University of Adelaide research shows that in cases where biodiversity metrics show no change or little change, there may still be reorganisation of ecological communities in our oceans.

“The belief that climate change will alter global marine biodiversity is one of the most widely accepted,” said Professor Ivan Nagelkerken from the University of Adelaide’s Environment Institute and Southern Seas Ecology Laboratories.

“Commonly used biodiversity measures don’t pick up reorganisation of marine communities due to ocean acidification because new species replace species that are lost.

“Little or no biodiversity change is detected when one community of marine species is replaced by another even under significant habitat loss.”

The team looked at research undertaken into how species communities located around undersea volcanic CO₂ vents and in laboratory mesocosms respond to changes in climate. They reviewed 58 research studies that examined communities in different types of temperate reefs, coral reefs and seagrass beds, and 23 studies carried out in outdoor experimental environments or laboratories.

Climate change due to human activity has a direct impact on marine species. It alters their abundance, diversity, distribution, feeding patterns, development and breeding, and the relationships between species are affected.

The University of Adelaide’s Professor Sean Connell, who is also from the Environment Institute and Southern Seas Ecology Laboratories, co-authored the study.

“Experiments done in the laboratory are weak in detecting biodiversity change, so natural systems experiencing advanced ocean acidification are emerging as an innovative way of studying biodiversity responses,” he said.

“No ecological study, whether in the laboratory or field, can fully replicate the complex ecological interactions that exist in nature across the time and spatial scales of relevance to climate change.”

Rising sea temperatures are causing lasting damage to many of the world’s significant ecosystems, including coral reefs and kelp forests.

“Future projections of ecosystem change and stability will be more meaningful if they focus on detections of species replacements and changes to the abundance of species rather than testing for signs of habitat loss or biodiversity loss per se,” said Professor Nagelkerken.

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Materials provided by University of Adelaide. Original written by Crispin Savage. Note: Content may be edited for style and length.

Cell biologists are very interested in actin, because actin — a protein of which we produce more than 100 kilograms in our lifetime — is a main component of the cell skeleton and one of the most abundant molecules in a cell. Large quantities can be found in every cell type and it has many purposes: it gives shape to the cell and makes it firmer, it plays an important role in cell division, it can propel cells forward, and provides strength to our muscles. People with faulty actin proteins often suffer from muscle disease. Much is known about the function of actin, but how the final form of this important protein is made and which gene is behind it? “We didn’t know,” says Brummelkamp, whose mission is to find out the function of our genes.

Genetics in haploid human cells

Brummelkamp has developed a number of unique methods for this purpose over the course of his career, which allowed him to be the first to inactivate genes on a large scale for his genetics research in human cells twenty years ago. “You can’t crossbreed people like fruit flies, and see what happens.” Since 2009, Brummelkamp and his team have been using haploid cells — cells containing only one copy of each gene instead of two (one from your father and one from your mother). While this combination of two genes forms the basis of our entire existence, it also creates unwanted noise when conducting a genetics experiment because mutations usually occur in just one version of a gene (the one from your father, for example) and not the other.

Multi-purpose method for genetics in human cells

Together with other researchers, Brummelkamp uses this multi-purpose method to find the genetic causes of particular conditions. He has already shown how the Ebola virus and a number of other viruses, as well as certain forms of chemotherapy, manage to enter a cell. He also investigated why cancer cells are resistant to certain types of therapy and discovered a protein found in cancer cells that acts as a brake on the immune system. This time he went looking for a gene that matures actin — and as a result, the skeleton of the cell.

In search of scissors

Before a protein is completely “finished” — or mature, as the researchers describe it in Science — and can fully perform its function in the cell, it usually has to be stripped of a specific amino acid first. This amino acid is then cut from a protein by a pair of molecular scissors. This is also what occurs with actin. It was known on which side of the actin the relevant amino acid is cut off. However, no one managed to find the enzyme that acts as scissors in this process.

Peter Haahr, postdoc in Brummelkamp’s group, worked on the following experiment: first he caused random mutations (mistakes) in random haploid cells. Then he selected the cells containing the immature actin by adding a fluorescently labeled antibody to his cells that fit in the exact spot where the amino acid is cut off. As a third and final step, he investigated which gene mutated after this process.

They called it ‘ACTMAP’

Then came the “eureka”-moment: Haahr had traced down the molecular scissors that cut the essential amino acid from actin. Those scissors turned out to be controlled by a gene with a previously unknown function; one no researcher had ever worked with. This means that the researchers were able to name the gene themselves, and they settled on ACTMAP (ACTin MAturation Protease).

To test whether a lack of ACTMAP leads to issues in living things, they switched off the gene in mice. They observed that the actin in the cell skeleton of these mice remained unfinished, as expected. They were surprised to find that that the mice did stay alive, but suffered from muscle weakness. The researchers conducted this research together with scientists from the VU Amsterdam.

More scissors found in the skeleton of the cell

ACTMAP is not the first mystery gene discovered by Brummelkamp that plays a role in our cell skeleton function. Using the same method, his group has been able to detect three unknown molecular scissors over recent years that cut an amino acid from tubulin, the other main component of the cell skeleton. These scissors allow tubulin to perform its dynamic functions properly inside the cell. The last scissors (MATCAP) were discovered and described in Science this year. Through this earlier work on the cell skeleton, Brummelkamp managed to arrive at actin.

Mission: mapping out all 23,000 genes

“Unfortunately, our new discovery about actin doesn’t tell us how to cure certain muscular conditions,” says Thijn Brummelkamp. “But we have provided new fundamental knowledge about the cell skeleton that may be useful to others later.” Moreover, Brummelkamp, whose mission is to be able to map out the function of all of our 23,000 genes one day, can tick another new gene off his gigantic list. After all, we don’t know what half of our genes do, which means that we cannot intervene when something goes wrong.

“Using sea-surface-height observations from satellites in the way we have independently verifies observations of Arctic and Greenland ice-mass loss and allows us to tease apart contributions to global sea-level rise from individual ice sheets and glacier systems,” said Sophie Coulson, a postdoctoral researcher in fluid dynamics and geophysics at Los Alamos National Laboratory. Coulson is lead author of a paper in the journal Scienceon detecting the “fingerprint” of sea-level change attributable to the melting of the Greenland ice sheet. “Accurately predicting regional patterns of sea-level change is absolutely central to understanding the impacts of future climate change and forecasting hazards.”

Theoretical models and computer simulations can predict sea level changes as ice sheets and glaciers melt.

“As this melting continues, and the water is redistributed around the global oceans, sea level does not rise uniformly,” Coulson said. “And since every glacier and ice sheet has a unique pattern of sea-level change, these patterns have come to be known as sea-level fingerprints. But despite over half a century of research, these fingerprints have never been unambiguously detected.”

Coulson’s search focused on satellite observations of sea-surface height in the oceans surrounding the Greenland ice sheet over the last three decades. The dominant effect in this region is that as the Greenland ice sheet loses mass, it exerts less gravitational attraction on water in the open ocean and so water migrates away from the ice sheet. This results in a lowering of sea level near Greenland, but progressively higher levels of sea-level rise outside the region.

“We predicted what the pattern of sea-level change would be around Greenland using new estimates of ice melting in the area,” Coulson said. “When we then compared this pattern to satellite observations of sea-level change the fit was remarkable. It was an incredible eureka moment for us when the team saw it — ‘there it is, the sea-level fingerprint!'”

Detection of the patterns has historically been hindered by the lack of sea-surface-height measurements around polar ice sheets and the variability of shorter-timescale processes, such as changing currents and ocean density. The research team on the Science paper took advantage of processed satellite observations that extend to much higher latitudes than previously possible, where the fingerprint signal is the largest. The team processed this satellite data using a powerful new technique to remove the variability due to ocean dynamics.

The new study confirms the accuracy of the geophysical predictions of sea-level change and adds confidence to projections of sea level rise across the next decades and century. As Coulson says, “It’s a powerful and sensitive approach to monitoring ice sheets and glaciers in our warming world.”

Sophie Coulson’s work on this research was supported by a Los Alamos National Laboratory Director’s Postdoctoral Fellowship.

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CSHL Associate Professor Florin Albeanu and Assistant Professor Arkarup Banerjee discovered tufted cells are better at recognizing smells than mitral cells. They’ve found tufted cells are essential to one of two parallel neural circuit loops that help the brain process different odor features. The findings help explain how the brain takes in sensory information that influences behavior and emotions.

The researchers exposed mice to various odors, from fresh mint to sweet bananas, at different concentrations. They simultaneously tracked the neural activity of the two cell types and found tufted cells outperformed mitral cells. They were faster and better at distinguishing smells. They also captured a wider range of concentrations. While this illuminated a new role for tufted cells, it also led to a new unanswered question. “If tufted cells are actually better at recognizing odors, what then, is the function of mitral cells?” said Albeanu.

Albeanu and Banerjee think mitral cells enhance important smells. They are part of a neural feedback loop that may help an animal prioritize, for example, the smell of food or a predator. In contrast, the tufted cells are part of a second feedback loop that helps process smell intensity and identity. This can guide animals locating odors in the environment. Banerjee explains:

“If you can’t tell whether it’s high [intensity] versus low [intensity], then you can’t track an odor. There’s no way to know that you’re actually getting closer to the odor source if you can’t tell the difference.”

The two neural circuit loops offer novel explanations for how the brain processes sensory information. Going forward, the new genetic and optical imaging tools used by the CSHL team, that include postdoc Honggoo Chae and graduate student Marie Dussauze, can uncover more undervalued neurons involved in sensory processing.

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Materials provided by Cold Spring Harbor Laboratory. Original written by Luis Sandoval. Note: Content may be edited for style and length.

The researchers, led by the University of Cambridge, used spacecraft laser-altimeter measurements of the shape of the upper surface of the ice cap to identify subtle patterns in its height. They then showed that these patterns match computer model predictions for how a body of water beneath the ice cap would affect the surface.

Their results agree with earlier ice-penetrating radar measurements that were originally interpreted to show a potential area of liquid water beneath the ice. There has been debate over the liquid water interpretation from the radar data alone, with some studies suggesting the radar signal is not due to liquid water.

The results, reported in the journal Nature Astronomy, provide the first independent line of evidence, using data other than radar, that there is liquid water beneath Mars’ south polar ice cap.

“The combination of the new topographic evidence, our computer model results, and the radar data make it much more likely that at least one area of subglacial liquid water exists on Mars today, and that Mars must still be geothermally active in order to keep the water beneath the ice cap liquid,” said Professor Neil Arnold from Cambridge’s Scott Polar Research Institute, who led the research.

Like Earth, Mars has thick water ice caps at both poles, roughly equivalent in combined volume to the Greenland Ice Sheet. Unlike Earth’s ice sheets however, which are underlain by water-filled channels and even large subglacial lakes, the polar ice caps on Mars have until recently been thought to be frozen solid all the way to their beds due to the cold Martian climate.

In 2018, evidence from the European Space Agency’s Mars Express satellite challenged this assumption. The satellite has an ice-penetrating radar called MARSIS, which can see through Mars’ southern ice cap. It revealed an area at the base of the ice that strongly reflected the radar signal, which was interpreted as an area of liquid water beneath the ice cap.

However, subsequent studies suggested that other types of dry materials, which exist elsewhere on Mars, could produce similar patterns of reflectance if they exist beneath the ice cap. Given the cold climate conditions, liquid water beneath the ice cap would require an additional heat source, such as geothermal heat from within the planet, at levels above those expected for present-day Mars. This left confirmation of the existence of this lake awaiting another, independent line of evidence.

On Earth, subglacial lakes affect the shape of the overlying ice sheet — its surface topography. The water in subglacial lakes lowers friction between the ice sheet and its bed, affecting the velocity of ice flow under gravity. This in turn affects the shape of the ice sheet surface above the lake, often creating a depression in the ice surface followed by a raised area further down-flow.

The team — which also included researchers from the University of Sheffield, the University of Nantes, University College, Dublin, and the Open University — used a range of techniques to examine data from NASA’s Mars Global Surveyor satellite of the surface topography of the part of Mars’ south polar ice cap where the radar signal was identified.

Their analysis revealed a 10-15 kilometre-long surface undulation comprising a depression and a corresponding raised area, both of which deviate from the surrounding ice surface by several metres. This is similar in scale to undulations over subglacial lakes here on Earth.

The team then tested whether the observed undulation on the surface of the ice could be explained by liquid water at the bed. They ran computer model simulations of ice flow, adapted to specific conditions on Mars. They then inserted a patch of reduced bed friction in the simulated ice sheet bed where water, if present, would allow the ice to slide and speed up. They also varied the amount of geothermal heat coming from inside the planet. These experiments generated undulations on the simulated ice surface that were similar in size and shape to those the team observed on the real ice cap surface.

The similarity between the model-produced topographic undulation and the actual spacecraft observations, together with the earlier ice-penetrating radar evidence suggest that there is an accumulation of liquid water beneath Mars’ south polar ice cap, and that magmatic activity occurred relatively recently in the subsurface of Mars to enable the enhanced geothermal heating needed to keep the water in a liquid state.

“The quality of data coming back from Mars, from orbital satellites as well as from the landers, is such that we can use it answer really difficult questions about conditions on, and even under the planet’s surface, using the same techniques we also use on Earth,” said Arnold. “It’s exciting to use these techniques to find out things about planets other than our own.”

The research was supported in part by the European Research Council.

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Materials provided by University of Cambridge. Original written by Sarah Collins. The text in this work is licensed under a Creative Commons Attribution 4.0 International License Note: Content may be edited for style and length.

“There is much noise about the direct effects of agrochemicals on pollinators, a subject of profound societal attention, but it now emerges that ozone is a silent threat to pollinators and thus pollination,” says lead author Evgenios Agathokleous, an ecologist at Nanjing University of Information Science & Technology. “These impacts of ozone have long been missed.”

Ozone gas can be both friend and foe to the planet. In the stratosphere, 12 kilometers above sea level, ozone forms naturally and helps protect the Earth from harmful sun rays. But below that zone, ozone is a damaging pollutant. Tropospheric-level ozone gas is created by a photochemical reaction between volatile organic compounds — emitted by vegetation and commonly found in substances such as paint and aerosols — and oxides of nitrogen, which are released when fossil fuels burn. Tropospheric ozone levels have been rising because a warming climate is creating optimal conditions for its formation.

“Ozone pollution can affect the timing and duration of flowering in such a way that the occurrence of flowering is asynchronous to the activities of pollinators,” says Agathokleous. “It can also change the color of flowers, disrupting the visual signals to pollinators. Ozone pollution can also directly react with pollen, decreasing its quality, but also indirectly changing the amount of pollen.”

Ozone pollution can also damage plant leaves almost instantly, leaving injury signs of diverse colors and shapes and discoloring leaves. When damaged, leaves have a hard time photosynthesizing and struggle to provide the plant with the energy it needs to grow. Plants emit their own organic volatile compounds that act as chemical signals facilitating communication from one plant to another and alert pollinators to the presence of a waiting flower. Ozone pollution appears to be disrupting these chemical signatures.

“Changes in the composition of the volatile blends could also have severe implications to pollinators because they might not recognize host plants and their qualities in the same way they did in the past,” says Agathokleous. “Within plant tissues, ozone pollution could decrease the amount of nutrients that are essential to insects, increase the abundance of chemicals that are harmful to insects ingesting them, and degrade the overall quality of plant tissues.”

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