and realized that she and her team had found something "very special," as she says. The strength of the magnetic field together with the seven-minute rotational speed of the object indicated that it was the result of two smaller white dwarfs coalescing into one.

Data from Swift, which observes ultraviolet light, helped nail down the size and mass of the white dwarf. With a diameter of 2,670 miles, ZTF J1901+1458 secures the title for the smallest known white dwarf, edging out previous record holders, RE J0317-853 and WD 1832+089, which each have diameters of about 3,100 miles.

In the future, Caiazzo hopes to use ZTF to find more white dwarfs like this one, and, in general, to study the population as a whole. "There are so many questions to address, such as what is the rate of white dwarf mergers in the galaxy, and is it enough to explain the number of type Ia supernovae? How is a magnetic field generated in these powerful events, and why is there such diversity in magnetic field strengths among white dwarfs? Finding a large population of white dwarfs born from mergers will help us answer all these questions and more."

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The study, titled "A highly magnetised and rapidly rotating white dwarf as small as the Moon," was funded by the Rose Hills Foundation, the Alfred P. Sloan Foundation, NASA, the Heising-Simons Foundation, the A. F. Morrison Fellowship of the Lick Observatory, the NSF, and the Natural Sciences and Engineering Research Council of Canada.

ABOUT LRIS

The Low Resolution Imaging Spectrometer (LRIS) is a very versatile and ultra-sensitive visible-wavelength imager and spectrograph built at the California Institute of Technology by a team led by Prof. Bev Oke and Prof. Judy Cohen and commissioned in 1993. Since then it has seen two major upgrades to further enhance its capabilities: the addition of a second, blue arm optimized for shorter wavelengths of light and the installation of detectors that are much more sensitive at the longest (red) wavelengths. Each arm is optimized for the wavelengths it covers. This large range of wavelength coverage, combined with the instrument's high sensitivity, allows the study of everything from comets (which have interesting features in the ultraviolet part of the spectrum), to the blue light from star formation, to the red light of very distant objects. LRIS also records the spectra of up to 50 objects simultaneously, especially useful for studies of clusters of galaxies in the most distant reaches, and earliest times, of the universe. LRIS was used in observing distant supernovae by astronomers who received the Nobel Prize in Physics in 2011 for research determining that the universe was speeding up in its expansion.

ABOUT W. M. KECK OBSERVATORY

The W. M. Keck Observatory telescopes are among the most scientifically productive on Earth. The two 10-meter optical/infrared telescopes atop Maunakea on the Island of Hawai?i feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems. Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

The Goldilocks Supernova
The discovery of a new type of supernova illuminates a medieval mysteryDate:June 28, 2021Source:University of California - Santa BarbaraSummary:Scientists have discovered the first convincing evidence for a new type of stellar explosion -- an electron-capture supernova. While they have been theorized for 40 years, real-world examples have been elusive. They are thought to arise from the explosions of massive super-asymptotic giant branch (SAGB) stars, for which there has also been scant evidence

Crab Nebula (stock image; elements furnished by NASA).
Credit: © allexxandarx / stock.adobe.com


A worldwide team led by UC Santa Barbara scientists at Las Cumbres Observatory has discovered the first convincing evidence for a new type of stellar explosion -- an electron-capture supernova. While they have been theorized for 40 years, real-world examples have been elusive. They are thought to arise from the explosions of massive super-asymptotic giant branch (SAGB) stars, for which there has also been scant evidence. The discovery, published in Nature Astronomy, also sheds new light on the thousand-year mystery of the supernova from A.D. 1054 that was visible all over the world in the daytime, before eventually becoming the Crab Nebula.


Historically, supernovae have fallen into two main types: thermonuclear and iron-core collapse. A thermonuclear supernova is the explosion of a white dwarf star after it gains matter in a binary star system. These white dwarfs are the dense cores of ash that remain after a low-mass star (one up to about 8 times the mass of the sun) reaches the end of its life. An iron core-collapse supernova occurs when a massive star -- one more than about 10 times the mass of the sun -- runs out of nuclear fuel and its iron core collapses, creating a black hole or neutron star. Between these two main types of supernovae are electron-capture supernovae. These stars stop fusion when their cores are made of oxygen, neon and magnesium; they aren't massive enough to create iron.

While gravity is always trying to crush a star, what keeps most stars from collapsing is either ongoing fusion or, in cores where fusion has stopped, the fact that you can't pack the atoms any tighter. In an electron capture supernova, some of the electrons in the oxygen-neon-magnesium core get smashed into their atomic nuclei in a process called electron capture. This removal of electrons causes the core of the star to buckle under its own weight and collapse, resulting in an electron-capture supernova.

If the star had been slightly heavier, the core elements could have fused to create heavier elements, prolonging its life. So it is a kind of reverse Goldilocks situation: The star isn't light enough to escape its core collapsing, nor is it heavy enough to prolong its life and die later via different means.

That's the theory that was formulated beginning in 1980 by Ken'ichi Nomoto of the University of Tokyo and others. Over the decades, theorists have formulated predictions of what to look for in an electron-capture supernova and their SAGB star progenitors. The stars should have a lot of mass, lose much of it before exploding, and this mass near the dying star should be of an unusual chemical composition. Then the electron-capture supernova should be weak, have little radioactive fallout, and have neutron-rich elements in the core.

The new study is led by Daichi Hiramatsu, a graduate student at UC Santa Barbara and Las Cumbres Observatory (LCO). Hiramatsu is a core member of the Global Supernova Project, a worldwide team of scientists using dozens of telescopes around and above the globe. The team found that the supernova SN 2018zd had many unusual characteristics, some of which were seen for the first time in a supernova.

It helped that the supernova was relatively nearby -- only 31 million light-years away -- in the galaxy NGC 2146. This allowed the team to examine archival images taken by the Hubble Space Telescope prior to the explosion and to detect the likely progenitor star before it exploded. The observations were consistent with another recently identified SAGB star in the Milky Way, but inconsistent with models of red supergiants, the progenitors of normal iron core-collapse supernovae.

The authors looked through all published data on supernovae, and found that while some had a few of the indicators predicted for electron-capture supernovae, only SN 2018zd had all six: an apparent SAGB progenitor, strong pre-supernova mass loss, an unusual stellar chemical composition, a weak explosion, little radioactivity and a neutron-rich core.

"We started by asking 'what's this weirdo?'" Hiramatsu said. "Then we examined every aspect of SN 2018zd and realized that all of them can be explained in the electron-capture scenario."

The new discoveries also illuminate some mysteries of the most famous supernova of the past. In A.D. 1054 a supernova happened in the Milky Way Galaxy that, according to Chinese and Japanese records, was so bright that it could be seen in the daytime for 23 days, and at night for nearly two years. The resulting remnant, the Crab Nebula, has been studied in great detail.

The Crab Nebula was previously the best candidate for an electron-capture supernova, but its status was uncertain partly because the explosion happened nearly a thousand years ago. The new result increases the confidence that the historic SN 1054 was an electron-capture supernova. It also explains why that supernova was relatively bright compared to the models: Its luminosity was probably artificially enhanced by the supernova ejecta colliding with material cast off by the progenitor star as was seen in SN 2018zd.

Ken Nomoto at the Kavli IPMU of the University of Tokyo expressed excitement that his theory had been confirmed. "I am very pleased that the electron-capture supernova was finally discovered, which my colleagues and I predicted to exist and have a connection to the Crab Nebula 40 years ago," he said. "I very much appreciate the great efforts involved in obtaining these observations. This is a wonderful case of the combination of observations and theory."

Hiramatsu added, "It was such a 'Eureka moment' for all of us that we can contribute to closing the 40-year-old theoretical loop, and for me personally because my career in astronomy started when I looked at the stunning pictures of the Universe in the high school library, one of which was the iconic Crab Nebula taken by the Hubble Space Telescope."

"The term Rosetta Stone is used too often as an analogy when we find a new astrophysical object," said Andrew Howell, a staff scientist at Las Cumbres Observatory and adjunct faculty at UCSB, "but in this case I think it is fitting. This supernova is literally helping us decode thousand-year-old records from cultures all over the world. And it is helping us associate one thing we don't fully understand, the Crab Nebula, with another thing we have incredible modern records of, this supernova. In the process it is teaching us about fundamental physics: how some neutron stars get made, how extreme stars live and die, and about how the elements we're made of get created and scattered around the universe." Howell also is the leader of the Global Supernova Project, and lead author Hiramatsu 's Ph.D. advisor.



Related Multimedia:
Image of electron-capture supernova 2018zd and host starburst galaxy NGC 2146


Journal Reference:
Daichi Hiramatsu, D. Andrew Howell, Schuyler D. Van Dyk, Jared A. Goldberg, Keiichi Maeda, Takashi J. Moriya, Nozomu Tominaga, Ken’ichi Nomoto, Griffin Hosseinzadeh, Iair Arcavi, Curtis McCully, Jamison Burke, K. Azalee Bostroem, Stefano Valenti, Yize Dong, Peter J. Brown, Jennifer E. Andrews, Christopher Bilinski, G. Grant Williams, Paul S. Smith, Nathan Smith, David J. Sand, Gagandeep S. Anand, Chengyuan Xu, Alexei V. Filippenko, Melina C. Bersten, Gastón Folatelli, Patrick L. Kelly, Toshihide Noguchi, Koichi Itagaki. The electron-capture origin of supernova 2018zd. Nature Astronomy, 2021; DOI: 10.1038/s41550-021-01384-2


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University of California - Santa Barbara. "The Goldilocks Supernova: The discovery of a new type of supernova illuminates a medieval mystery." ScienceDaily. ScienceDaily, 28 June 2021. <www.sciencedaily.com/releases/2021/06/210628114136.htm>.

Physicists observationally confirm Hawking's black hole theorem for the first time

by Jennifer Chu, Massachusetts Institute of Technology

Physicists at MIT and elsewhere have used gravitational waves to observationally confirm Hawking’s black hole area theorem for the first time. This computer simulation shows the collision of two black holes that produced the gravitational wave signal, GW150914. Credit: Simulating eXtreme Spacetimes (SXS) project. Courtesy of LIGO

There are certain rules that even the most extreme objects in the universe must obey. A central law for black holes predicts that the area of their event horizons—the boundary beyond which nothing can ever escape—should never shrink. This law is Hawking's area theorem, named after physicist Stephen Hawking, who derived the theorem in 1971.


Fifty years later, physicists at MIT and elsewhere have now confirmed Hawking's area theorem for the first time, using observations of gravitational waves. Their results appear today in Physical Review Letters.

In the study, the researchers take a closer look at GW150914, the first gravitational wave signal detected by the Laser Interferometer Gravitational-wave Observatory (LIGO), in 2015. The signal was a product of two inspiraling black holes that generated a new black hole, along with a huge amount of energy that rippled across space-time as gravitational waves.

If Hawking's area theorem holds, then the horizon area of the new black hole should not be smaller than the total horizon area of its parent black holes. In the new study, the physicists reanalyzed the signal from GW150914 before and after the cosmic collision and found that indeed, the total event horizon area did not decrease after the merger—a result that they report with 95 percent confidence.

Their findings mark the first direct observational confirmation of Hawking's area theorem, which has been proven mathematically but never observed in nature until now. The team plans to test future gravitational-wave signals to see if they might further confirm Hawking's theorem or be a sign of new, law-bending physics.

"It is possible that there's a zoo of different compact objects, and while some of them are the black holes that follow Einstein and Hawking's laws, others may be slightly different beasts," says lead author Maximiliano Isi, a NASA Einstein Postdoctoral Fellow in MIT's Kavli Institute for Astrophysics and Space Research. "So, it's not like you do this test once and it's over. You do this once, and it's the beginning."

Isi's co-authors on the paper are Will Farr of Stony Brook University and the Flatiron Institute's Center for Computational Astrophysics, Matthew Giesler of Cornell University, Mark Scheel of Caltech, and Saul Teukolsky of Cornell University and Caltech.

An age of insights

In 1971, Stephen Hawking proposed the area theorem, which set off a series of fundamental insights about black hole mechanics. The theorem predicts that the total area of a black hole's event horizon—and all black holes in the universe, for that matter—should never decrease. The statement was a curious parallel of the second law of thermodynamics, which states that the entropy, or degree of disorder within an object, should also never decrease.

The similarity between the two theories suggested that black holes could behave as thermal, heat-emitting objects—a confounding proposition, as black holes by their very nature were thought to never let energy escape, or radiate. Hawking eventually squared the two ideas in 1974, showing that black holes could have entropy and emit radiation over very long timescales if their quantum effects were taken into account. This phenomenon was dubbed "Hawking radiation" and remains one of the most fundamental revelations about black holes.

"It all started with Hawking's realization that the total horizon area in black holes can never go down," Isi says. "The area law encapsulates a golden age in the '70s where all these insights were being produced."

Hawking and others have since shown that the area theorem works out mathematically, but there had been no way to check it against nature until LIGO's first detection of gravitational waves.

Hawking, on hearing of the result, quickly contacted LIGO co-founder Kip Thorne, the Feynman Professor of Theoretical Physics at Caltech. His question: Could the detection confirm the area theorem?

At the time, researchers did not have the ability to pick out the necessary information within the signal, before and after the merger, to determine whether the final horizon area did not decrease, as Hawking's theorem would assume. It wasn't until several years later, and the development of a technique by Isi and his colleagues, when testing the area law became feasible.

Before and after

In 2019, Isi and his colleagues developed a technique to extract the reverberations immediately following GW150914's peak—the moment when the two parent black holes collided to form a new black hole. The team used the technique to pick out specific frequencies, or tones of the otherwise noisy aftermath, that they could use to calculate the final black hole's mass and spin.

A black hole's mass and spin are directly related to the area of its event horizon, and Thorne, recalling Hawking's query, approached them with a follow-up: Could they use the same technique to compare the signal before and after the merger, and confirm the area theorem?

The researchers took on the challenge, and again split the GW150914 signal at its peak. They developed a model to analyze the signal before the peak, corresponding to the two inspiraling black holes, and to identify the mass and spin of both black holes before they merged. From these estimates, they calculated their total horizon areas—an estimate roughly equal to about 235,000 square kilometers, or roughly nine times the area of Massachusetts.

They then used their previous technique to extract the "ringdown," or reverberations of the newly formed black hole, from which they calculated its mass and spin, and ultimately its horizon area, which they found was equivalent to 367,000 square kilometers (approximately 13 times the Bay State's area).

"The data show with overwhelming confidence that the horizon area increased after the merger, and that the area law is satisfied with very high probability," Isi says. "It was a relief that our result does agree with the paradigm that we expect, and does confirm our understanding of these complicated black hole mergers."

The team plans to further test Hawking's area theorem, and other longstanding theories of black hole mechanics, using data from LIGO and Virgo, its counterpart in Italy.

"It's encouraging that we can think in new, creative ways about gravitational-wave data, and reach questions we thought we couldn't before," Isi says. "We can keep teasing out pieces of information that speak directly to the pillars of what we think we understand. One day, this data may reveal something we didn't expect."


Explore furtherGravitational wave echoes may confirm Stephen Hawking's hypothesis of quantum black holes
More information: Testing the black-hole area law with GW150914, Physical Review Letters (2021). journals.aps.org/prl/accepted/ … 4336d883136eb53c122b


On Arxiv: arxiv.org/abs/2012.04486
Journal information: Physical Review Letters , arXiv

Greece sizzles on hottest day of year

The Acropolis, one of the most visited tourist sites in Greece, was shut during the afternoon due to soaring temperatures.

Greece sizzled Thursday as temperatures topped 43 degrees Celsius (109 Fahrenheit), the year's hottest, with authorities warning the public to stay indoors if possible.

Temperatures have remained high for ten consecutive days, with the warmest weather expected in central Greece according to the national meteorological service.

Slightly higher temperatures had been recorded in July 2007 and 2000.

In Athens, authorities have made air conditioned halls available to the homeless, elderly and other vulnerable sections of the population.

The Acropolis, one of the most visited tourist sites in the country, was shut during the afternoon as a precaution.

Greece's civil protection has called for vigilance this week, in particular for the elderly and children who must hydrate regularly and avoid unnecessary sun exposure.

There is also a high risk of fire in several parts of the country, the agency said.

The fire department on Thursday said it was battling three notable blazes, the largest of them on the island of Crete.

In July 1987, nearly 1,500 people died following one of the worst heat waves in Greek history.

Temperatures at the time had hovered around 43 degrees Celsius in Athens for several days in a row, at a time when few homes were equipped with air conditioning.


Explore furtherHot weather in Greek capital shuts down Acropolis

 

People keep riding a friendly dolphin in Texas. Experts warn it could be deadly mistake

by Mitchell Willetts

Credit: CC0 Public Domain

Texas wildlife experts are urging people to steer clear of a dolphin with a friendly reputation, out of concern for its safety.

The dolphin first started getting human attention over a year ago when it made the canals near a North Padre Island neighborhood just south of Corpus Christi its home, according to the National Oceanic and Atmospheric Administration's (NOAA) fisheries division.

"Over the past year the public has become more and more interested in the animal—even showing up to swim with, ride, jump on and pet the dolphin," NOAA said.

People have recorded their interactions with the dolphin, sharing them on social media and with friends, spurring even more residents and visitors to seek out the animal and interact with it.

"These actions could be dangerous—even fatal—for the dolphin," according to NOAA.

By interacting with the dolphin, it becomes comfortable around people, drawn to them, and even more likely to approach things it associates with humans, such as boats. This can lead to dolphins being hit by boats or getting stuck in fishing equipment.

Experts say the seemingly extroverted dolphin was recently spotted with a wound along its left side that appears to be from a boat propeller.

"It is clear that the dolphin is already in danger from the human interactions that are occurring," officials said.

NOAA is working with the Texas Marine Mammal Stranding Network (TMMSN) to keep tabs on the dolphin, monitoring its behavior and the severity of its injury.

While some have suggested relocating the dolphin, that won't work for several reasons, TMMSN said on social media.

First, the area is the dolphin's home, and moving it from a familiar place could leave the dolphin vulnerable, as it "may not be accepted by other dolphins," and may not know how to catch different kinds of prey in the new environment.

There's also the possibility that, if moved, it will continue doing what it has been in a different place—or worse, and teach other dolphins to interact with people, according to TMMSN.

Finally, the dolphin might just find its way back to where it was moved from.

"We view this as a human behavior problem," TMMSN said. "We know if people change their behavior, the dolphin's behavior will also change, and we can prevent future injuries to people and the dolphin."

NOAA says its Office of Law Enforcement will begin ticketing people seen petting, feeding, or riding the dolphin, with fines ranging from $100 to $250.

"Loving them from afar is the best way to insure a dolphin's ability to thrive and live a full life," the organization said.

To report violations, call the enforcement hotline at (800) 853-1964.

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Explore further

$11,500 reward for killer of pregnant dolphin in Mississippi

 

Dolichomitus meii wasp discovered in Amazonia is like a flying jewel

UNIVERSITY OF TURKU

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IMAGE: THE DOLICHOMITUS MEII WASP WAS DISCOVERED IN WESTERN AMAZONIA. ITS BODY LOOKS BLACK BUT GLITTERS ELECTRIC BLUE IN LIGHT. THE WASP LAYS ITS EGGS ON INSECT LARVAE LIVING DEEP IN... view more 

CREDIT: FILIPPO DE GIOVANNI AND RODRIGO ARAÚJO

Researchers at the Biodiversity Unit of the University of Turku, Finland, study insect biodiversity particularly in Amazonia and Africa. In their studies, they have discovered hundreds of species previously unknown to science. Many of them are exciting in their size, appearance, or living habits.

"The species we have discovered show what magnificent surprises the Earth's rainforests can contain. The newly discovered Dolichomitus meii wasp is particularly interesting for its large size and unique colouring. With a quick glance, its body looks black but glitters electric blue in light. Moreover, its wings are golden yellow. Therefore, you could say it's like a flying jewel," says Postdoctoral Researcher Diego Pádua from the Instituto Nacional de Pesquisas da Amazônia (INPA) in Brazil, who has also worked at the Biodiversity Unit of the University of Turku.

Dolichomitus parasitoid wasps are parasitic on insect larvae living deep in tree trunks. They lay a single egg on the insect larva and the wasp hatchling eats the host larva as it develops.

"The ovipositor of the Dolichomitus meii wasp is immensely long. It sticks the ovipositor into holes in the wood and tries to find host larvae inside. The species' striking colouring protects it from birds that prey on insects. They do not snatch the wasp sitting on the tree trunk as they think it will taste bad or that it is dangerous," says Professor of Biodiversity Research Ilari E. Sääksjärvi from the University of Turku.

Polysphincta parasitoid wasps manipulate the behaviour of the host spider

At the same time as the publication on the Dolichomitus meii species, the researchers published another research article on South American wasp species. The article describes altogether seven new wasp species belonging to the Polysphincta genus.

The Polysphincta parasitoid wasps are parasitic on spiders. The female attacks a spider in its web and temporarily paralyses it with a venomous sting. After this, the wasp lays a single egg on the spider, and a larva hatches from the egg. The larva gradually consumes the spider and eventually pupates.

"The wasps that are parasitic on spiders are extremely interesting as many of them can manipulate the behaviour of the host spider. They can change the way a spider spins its web, so that before its death, the spider does not spin a normal web to catch prey. Instead, they spin a safe nest for the parasitoid wasp pupa," describes Professor Sääksjärvi.

Researchers at University of Turku have already discovered 53 new species this year

The new species are often discovered through extensive international collaboration. This was also the case with the newly published studies.

"For example, the discovery of the Dolichomitus meii species was an effort of six researchers. Moreover, these researchers all come from different countries," says Professor Sääksjärvi.

The work to map out biodiversity previously unknown to science continues at the University of Turku and there are interesting species discoveries ahead.

"I just counted that, in 2021, the researchers of the Biodiversity Unit at the University of Turku have described already 53 new species from different parts of the globe - and we're only halfway through the year," Sääksjärvi announces cheerfully.

The discoveries of the research group were published in the Biodiversity Data Journal and ZooKeys.

CAPTION

The name Polysphincta bonita refers to the species' beautiful appearance. The species is parasitic on spiders.

CREDIT

Diego Padúa and Ilari E. Sääksjärvi

 

Astonishing altitude changes in marathon flights of migratory birds

LUND UNIVERSITY

Research News

Extreme differences in flight altitude between day and night may have been an undetected pattern amongst migratory birds - until now. The observation was made by researchers at Lund University in Sweden in a study of great snipes, where they also measured a new altitude record for migratory birds, irrespective of the species, reaching 8 700 metres.

Great snipes are shorebirds that breed in Sweden, among other places, and spend the winter in areas near the equator in Africa. Previous studies have shown that great snipes make long marathon flights of up to 6 000 kilometres lasting 60-90 hours when they migrate between breeding sites in Sweden and wintering sites close to the equator.

In a new study published in Current Biology, the international research team describe how the great snipes fly at a higher altitude during the day than at night. The difference can be as much as several thousand metres. The birds regularly flew at an altitude of over 6 000 metres during the day, compared to an average altitude of about 2 000 metres at night. One bird even flew at over 8 000 metres for five hours during the autumn migration to Africa, reaching a maximum altitude of 8 700 metres.

"It is the highest flight altitude that has ever been recorded for a migratory bird", says Åke Lindström at the Department of Biology in Lund who led the study.

Researchers used small data loggers developed at Lund University and attached these to the great snipes in order to follow changes in flight altitude during the long flights. The record height of 8 700 metres is astonishing.

However, the researchers are even more fascinated by the pattern among migratory birds that they may have detected. A recently published study on great reed warblers, which was also led by researchers in Lund, found that on the few occasions during the migration when the small passerines prolonged their otherwise nocturnal flights into the day, they flew at much higher flight altitudes during the day than at night. This occurred when great reed warblers crossed inhospitable terrain such as the Sahara Desert and the Mediterranean Sea.

The considerably larger great snipes do the same. However, not only when they fly over so-called ecological barriers such as deserts and seas, but also when they fly over the tropics and over Europe.

"Other species that that make long migratory flights are also likely to use this day-and-night rhythm. We may well be tracking a general pattern, it will be up to future studies to show this", says Åke Lindström.

If it transpires to be a pattern amongst many migratory birds, it would enhance our understanding of which environmental factors are important for migratory birds. This knowledge may in turn bring us closer to explaining the great variation in the behaviour of these birds. Why do some species migrate at night and others during the day? Why do some birds only fly short distances at a time while others, such as great snipes fly for several days in a row?

As yet, no one knows for certain why great snipes and great reed warblers fly at a higher altitude in the day than at night during migration. The research team mention three explanations as the most probable: birds can navigate more easily via landmarks, they avoid birds of prey, the cold temperature at high altitudes helps prevent overheating during strenuous exercise under the blazing sun.

"Our main line of inquiry is that they fly at a high altitude to cool down, but we must be humble and acknowledge that there may be other or additional explanations", concludes Åke Lindström.

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Why are some fish warm-blooded? Predatory sharks gain speed advantage

TRINITY COLLEGE DUBLIN

Research News

IMAGE: A TIGER SHARK (GALEOCERDO CUVIER) SWIMMING AT THE SURFACE WITH A BIOLOGGING PACKAGE ATTACHED TO DORSAL FIN. THIS PACKAGE RECORDS TEMPERATURE, SWIMMING SPEED, DEPTH, BODY MOVEMENT AND VIDEO FOOTAGE. view more 

CREDIT: DIEGO CAMEJO (BENEATH THE WAVES).

New research from marine biologists offers answers to a fundamental puzzle that had until now remained unsolved: why are some fish warm-blooded when most are not?

It turns out that while (warm-blooded) fish able to regulate their own body temperatures can swim faster, they do not live in waters spanning a broader range of temperatures.

The research therefore provides some of the first direct evidence as to the evolutionary advantage of being warm-blooded as well as underlining that species in this demographic - such as the infamous white shark and the speedy bluefin tuna - are likely just as vulnerable to changing global ocean temperatures as their cold-blooded relatives.

Lucy Harding, PhD Candidate in Trinity College Dublin's School of Natural Sciences, is the first author of the associated research article, which has just been published in the journal, Functional Ecology. She said:

"Scientists have long known that not all fish are cold-blooded. Some have evolved the ability to warm parts of their bodies so that they can stay warmer than the water around them, but it has remained unclear what advantages this ability provided.

"Some believed being warm-blooded allowed them to swim faster, as warmer muscles tend to be more powerful, while others believed it allowed them to live in a broader range of temperatures and therefore be more resilient to the effects of ocean warming as a result of climate change."

Lucy and her international team of collaborators assessed these two possibilities by collecting data from wild sharks and bony fish, as well as using existing databases.

By attaching biologging devices to the fins of the animals they caught, they were able to collect information such as water temperatures encountered by the fish in their habitats; the speeds at which the fish swam for most of the day; and the depths of water the fish swam in.

The results showed that warm-blooded fishes swim approximately 1.6 times faster than their cold-blooded relatives, but they did not live in broader temperature ranges.

Nick Payne, Assistant Professor in Zoology in Trinity's School of Natural Sciences, said:

"The faster swimming speeds of the warm-blooded fishes likely gives them competitive advantages when it comes to things like predation and migration. With predation in mind, the hunting abilities of the white shark and bluefin tuna help paint a picture of why this ability might offer a competitive advantage.

"Additionally, and contrary to some previous studies and opinions, our work shows these animals do not live in broader temperature ranges, which implies that they may be equally at risk from the negative impacts of ocean warming. Findings like these - while interesting on their own - are very important as they can aid future conservation efforts for these threatened animals."

The research was supported by Science Foundation Ireland.

CAPTION

A white shark (Carcharodon carcharias) swimming at the surface with a biologging package attached to dorsal fin. This package records temperature, swimming speed, depth, body movement and video footage.

CREDIT

Andrew Fox.

 

Underwater seismometer can hear how fast a glacier moves

HOKKAIDO UNIVERSITY

Research News

 

IMAGE: KEY ADVANTAGES OF DEPLOYING AN OCEAN-BOTTOM SEISMOMETER NEAR THE CALVING FRONT OF A TIDEWATER GLACIER. SUBGLACIAL AND OCEAN SEISMO-ACOUSTIC SIGNALS CAN BE DETECTED, WHILE THE IMPACT OF SURFACE SEISMIC SOURCES... view more 

CREDIT: EVGENY A. PODOLSKIY, YOSHIO MURAI, NAOYA KANNA, SHIN SUGIYAMA. NATURE COMMUNICATIONS. JUNE 24, 2021

Scientists show that an ocean-bottom seismometer deployed close to the calving front of a glacier in Greenland can detect continuous seismic radiation from a glacier sliding, reminiscent of a slow earthquake.

Basal slip of marine-terminating glaciers controls how fast they discharge ice into the ocean. However, to directly observe such basal motion and determine what controls it is challenging: the calving-front environment is one of the most difficult-to-access environments and seismically noisy -- especially on the glacier surface -- due to heavily crevassed ice and harsh weather conditions.

A team of scientists from Hokkaido University, led by Assistant Professor Evgeny A. Podolskiy from the Arctic Research Center, have used ocean-bottom and surface seismometers to detect previously unknown persistent coastal shaking generated by a sliding of a glacier. Their findings were published in the journal Nature Communications.

Sensors to measure glacial motion can potentially be placed on top of, within, or below the glacier; however, each approach has its own drawbacks. For example, the surface of glaciers is 'noisy' due to wind and tide-modulated crevassing, which can overwhelm all other signals; while the interior is quieter, it is the hardest area to access. However, all of these locations are plagued by common issues such as station drift, melt out and level loss, cold temperatures, and potential instrument destruction by iceberg calving.

In the current study, the scientists used an ocean-bottom seismometer (OBS) that was deployed near the calving front of Bowdoin Glacier (Kangerluarsuup Sermia) to listen to icequakes caused by glacial basal motion. By doing so, they insulated the sensor from the near-surface seismic noise, and also circumvented all the issues that accompany the deployment of sensors on the glacier itself and nearby. The data they collected from the OBS was correlated with data from seismic and ice-speed measurements at the ice surface.

CAPTION

Evgeny A. Podolskiy, lead author of the study, assembling the ocean-bottom seismometer in Qaanaaq, northwest Greenland, July 2019 (Photo: I. Asaji).

CREDIT

I. Asaji

The analysis of the data revealed that there is a continuous seismic tremor generated by the glacier. In particular, the broad-band seismic signal (3.5 Hz to 14.0 Hz) detected by the OBS correlated well with the movement of the glacier. The scientists were able to identify signals that were not associated with glacial basal dynamics. Data from the OBS were necessary to establish a correlation between tremors detected by the surface stations and GPS-recorded displacement of the glacier. In the process, they demonstrated that continuous seismic data that was historically considered 'noise' contains signals that can be used to study glacier dynamics.

The scientists also suggested that glacier slip is similar to slow earthquakes. The characteristics of the Bowdoin-Glacier tremor remind those of tectonic tremors in Japan and Canada. Moreover, the presence of the tremor is in line with recent theoretical models and cold-laboratory experiments.

The scientists have presented a novel method to collect continuous glacioseismic information about glacier motion in an extremely noisy and harsh polar environment using ocean-bottom seismology. "Future research in this area could focus on replicating and expanding upon the findings of this study at other glaciers," says Evgeny A. Podolskiy. "The experimental support for the relationship between glacier tremors and tectonic tremors suggests that a long-term multidisciplinary approach would be beneficial in fully understanding this phenomenon."

CAPTION

The ocean-bottom seismometer being deployed by the authors and colleagues, 21 July 2019, Bowdoin Fjord (Photo: I. Asaji).

CREDIT

I. Asaji