Many Wayuu families are forced to migrate in search of essential resources, putting even more pressure on already overcrowded urban areas.

It comes as OPEC+ met Monday and agreed to proceed with an increase in oil production starting in April, which is likely to push down oil prices further.

It’s not a stretch to suggest that when we disagree with other people, we often regard them as being irrational. Kevin Dorst PhD ’19 has developed a body of research with surprising things to say about that.

Dorst, an associate professor of philosophy at MIT, studies rationality: how we apply it, or think we do, and how that bears out in society. The goal is to help us think clearly and perhaps with fresh eyes about something we may take for granted.

Throughout his work, Dorst specializes in exploring the nuances of rationality. To take just one instance, consider how ambiguity can interact with rationality. Suppose there are two studies about the effect of a new housing subdivision on local traffic patterns: One shows there will be a substantial increase in traffic, and one shows a minor effect. Even if both studies are sound in their methods and data, neither may have a totally airtight case. People who regard themselves as rationally assessing the numbers will likely disagree about which is most valid, and — though this may not be entirely rational — may use their prior beliefs to poke holes in the study that does not represent their prior beliefs. 

Among other things, this process also calls into question the widespread “Bayesian” conception that people’s views shift and come into alignment as they’re presented with new evidence. It may be that instead, people apply rationality while their views diverge, not converge.

This is also the kind of phenomenon Dorst explores in the paper “Rational Polarization,” published in The Philosophical Review in 2023; currently Dorst is working on a book about how people can take rational approaches but still wind up with different conclusions about the world. Dorst combines careful argumentation, mathematically structured descriptions of thinking, and even experimental evidence about cognition and people’s views, an increasing trend in philosophy.

“There’s something freeing about how methodologically open philosophy is,” says Dorst, a good-humored and genial conversationalist. “A question can be philosophical if it’s important and we don’t yet have settled methods for answering it, because in philosophy it’s always okay to ask what methods we should be using. It’s one of the exciting things about philosophy.”

For his research and teaching, Dorst was awarded tenure at MIT last year.

Show me your work

Dorst grew up in Missouri, not exactly expecting to become a philosopher, but he started following in the academic trail of his older brother, who had become interested in philosophy.

“We didn’t know what philosophy was growing up, but once my brother started getting interested, there was a little bootstrapping, egging each other on, and having someone to talk to,” Dorst says.

As an undergraduate at Washington University in St. Louis, Dorst majored in philosophy and political science. By graduation, he had become sold on studying philosophy full-time, and was accepted into MIT’s program as a doctoral student.

At the Institute, he started specializing in the problems he now studies full-time, about how we know things and how much we are thinking rationally, while working with Roger White as his primary adviser, along with faculty members Robert Stalnaker and Kieran Setiya of MIT and Branden Fitelson of Northeastern University.

After earning his PhD, Dorst spent a year as a fellow at Oxford University’s Magdalen College, then joined faculty of the University of Pittsburgh. He returned to MIT, this time on the faculty, in 2022. Now settled in the MIT philosophy faculty, Dorst tries to continue the department’s tradition of engaged teaching with his students.

“They wrestle like everyone does with the conceptual and philosophical questions, but the speed with which you can get through technical things in a course is astounding,” Dorst says of MIT undergraduates.

New methods, time-honored issues

At present Dorst, who has published widely in philosophy journals, is grinding through the process of writing a book manuscript about the complexity of rationality. Chapter subjects include hindsight bias, confirmation bias, overconfidence, and polarization.

In the process, Dorst is also developing and conducting more experiments than ever before, to look at the way people process information and regard themselves as being rational.

“There’s this whole movement of experimental philosophy, using experimental data, being sensitive to cognitive science and being interested in connecting questions we have to it,” Dorst says.

In his case, he adds, “The big picture is trying to connect the theoretical work on rationality with the more empirical work about what leads to polarization,” he says. The salience of the work, meanwhile, applies to a wide range of subjects:  “People have been polarized forever over everything.”

As he explains all of this, Dorst looks up at the whiteboard in his office, where an extensive set of equations represents the output of some experiments and his ongoing effort to comprehend the results, as part of the book project. When he finishes, he hopes to have work broadly useful in philosophy, cognitive science, and other fields.

“We might use some different models in philosophy,” he says, “but let’s all try to figure out how people process information and regard arguments.”

Building on more than two decades of research, a study by MIT neuroscientists at The Picower Institute for Learning and Memory reports a new way to treat pathology and symptoms of fragile X syndrome, the most common genetically-caused autism spectrum disorder. The team showed that augmenting a novel type of neurotransmitter signaling reduced hallmarks of fragile X in mouse models of the disorder.

The new approach, described in Cell Reports, works by targeting a specific molecular subunit of “NMDA” receptors that they discovered plays a key role in how neurons synthesize proteins to regulate their connections, or “synapses,” with other neurons in brain circuits. The scientists showed that in fragile X model mice, increasing the receptor’s activity caused neurons in the hippocampus region of the brain to increase molecular signaling that suppressed excessive bulk protein synthesis, leading to other key improvements.

Setting the table

“One of the things I find most satisfying about this study is that the pieces of the puzzle fit so nicely into what had come before,” says study senior author Mark Bear, Picower Professor in MIT’s Department of Brain and Cognitive Sciences. Former postdoc Stephanie Barnes, now a lecturer at the University of Glasgow, is the study’s lead author.

Bear’s lab studies how neurons continually edit their circuit connections, a process called “synaptic plasticity” that scientists believe to underlie the brain’s ability to adapt to experience and to form and process memories. These studies led to two discoveries that set the table for the newly published advance. In 2011, Bear’s lab showed that fragile X and another autism disorder, tuberous sclerosis (Tsc), represented two ends of a continuum of a kind of protein synthesis in the same neurons. In fragile X there was too much. In Tsc there was too little. When lab members crossbred fragile X and Tsc mice, in fact, their offspring emerged healthy, as the mutations of each disorder essentially canceled each other out.

More recently, Bear’s lab showed a different dichotomy. It has long been understood from their influential work in the 1990s that the flow of calcium ions through NMDA receptors can trigger a form of synaptic plasticity called “long-term depression” (LTD). But in 2020, they found that another mode of signaling by the receptor — one that did not require ion flow — altered protein synthesis in the neuron and caused a physical shrinking of the dendritic “spine” structures housing synapses.

For Bear and Barnes, these studies raised the prospect that if they could pinpoint how NMDA receptors affect protein synthesis they might identify a new mechanism that could be manipulated therapeutically to address fragile X (and perhaps tuberous sclerosis) pathology and symptoms. That would be an important advance to complement ongoing work Bear’s lab has done to correct fragile X protein synthesis levels via another receptor called mGluR5.

Receptor dissection

In the new study, Bear and Barnes’ team decided to use the non-ionic effect on spine shrinkage as a readout to dissect how NMDARs signal protein synthesis for synaptic plasticity in hippocampus neurons. They hypothesized that the dichotomy of ionic effects on synaptic function and non-ionic effects on spine structure might derive from the presence of two distinct components of NMDA receptors: “subunits” called GluN2A and GluN2B. To test that, they used genetic manipulations to knock out each of the subunits. When they did so, they found that knocking out “2A” or “2B” could eliminate LTD, but that only knocking out 2B affected spine size. Further experiments clarified that 2A and 2B are required for LTD, but that spine shrinkage solely depends on the 2B subunit.

The next task was to resolve how the 2B subunit signals spine shrinkage. A promising possibility was a part of the subunit called the “carboxyterminal domain,” or CTD. So, in a new experiment Bear and Barnes took advantage of a mouse that had been genetically engineered by researchers at the University of Edinburgh so that the 2A and 2B CTDs could be swapped with one another. A telling result was that when the 2B subunit lacked its proper CTD, the effect on spine structure disappeared. The result affirmed that the 2B subunit signals spine shrinkage via its CTD.

Another consequence of replacing the CTD of the 2B subunit was an increase in bulk protein synthesis that resembled findings in fragile X. Conversely, augmenting the non-ionic signaling through the 2B subunit suppressed bulk protein synthesis, reminiscent of Tsc.

Treating fragile X

Putting the pieces together, the findings indicated that augmenting signaling through the 2B subunit might, like introducing the mutation causing Tsc, rescue aspects of fragile X.

Indeed, when the scientists swapped in the 2B subunit CTD of NMDA receptor in fragile X model mice they found correction of not only the excessive bulk protein synthesis, but also altered synaptic plasticity, and increased electrical excitability that are hallmarks of the disease. To see if a treatment that targets NMDA receptors might be effective in fragile X, they tried an experimental drug called Glyx-13. This drug binds to the 2B subunit of NMDA receptors to augment signaling. The researchers found that this treatment can also normalize protein synthesis and reduced sound-induced seizures in the fragile X mice.

The team now hypothesizes, based on another prior study in the lab, that the beneficial effect to fragile X mice of the 2B subunit’s CTD signaling is that it shifts the balance of protein synthesis away from an all-too-efficient translation of short messenger RNAs (which leads to excessive bulk protein synthesis) toward a lower-efficiency translation of longer messenger RNAs.

Bear says he does not know what the prospects are for Glyx-13 as a clinical drug, but he noted that there are some drugs in clinical development that specifically target the 2B subunit of NMDA receptors.

In addition to Bear and Barnes, the study’s other authors are Aurore Thomazeau, Peter Finnie, Max Heinreich, Arnold Heynen, Noboru Komiyama, Seth Grant, Frank Menniti, and Emily Osterweil.

The FRAXA Foundation, The Picower Institute for Learning and Memory, The Freedom Together Foundation, and the National Institutes of Health funded the study.

When Zoe Fisher was in fourth grade, her art teacher asked her to draw her vision of a dream job on paper. At the time, those goals changed like the flavor of the week in an ice cream shop — “zookeeper” featured prominently for a while — but Zoe immediately knew what she wanted to put down: a mad scientist.

When Fisher stumbled upon the drawing in her parents’ Chicago home recently, it felt serendipitous because, by all measures, she has realized that childhood dream. The second-year doctoral student at MIT's Department of Nuclear Science and Engineering (NSE) is studying materials for fusion power plants at the Plasma Science and Fusion Center (PSFC) under the advisement of Michael Short, associate professor at NSE. Dennis Whyte, Hitachi America Professor of Engineering at NSE, serves as co-advisor.

On track to an MIT education

Growing up in Chicago, Fisher had heard her parents remarking on her reasoning abilities. When she was barely a preschooler she argued that she couldn’t have been found in a purple speckled egg, as her parents claimed they had done.

Fisher didn’t put together just how much she had gravitated toward science until a high school physics teacher encouraged her to apply to MIT. Passionate about both the arts and sciences, she initially worried that pursuing science would be very rigid, without room for creativity. But she knows now that exploring solutions to problems requires plenty of creative thinking.

It was a visit to MIT through the Weekend Immersion in Science and Engineering (WISE) that truly opened her eyes to the potential of an MIT education. “It just seemed like the undergraduate experience here is where you can be very unapologetically yourself. There’s no fronting something you don’t want to be like. There’s so much authenticity compared to most other colleges I looked at,” Fisher says. Once admitted, Campus Preview Weekend confirmed that she belonged. “We got to be silly and weird — a version of the Mafia game was a hit — and I was like, ‘These are my people,’” Fisher laughs.

Pursuing fusion at NSE

Before she officially started as a first-year in 2018, Fisher enrolled in the Freshman Pre-Orientation Program (FPOP), which starts a week before orientation starts. Each FPOP zooms into one field. “I’d applied to the nuclear one simply because it sounded cool and I didn’t know anything about it,” Fisher says. She was intrigued right away. “They really got me with that ‘star in a bottle’ line,” she laughs. (The quest for commercial fusion is to create the energy equivalent of a star in a bottle). Excited by a talk by Zachary Hartwig, Robert N. Noyce Career Development Professor at NSE, Fisher asked if she could work on fusion as an undergraduate as part of an Undergraduate Research Opportunities Program (UROP) project. She started with modeling solders for power plants and was hooked. When Fisher requested more experimental work, Hartwig put her in touch with Research Scientist David Fischer at the Plasma Science and Fusion Center (PSFC). Fisher eventually moved on to explore superconductors, which eventually morphed into research for her master’s thesis.

For her doctoral research, Fisher is extending her master’s work to explore defects in ceramics, specifically in alumina (aluminum oxide). Sapphire coatings are the single-crystal equivalent of alumina, an insulator being explored for use in fusion power plants. “I eventually want to figure out what types of charge defects form in ceramics during radiation damage so we can ultimately engineer radiation-resistant sapphire,” Fisher says.

When you introduce a material in a fusion power plant, stray high-energy neutrons born from the plasma can collide and fundamentally reorder the lattice, which is likely to change a range of thermal, electrical, and structural properties. “Think of a scaffolding outside a building, with each one of those joints as a different atom that holds your material in place. If you go in and you pull a joint out, there’s a chance that you pulled out a joint that wasn’t structurally sound, in which case everything would be fine. But there’s also a chance that you pull a joint out and everything alters. And [such unpredictability] is a problem,” Fisher says. “We need to be able to account for exactly how these neutrons are going to alter the lattice property,” Fisher says, and it’s one of the topics her research explores.

The studies, in turn, can function as a jumping-off point for irradiating superconductors. The goals are two-fold: “I want to figure out how I can make an industry-usable ceramic you can use to insulate the inside of a fusion power plant, and then also figure out if I can take this information that I’m getting with ceramics and make it superconductor-relevant,” Fisher says. “Superconductors are the electromagnets we will use to contain the plasma inside fusion power plants. However, they prove pretty difficult to study. Since they are also ceramic, you can draw a lot of parallels between alumina and yttrium barium copper oxide (YBCO), the specific superconductor we use,” she adds. Fisher is also excited about the many experiments she performs using a particle accelerator, one of which involves measuring exactly how surface thermal properties change during radiation.

Sailing new paths

It’s not just her research that Fisher loves. As an undergrad, and during her master’s, she was on the varsity sailing team. “I worked my way into sailing with literal Olympians, I did not see that coming,” she says. Fisher participates in Chicago’s Race to Mackinac and the Melges 15 Series every chance she gets. Of all the types of boats she has sailed, she prefers dinghy sailing the most. “It’s more physical, you have to throw yourself around a lot and there’s this immediate cause and effect, which I like,” Fisher says. She also teaches sailing lessons in the summer at MIT’s Sailing Pavilion — you can find her on a small motorboat, issuing orders through a speaker.

Teaching has figured prominently throughout Fisher’s time at MIT. Through MISTI, Fisher has taught high school classes in Germany and a radiation and materials class in Armenia in her senior year. She was delighted by the food and culture in Armenia and by how excited people were to learn new ideas. Her love of teaching continues, as she has reached out to high schools in the Boston area. “I like talking to groups and getting them excited about fusion, or even maybe just the concept of attending graduate school,” Fisher says, adding that teaching the ropes of an experiment one-on-one is “one of the most rewarding things.”

She also learned the value of resilience and quick thinking on various other MISTI trips. Despite her love of travel, Fisher has had a few harrowing experiences with tough situations and plans falling through at the last minute. It’s when she tells herself, “Well, the only thing that you’re gonna do is you’re gonna keep doing what you wanted to do.”

That eyes-on-the-prize focus has stood Fisher in good stead, and continues to serve her well in her research today.

At EFF we spend a lot of time thinking about Street Level Surveillance technologies—the technologies used by police and other authorities to spy on you while you are going about your everyday life—such as automated license plate readers, facial recognition, surveillance camera networks, and cell-site simulators (CSS). Rayhunter is a new open source tool we’ve created that runs off an affordable mobile hotspot that we hope empowers everyone, regardless of technical skill, to help search out CSS around the world. 

CSS (also known as Stingrays or IMSI catchers) are devices that masquerade as legitimate cell-phone towers, tricking phones within a certain radius into connecting to the device rather than a tower. 

CSS operate by conducting a general search of all cell phones within the device’s radius. Law enforcement use CSS to pinpoint the location of phones often with greater accuracy than other techniques such as cell site location information (CSLI)  and without needing to involve the phone company at all. CSS can also log International Mobile Subscriber Identifiers (IMSI numbers) unique to each SIM card, or hardware serial numbers (IMEIs) of all of the mobile devices within a given area. Some CSS may have advanced features allowing law enforcement to intercept communications in some circumstances.

What makes CSS especially interesting, as compared to other street level surveillance, is that so little is known about how commercial CSS work. We don’t fully know what capabilities they have or what exploits in the phone network they take advantage of to ensnare and spy on our phones, though we have some ideas. 

We also know very little about how cell-site simulators are deployed in the US and around the world. There is no strong evidence either way about whether CSS are commonly being used in the US to spy on First Amendment protected activities such as protests, communication between journalists and sources, or religious gatherings. There is some evidence—much of it circumstantial—that CSS have been used in the US to spy on protests. There is also evidence that CSS are used somewhat extensively by US law enforcement, spyware operators, and scammers. We know even less about how CSS are being used in other countries, though it's a safe bet that in other countries CSS are also used by law enforcement.

Much of these gaps in our knowledge are due to a lack of solid, empirical evidence about the function and usage of these devices. Police departments are resistant to releasing logs of their use, even when they are kept. The companies that manufacture CSS are unwilling to divulge details of how they work. 

Until now, to detect the presence of CSS, researchers and users have had to either rely on Android apps on rooted phones, or sophisticated and expensive software-defined radio rigs. Previous solutions have also focused on attacks on the legacy 2G cellular network, which is almost entirely shut down in the U.S. Seeking to learn from and improve on previous techniques for CSS detection we have developed a better, cheaper alternative that works natively on the modern 4G network.

Introducing Rayhunter

To fill these gaps in our knowledge, we have created an open source project called Rayhunter.1 It is developed to run on an Orbic mobile hotspot (Amazon, Ebay) which is available for $20 or less at the time of this writing. We have tried to make Rayhunter as easy as possible to install and use, regardless of your level of technical knowledge. We hope that activists, journalists, and others will run these devices all over the world and help us collect data about the usage and capabilities of cell-site simulators (please see our legal disclaimer.) 

Rayhunter works by intercepting, storing, and analyzing the control traffic (but not user traffic, such as web requests) between the mobile hotspot Rayhunter runs on and the cell tower to which it’s connected. Rayhunter analyzes the traffic in real-time and looks for suspicious events, which could include unusual requests like the base station (cell tower) trying to downgrade your connection to 2G which is vulnerable to further attacks, or the base station requesting your IMSI under suspicious circumstances. 

Rayhunter notifies the user when something suspicious happens and makes it easy to access those logs for further review, allowing users to take appropriate action to protect themselves, such as turning off their phone and advising other people in the area to do the same. The user can also download the logs (in PCAP format) to send to an expert for further review. 

The default Rayhunter user interface is very simple: a green (or blue in colorblind mode) line at the top of the screen lets the user know that Rayhunter is running and nothing suspicious has occurred. If that line turns red, it means that Rayhunter has logged a suspicious event. When that happens the user can connect to the device's WiFi access point and check a web interface to find out more information or download the logs. 

Rayhunter in action

Installing Rayhunter is relatively simple. After buying the necessary hardware, you’ll need to download the latest release package, unzip the file, plug the device into your computer, and then run an install script for either Mac or Linux (we do not support Windows as an installation platform at this time.)

We have a few different goals with this project. An overarching goal is to determine conclusively if CSS are used to surveil free expression such as protests or religious gatherings, and if so, how often it’s occurring. We’d like to collect empirical data (through network traffic captures, i.e. PCAPs) about what exploits CSS are actually using in the wild so the community of cellular security researchers can build better defenses. We also hope to get a clearer picture of the extent of CSS usage outside of the U.S., especially in countries that do not have legally enshrined free speech protections.

Once we have gathered this data, we hope we can help folks more accurately engage in threat modeling about the risks of cell-site simulators, and avoid the fear, uncertainty, and doubt that comes from a lack of knowledge. We hope that any data we do find will be useful to those who are fighting through legal process or legislative policy to rein in CSS use where they live. 

If you’re interested in running Rayhunter for yourself, pick up an Orbic hotspot (Amazon, Ebay), install Rayhunter, and help us collect data about how IMSI catchers operate! Together we can find out how cell site simulators are being used, and protect ourselves and our communities from this form of surveillance

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Legal disclaimer: Use Rayhunter at your own risk. We believe running this program does not currently violate any laws or regulations in the United States. However, we are not responsible for civil or criminal liability resulting from the use of this software. If you are located outside of the US please consult with an attorney in your country to help you assess the legal risks of running this program

• 1. A note on the name: Rayhunter is named such because Stingray is a brand name for cell-site simulators which has become a common term for the technology. One of the only natural predators of the stingray in the wild is the orca, some of which hunt stingrays for pleasure using a technique called wavehunting. Because we like Orcas, we don’t like stingray technology (though the animals are great!), and because it was the only name not already trademarked, we chose Rayhunter.

For as long as people have been communicating through writing, they have found ways to keep their messages private. Before the invention of the gummed envelope in 1830, securing correspondence involved letterlocking, an ingenious process of folding a flat sheet of paper to become its own envelope, often using a combination of folds, tucks, slits, or adhesives such as sealing wax. Letter writers from Erasmus to Catherine de’ Medici to Emily Dickinson employed these techniques, which Jana Dambrogio, the MIT Libraries’ Thomas F. Peterson (1957) Conservator, has named “letterlocking.”

“The study of letterlocking very consciously bridges humanities and sciences,” says Dambrogio, who first became interested in the practice as a fellow in the conservation studio of the Vatican Apostolic Archives, where she discovered examples from the 15th and 16th centuries. “It draws on the perspectives of not only conservators and historians, but also engineers, imaging experts, and scientists.”

Now the rich history of this centuries-old document security technology is the subject of a new book, “Letterlocking: The Hidden History of the Letter,” published by the MIT Press and co-authored with Daniel Starza Smith, a lecturer in early modern English literature at King’s College London. Dambrogio and Smith have pioneered the field of letterlocking research over the last 10 years, working with an international and interdisciplinary collection of experts, the Unlocking History Research Group.

With more than 300 images and diagrams, “Letterlocking” explores the practice’s history through real examples from all over the world. It includes a dictionary of 60 technical terms and concepts, systems the authors developed while studying more than 250,000 historic letters. The book aims to be a springboard for new discoveries, whether providing a new lens on history or spurring technological advancements.

In working with the Brienne Collection — a 17th-century postal trunk full of undelivered letters — the Unlocking History Research Group sought to study intact examples of locked letters without destroying them in the process. This stimulated advances in conservation, radiology, and computational algorithms. In 2020, the team collaborated with researchers from the MIT Computer Science and Artificial Intelligence Laboratory (CSAIL), Amanda Ghassaei SM ’17, and Holly Jackson ’22, to develop new algorithms that could virtually read an unopened letter, publishing the results in Nature Communications in 2021.

“Letterlocking” also offers a comprehensive guide to making one’s own locked letters. “The best introduction to letterlocking is to make some models,” says Dambrogio. “Feel the shape and the weight; see how easy it would be to conceal or hard to open without being noticed. We’re inviting people to explore and expand this new field of study through ‘mind and hand.’”

This is a sad story of someone who downloaded a Trojaned AI tool that resulted in hackers taking over his computer and, ultimately, costing him his job.

A document obtained by POLITICO's E&E News lists terminated contracts, including those that support enhanced energy security in Ukraine and reducing deforestation.

Court documents indicate the administration has begun a campaign to block states from receiving funds for projects that would reduce climate-related damage.

The move marks growing concern among states over being frozen out of federal funding for energy efficiency programs.

The Environmental Defense Fund is pushing the Trump administration to reveal its thinking on an effort to undo the influential climate finding.

Lawmakers want to avoid big rate hikes if power companies must pay for wildfire damage. Utilities could charge customers for wildfire mitigation.

The GOP lawmakers want to kill a Biden-era emissions rule on coal- and gas-fired plants.

The Arbor Day Fund's grant came from the Inflation Reduction Act, which provided $1.5 billion to the Forest Service's Urban and Community Forestry Program.

Discovered more than a century ago in South Sudan, excelsa coffee is exciting cash-strapped locals and drawing interest from the international community.

The Fire and Disaster Management Agency said at least 84 homes have been damaged and over 1,200 people evacuated.

The search for five remaining missing workers is continuing, with multiple teams of rescuers and military helicopters scanning the incident site.

Nature Climate Change, Published online: 04 March 2025; doi:10.1038/s41558-025-02253-w

Species are shifting their distributions in response to climate change, which on land depends on routes connecting intact habitat patches. Now, an analysis exploring the interaction between climate-driven shifts and human activities across ocean depths reveals threats for deep-sea biodiversity.

Nature Climate Change, Published online: 04 March 2025; doi:10.1038/s41558-025-02256-7

The authors demonstrate that warming will reduce connectivity for ocean species, potentially limiting their capacity to adapt to warming through habitat shifts. The results show particularly strong losses of connectivity in deeper ocean strata, affecting 95% of abyssopelagic species.