Comment

Comment by Dr. Krishna Kumari Challa on July 16, 2024 at 8:49am

If water temperatures rise, the solubility of oxygen in the water decreases. In addition, global warming enhances stratification of the water column, because warmer, low-salinity water with a lower density lies on top of the colder, saltier deep water below.

This hinders the exchange of the oxygen-poor deep layers with the oxygen-rich surface water. In addition, nutrient inputs from land support algal blooms, which lead to more oxygen being consumed as more organic material sinks and is decomposed by microbes at depth.
Areas in the sea where there is so little oxygen that fish, mussels or crustaceans can no longer survive threaten not only the organisms themselves, but also ecosystem services such as fisheries, aquaculture, tourism and cultural practices.

Microbiotic processes in oxygen-depleted regions also increasingly produce potent greenhouse gases such as nitrous oxide and methane, which can lead to a further increase in global warming and thus a major cause of oxygen depletion.
The authors warn: We are approaching critical thresholds of aquatic deoxygenation that will ultimately affect several other planetary boundaries.
Failure to address aquatic deoxygenation will, ultimately, not only affect ecosystems but also economic activity, and society at a global level.

 Kevin C. Rose et al, Aquatic deoxygenation as a planetary boundary and key regulator of Earth system stability, Nature Ecology & Evolution (2024). DOI: 10.1038/s41559-024-02448-y

Part 2

Comment by Dr. Krishna Kumari Challa on July 16, 2024 at 8:48am

Loss of oxygen in bodies of water identified as new tipping point

Oxygen concentrations in our planet's waters are decreasing rapidly and dramatically—from ponds to the ocean. The progressive loss of oxygen threatens not only ecosystems, but also the livelihoods of large sectors of society and the entire planet, according to the authors of an international study involving GEOMAR published recently in Nature Ecology & Evolution.

Oxygen is a fundamental requirement of life on planet Earth. The loss of oxygen in water, also referred to as aquatic deoxygenation, is a threat to life at all levels. The international team of researchers describes how ongoing deoxygenation presents a major threat to the livelihoods of large parts of society and for the stability of life on our planet.

Previous research has identified a suite of global scale processes, referred to as planetary boundaries, that regulate the overall habitability and stability of the planet. If critical thresholds in these processes are passed, the risk of large-scale, abrupt or irreversible environmental changes ("tipping points") increases and the resilience of our planet, its stability, is jeopardized.

Among the nine planetary boundaries are climate change, land use change, and biodiversity loss. The authors of the new study argue that aquatic deoxygenation both responds to, and regulates, other planetary boundary processes.

Across all aquatic ecosystems, from streams and rivers, lakes, reservoirs, and ponds to estuaries, coasts, and the open ocean, dissolved oxygen concentrations have rapidly and substantially declined in recent decades.

Lakes and reservoirs have experienced oxygen losses of 5.5% and 18.6% respectively since 1980. The ocean has experienced oxygen losses of around 2% since 1960. Although this number sounds small, due to the large ocean volume it represents an extensive mass of oxygen lost.

Marine ecosystems have also experienced substantial variability in oxygen depletion.

The volumes of aquatic ecosystems affected by oxygen depletion have increased dramatically across all types.

The causes of aquatic oxygen loss are global warming due to greenhouse gas emissions and the input of nutrients as a result of land use.

Part 1

Comment by Dr. Krishna Kumari Challa on July 16, 2024 at 7:13am

Study finds abortion restrictions harm mental health, with low-income women hardest hit

People living in states that enacted tighter abortion restrictions in the wake of the Dobbs v. Jackson Women's Health decision, which returned regulation of abortion access to state legislatures, are more likely to report elevated levels of mental distress. This is particularly true for people of lower socioeconomic means.

These are the key takeaways of July 2024 paper published in Science Advances.

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Comment by Dr. Krishna Kumari Challa on July 16, 2024 at 7:03am

Deep in the Earth's mantle, where the rock becomes viscous due to high pressure, displacements occur over long periods of time. And there are also heat flows in the liquid metal of Earth's outer core, which are responsible for both generating the Earth's magnetic field and leading to shifts in mass.

In the most comprehensive modeling to date, researchers have now shown how polar motion results from individual processes in the core, in the mantle and from the climate at the surface.
One finding in particular that stands out in their study is that the processes on and in the Earth are interconnected and influence each other. Climate change is causing the Earth's axis of rotation to move, and it appears that the feedback from the conservation of angular momentum is also changing the dynamics of the Earth's core.
Ongoing climate change could therefore even be affecting processes deep inside the Earth and have a greater reach than previously assumed. However, there is little cause for concern, as these effects are minor and it's unlikely that they pose a risk.
Implications for space travel
Even if the Earth's rotation is changing only slowly, this effect has to be taken into account when navigating in space—for example, when sending a space probe to land on another planet. Even a slight deviation of just one centimeter on Earth can grow to a deviation of hundreds of meters over the huge distances involved.

"Otherwise, it won't be possible to land in a specific crater on Mars".

 Kiani Shahvandi, Mostafa, The increasingly dominant role of climate change on length of day variations, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2406930121. doi.org/10.1073/pnas.2406930121

Mostafa Kiani Shahvandi et al, Contributions of core, mantle and climatological processes to Earth's polar motion, Nature Geoscience (2024). DOI: 10.1038/s41561-024-01478-2. www.nature.com/articles/s41561-024-01478-2

Part 2

Comment by Dr. Krishna Kumari Challa on July 16, 2024 at 7:00am

How climate change is altering the Earth's rotation

For the first time, researchers have been able to fully explain the various causes of long-term polar motion in the most comprehensive modeling to date, using AI methods. Their model and their observations show that climate change and global warming will have a greater influence on the Earth's rotational speed than the effect of the moon, which has determined the increase in the length of the day for billions of years.

Climate change is causing the ice masses in Greenland and Antarctica to melt. Water from the polar regions is flowing into the world's oceans—and especially into the equatorial region.

This means that a shift in mass is taking place, and this is affecting the Earth's rotation.

It's like when a figure skater does a pirouette, first holding her arms close to her body and then stretching them out. The initially fast rotation becomes slower because the masses move away from the axis of rotation, increasing physical inertia.

In physics, we speak of the law of conservation of angular momentum, and this same law also governs the Earth's rotation. If the Earth turns more slowly, the days get longer. Climate change is therefore also altering the length of the day on Earth, albeit only minimally for now.

Another cause of this slowdown is tidal friction, which is triggered by the moon. However, the new study comes to a surprising conclusion: if humans continue to emit more greenhouse gases and the Earth warms up accordingly, this would ultimately have a greater influence on the Earth's rotational speed than the effect of the moon, which has determined the increase in the length of the day for billions of years.

We humans have a greater impact on our planet than we realize and this naturally places great responsibility on us for the future of our planet.

However, shifts in mass on the Earth's surface and in its interior caused by the melting ice not only change the Earth's rotational speed and the length of day: as the researchers show in Nature Geoscience, they also alter the axis of rotation. This means that the points where the axis of rotation actually meets the Earth's surface move.

Researchers can observe this polar motion, which, over a longer timeframe, comes to some ten meters per hundred years. It's not only the melting of the ice sheets that plays a role here, but also movements taking place in the Earth's interior.

Part 1

Comment by Dr. Krishna Kumari Challa on July 16, 2024 at 6:50am

Using epigenetic techniques, the researchers were able to track how these three key histone modifications changed as cells transitioned through different stages of development. The observations gathered in their experiments allowed them to identify dynamic epigenetic "switches" that regulate the fate of individual cells.
They discovered that the switching of repressive and activating histone modifications happens before cell fate decisions.
Additionally, they demonstrated that removing H3K27me3 at the neuroectoderm stage disrupts fate restriction, leading to aberrant cell identities.

Fides Zenk et al, Single-cell epigenomic reconstruction of developmental trajectories from pluripotency in human neural organoid systems, Nature Neuroscience (2024). DOI: 10.1038/s41593-024-01652-0

Part 2

Comment by Dr. Krishna Kumari Challa on July 16, 2024 at 6:48am

Study identifies epigenetic 'switches' that regulate the developmental trajectories of single cells

Individual cells in the human body develop progressively over time, ultimately becoming specialized in specific functions. This process, known as cell differentiation or specialization, is central to the formation of distinct cell populations that serve different purposes.

Past studies suggest that the fate of cells is also modulated by epigenetic mechanisms (i.e., interactions between genes and environmental factors). These epigenetic mechanisms, however, have so far been proved difficult to pinpoint.

Researchers recently carried out a study aimed at exploring the epigenetic processes influencing the developmental trajectories of individual cells, using human brain and retina organoids derived from pluripotent stem cells.  

Their paper, published in Nature Neuroscience, outlines a single-cell epigenome-wide map that could aid the study of human cell fate determination.

This paper was inspired by the need to better understand the epigenetic mechanisms that regulate cell fate decisions during human brain and retina development.

The primary objective was to create a comprehensive single-cell epigenomic map that could capture the transitions from pluripotent stem cells to differentiated neural cells.

To study the epigenetic mechanisms underpinning the diversification of human cells, the researchers carried out experiments on human brain and retina organoids, three-dimensional (3D), miniaturized versions of human organs created in laboratory settings, using pluripotent stem cells.

Part 1

Comment by Dr. Krishna Kumari Challa on July 15, 2024 at 11:22am

The Exact Part of The Brain Behind Your Curiosity
Being curious is a quintessential part of being human, driving us to learn and adapt to new environments. For the first time, scientists have pinpointed the spot in the brain where curiosity emerges.
The discovery was made by researchers  who used functional magnetic resonance imaging (fMRI) scans to measure oxygen levels in different parts of the brain, indicating how busy each region is at any one time.

Knowing where curiosity originates could help us understand more about how human beings tick, and potentially lead to therapies for conditions where curiosity is lacking, such as chronic depression.
This is really the first time we can link the subjective feeling of curiosity about information to the way your brain represents that information.
In the experiments conducted on curiosity and fMRI scans, notable activity was spotted in three regions: the the occipitotemporal cortex (linked to vision and object recognition), the ventromedial prefrontal cortex or vmPFC (which manages perceptions of value and confidence), and the anterior cingulate cortex (used for information gathering).
The vmPFC appears to act as a sort of neurological bridge between levels of certainty recorded by the occipitotemporal cortex, and subjective feelings of curiosity – almost like a trigger telling us when to be curious. The less confident the volunteers were about the image subject, the more curious they were about it.
These results illuminate how perceptual input is transformed by successive neural representations to ultimately evoke a feeling of curiosity," write the researchers in their published paper.

https://www.jneurosci.org/content/early/2024/07/04/JNEUROSCI.0974-2...

Comment by Dr. Krishna Kumari Challa on July 15, 2024 at 10:42am

LUCA, they found, was probably very similar to a prokaryote, a single-celled organism that doesn't have a nucleus. It was obviously not reliant on oxygen, since there would have been little oxygen available; that's not unexpected for a microbe. As such, its metabolic processes probably produced acetate.

But there was something else interesting. LUCA appears not to have been alone.
This study showed that LUCA was a complex organism, not too different from modern prokaryotes.
But what is really interesting is that it's clear it possessed an early immune system, showing that even by 4.2 billion years ago, our ancestor was engaging in an arms race with viruses.
Because its metabolic processes would have produced waste products that could be used by other lifeforms, they could have emerged not long after LUCA did.

This implies that it takes relatively little time for a full ecosystem to emerge in the evolutionary history of a planet – a finding that has implications far beyond our own little pale blue dot.

https://www.nature.com/articles/s41559-024-02461-1

Part 2

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Comment by Dr. Krishna Kumari Challa on July 15, 2024 at 10:41am

Study Finds Life on Earth Emerged 4.2 Billion Years Ago

Once upon a time, Earth was barren. Everything changed when, somehow, out of the chemistry available early in our planet's history, something started squirming – processing available matter to survive, to breed, to thrive.

What that something was, and when it first squirmed, have been burning questions that have puzzled humanity probably for as long as we've been able to ask "what am I?"

Now, a new study has found some answers – and life emerged surprisingly early.

By studying the genomes of organisms that are alive today, scientists have determined that the last universal common ancestor (LUCA), the first organism that spawned all the life that exists today on Earth, emerged as early as 4.2 billion years ago.

Earth, for context, is around 4.5 billion years old. That means life first emerged when the planet was still practically a newborn.

Back when it was new, Earth was a very different place, with an atmosphere that we would find extremely toxic today. Oxygen, in the amount current life seems to need, didn't emerge until relatively late in the planet's evolutionary history, only as early as around 3 billion years ago.

But life emerged prior to that; we have fossils of microbes from 3.48 billion years ago. And scientists think that conditions on Earth may have been stable enough to support life from around 4.3 billion years ago.

But our planet is subject to erosional, geological, and organic processes that make evidence of that life, from that time, almost impossible to find.

a team of scientists went looking somewhere else: in genomes from living organisms, and the fossil record.

Their study is based on something called a molecular clock. Basically, we can estimate the rate at which mutations occur, and count the number to determine how much time has passed since the organisms in question diverged from common ancestors.

All organisms, from the humblest microbe to the mightiest fungus, have some things in common. There's a universal genetic code. The way we make proteins is the same. There's an almost universal set of 20 amino acids that are all oriented the same way. And all living organisms use adenosine triphosphate (ATP) as a source of energy in their cells.

Researchers  worked out, based on these similarities and differences, how long it has been since LUCA's successors started to diverge. And, using complex evolutionary modeling, they were able to learn more about LUCA itself – what it was, and how it survived on an Earth so very inhospitable to its descendants.

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