While calcifying organisms like oysters and corals have difficulty forming their shells and skeletons in more acidic seawater, diatoms have been considered less susceptible to the effects of ocean acidification — a chemical change triggered by the uptake of carbon dioxide (CO2). The globally widespread tiny diatoms use silica, a compound of silicon, oxygen and hydrogen, as a building material for their shells. That diatoms are nevertheless under threat has now been demonstrated for the first time by researchers from GEOMAR Helmholtz Centre for Ocean Research Kiel, the Institute of Geological and Nuclear Sciences Limited New Zealand and the University of Tasmania in a study published in Nature. For the study, researchers linked an overarching analysis of various data sources with Earth system modeling. The findings provide a new assessment of the global impact of ocean acidification.

As a result of ocean acidification, the silicon shells of diatoms dissolve more slowly. This is not an advantage — it causes diatoms to sink into deeper water layers, before they chemically dissolve and are converted back into silica. Consequently, this nutrient is more efficiently exported to the deep ocean and thus becomes scarcer in the light-flooded surface layer, where it is needed to form new shells. This causes a decline in diatoms, according to the scientists in their recent publication. Diatoms contribute 40 percent of the production of plant biomass in the ocean and are the basis of many marine food webs. They are also the main driver of the biological carbon pump that transports CO₂ into the deep ocean for long-term storage.

Dr. Jan Taucher, marine biologist at GEOMAR and first author of the study says: “With an overarching analysis of field experiments and observational data, we wanted to find out how ocean acidification affects diatoms on a global scale. Our current understanding of ecological effects of ocean change is largely based on small-scale experiments, that is, from a particular place at a particular time. These findings can be deceptive if the complexity of the Earth system is not taken into account. Our study uses diatoms as an example to show how small-scale effects can lead to ocean-wide changes with unforeseen and far-reaching consequences for marine ecosystems and matter cycles. Since diatoms are one of the most important plankton groups in the ocean, their decline could lead to a significant shift in the marine food web or even a change for the ocean as a carbon sink.”

The meta-analysis examined data from five mesocosm studies from 2010 to 2014, from different ocean regions ranging from Arctic to subtropical waters. Mesocosms are a type of large-volume, oversized test tube in the ocean with a capacity of tens of thousands of liters, in which changes in environmental conditions can be studied in a closed but otherwise natural ecosystem. For this purpose, the water enclosed in the mesocosms was enriched in carbon dioxide to correspond to future scenarios with moderate to high increases in atmospheric CO₂ levels. For the present study, the chemical composition of organic material from sediment traps was evaluated as it sank through the water contained in the experimental containers over the course of several weeks of experiments. Combined with measurements from the water column, an accurate picture of biogeochemical processes within the ecosystem emerged.

The findings obtained from the mesocosm studies could be confirmed using global observational data from the open ocean. They show — in line with the results of the meta-analysis — a lower dissolution of the silicon shells at higher seawater acidity. With the resulting data sets, simulations were performed in an Earth system model to assess the ocean-wide consequences of the observed trends.

“Already by the end of this century, we expect a loss of up to ten percent of diatoms. That’s immense when you consider how important they are to life in the ocean and to the climate system,” Dr. Taucher continued. “However, it is important to think beyond 2100. Climate change will not stop abruptly, and global effects in particular take some time to become clearly visible. Depending on the amount of emissions, our model in the study predicts a loss of up to 27 percent silica in surface waters and an ocean-wide decline in diatoms of up to 26 percent by the year 2200 — more than a quarter of the current population.”

This finding of the study is in sharp contrast to the previous state of ocean research, which sees calcifying organisms as losers and diatoms being less affected by ocean acidification. Professor Ulf Riebesell, marine biologist at GEOMAR and head of the mesocosm experiments adds: “This study once again highlights the complexity of the Earth system and the associated difficulty in predicting the consequences of human-made climate change in its entirety. Surprises of this kind remind us again and again of the incalculable risks we run if we do not counteract climate change swiftly and decisively.”

The study is published in the peer-reviewed journal PLOS ONE.

Gestational diabetes causes blood sugar levels to rise, creating risks for baby and mother alike. It can lead to high blood pressure, risk of future diabetes and a higher chance of c-section in the mother as well as excessive birth weight, premature delivery and other issues in her baby. Diagnosing the condition currently relies on conventional screening and lab work in the late second and third trimesters. The ability to predict the condition earlier is one key to reducing its impact.

“As pregnancy complications continue to rise worldwide, there have been increasing efforts to study with urgency the first-trimester as a window of opportunity for early identification and prediction of GDM, and the optimal point to take action to prevent maternal disease,” said Dr. Sherin Devaskar, lead author of the study and physician-in-chief of UCLA Mattel Children’s Hospital and distinguished professor of pediatrics at the David Geffen School of Medicine at UCLA.

Identifying biomarkers of GDM in early pregnancy could lead to better monitoring and development of safe and timely interventions and treatments that would reduce disease severity, thus improving long-term health prospects for mother and offspring.

For the current study, researchers focused on extracellular vesicles (EVs), circulating “communicators” that carry and deliver microRNA genes (miRNAs) within maternal blood. They are secreted from the placenta, and play a key role in pregnancy and in complications of pregnancy, including GDM. Researchers took blood samples during each trimester and at delivery from miRNA expression in EVs in 24 pregnant women and found there was distinct expression of miRNA in EVs isolated from blood samples taken in the first trimester, from women eventually diagnosed with GDM compared to those with normal healthy pregnancies. The authors noted changes in these miRNAs prior to clinical diagnosis, suggesting that they were involved in the development of the disease rather than due to factors secondary to the condition itself or treatments like insulin, which may influence miRNA content of circulating EVs.

Researchers also found upregulation in certain miRNA in first trimester pregnancies that went on to be diagnosed with GDM, further suggesting that the miRNA cargo within circulating EVs may be communicating with other maternal organs and cell types, and interacting with signaling pathways involved in metabolism and inflammation, which could be influencing the maternal metabolic adaptions observed in women who develop GDM.

“This is a promising initial step in finding a robust and accurate biomarker panel that performs much better than one single feature in predicting GDM during early pregnancy,” said Dr. Devaskar. “This study provides more evidence that GDM is a condition that begins developing far earlier than when currently clinically diagnosed, after the midpoint of pregnancy — when sadly, complications may already be irreversible. As providers of care for high risk pregnant patients and their babies, we are excited about this step towards the potential of more reliable and earlier diagnosis so that we may intervene before the development of adverse conditions for mother and baby that are often lifelong.”

The authors say further study is needed to investigate the mechanistic role of circulating EVs during pregnancy, their role in pregnancy complications and utilization of EV associated miRNAs as noninvasive predictors of disease in pregnancy, but that EV-associated miRNAs from the first trimester of pregnancy have the potential to act as an early gestation predictor of the subsequent development of GDM, prior to the emergence of characteristic clinical or biochemical features.

Other authors on the study included Shanthie Thamotharan, staff research associate, Shubhamoy Ghosh, PhD, assistant project scientist, and Laura James-Allan, PhD, post-doctoral fellow, all three in the department of Pediatrics-Neonatology at UCLA; Margarida Y.Y. Lei, staff research associate and Dr. Carla Janzen, associate professor, in the department of obstetrics and gynecology, division of maternal-fetal medicine at UCLA.

Research was supported by the National Institutes of Health under grant numbers NU01HD087221 (to SUD, CJ, KS), R01HD089714 (to SUD) and R01HD100015 (to SUD).

The seven cardiovascular and brain health factors, known as the American Heart Association’s Life’s Simple 7, are: being active, eating better, losing weight, not smoking, maintaining a healthy blood pressure, controlling cholesterol, and reducing blood sugar.

“These healthy habits in the Life’s Simple 7 have been linked to a lower risk of dementia overall, but it is uncertain whether the same applies to people with a high genetic risk,” said study author Adrienne Tin, PhD, of the University of Mississippi Medical Center in Jackson. “The good news is that even for people who are at the highest genetic risk, living by this same healthier lifestyle are likely to have a lower risk of dementia.”

The study looked at 8,823 people with European ancestry and 2,738 people with African ancestry who were followed for 30 years. People had an average age of 54 at the beginning of the study.

Study participants reported their levels in all seven health factors. Total scores ranged from 0 to 14, with 0 representing the most unhealthy score and 14 representing the most healthy score. The average score among those with European ancestry was 8.3 and the average score amongst those with African ancestry was 6.6.

Researchers calculated genetic risk scores at the start of the study using genome-wide statistics of Alzheimer’s disease, which have been used to study the genetic risk for dementia.

Participants with European ancestry were divided into five groups and those with African ancestry were divided into three groups based on genetic risk scores. The group with the highest genetic risk included people who had at least one copy of the APOE gene variant associated with Alzheimer’s disease, APOE e4. Of those with European ancestry, 27.9% had the APOE e4 variant, while of those who had African ancestry, 40.4% had the APOE e4 variant. The group with the lowest risk had the APOE e2 variant, which has been associated with a decreased risk of dementia.

By the end of the study, 1,603 people with European ancestry developed dementia and 631 people with African ancestry developed dementia.

For people with European ancestry, researchers found that people with the highest scores in the lifestyle factors had a lower risk of dementia across all five genetic risk groups, including the group with the highest genetic risk of dementia. For each one-point increase in the lifestyle factor score, there was a 9% lower risk of developing dementia. Among those with European ancestry, compared with the low category of the lifestyle factor score, the intermediate and high categories were associated with 30% and 43% lower risk for dementia, respectively. Among those with African ancestry, the intermediate and high categories were associated with 6% and 17% lower risk for dementia, respectively.

Among people with African ancestry, researchers found a similar pattern of declining dementia risk across all three groups among those with higher scores on the lifestyle factors. But researchers said the smaller number of participants in this group limited the findings, so more research is needed.

“Larger sample sizes from diverse populations are needed to get more reliable estimates of the effects of these modifiable health factors on dementia risk within different genetic risk groups and ancestral backgrounds,” Tin said.

A limitation of the study was the smaller sample size among people with African ancestry and that many African American participants were recruited from one location.

The study was supported by the National Heart, Lung, and Blood Institute, the National Institutes of Health, the Department of Health and Human Services, and the National Human Genome Research Institute.

“The new cell is more efficient and has a simpler design that may be useful for a variety of new applications, such as highly area-constrained applications or low-radiation space applications,” said Myles Steiner, a senior scientist in NREL’s High-Efficiency Crystalline Photovoltaics (PV) Group and principal investigator on the project. He worked alongside NREL colleagues Ryan France, John Geisz, Tao Song, Waldo Olavarria, Michelle Young, and Alan Kibbler.

Details of the development are outlined in the paper “Triple-junction solar cells with 39.5% terrestrial and 34.2% space efficiency enabled by thick quantum well superlattices,” which appears in the May issue of the journal Joule.

NREL scientists previously set a record in 2020 with a 39.2% efficient six-junction solar cell using III-V materials.

Several of the best recent solar cells have been based on the inverted metamorphic multijunction (IMM) architecture that was invented at NREL. This newly enhanced triple-junction IMM solar cell has now been added to the Best Research-Cell Efficiency Chart. The chart, which shows the success of experimental solar cells, includes the previous three-junction IMM record of 37.9% established in 2013 by Sharp Corporation of Japan.

The improvement in efficiency followed research into “quantum well” solar cells, which utilize many very thin layers to modify solar cell properties. The scientists developed a quantum well solar cell with unprecedented performance and implemented it into a device with three junctions with different bandgaps, where each junction is tuned to capture and utilize a different slice of the solar spectrum.

The III-V materials, so named because of where they fall on the periodic table, span a wide range of energy bandgaps that allow them to target different parts of the solar spectrum. The top junction is made of gallium indium phosphide (GaInP), the middle of gallium arsenide (GaAs) with quantum wells, and the bottom of lattice-mismatched gallium indium arsenide (GaInAs). Each material has been highly optimized over decades of research.

“A key element is that while GaAs is an excellent material and generally used in III-V multijunction cells, it does not have quite the correct bandgap for a three-junction cell, meaning that the balance of photocurrents between the three cells is not optimal,” said France, senior scientist and cell designer. “Here, we have modified the bandgap while maintaining excellent material quality by using quantum wells, which enables this device and potentially other applications.”

The scientists used quantum wells in the middle layer to extend the bandgap of the GaAs cell and increase the amount of light that the cell can absorb. Importantly, they developed optically thick quantum well devices without major voltage loss. They also learned how to anneal the GaInP top cell during the growth process in order to improve its performance and how to minimize the threading dislocation density in lattice-mismatched GaInAs, discussed in separate publications. Altogether, these three materials inform the novel cell design.

III-V cells are known for their high efficiency, but the manufacturing process has traditionally been expensive. So far, III-V cells have been used to power applications such as space satellites, unmanned aerial vehicles, and other niche applications. Researchers at NREL have been working toward drastically reducing the manufacturing cost of III-V cells and providing alternate cell designs, which will make these cells economic for a variety of new applications.

The new III-V cell was also tested for how efficient it would be in space applications, especially for communications satellites, which are powered by solar cells and for which high cell efficiency is crucial, and came in at 34.2% for a beginning-of-life measurement. The present design of the cell is suitable for low-radiation environments, and higher-radiation applications may be enabled by further development of the cell structure.

Arrhythmogenic cardiomyopathy (ACM) is a familial heart disease in which heart muscle tissue is replaced by fat cells. It can lead to life threatening, irregular heartbeats. Currently, no therapy exists to cure arrhythmogenic cardiomyopathy and patients may ultimately need a heart transplantation. Therefore, the group of Eva van Rooij at the Hubrecht Institute collaborated with the UMC Utrecht with the aim to better understand the process of heart muscle degeneration in ACM, to ultimately contribute to the identification of new therapeutic targets to treat the disease.

Local differences

Previous studies on ACM used methods that take a snapshot of the gene expression in diseased tissue to aim at understanding what happens in the disease, but lacked the spatial resolution that is required to identify local differences within the heart. Therefore, the group of Eva van Rooij collaborated with the group of Alexander van Oudenaarden to use a technique called Tomo-Seq, that enabled the researchers to study gene expression within different areas of the heart. It turned out that knowing the location of the cells with changed gene activity was key to the discovery of novel areas of heart muscle degeneration.

Human hearts

The researchers used explanted hearts from ACM patients that received a heart transplantation. Heart disease is often studied in cultured cells or animal models, since the use of patient heart tissue is usually not possible. However, due to a collaboration with Aryan Vink from the Pathology Department of UMC Utrecht, the researchers had access to one of the largest and best documented heart tissue biobanks of the world. This gave them the unique opportunity to study the disease process in patient material. The researchers were able to closely look at the patient heart muscle cells that are degenerating, and identified new genes that may play an important role in this process. Among these genes is the transcription factor ZBTB11, a gene that was not previously known to be involved in arrhythmogenic cardiomyopathy.

Fat cells

The gene ZBTB11 is specifically expressed in the heart muscle cells that are close to the fat cells. The researchers showed that the activity of ZBTB11 induced degeneration of heart muscle cells, a process that is key in arrhythmogenic cardiomyopathy. This indicates that the fatty regions in the heart induce damage to the neighboring heart muscle cells. In the future, the researchers aim to study if heart muscle damage can be slowed down or even reversed in arrhythmogenic cardiomyopathy.

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