During the heat wave, also called a heat dome, scientists and community members alike noticed a disturbing uptick of dying and dead shellfish on some beaches in Washington and British Columbia, both in the Salish Sea and along the outer coast. The observers quickly realized they were living through an unprecedented event and they organized to document the shellfish die-offs as they happened in real time.

Now, a team led by the University of Washington has compiled and analyzed hundreds of these field observations to produce the first comprehensive report of the impacts of the 2021 heat wave on shellfish. The researchers found that many shellfish were victims of a “perfect storm” of factors that contributed to widespread death: The lowest low tides of the year occurred during the year’s hottest days — and at the warmest times of day. The results were published online June 20 in the journal Ecology.

“You really couldn’t have come up with a worse scenario for intertidal organisms,” said lead author Wendel Raymond, a research scientist at UW Friday Harbor Laboratories. “This analysis has given us a really good general picture of how shellfish were impacted by the heat wave, but we know this isn’t even the full story.”

The research team leveraged existing collaborations across tribes, state and federal agencies, academia and nonprofits. They devised a simple survey and five-point rating system (1 = much worse than normal to 5 = much better than normal) and asked participants to provide ratings based on their knowledge of a species in that location. In total, they gathered 203 observations from 108 unique locations, from central British Columbia down to Willapa Bay, Washington.

“The strength of this study and what it really highlights is the value of local knowledge and also the importance of understanding natural history,” said co-author P. Sean McDonald, a UW associate teaching professor in environmental studies and aquatic and fishery sciences. “This is the first step and a snapshot, if you will, of what shellfish experienced on the beaches during the heat wave.”

The researchers found that each species’ ecology contributed to its general success or failure to survive the extreme heat. For example, some shellfish that naturally burrow deep beneath the surface, like butter clams, usually fared better than ones that typically ride out low tide just below the sand’s surface, such as cockles.

They also found that location mattered. Shellfish on the outer coast experienced low tide about four hours earlier than shellfish on inland beaches. For inland shellfish, low tide — or when the most shellfish were exposed — hit around solar noon, when the sun was directly overhead.

Additionally, air temperatures were much higher at inland sites compared to the outer coast, causing more stress on inland populations. For example, California mussels, found almost exclusively on the outer coast, mostly survived the heat while bay mussels, found in more inner coastal sites, were more likely to die from heat exposure. More water movement and wave action on the outer coast also likely helped lessen the impacts of the heat on shellfish along those beaches.

“The timing of low tide helps determine when and where organisms may be exposed to heat stress and can structure behavior and distribution. In this case, organisms at locations that are already exposed to air at the hottest time of day were very unlucky that temperatures soared so high,” said co-author Hilary Hayford, habitat research director at Puget Sound Restoration Fund.

Many shellfish don’t tend to move much on any given beach, so where they naturally live in the intertidal zone also contributed to their success or failure, the researchers found. For example, acorn barnacles that live higher on the shore generally were more impacted than clams and oysters that are lower on the beach and more likely to remain under water.

“Although this event had negative effects on marine life, there is hope that can be found in this work. Not all locations and species were affected equally, offering clues to pathways to resiliency in the future,” said co-author Annie Raymond, a shellfish biologist with Jamestown S’Klallam Tribe.

Perhaps most surprisingly, the researchers noticed interesting patterns in survival rates among shellfish on the same beach. In some locations, shellfish in the path of freshwater runoff on one section of beach survived, while others just a few miles away perished. If a tree hung over part of a beach and shaded the sand, those shellfish generally made it while others didn’t. Co-author Julie Barber, senior shellfish biologist with the Swinomish Indian Tribal Community, remembers seeing those patterns while walking the beaches of Skagit Bay and, in some locations, being surrounded by dead cockles in every direction.

“It was pretty unsettling, and I’ve never seen anything like it,” Barber said. She remembers exchanging emails with colleagues from around the region as they noticed similar mass die-offs on their local beaches, then realizing that they urgently needed to coordinate and document what was happening.

“This effort was a beautiful demonstration of how collaborators can come together with one common cause — which in our case was trying to understand what happened to these shellfish,” Barber said.

Because the heat wave occurred during the time frame when many shellfish are reproducing, the mass die-offs could impact those populations for at least several years, highlighting the need for long-term monitoring, the researchers said. And as climate change continues to produce more frequent extreme heat events, shellfish deaths like those of last summer may become more of a common reality.

“The Swinomish Indian Tribal Community is proud to be a leader in this important scientific research that assessed in real-time the devastating impacts to our shellfish resources from the unprecedented heat dome last summer. Shellfish are a priority first food that our tribal community relies on for spiritual and subsistence nourishment. Last summer’s extreme weather event reinforced to us that we must act faster to ensure climate resiliency for our community’s long-term health and well-being,” said Swinomish Tribal Chairman Steve Edwards.

“Once the effects of the heat wave started to become apparent, the collaboration that emerged was amazing as managers and scientists worked quickly to put together a rapid response to capture information,” said co-author Camille Speck, Puget Sound intertidal bivalve manager for Washington Department of Fish and Wildlife. “We still have so much to learn about the effects of the heat wave on Salish Sea marine ecosystems, and more work to do as managers to prepare for the next one and develop informed responses. These conversations are happening now, and it is our hope that we will be better prepared for whatever comes next.”

Other co-authors are Megan Dethier of the UW; Teri King of UW-based Washington Sea Grant; Christopher Harley of University of British Columbia; Blair Paul of Skokomish Indian Tribe; and Elizabeth Tobin of Jamestown S’Klallam Tribe. More than two dozen individuals contributed data to this project.

This analysis was funded by Washington Sea Grant with data contributions from tribes, state and federal agencies, academic institutions and nonprofits.

The new method, for which the team has already applied for patent protection, is described in the journal Physical Review X, in a paper by graduate student Guoqing Wang, professor of nuclear science and engineering and of physics Paola Cappellaro, and four others at MIT and Lincoln Laboratory.

Quantum sensors can take many forms; they’re essentially systems in which some particles are in such a delicately balanced state that they are affected by even tiny variations in the fields they are exposed to. These can take the form of neutral atoms, trapped ions, and solid-state spins, and research using such sensors has grown rapidly. For example, physicists use them to investigate exotic states of matter, including so-called time crystals and topological phases, while other researchers use them to characterize practical devices such as experimental quantum memory or computation devices. But many other phenomena of interest span a much broader frequency range than today’s quantum sensors can detect.

The new system the team devised, which they call a quantum mixer, injects a second frequency into the detector using a beam of microwaves. This converts the frequency of the field being studied into a different frequency — the difference between the original frequency and that of the added signal — which is tuned to the specific frequency that the detector is most sensitive to. This simple process enables the detector to home in on any desired frequency at all, with no loss in the nanoscale spatial resolution of the sensor.

In their experiments, the team used a specific device based on an array of nitrogen-vacancy centers in diamond, a widely used quantum sensing system, and successfully demonstrated detection of a signal with a frequency of 150 megahertz, using a qubit detector with frequency of 2.2 gigahertz — a detection that would be impossible without the quantum multiplexer. They then did detailed analyses of the process by deriving a theoretical framework, based on Floquet theory, and testing the numerical predictions of that theory in a series of experiments.

While their tests used this specific system, Wang says, “the same principle can be also applied to any kind of sensors or quantum devices.” The system would be self-contained, with the detector and the source of the second frequency all packaged in a single device.

Wang says that this system could be used, for example, to characterize in detail the performance of a microwave antenna. “It can characterize the distribution of the field [generated by the antenna] with nanoscale resolution, so it’s very promising in that direction,” he says.

There are other ways of altering the frequency sensitivity of some quantum sensors, but these require the use of large devices and strong magnetic fields that blur out the fine details and make it impossible to achieve the very high resolution that the new system offers. In such systems today, Wang says, “you need to use a strong magnetic field to tune the sensor, but that magnetic field can potentially break the quantum material properties, which can influence the phenomena that you want to measure.”

The system may open up new applications in biomedical fields, according to Cappellaro, because it can make accessible a range of frequencies of electrical or magnetic activity at the level of a single cell. It would be very difficult to get useful resolution of such signals using current quantum sensing systems, she says. It may be possible using this system to detect output signals from a single neuron in response to some stimulus, for example, which typically include a great deal of noise, making such signals hard to isolate.

The system could also be used to characterize in detail the behavior of exotic materials such as 2D materials that are being intensely studied for their electromagnetic, optical, and physical properties.

In ongoing work, the team is exploring the possibility of finding ways to expand the system to be able to probe a range of frequencies at once, rather than the present system’s single frequency targeting. They will also be continuing to define the system’s capabilities using more powerful quantum sensing devices at Lincoln Laboratory, where some members of the research team are based.

The team included Yi-Xiang Liu at MIT and Jennifer Schloss, Scott Alsid and Danielle Braje at Lincoln Laboratory. The work was supported by the Defense Advanced Research Projects Agency (DARPA) and Q-Diamond.

The study acquainted 49 bats with a series of ringtones that attracted their attention, and trained them to associate flying toward just one of the tones with a reward: a baitfish snack.

Between one and four years later, eight of those bats were recaptured and exposed again to the food-related ringtone. All of them flew toward the sound, and six flew all the way to the speaker and grabbed the food reward, meaning they expected to find food. Control bats without previous training on the sounds were comparatively unmoved by the exposure to the unfamiliar tones.

“I was surprised — I went into this thinking that at least a year would be a reasonable time for them to remember, given all the other things they need to know and given that long-term memory does have real costs. Four years strikes me as a long time to hold on to a sound that you might never hear again,” said lead author May Dixon, a postdoctoral scholar in evolution, ecology and organismal biology at The Ohio State University.

Dixon led this study at the Smithsonian Tropical Research Institute in Panama while she was a graduate student at the University of Texas at Austin.

“The environment that previous generations experienced can be extremely different from the environment an animal is born into — and it may also change throughout an animal’s life,” she said. “Trying to figure out how animals use learning and memory is one way to figure out how they’re going to make it in a life full of change in the modern world.”

The study is published today (June 20, 2022) in Current Biology.

In the first phase, individual frog-eating bats captured for a series of cognition tests were exposed to a highly attractive sound in the lab: the mating call of the male túngara frog, one of this species of bats’ preferred prey. Flying to that sound was rewarded with a piece of baitfish placed on mesh above the speaker.

Over time, the sound was mingled with and gradually replaced by a ringtone, but the reward was the same. Researchers then introduced three other ringtones, none of which was connected to a food reward. Bats were trained to discern the differences and eventually no longer flew toward the unrewarded sounds. Each bat secured at least 40 snacks by flying to the trained ringtone over 11 to 27 days. All bats were microchipped and returned to the wild.

Beginning a year later and for three additional years, Dixon captured bats and identified eight from the initial trial by their microchips. In a follow-up test of their response to the original rewarded ringtone, all eight trained bats quickly flew to the sound and were able to tell the difference between that ringtone and a new, steady tone, though many of the bats did fly to an unrewarded sound from the initial training.

When 17 untrained bats were exposed to these sounds, they mostly twitched their ears in response to the sounds, but didn’t fly toward them.

“The study taught us a lot because there are relatively few studies of long-term memory in wild animals and we don’t have systematic understanding of long-term memories in nature yet,” Dixon said. “If we can collect additional data on different species of bats, we could pick this apart and see what life histories select for long memories.”

The paper lists 39 previous studies that have documented memory in species ranging from fish, birds and bats to goats and primates. Some of the longest of those experiments — documenting memory in sea lions for 10 years, tortoises for nine years and dolphins for 20 years — were all conducted on animals that lived in captivity the entire time.

“Being able to study memory in the wild is important,” said study co-author Gerald Carter, assistant professor of evolution, ecology and organismal biology at Ohio State. “You can’t necessarily extrapolate from the wealth of data we have on animals in the lab to what they’re facing in the wild, where there are many more things they have to remember. The environment is different and the brain is different in the wild versus captivity.”

Despite the human tendency to assume a long memory gives our species the intelligence advantage, nature shows us that memory flexibility — also called adaptive forgetting — may be important for survival.

“It’s not always true that being the smartest or having the longest memory is actually advantageous. Research has shown that fruitflies selected for improved memories can’t compete as well against other fruitflies,” Dixon said. “Just because it’s useful for humans to be so smart and have such good memories doesn’t necessarily mean it’s going to be the best thing for other animals.

“That’s why we want to figure out when these skills are actually going to help animals and when they could be a liability.”

This work was supported by the National Science Foundation and the Smithsonian Tropical Research Institute (STRI). Co-authors include Patricia Jones of Bowdoin College, Michael Ryan of STRI and UT Austin, and Rachel Page of STRI.

As light passes through the slide, an image of Australia can be seen, but when you flip the slide and look again, an image of the Sydney Opera House is visible. The pair of images created is just one example of an untapped number of possibilities.

The ability to produce two distinctly different images is possible thanks to the ANU scientists’ ability to control the direction in which light can and can’t travel at the nanoscale. The development could pave the way for new light-based devices that could lead to faster, cheaper and more reliable Internet. It could also serve as the foundation for many of the technologies of tomorrow.

Developed in collaboration with colleagues from China, Germany and Singapore, the new technology uses nanoparticles, so small that about 12,000 of them can fit within a cross-section of a human hair. These tiny particles are arranged into unique patterns on the slides.

“The particles control the flow of light like road signs control traffic on a busy road by manipulating the direction in which light can, or can’t, travel,” project leader Dr Sergey Kruk said.

“Some particles allow light to flow from left to right only, others from right to left or the pathway might be blocked in either direction.”

Dr Lei Wang, from Southeast University in China said: “While the purpose of these images is mainly artistic, they demonstrate the potential for this new technology.

“In real-world applications these nanoparticles can be assembled into complex systems that would control the flow of light in a useful manner — such as in next-generation communications infrastructure.”

According to Dr Kruk, the ability to control the flow of light at the nanoscale ensures light “goes where it’s supposed to go and doesn’t go where it’s not supposed to.”

“We exchange enormous amounts of information with the help of light. When you make a video call, say, from Australia to Europe, your voice and image get converted into short pulses of light that travel thousands of kilometres through an optical fibre over the continents and oceans,” Dr Kruk, from the ANU Nonlinear Physics Centre, said.

“Unfortunately, when we use current light-based technologies to exchange information a lot of parasitic effects might occur. Light might get scattered or reflected, which compromises your communication.

“By ensuring light flows exactly where it needs to flow, we would resolve many issues with current technologies.”

According to Dr Kruk, the development of many technologies of tomorrow will rely heavily on our ability to control light at a tiny scale.

“A wide deployment of tiny components that can control the flow of light could potentially bring technological and social changes similar to transformations brought about in the past by the development of tiny components that control the flow of electricity, which are known as diodes and transistors,” he said.

“Control over the flow of electricity at the nanoscale is what ultimately brought us modern computers and smartphones. It is therefore exciting to envision the potential of our emerging technology for controlling flow of light.”

This research was a collaboration between the Nonlinear Physics Centre at the ANU Research School of Physics, Paderborn University in Germany, Southeast University in China and A*STAR Singapore.