Publisher Health

While some people are concerned about America’s falling birth rate, a new study suggests young people don’t need to be convinced to have more children.
In fact, young Americans haven’t changed the number of children they intend to have in decades.
Women born in 1995-1999 wanted to have 2.1 children on average when they were 20-24 years old — essentially the same as the 2.2 children that women born in 1965-1969 wanted at the same age, the study found.
Still, the total fertility rate in the United States was 1.71 in 2019, the lowest level since the 1970s.
What’s going on?
The results suggest that today’s young adults may be having a more difficult time achieving their goals of having children, said Sarah Hayford, co-author of the study and professor of sociology at The Ohio State University.

The data in the study can’t explain why, but the results fit evidence indicating that young people today don’t think now is a good time for them to have children.
“It’s hard to have children in the United States right now,” said Hayford, who is also director of Ohio State’s Institute for Population Research.
“People feel more worried about the future than they might have been several decades ago. They worry about the economy, child care and whether they can afford to have children.”
Hayford conducted the study with Karen Benjamin Guzzo, professor of sociology at the University of North Carolina at Chapel Hill and director of the Carolina Population Center. Their results were published online Jan. 10, 2023 in the journal Population and Development Review.
The researchers used data from the National Survey of Family Growth, which has been asking people about their childbearing goals and behaviors for several decades.

The NSFG doesn’t interview the same people each time, but it allowed the researchers to track a group of people born around the same time — a cohort, as scientists call these groups — as they passed through their childbearing years.
They looked at 13 cohorts of women and 10 cohorts of men born between the 1960s and the 2000s. They were all asked how many children they intended to have, if any.
“Americans have been pretty consistent with how many children they say they want to have from the 60s to the 2000s,” Hayford said. “Men generally say they want slightly fewer children than women do, but, like women, their preferred number of children hasn’t changed much.”
The percentage of people who said they don’t plan to have any children has increased, from about 5-8% in the 1960s and 1970s to 8-16% in the 1990s and 2000s. But that alone can’t explain the decline in the number of babies being born.
Hayford noted that the number of unintended births, especially among people in their 20s, has declined in recent decades, which has helped reduce the birth rate.
“But that doesn’t change the fact that people aren’t having as many children as they say they want, especially at earlier ages,” Hayford said.
“It may be that they’re going to have those kids when they’re 35, but maybe they won’t.”
For example, the study found some evidence that people are reducing the number of children they say they intend to have as they get older.
“As they age, they may be realizing how hard it is to have kids and raise kids in the United States and they’re saying they only want to have the one child, and don’t want a second one,” she said.
In addition, would-be parents may have more difficult conceiving as they get older.
Larger economic and social forces are also having an impact on birth rates.
The birth rate declined significantly during the Great Recession that started in 2008, which is a typical response to an economic downturn. However, the birth rate continued to decline even after the recession was over, Hayford said.
This study ended before COVID-19, but the pandemic served as another fertility shock, at least at first.
“It remains to be seen whether fertility will be able to rebound not just from the Great Recession, but from the pandemic as well,” she said.
For those who are concerned about America’s dropping birth rates, this study suggests that there is no need to pressure young people into wanting more kids, Hayford said.
“We need to make it easier for people to have the children that they want to have,” she said. “There are clear barriers to having children in the United States that revolve around economics, around child care, around health insurance.”
The research was supported by grants from the Eunice Kennedy Shriver National Institute of Child Health and Human Development.

People don’t always behave impeccably in relationship to others. When we notice that this has inadvertently caused harm, we often feel guilty. This is an uncomfortable feeling and motivates us to take remedial action, such as apologizing or owning up.
This is why guilt is considered an important moral emotion, as long as it is adaptive — in other words, appropriate and in proportion to the situation. “It can improve interpersonal relationships and is therefore valuable for social cohesion,” says Dilan Sezer, researcher at the Division of Clinical Psychology and Psychotherapy at the University of Basel.
Whether feelings of guilt can be reduced by taking placebos is something that researchers at the Faculty of Psychology at the University of Basel have been exploring. Their findings have now been published in the journal Scientific Reports.
Open-label placebos work
In order to arouse feelings of guilt, test subjects in the study were asked to write about a time when they had disregarded important rules of conduct, or treated someone close to them unfairly, hurt or even harmed them. The idea was that the study participants should still feel bad about the chosen situation.
Participants were then randomized to three conditions: Participants in one group were given placebo pills with being deceptively told that this was a real medication while participants in another group were told that they are given a placebo. Both groups were told that what they had been given will be effective against feelings of guilt. The control group was given no treatment at all. The results showed that feelings of guilt were significantly reduced in both placebo groups compared with those without medication.
This was also the case when the subjects knew they had been given a placebo. “Our study therefore supports the intriguing finding that placebos work even when they are administered openly, and that explanation of the treatment is key to its effectiveness,” states the study’s lead author, Dilan Sezer. Participants in this study were all healthy, had no psychiatric disorders and were not being treated with psychotropics.
Clinical applicability not yet proven
Where feelings of guilt are irrational and continue for longer periods of time, they are considered maladaptive — in other words, disproportionate. These emotions can affect people’s health and are also, among other things, a common symptom of depression.
Scientific studies have shown that placebo effects can be powerful in treating depression. But the finding that open-label placebos can also be useful for such strong emotions as guilt is new. It stands to reason, says Dilan Sezer, that we should try to harness these effects to help those affected. “The administering of open-label placebos, in particular, is a promising approach, as it preserves patient autonomy by allowing patients to be fully aware of how the intervention works.” The results of the study are an initial promising step in the direction of symptom-specific and more ethical treatments for psychological complaints using open-label placebos, Sezer continues.
Further research will need to be done into whether it is possible to treat maladaptive guilt with placebos. And it is still not known whether similar effects are also possible with other feeling states. For Dilan Sezer, one thing is certain: “Using open-label placebos would be an inexpensive and straightforward treatment option for many psychological and physical complaints.”

Six minutes of high-intensity exercise could extend the lifespan of a healthy brain and delay the onset of neurodegenerative disorders, such as Alzheimer’s disease and Parkinson’s disease. New research published in The Journal of Physiology shows that a short but intense bout of cycling increases the production of a specialised protein that is essential for brain formation, learning and memory, and could protect the brain from age-related cognitive decline. This insight on exercise is part of the drive to develop accessible, equitable and affordable non-pharmacological approaches that anyone can adopt to promote healthy ageing.  
The specialised protein named brain-derived neurotrophic factor (BDNF) promotes neuroplasticity (the ability of the brain to form new connections and pathways) and the survival of neurons. Animal studies have shown that increasing the availability of BDNF encourages the formation and storage of memories, enhances learning and overall boosts cognitive performance. These key roles and its apparent neuroprotective qualities have led to the interest in BDNF for ageing research.
Lead author Travis Gibbons from University of Otago, New Zealand said: “BDNF has shown great promise in animal models, but pharmaceutical interventions have thus far failed to safely harness the protective power of BDNF in humans. We saw the need to explore non-pharmacological approaches that can preserve the brain’s capacity which humans can use to naturally increase BDNF to help with healthy ageing.”
To tease apart the influence of fasting and exercise on BDNF production the researchers, from the University of Otago, New Zealand, compared the following factors to study the isolated and interactive effects: Fasting for 20 hours, Light exercise (90-minute low intensity cycling), High-intensity exercise (six-minute bout of vigorous cycling), Combined fasting and exercise.They found that brief but vigorous exercise was the most efficient way to increase BDNF compared to one day of fasting with or without a lengthy session of light exercise. BDNF increased by four to five-fold (396 pg L-1 to 1170 pg L-1) more compared to fasting (no change in BDNF concentration) or prolonged activity (slight increase in BDNF concentration, 336 pg L-1 to 390 pg L-1).
The cause for these differences is not yet known and more research is needed to understand the mechanisms involved. One hypothesis is related to the cerebral substrate switch and glucose metabolism, the brain’s primary fuel source. The cerebral substrate switch is when the brain switches its favoured fuel source for another to ensure the body’s energy demands are met, for example metabolising lactate rather than glucose during exercise. The brain’s transition from consuming glucose to lactate initiates pathways that result in elevated levels of BDNF in the blood.
The observed increase in BDNF during exercise could be due to the increased number of platelets (the smallest blood cell) which store large amounts of BDNF. The concentration of platelets circulating in the blood is more heavily influenced by exercise than fasting and increases by 20%.
12 physically active participants (six males, six females aged between 18 and 56 years) took part in the study. The balanced ratio of male and female participants was to provide a better representation of the population rather than indicate sex differences.
Further research is underway to delve deeper into the effects of calorie restriction and exercise to distinguish the influence on BDNF and the cognitive benefits.
Travis Gibbons said: “We are now studying how fasting for longer durations, for example up to three days, influences BDNF. We are curious whether exercising hard at the start of a fast accelerates the beneficial effects of fasting. Fasting and exercise are rarely studied together. We think fasting and exercise can be used in conjunction to optimise BDNF production in the human brain.”

Irritable bowel syndrome (IBS) is a difficult disease to treat, characterized by chronic abdominal pain related to bowel movements, of which there are four types: diarrheal, constipation, mixed, and unclassifiable. Patients with IBS report a reduction in quality of life and experiences of social discomfort, as they are forced to restrict their activity, such as work or travel, because of the sudden and unpredictable need to use the bathroom. While there have been studies of IBS-related abnormalities in the autonomic nervous system based on 24-hour electrocardiogram measurement, until now none of them examined changes in the autonomic nervous system during bowel movements.

Associate Professor Fumio Tanaka and his research group at the Osaka Metropolitan University Graduate School of Medicine recorded the autonomic nervous system activity of IBS patients and healthy subjects using a wearable device and tracked activities such as defecation and sleep. As a result, they found that unlike healthy subjects, the sympathetic nervous system of IBS patients was activated 2 minutes before defecation and persisted until 9 minutes after defecation. Furthermore, the activation of the sympathetic nervous system was found to be associated with greater abdominal pain and lower quality of life. The research results were published online in PLOS ONE on December 9, 2022.
“This research is characterized by the fact that autonomic nervous system functions are measured using a clothing-type wearable device, and that lifestyle events such as defecation and abdominal symptoms are input simultaneously in real time, using a smartphone application originally developed by our group. As a result, autonomic nervous system activity during defecation was accurately evaluated. We hope that further research will improve the quality of life of IBS patients and help elucidate the pathophysiology,” Professor Tanaka concluded.

Ambulance bosses have apologised to the family of a man who died after he had a heart attack but no ambulance came.Martin Clark, 68, started suffering with chest pains at his home in East Sussex on 18 November – before any strike action started in the NHS.His family rang three times for an ambulance and after waiting 45 minutes drove him in their car to hospital.He died after arriving at hospital.Average waiting times in England for category 2 999 calls in November, when Martin died, were the worst since records began.Read more on this story.

An M.R.I. ruled out the most common cause of sciatica. Then her rheumatologist asked about her asthma.The 56-year-old woman eased herself into her desk chair. Sitting was wildly uncomfortable these days. She clicked on the link to her Facebook page and began her post: “I’ve been struggling mightily for the past few weeks with sciatica, which is excruciating leg pain caused by a pinched or irritated nerve.” It hurt to stand; it hurt even more to sit — the weight of her body was torture on her thighs. The only times she was mostly pain free were when she was lying down and when she was walking. She was a journalist, and for the past several weeks she had to do all her reporting and writing from her couch. She’d seen her doctor, who gave her a muscle relaxer, and her chiropractor, who adjusted her back. Neither provided any relief. The patient had been healthy her entire life. Then at 50 she wrestled with an ugly bout of colon cancer. She recovered completely with lots of help from surgery and chemotherapy. Four years later, she developed severe asthma out of the blue. A thoughtful pulmonologist helped her get that under control, but she hadn’t felt well since. It was as if she had crossed some threshold. She got these strange bouts of aches and pains, occasional numbness and weakness that lasted for days. Lymph nodes blew up to a painful size, then disappeared. Now this terrible leg pain. Strangely, her back didn’t hurt at all, but her legs, especially the left, were killing her. It was her husband who gave her pain a name — sciatica. But he didn’t know how to fix it. Finally, she decided to ask the crowd — or at least her crowd of Facebook friends. “Any suggestions out there from people who have gone through this?” Within hours she got more than 60 responses. Most offered sympathy, heartfelt and welcome but not helpful. Finally, a Facebook friend who was married to a physical therapist messaged her: See my husband. He can tell you right away if you need an M.R.I. or if P.T. is likely to be enough. Nothing on the M.R.I.She saw her friend’s husband, who gave her some exercises and told her that if they helped, great, but if they didn’t, she probably needed an M.R.I. She was religiously adherent to the prescribed regimen, but the pain persisted. The sciatic nerve is the largest nerve in the body, and the irritation of that nerve that causes the pain better known as sciatica is usually a result of pressure from the bony spinal column. Those points can often be seen on an M.R.I. But not, as it turned out, on her M.R.I. And that was why, three days later, she made her way to the office of Dr. Dustin Nowacek, a neurologist at Bronson Methodist Hospital in Kalamazoo, Mich. The patient detailed her weeks of pain and weakness. Reclining was OK; walking was mostly painless, though she tired out much too quickly. But just about anything else — especially sitting or standing still — was excruciating. Nowacek noted that the patient limped as she moved from the chair to the examination table. On exam, her left foot was clearly weaker than the right. Indeed, she was unable to keep her left foot pointed up when he applied any downward pressure. And on the right, the foot was strong, but her big toe was not. She couldn’t keep it pointed up when he pressed on it with his thumb. When the doctor tapped the Achilles’ tendon on her right leg, the foot twitched in the expected response. But on the left side, nothing: no reflex movement at all. She was a little alarmed when the doctor pulled out a safety pin and explained that he was going to poke her with it to check her ability to feel pain. Oh, she could feel pain, she assured him. And she could feel the sharp tip of the point everywhere — until he pricked the top of her left foot. There she felt nothing. This kind of nerve injury, which affects both the ability to feel and the ability to move, can have many causes. It was patchy rather than symmetrical, which narrowed the possibilities. Could it be caused by her cancer, back after six years? It seemed unlikely. Thyroid disease was possible, but her symptoms didn’t really fit. This was more likely to be some type of infection: Lyme disease, or H.I.V. or hepatitis. Autoimmune diseases could do this as well. Nowacek sent off a slew of blood tests to look for all of these.Photo illustration by Ina JangThe results trickled in. Her thyroid was normal. It wasn’t H.I.V. or Lyme disease, or any of the usual types of hepatitis. Indeed, the only abnormalities were those suggestive of some kind of autoimmune disease. He had no idea which, so he referred her to a rheumatologist in his practice, Dr. Lakshmi Kocharla. As her physician assistant interviewed the patient, Kocharla carefully reviewed her records and test results. This kind of neuropathy was not uncommon in autoimmune disorders. Sjogren’s syndrome and lupus were probably the most common, but there were others. She would have to keep an open mind and look for other symptoms that might narrow the field. These kinds of mysteries were one of the great pleasures of working in rheumatology. The P.A. summarized her findings, and Kocharla entered the exam room and introduced herself to the middle-aged woman and her husband. She’d heard about the painful legs, Kocharla began, but what else has been going on? So much! She had aches and pains everywhere, and she’d lost more than 20 pounds over the past few months. Maybe the pain had stolen her appetite, but she hadn’t really felt well since she developed asthma two years earlier. That seemed to get the rheumatologist’s attention — which surprised the patient. She had told many doctors about her out-of-the-blue asthma, but none seemed to think it was important. Until now. A New List of Symptoms“Hang on a second,” Kocharla said, after hearing this part of the story. She turned to her laptop computer and typed something in it. Then she passed it to the patient. “Do any of these symptoms seem familiar?” she asked. The patient looked through the list. Fatigue: Sure, but who isn’t tired? Weight loss: check. Swollen lymph nodes: check. Muscle pain: check.And she had the asthma and the numbness and weakness in her left foot and right big toe. “I think you have something called eosinophilic granulomatosis with polyangiitis,” Kocharla said. E.G.P.A. was formerly called Churg-Strauss syndrome for the two physicians, Jacob Churg and Lotte Strauss, who first described the condition in 1951. The disease is linked to an elevated level of white blood cells called eosinophils — the cells that respond in allergic reactions. Somehow these cells become involved in the destruction of small blood vessels all over the body. That’s what causes the numbness and the loss of strength and reflexes. These cells can lead an attack on blood vessels anywhere in the body. It is not clear what triggers this disorder, but it is a destructive, sometimes deadly, disease.Kocharla checked the patient’s blood count. Indeed, her eosinophil count was quite high — eight times the level normally seen. The rheumatologist had never seen this disease in a patient before but had certainly learned about it in her fellowship. It would take a biopsy to confirm the diagnosis, but doing that could permanently damage the already-injured nerve. This patient fit nearly all the diagnostic criteria. She started the patient on a high dose of prednisone to weaken the white-cell-led attack. But because she had never seen a patient with E.G.P.A., she wanted the diagnosis confirmed by someone with more experience: She sent the patient to the Mayo Clinic in Rochester, Minn., to get a second opinion. Even before the patient saw the doctors at Mayo, she had no doubt that Kocharla had been right. After just a week on the steroids she felt great. The pain was gone. She could sit and stand. The level of eosinophils dropped to normal. She could go back to work. The rheumatologist at Mayo had seen many cases of E.G.P.A. before and agreed with Kocharla’s diagnosis. They started her on a second immune-suppressing medication. Following her instincts as a reporter, the patient began to read up on the disease. One article suggested that walking can help control this and other autoimmune diseases, so the patient started taking walks. She averages six to seven miles a day. It has allowed her doctors to lower her medication doses, and she says that even though she is sick — in a very real way sicker than she has ever been — she has never felt healthier.Lisa Sanders, M.D., is a contributing writer for the magazine. Her latest book is “Diagnosis: Solving the Most Baffling Medical Mysteries.” If you have a solved case to share, write her at Lisa.Sandersmdnyt@gmail.com.

Over the course of the long and brutal N.F.L. season, players’ feet and hands take a beating on nearly every […]

Combing computational physics with experimental data, University of Arkansas researchers have developed computer models for determining a drug candidate’s ability to target and bind to proteins within cells.
If accurate, such an estimator could computationally demonstrate binding affinity and thus prevent experimental researchers from needing to investigate millions of chemical compounds. The work could substantially reduce the cost and time associated with developing new drugs.
“We developed a theoretical framework for estimating ligand-protein binding,” said Mahmoud Moradi, associate professor of chemistry and biochemistry in the Fulbright College of Arts and Sciences. “The proposed method assigns an effective energy to the ligand at every grid point in a coordinate system, which has its origin at the most likely location of the ligand when it is in its bound state.”
A ligand is a substance — an ion or molecule — such as a drug that binds to another molecule, such as a protein, to form a complex system that may cause or prevent a biological function.
Moradi’s research focuses on computational simulations of diseases, including coronavirus. For this project, he collaborated with Suresh Thallapuranam, professor of biochemistry and the Cooper Chair of Bioinformatics Research.
Moradi and Thallapuranam used biased simulations — as well as non-parametric re-weighting techniques to account for the bias — to create a binding estimator that was computationally efficient and accurate. They then used a mathematically robust technique called orientation quaternion formalism to further describe the ligand’s conformational changes as it bound to targeted proteins.
The researchers tested this approach by estimating the binding affinity between human fibroblast growth factor 1 — a specific signaling protein — and heparin hexasaccharide 5, a popular medication.
The project was conceived because Moradi and Thallapuranam were studying human fibroblast growth factor 1 protein and its mutants in the absence and presence of heparin. They found strong qualitative agreement between simulations and experimental results.
“When it came to binding affinity, we knew that the typical methods we had at our disposal would not work for such a difficult problem,” Moradi said. “This is why we decided to develop a new method. We had a joyous moment when the experimental and computational data were compared with each other, and the two numbers matched almost perfectly.”
The researchers’ work was published in Nature Computational Science.
Moradi previously received attention for developing computational simulations of the behavior of SARS-CoV-2 spike proteins prior to fusion with human cell receptors. SARS-CoV-2 is the virus that causes COVID-19.

Water clarity is key to the health and restoration of marine plants and animals worldwide, particularly in shallow coastal systems such as the Chesapeake Bay. But it turns out that measuring water clarity isn’t as clear-cut as it might appear.
Research at the Virginia Institute of Marine Science led by Dr. Jessie Turner reveals that the “clarity” of a water parcel depends on the method used to measure it, and that different research questions and management decisions merit different clarity-measuring tools and techniques. Turner and her co-authors, Drs. Kelsey Fall and Carl Friedrichs, lay out their recommendations in a recent article in Limnology and Oceanography Letters.
“In coastal and inland waters,” says Turner, “the methods we use to gauge water clarity can misrepresent the underwater light climate used to determine restoration goals, such as the potential habitat available for underwater grasses. It’s thus really important to choose the most appropriate measurement method, and to clearly communicate the method used. Not all water-clarity metrics are created equal.”
Underwater grasses serve many key ecological functions and are among the most closely monitored habitats in the Bay. They provide food and shelter for numerous marine species, help oxygenate the water, and can mitigate global warming by removing carbon dioxide from the air. To do so, they need clear water for photosynthesis and growth. Their dependence on clear water makes them a “canary in the coal mine” for water clarity in shallow coastal systems.
Turner (VIMS Ph.D. ’21) is currently a postdoctoral research associate at the University of Connecticut. Fall (VIMS Ph.D. ’20) is now at the U.S. Army Engineer Research and Development Center in Vicksburg, Mississippi. Friedrichs is Glucksman Professor in William & Mary’s School of Marine Science at VIMS and Associate Director of the Chesapeake Bay National Estuarine Research Reserve in Virginia.
Water and beer
To explain the complexities of water clarity and its measurement, Turner turns to an analogy with beer — another liquid whose “clarity” is of widespread interest. Ironically, the scientific principle used to define the clarity of beer and other liquids is known as Beer’s Law (ironic as the principle was first applied to wine, not beer, and doubly so as the law is named after German chemist August Beer, not the hoppy beverage).

“Beer’s Law tells us that how much light gets through a liquid depends on the concentration of stuff in the liquid and the distance over which you’re measuring,” says Turner.
What’s the “stuff?” “In beer,” she says, “it’s either particles like yeast and hops, or dissolved things like sugar or tannins from the brewing process. In Chesapeake Bay, the “stuff” can be particles such as tiny pieces of dirt and microscopic plants, or dissolved organic matter and other solutes.” Dissolved organic matter is an earthy tea steeped from leaf litter, crop residue, soil, and other carbon-based materials from the Bay and its watershed.
Crucially, particulate matter and dissolved substances impede light in different ways. “When light hits water or beer it can either get scattered, or it can get absorbed,” says Turner. “Particles scatter light, dissolved substances absorb light.”
The relative abundances of particulate and dissolved materials combine to produce different light environments. In areas of Chesapeake Bay with high levels of both light-scattering particles and light-absorbing solutes, the water is dark like a stout. In areas with lots of light-scattering particles but few light-absorbing solutes, the water is cloudy yet bright, like a hazy ale. Areas with few particles or solutes are clearest, like a cider.
Secchi disks & light sensors
These differences have important ramifications when considered in light of the multiple tools and techniques scientists use to measure water clarity. Two common optical tools are Secchi disks and light sensors. Scientists also directly measure the concentration of suspended particles, dissolved materials, and chlorophyll (the pigment that plants and plankton use to capture sunlight for photosynthesis).

“A Secchi disc is a simple black-and-white disc that you lower horizontally through the water,” explains Turner. “The depth at which it disappears from view is known as the Secchi depth.” This cheap, easy-to-deploy, and long-used tool measures water transparency and the depth of object visibility.
Light sensors measure the loss or attenuation of sunlight as it penetrates deeper into the water, with a focus on the wavelengths plants use for photosynthesis. Recorded values are compared to those collected by a surface sensor to account for differences in incoming light due to clouds and time of day.
Though advances in electronics and materials have reduced the cost and increased the use of light sensors, Secchi discs remain the everyday workhorse of many water-clarity studies, both by professional researchers and a growing cadre of community scientists.
Problems arise, according to Turner and her co-authors, when practitioners apply a traditional one-size-fits-all equation to estimate light attenuation from Secchi depth values. That’s because the relationship between these two metrics can vary greatly depending on the local light climate — whether an underwater study site is dark like a stout, bright yet cloudy like an ale, or clear like a cider.
“The relationship between these two metrics can vary widely between and within estuaries and other aquatic environments based on latitude, hydrology, and climate,” says Turner. “Using a single conversion factor to estimate light attenuation based on Secchi depth can thus either under- or overestimate the underwater light climate.”
For example, in the turbid waters of the York River, a major Chesapeake Bay tributary, use of the traditional conversion factor would underestimate the light available for seagrasses, and thus short-sell potential restorations targets.
Recommendations
To counter this and related difficulties, Turner and colleagues recommend several changes in how water clarity is measured and reported. Most important is to clearly communicate the method used — whether a Secchi depth from a Secchi disk, light attenuation, or another method.
For studies related to underwater grasses and other light-loving organisms, the authors advise colleagues to collect light-attenuation values directly.
“Measures of light attenuation with depth are most relevant for most research in aquatic ecosystems,” says Turner. “They are well-suited to research involving underwater grasses, kelp, and corals, as these and other similar organisms are adapted to harvest downwelling light.” The authors recommend use of a separate, “scalar” measure of light attenuation when studying phytoplankton, which as floating organisms can harvest light from all directions, both downwelling and scattered from the side and below.
If cost concerns or other factors encourage use of Secchi discs, the authors advise researchers to forgo use of the traditional one-size-fits-all equation, recommending instead they calibrate the Secchi-depth to light-attenuation formula using localized measures. “The equation needs to be locally calibrated because the characteristics of the water’s dissolved and particulate matter vary greatly, sometimes over very short distances,” says Turner. “These characteristics can also vary seasonally.”
Because Secchi depth values measure visibility and transparency, the authors say their direct application is most appropriate for studies of fish and other visual predators. They note they are also of value in a human context, in areas such as in-water recreation and the value of coastal property and viewscapes.
Whatever methods a research team might use, the authors urge them to select the most useful metric or metrics according to the specific research question or management goal.
“When relevant to the goal,” says Turner, “even the simplest water clarity measurements are valuable for environmental monitoring and restoration, whether collected by scientific sampling programs, non-profit organizations, or community scientists.”

Published9 hours agoShareclose panelShare pageCopy linkAbout sharingImage source, Getty ImagesBy Sam CabralBBC News, WashingtonUS First Lady Jill Biden has undergone surgery to remove two cancerous skin lesions, the president’s doctor has said.Both were consistent with basal cell carcinoma, the most common form of skin cancer, Dr Kevin O’Connor wrote in a memo on Wednesday.All cancerous tissue was fully removed from the lesions in a procedure known as Mohs surgery, it said.Mrs Biden is “in good spirits and is feeling well”, Dr O’Connor said.Following a routine skin cancer screening earlier this month, doctors recommended that a small lesion above Mrs Biden’s right eye should be excised out of “an abundance of caution”.The Wednesday morning procedure confirmed the lesion was basal cell carcinoma (BCC).Diagnosed in 3.6 million Americans every year, it is the the most frequently occurring form of all cancers, according to the Skin Cancer Foundation. BCCs are slow-growing, curable and cause minimal damage if treated early.A second lesion, on the first lady’s left eyelid, and a third lesion, on the left side of her chest, were also excised. The latter had an appearance consistent with potential BCC.Mohs surgery involves surgeons cutting away and analysing thin layers of skin until no signs of cancer are found. Patients are typically discharged on the same day.Mrs Biden is said to be experiencing some facial swelling and bruising, but is expected back at the White House later on Wednesday.President Joe Biden accompanied his wife to the Walter Reed National Military Medical Center in Maryland, some 15 miles from the White House, for the procedure, which came hours after their return to Washington from a trilateral summit in Mexico City.Mr Biden has had several non-melanoma skin cancers removed with Mohs surgery in the past, before he became president. In a 2021 summary of his health, Dr O’Connor wrote that the president’s lesions had been excised and “there are no areas suspicious for skin cancer at this time”.