Unlocking the secrets of cell antennas

 The non-specific lethal (NSL) complex is a chromatin-associated factor that has been shown to regulate the expression of thousands of genes in both fruit flies and mammals. Abrogation of the NSL genes leads to the death of the organism, and this phenotype gives rise to this complex's curious name. Max Planck researchers have now identified the NSL complex as a "master" epigenetic regulator of intraciliary transport genes across multiple cell types and species. The study reveals that this class of genes is "turned on" by the NSL complex irrespective of whether a particular cell has cilia or not. Additionally, the researchers uncovered that this class of cilia-associated genes is in fact vitally important for the function of kidney podocytes, a highly specialized cell type that paradoxically does not carry cilia. These findings have important implications for ciliopathies and kidney disease.

Cilia are thin, eyelash-like extensions on the surface of cells. They perform a wide variety of functions, acting as mechanosensors or chemosensors, and play a crucial role in many signaling pathways. In the last few decades, the organelle has undergone a remarkable, but at the same time sinister, career transformation. It evolved from an organelle whose relevance was unclear to becoming a central player in the pathogenesis of a large group of diseases. These so-called ciliopathies are associated with a wide range of symptoms, including hearing loss, visual impairment, obesity, kidney disease, and mental disability. Different gene mutations impair cilia formation, maintenance, and function, resulting in these ciliopathies, which can sometimes be multi-organ, syndromic disorders.

The proper assembly, maintenance, and function of cilia rely on a process called "intraciliary transport." Components of the intraciliary transport system "walk" on the microtubule to deliver cargo between the cell body and the ciliary tip to ensure a constant supply of materials. Mutation of genes encoding components within the intraciliary transport machinery could lead to ciliopathies. In their recent study in the journal Science Advances, the lab of Asifa Akhtar identified the NSL complex as a transcriptional regulator of genes known for their roles in the intraciliary transport system of cilia across multiple cell types.

The NSL complex enables intraciliary transport

The NSL complex is a potent epigenetic modifier that regulates thousands of genes in fruit flies, mice, and humans. However, most of the functions of the NSL complex remain mysterious and have only recently begun to be elucidated. "Previous research from our lab indicates that the NSL complex controls many pathways critical for organismal development and cellular homeostasis," says Asifa Akhtar, Director at the MPI of Immunobiology and Epigenetics in Freiburg.

The complex comprises several proteins and is a histone acetyltransferase (HAT) complex that prepares the genes for activation. "Think of gene regulation as a team effort with different players. One important player is the NSL complex. It puts special marks on the histone proteins on which the DNA is wrapped around in the nucleus, like putting up green flags. These flags tell other regulators to switch on specific genes. We now found that the NSL complex does exactly this for a group of genes linked to moving materials within cilia," says Tsz Hong Tsang, the first author of the study.

Without components of the NSL complex, the cell cannot build a cilium

The intraciliary transport system is essential because it is needed to build a functional cilium. The cell uses the intraciliary transport system to move material from the cilium base to the growing tip -- similar to building a tower. In the study, the researchers used mouse cells to determine the functional consequences of the loss of the NSL complex in the cells.

They found that fibroblast cells lacking the NSL complex protein KANSL2 could not activate the transport genes nor assemble cilia. "As cilia are the sensory and signaling hubs for cells, loss of KANSL2 leads to the inability of cells to activate the sonic hedgehog signaling pathway, which plays important roles in the regulation of embryonic development, cell differentiation, and maintenance of adult tissues as well as cancer," says Asifa Akhtar.

Although tiny protrusions, these sensory organelles are incredibly important to cells. Ciliopathies, which affect organs as diverse as the kidney, liver, eye, ear, and central nervous system, remain challenging for biological and clinical studies. The researchers at the Max Planck Institute in Freiburg hope that their analysis of the role of the NSL complex has provided important insights into the regulation of these organelles and the genes associated with them, thus contributing to human health.

Consequences of NSL loss in non-ciliated cells

Cilia are found in most cell types in the human body. This explains why ciliopathies can affect so many different organs and tissues, but there are also cells that are not ciliated. One of the cell types that do not have cilia is mature glomerular podocytes, which are special filtration cells in the kidney. "Interestingly, we found that podocytes also express these intraciliary transport genes that are regulated by the NSL complex. So, we wondered what would happen if they are unable to switch on these genes," says Tsz Hong Tsang.

The researchers found that in non-ciliated mouse podocytes, the loss of KANSL2 leads to changes in microtubule dynamics in the cells. Microtubules are cytoskeletal components responsible for the mechanical stabilization of the cell and intracellular transport between different organelles. While lacking cilia, mature podocytes have specialized cell processes extending from the cell body called primary and secondary processes, whose functions rely heavily on cytoskeletal components. Although apparently milder than the defect in ciliated cells, the Akhtar lab found that the cytoskeletal defects are likely the cause of severe glomerulopathy and kidney failure observed in mice lacking the NSL complex. These and other extraciliary functions of intraciliary transport genes may help explain the complexity of symptoms presented by ciliopathies.

Scientists solve mystery of why thousands of octopus migrate to deep-sea thermal springs

 In 2018, researchers from NOAA's Monterey Bay National Marine Sanctuary and Nautilus Live observed thousands of octopus nesting on the deep seafloor off the Central California coast. The discovery of the "Octopus Garden" captured the curiosity of millions of people around the world, including MBARI scientists. For three years, MBARI and collaborators used high-tech tools to monitor the Octopus Garden and learn exactly why this site is so attractive for deep-sea octopus.

In a new study published today in Science Advances, a team of researchers from MBARI, NOAA's Monterey Bay National Marine Sanctuary, Moss Landing Marine Laboratories, the University of Alaska Fairbanks, the University of New Hampshire, and the Field Museum confirmed that deep-sea octopus migrate to the Octopus Garden to mate and nest. The Octopus Garden is one of a handful of known deep-sea octopus nurseries. At this nursery, warmth from deep-sea thermal springs accelerates the development of octopus eggs. Scientists believe the shorter brooding period increases a hatchling octopus' odds for survival. The Octopus Garden is the largest known aggregation of octopus on the planet -- researchers counted more than 6,000 octopus in a portion of the site and expect there may be 20,000 or more at this nursery.

"Thanks to MBARI's advanced marine technology and our partnership with other local researchers, we were able to observe the Octopus Garden in tremendous detail, which helped us discover why so many deep-sea octopus gather there. These findings can help us understand and protect other unique deep-sea habitats from climate impacts and other threats," said MBARI Senior Scientist Jim Barry, lead author of the new study.

The Octopus Garden is located 3,200 meters (10,500 feet, or about two miles) below the ocean's surface on a small hill near the base of Davidson Seamount, an extinct underwater volcano 130 kilometers (80 miles) southwest of Monterey, California. The site is full of Muusoctopus robustus -- a species MBARI researchers nicknamed the pearl octopus because from a distance, nesting individuals look like opalescent pearls on the seafloor.

Over the course of 14 dives with MBARI's remotely operated vehicle (ROV) Doc Ricketts, the research team learned why such large numbers of pearl octopus are attracted to this location. The presence of adult male and female octopus, developing eggs, and octopus hatchlings indicated that the site is used exclusively for reproduction. The team did not observe any intermediate-sized individuals or any evidence of feeding. Pearl octopus gather at this site solely to mate and nest.

When researchers from NOAA and Nautilus Live first discovered the Octopus Garden, they observed "shimmering" waters. This phenomenon occurs when warm and cool waters mix, suggesting the region had previously unknown thermal springs. Further investigation by MBARI researchers and their collaborators confirmed octopus nests are clustered in crevices bathed by hydrothermal springs where warmer waters flow from the seafloor.

The ambient water temperature at 3,200 meters (10,500 feet) deep is 1.6 degrees Celsius (about 35 degrees Fahrenheit). However, the water temperature within the cracks and crevices at the Octopus Garden reaches nearly 11 degrees Celsius (about 51 degrees Fahrenheit).

advertisement

---

Octopuses are ectotherms, or cold-blooded animals. The frigid temperatures of the deep sea slow their metabolism as well as their rate of embryonic development. Most deep-sea octopuses have very long incubation periods compared to their relatives inhabiting warmer shallow seas. Past experiments have measured egg incubation time for a number of octopus species in habitats and locations around the world. Comparing those egg incubation times clearly demonstrates how temperature affects the rate of embryo development -- the colder the water, the slower the embryos grow.

At the near-freezing temperatures of the abyss, researchers expected pearl octopus eggs to take five to eight years, if not longer, to hatch. A 4K camera on MBARI's ROV Doc Ricketts provided a close-up look at nesting mothers. MBARI researchers and their collaborators used the scars and other distinguishing features of individual octopus moms to monitor the development of their broods. Surprisingly, the eggs hatched in less than two years. Warmth from thermal springs increased the metabolism of female octopus and their broods, reducing the time required for incubation.

Researchers believe the shorter brood period in warmer waters greatly reduces the risk that developing octopus embryos will be injured or eaten by predators. Nesting in warmer water boosts the reproductive success of the pearl octopus, better ensuring the offspring's survival.

"The deep sea is one of the most challenging environments on Earth, yet animals have evolved clever ways to cope with frigid temperatures, perpetual darkness, and extreme pressure. Very long brooding periods increase the likelihood that a mother's eggs won't survive. By nesting at hydrothermal springs, octopus moms give their offspring a leg up," said Barry.

The massive number of octopus in one area attracts both predators and scavengers. Like most other cephalopods, pearl octopus die after they reproduce. Dead octopus at the Octopus Garden provide a feast for scavengers. A rich community of invertebrates lives alongside the nesting females, undoubtedly benefiting from unhatched eggs, vulnerable hatchlings, or adult octopus that have died.

Davidson Seamount and its Octopus Garden are protected as part of Monterey Bay National Marine Sanctuary. Previous MBARI expeditions to Davidson Seamount in 2002 and 2006 revealed the stunning community of life on its rocky slopes. MBARI's images and video of beautiful deep-sea corals, vibrant sponges, and curious fishes engaged and inspired audiences worldwide. Ocean champions spoke up to protect this unique, and still untouched, ocean wilderness. In 2008, resource managers expanded the Monterey Bay National Marine Sanctuary to include Davidson Seamount.

advertisement

---

"Essential biological hotspots like this deep-sea nursery need to be protected," said Barry. "Climate change, fishing, and mining threaten the deep sea. Protecting the unique environments where deep-sea animals gather to feed or reproduce is critical, and MBARI's research is providing the information that resource managers need for decision-making."

This work is funded as part of the David and Lucile Packard Foundation's long-term support of MBARI's ocean research and technology.

Background

For more than two decades, researchers from MBARI and NOAA have collaborated to study Davidson Seamount. Since the first expedition to the seamount in 2002, NOAA has leveraged MBARI expertise in marine geology and benthic biology and ecology to develop a comprehensive research program that aims to understand the unique community of life on and around Davidson Seamount. Now, Davidson Seamount is considered one of the best-studied and well-protected seamounts in the world.

In October 2018, a team of researchers from NOAA, the Ocean Exploration Trust, and collaborators made an expedition to Davidson Seamount aboard the E/V Nautilus. At the suggestion of MBARI geologists and NOAA researchers, the Nautilus Live team decided to expand their exploration from the top of the seamount to its surrounding foothills. The researchers discovered thousands of octopus aggregated around a rocky ridge adjacent to the towering seamount.

Most of the octopus were oriented upside down, inverting their arms and folding them around their bodies. This posture was an indication of pearl octopus (Muusoctopus robustus) mothers protecting, or brooding, their eggs. The pearl octopus is a pale purple species about the size of a grapefruit that occurs in the northeastern Pacific Ocean from Oregon to Baja California. MBARI has observed this species at depths of 2,300 to 3,600 meters (7,500 to 11,800 feet).

MBARI researchers and their collaborators deployed a suite of advanced scientific instruments developed by MBARI engineers to better understand the Octopus Garden.

"The expertise of the MBARI team -- the engineers, pilots of our submersible vehicles, and crew of our research vessels -- was integral to studying this hotspot of life two miles below the surface. We leveraged decades of experience in deep-sea exploration to develop and deploy instruments to study the Octopus Garden without disturbing the nesting mothers," said Barry.

MBARI's ROV Doc Ricketts recorded high-definition and 4K video of the brooding pearl octopus and their neighbors. MBARI's skilled submersible pilots maneuvered the ROV close to brooding pearl octopus to deploy instruments to measure the environmental conditions within their nests, including temperature and oxygen levels, and to film mothers and their eggs up close in ultra-high definition resolution. A stereoscopic camera allowed MBARI engineers to visualize sites within the Octopus Garden in 3D. The team also launched one of MBARI's autonomous underwater vehicles to map the Octopus Garden at meter-scale resolution.

MBARI engineers outfitted the ROV Doc Ricketts with an innovative, custom-built sensor suite, the Low-Altitude Survey System (LASS), to see the Octopus Garden in even greater detail.

The LASS gathered detailed bathymetry information to help researchers characterize the seafloor habitat at centimeter-scale resolution. The LASS also took high-resolution photographs of the Octopus Garden. Researchers assembled these photographs into a photomosaic to count the number of nests within this deep-sea nursery. They documented 5,718 octopus within a 2.5-hectare (6.2-acre) area at the center of the Octopus Garden. The team estimated the total population of the 333-hectare (823-acre) hillock could easily exceed 20,000 individuals.

A time-lapse camera collected long-term observations of the octopus' behavior and changes in the community over a period of more than six months, allowing researchers to keep watch on the octopus nursery between research expeditions. The camera recorded an image every 20 minutes and amassed a trove of more than 12,200 images from March 2022 to August 2022. These photographs revealed various activities and behaviors of octopus, their predators, and local scavengers.

Both male and female pearl octopus migrate to the Octopus Garden. Females search for a warm nesting spot to deposit a clutch of approximately 60 elongate, sausage-shaped eggs. When brooding, mothers cover their eggs with their body and protect them from predators that creep too close. She lives off food reserves from her own tissues while tending to her developing eggs.

The transformation from egg to hatchling is not easy. In addition to going through development successfully, embryos must avoid injury, predation, infection, and other external sources of mortality. Maternal care protects them from most external risks, but a shorter brooding period generally allows more eggs to survive.

As is typical of cephalopods, male and female pearl octopus die after reproducing -- the Octopus Garden will be their final resting spot. Most females live until their eggs have hatched. Sometimes, however, a mother octopus runs out of energy and dies before her eggs complete their development, exposing the developing eggs to greater risk.

The time-lapse camera revealed that nesting mothers push aside the carcasses of dead octopus. Food is scarce in the deep sea and nothing goes to waste. Larger scavengers like rattail fishes (family Macrouridae), cusk eels (family Ophidiidae), whelks, and sea anemones feast on octopus remains. Near Davidson Seamount, life on the deep seafloor depends on the rain of organic matter from above. Researchers estimated the turnover of male octopus and nesting females to calculate how much nutrition this massive aggregation provides. Biomass from dying octopus represents a substantial carbon subsidy to the local seafloor community, providing 72 percent more food than is available outside the Octopus Garden.

Many questions still remain about the Octopus Garden, including where pearl octopus go after hatching, how this octopus species became adapted to breeding in thermal springs, how adult octopus find the thermal springs, what advantage individuals breeding in these hydrothermal springs have over those that breed elsewhere, and how common hydrothermal springs are in the deep sea.

The deep sea is not immune to threats like fishing, pollution, and climate change. By documenting deep-sea biodiversity and identifying hotspots of life on the ocean floor, scientists are gathering important information that resource managers can use to guide protections for this unique environment and its inhabitants.

"Technological advances in our ability to study the ocean have helped us discover and document incredible biodiversity across an array of deep-sea environments. As the imprint of human activities reaches deeper into ocean ecosystems, we need to protect not only the octopus nurseries found off California and Costa Rica, but also the many other biological treasures that remain undiscovered," emphasized Barry.

Deep-sea octopus nurseries: A new field of exploration

Researchers have documented four deep-sea octopus nurseries to date -- two off the coast of Central California and two off the coast of Costa Rica -- and are continuing to study these sites to learn more about octopus behavior.

December 2013: Discovery of first octopus nursery at Dorado Outcrop (Costa Rica) Researchers from the University of Akron, the Field Museum, and the University of Alaska Fairbanks observed an aggregation of more than 100 octopus at the Dorado Outcrop, a hydrothermal spring located approximately 160 kilometers (100 miles) off the Pacific coast of Costa Rica at a depth of 3,000 meters (9,800 feet). The team identified the octopus as a potentially undescribed species of Muusoctopus. Nearly all of the individuals were in a brooding position, however, none of the eggs that researchers observed were viable.

April 2018: Researchers publish findings from the Dorado Outcrop (Costa Rica) The team of researchers from the University of Akron, the Field Museum, and the University of Alaska Fairbanks published their observations of deep-sea octopus brooding unviable eggs at the Dorado Outcrop in Deep Sea Research Part I.

October 2018: Discovery of second octopus nursery at the Octopus Garden (Davidson Seamount, United States) During a Nautilus Live expedition with the E/V Nautilus, researchers from NOAA's Monterey Bay National Marine Sanctuary, the Ocean Exploration Trust, and collaborators observed a large aggregation of brooding octopus on a hillock approximately 12 kilometers (7.5 miles) southeast of Davidson Seamount at a depth of 3,200 meters (10,500 feet). Researchers identified the octopus as Muusoctopus robustus. A second visit by researchers from NOAA and the Woods Hole Oceanographic Institution (WHOI) in March 2019 confirmed the presence of warm hydrothermal springs at this site. The expedition team also confirmed that the octopus were brooding viable eggs and observed baby octopus hatching from the eggs.

April 2019: First MBARI expedition to Octopus Garden (Davidson Seamount, United States) MBARI researchers made their first visit to the Octopus Garden as part of the 2019 Seafloor Ecology expedition. Along with collaborators, they visited the site 14 times with the R/V Western Flyer between April 2019 and August 2022. Additionally, MBARI researchers visited the Octopus Garden with the R/V Rachel Carson in February 2022 to launch a mapping autonomous underwater vehicle and create meter-scale maps of the site.

October 2019: Discovery of third octopus nursery at Octocone (Davidson Seamount, United States) During a Nautilus Live expedition with the E/V Nautilus, researchers from NOAA, the Ocean Exploration Trust, and collaborators observed a second aggregation of brooding octopus on a volcanic cone to the east of Davidson Seamount. This site is approximately 17 kilometers (10.5 miles) northeast of the Octopus Garden. Researchers identified the octopus as Muusoctopus robustus. The octopus were confirmed to be brooding viable eggs.

June 2023: Discovery of fourth octopus nursery (Costa Rica) During a Schmidt Ocean Institute expedition with the R/V Falkor (too), researchers from the Bigelow Laboratory for Ocean Sciences and the University of Costa Rica observed a previously unknown octopus nursery near an unexplored and still-unnamed seamount off the Pacific coast of Costa Rica. Upon returning to the nearby Dorado Outcrop, the team also observed octopus brooding viable eggs, confirming this location is indeed an active octopus nursery. Both Costa Rican nurseries host a potentially undescribed species of Muusoctopus.

August 2023: MBARI researchers publish findings from the Octopus Garden (Davidson Seamount, United States) MBARI researchers and their collaborators from NOAA, Moss Landing Marine Laboratories, the University of Alaska Fairbanks, the University of New Hampshire, and the Field Museum published their research on brooding pearl octopus in Science Advances, confirming that deep-sea octopus migrate to the Octopus Garden to mate and nest.

Malaysian rock art found to depict elite -- Indigenous conflict

 A team of researchers led by the Griffith Centre for Social and Cultural Research in collaboration with The Sarawak Museum Department have become the first to date drawings of Gua Sireh Cave in Sarawak, uncovering a sad story of conflict in the process.

The limestone cave of Gua Sireh in western Sarawak (Malaysian Borneo) is famous for the hundreds of charcoal drawings lining the walls of its main chambers, attracting hundreds of visitors each year.

Approximately 55km southeast of Sarawak's Capital, Kuching, the site is managed by the Bidayuh (local Indigenous peoples) in collaboration with The Sarawak Museum Department, with the drawings depicting Indigenous resistance to frontier violence in the 1600s and 1800s AD.

Radiocarbon ages for the drawings date them between 280 and 120 cal BP (AD 1670 to 1830), corresponding with a period of increasing conflict in the region when the Malay elites controlling the region exacted heavy tolls on Indigenous hill tribes, including the Bidayuh.

To the best of the team's knowledge, these radiocarbon dates are the first chronometric age determinations for Malaysian rock art.

Study co-lead, Dr Jillian Huntley said the first step was establishing what had been used to make the drawings.

"We wanted to confirm the images were drawn with charcoal, as there are a limited number of substances you can actually radiocarbon date," she said.

"We were looking at the decay isotopes of carbon, which meant the material had to be carbon bearing, and our analyses (with collaborator Dr Emilie Dotte-Sarout at University of Western Australia) determined charcoal from different species of bamboo had been used.

"Being drawn on limestone, they're remarkably well preserved."

The art at Gua Sireh is part of a wider distribution of black drawings found from the Philippines through central Island Southeast Asia across Borneo and Sulawesi to Peninsular Malaysia. They are thought to be associated with the diaspora of Austronesian speaking peoples.

Previous dating work, also led by the Griffith Centre for Social and Cultural Research, has established similar drawings in the Philippines were made as early as ~3500 cal BP and ~1500 cal BP in southern Sulawesi.

"Black drawings in the region have been made for thousands of years," Dr Huntley said.

"Our work at Gua Sireh indicates this art form was used up to the recent past to record Indigenous peoples' experiences of colonisation and territorial violence."

Co-lead Distinguished Professor Paul Tacon said the team knew from previous work in the region that northwest Borneo's rock art (the Malaysian states of Sabah and Sarawak) is dominated by drawings of people, animals, ships and abstract geometric/linear design.

advertisement

---

"At Gua Sireh, people are drawn wearing headdresses -- some armed with shields, knives and spears, in scenes showing activities such as hunting, butchering, fishing, fighting and dancing," he said.

"We had clues about their age based on subjects such as introduced animals, but we really didn't know how old they were, so it was difficult to interpret what they might mean."

Bidayuh descendant and curator at The Sarawak Museum Department Mr Mohammad Sherman Sauffi William said understanding of the dates had been informed by the oral histories of the Bidayuh who have continuing custodial responsibilities over the site today.

"The Bidayuh recall Gua Sireh's use as a refuge during territorial violence in the early 1800s when a very harsh Malay Chief had demanded they hand over their children," he said.

"They refused and retreated to Gua Sireh, where they initially held off a force of 300 armed men trying to enter the cave from the valley about 60 meters below.

"Suffering some losses (two Bidayuh were shot and seven taken prisoner/enslaved), they saved their children when most of the tribe escaped through a passageway at the back of the largest entrance chamber which leads hundreds of meters through the Gunung Nambi limestone hill.

"The figures were drawn holding distinctive weapons such as a Pandat which was used exclusively for fighting or protection, as well two short-bladed Parang Ilang, the main weapons used during warfare that marked the first decades of white rule in Borneo."

2023 Global Heat Wave: July brought the hottest three weeks observed so far

 The first three weeks of July 2023 have been the hottest global three-week period so far. In the summer months of 2023, twice as many people in Germany were exposed to daily temperatures of 35 degrees and higher than the average from 1980 to 1999. This is obvious from a study published recently by Karlsruhe Institute of Technology (KIT). Researchers from KIT's Center for Disaster Management and Risk Reduction Technology (CEDIM) report that the European population's exposure to heat was highest in Italy.

In the summer of the year 2023, several hot spells of variable length and intensity occurred partly simultaneously in different regions of the northern hemisphere. In their "Untersuchung der globalen Hitzewelle im Jahr 2023" (investigation of the global heat wave in 2023), researchers of the Forensic Disaster Analysis (FDA) Task Force Group of KIT's CEDIM analyzed the record temperatures reached and the population's exposure to heat.

Ocean Surface Temperatures in June 2023 Were as High as Never Before since records began

In some regions, previous all-time record temperatures were exceeded by far, in other areas new daily or monthly records were recorded. In June 2023, global mean ocean surface temperatures were as high as never before. As regards the Earth's surface, including landmass, June 2023 has been the warmest June since 1850. On a global scale, the first three weeks of July 2023 were the hottest three-week period ever. The daily record, a global surface temperature of 17.08 degrees Celsius was reached on July 6, closely followed by July 5 and 7 with 17.07 degrees Celsius each. In July 2023, extreme temperatures and new country records -- official confirmation by the World Meteorological Organization (WMO) is still pending -were reached in the Mediterranean countries, including North Africa and the Middle East. Record-breaking temperatures were also reported by the USA, Canada, and China.

"For a big temperature anomaly to develop over a longer term, a long-lasting and unusually large-scale flow pattern is required," says Dr. Andreas Schäfer from the FDA Task Force Group of CEDIM. Pressure distribution in the middle troposphere at about 5.5 kilometers altitude plays an important role, as it influences upper airflow and the associated air mass transport. "In July 2023, extraordinarily persistent high-pressure areas prevailed in the regions affected by the high temperatures. Here, descending air masses contributed significantly to warming and the local development of the heat wave," Schäfer says.

The researchers also studied the population's exposure to heat. In Germany, about seven million people were exposed to daily maximum temperatures higher than 25 degrees Celsius. These were about 40 percent more than the average number of the years 1980 to 1999. The number of persons exposed to daily temperatures of 35 degrees Celsius and higher even doubled to about 206,000. Compared to previous decades, heat exposure during the summer months was also much higher in Italy, Greece, Spain, the USA, China, and India.

Paper drinking straws may be harmful and may not be better for the environment than plastic versions

 "Eco-friendly" paper drinking straws contain long-lasting and potentially toxic chemicals, a new study has concluded.

In the first analysis of its kind in Europe, and only the second in the world, Belgian researchers tested 39 brands of straws for the group of synthetic chemicals known as poly- and perfluoroalkyl substances (PFAS).

PFAS were found in the majority of the straws tested and were most common in those made from paper and bamboo, the study, published in the peer-reviewed journal Food Additives and Contaminants, found.

PFAS are used to make everyday products, from outdoor clothing to non-stick pans, resistant to water, heat and stains. They are, however, potentially harmful to people, wildlife and the environment.

They break down very slowly over time and can persist over thousands of years in the environment, a property that has led to them being known as "forever chemicals."

They have been associated with a number of health problems, including lower response to vaccines, lower birth weight, thyroid disease, increased cholesterol levels, liver damage, kidney cancer and testicular cancer.

"Straws made from plant-based materials, such as paper and bamboo, are often advertised as being more sustainable and eco-friendly than those made from plastic," says researcher Dr Thimo Groffen, an environmental scientist at the University of Antwerp, who is involved in this study.

"However, the presence of PFAS in these straws means that's not necessarily true."

A growing number of countries, including the UK and Belgium, have banned sale of single-use plastic products, including drinking straws, and plant-based versions have become popular alternatives.

A recent study found PFAS in plant-based drinking straws in the US. Dr Groffen and colleagues wanted to find out if the same was true of those on sale in Belgium.

To explore this further, the research team purchased 39 different brands of drinking straw made from five materials -- paper, bamboo, glass, stainless steel and plastic.

The straws, which were mainly obtained from shops, supermarkets and fast-food restaurants, then underwent two rounds of testing for PFAS.

The majority of the brands (27/39, 69%) contained PFAS, with 18 different PFAS detected in total.

The paper straws were most likely to contain PFAS, with the chemicals detected in 18/20 (90%) of the brands tested. PFAS were also detected in 4/5 (80%) brands of bamboo straw, 3/4 (75%) of the plastic straw brands and 2/5 (40%) brands of glass straw. They were not detected in any of the five types of steel straw tested.

The most commonly found PFAS, perfluorooctanoic acid (PFOA), has been banned globally since 2020.

Also detected were trifluoroacetic acid (TFA) and trifluoromethanesulfonic acid (TFMS), "ultra-short chain" PFAS which are highly water soluble and so might leach out of straws into drinks.

The PFAS concentrations were low and, bearing in mind that most people tend to only use straws occasionally, pose a limited risk to human health. However, PFAS can remain in the body for many years and concentrations can build up over time.

"Small amounts of PFAS, while not harmful in themselves, can add to the chemical load already present in the body," says Dr Groffen.

It isn't known whether the PFAS were added to the straws by the manufacturers for waterproofing or whether were the result of contamination. Potential sources of contamination include the soil the plant-based materials were grown in and the water used in the manufacturing process.

However, the presence of the chemicals in almost every brand of paper straw means it is likely that it was, in some cases, being used as a water-repellent coating, say the researchers.

The study's other limitations include not looking at whether the PFAS would leach out of the straws into liquids.

Dr Groffen concludes: "The presence of PFAS in paper and bamboo straws shows they are not necessarily biodegradable.

"We did not detect any PFAS in stainless steel straws, so I would advise consumers to use this type of straw -- or just avoid using straws at all