Antarctic-wide survey of plant life to aid conservation efforts

The first continent-wide mapping study of plant life across Antarctica reveals growth in previously uncharted areas and is set to inform conservation measures across the region.

The satellite survey of mosses, lichens and algae across the continent will form a baseline for monitoring how Antarctica's vegetation responds to climate change.

Scientists used a European Space Agency satellite to sweep the continent, combined with field measurements taken over several summer seasons, and detected almost 45 square kilometers of vegetation -- roughly three times the size of Lake Windermere in the Lake District, UK.

The international team, led by the University of Edinburgh with the Norwegian Institute for Nature Research, British Antarctic Survey and Scottish Association for Marine Science, found that over 80 per cent of the vegetation growth was contained within the Antarctic Peninsula and neighbouring islands.

The team estimates this growth makes up only 0.12 percent of Antarctica's total ice-free area, highlighting the importance of monitoring key areas of vegetation abundance, which is inadequately protected under the existing Antarctic Specially Protected Area (ASPA) system, experts say.

Antarctic vegetation, dominated by mosses and lichens, has adapted to survive the harsh polar conditions and each type plays an important role in carbon and nutrient recycling on a local level, experts say.

Until now, their spatial coverage and abundance across the continent remained unknown.

Previous research has shown that the environmental sensitivity of Antarctica's vegetative species makes them excellent barometers of regional climate change.

Monitoring their presence in Antarctica, a minimally disturbed landscape, could provide clues as to how similar vegetation types may respond to climate in other fragile ecosystems across the globe, such as parts of the Arctic.

Charlotte Walshaw, PhD researcher from the School of GeoSciences, University of Edinburgh, who led the study, said: "Our continent-scale map provides key information on vegetation presence in areas that are rarely visited by people. This will have profound implications for our understanding of where vegetation is located across the continent, and what factors influence this distribution."

Dr Claudia Colesie, researcher at the University of Edinburgh's School of GeoSciences, who took part in the study, said: "Lichens and mosses in Antarctica encounter the harshest living conditions on the planet on a daily basis. Only the most resilient organisms can thrive there. Now that we know where to look for them, we can provide more targeted conservation measures to safeguard their future."

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Researchers shed light on river resiliency to flooding

Researchers at theUniversity of Nevada, Renohave completed one of the most extensive river resilience studies, examining how river ecosystems recover following floods. They developed a novel modeling approach that used data from oxygen sensors placed in rivers to estimate daily growth in aquatic plants and algae. The researchers then modeled the algal and plant biomass in 143 rivers across the contiguous U.S. to quantify what magnitude of flooding disturbs the biomass and how long the rivers take to recover from floods. Increased understanding of rivers' resiliency is important to maintaining healthy rivers, as human actions can affect flood regimes and change the conditions in rivers for other aquatic life that may rely on algae and plants as a food source.

Assistant Professor Joanna Blaszczak and Postdoctoral Scholar Heili Lowman, both in the University'sCollege of Agriculture, Biotechnology & Natural ResourcesandGlobal Water Centerled the research, which was published in two separate journal articles. The preliminary work, led by Blaszczak andpublished in Ecology Letters last June, first studied six rivers and laid the groundwork and methodology for the second study, which Blaszczak hired Lowman to conduct, examining the 143 rivers. The results of that research were justpublished last month in PNAS (the Proceedings of the National Academy of Sciences).

The research is unique because it estimates changes in biomass in rivers more frequently than ever before without needing to directly sample rivers. This is done by using both data from oxygen sensors placed in the rivers by the U.S. Geological Survey and a population model of algal and plant biomass -- similar to a human population model that models change in the number of people over time, but instead modeling the change in the amount of algae and plants. The oxygen sensors began collecting data in 2007, and the most recent Nevada-led study of 143 rivers includes some data that are for nine years running, among the longest such records on file for rivers across the globe.

"Previously, you would have to go to a river and scrub rocks to measure the algae, and do that several times for an extended period of time in order to estimate changes in biomass growth and loss," Blaszczak said. "This is very time consuming, so the data have been extremely limited relative to how extensive our sensor networks are."

Blaszczak said that with the oxygen sensors that take data as frequently as every five minutes, the team found that they could use statistical models to extract the amount of photosynthesis that occurs daily and estimate daily changes in the amount of biomass in a river over time.

"The dissolved oxygen sensors show the peak during the day, and the low during the night, and from those patterns, you can estimate how much new algae and other biomass grew that day," she said. "With the sensors measuring data continuously in hundreds of rivers for years now, we can get a much bigger, clearer picture. The data is there, and we can use it to model the size of flood needed to disturb the biomass in a river, as well as the rate at which a river recovers from flood disturbances, which can help us manage rivers more effectively."

Getting started

In the first study, Blaszczak used two years of data from oxygen sensors placed in six rivers. She found that she could successfully use this data to model the flood threshold specific to a river that disturbed the underlying biomass, and that generally, the magnitude of flood necessary to disturb biomass and reduce ecosystem productivity was lower than the disturbance flow threshold necessary to mobilize river bed sediment, a metric of disturbance commonly used by those studying rivers. In other words, instead of estimating the disturbance of the river by the movement of the rocks on the river bed, this study used the biology -- the changes in algae and plant growth -- to quantify disturbance to the river and found that the biological disturbance threshold was lower.

"The amount of biomass is important for water quality and a food source for everything that lives in a river," Blaszczak explained, "so it is more important than rock movement, in terms how a river ecosystem is affected by a disturbance."

Blaszczak, a freshwater ecologist, began this work with Robert O. Hall Jr. of the Flathead Lake Biological Station at the University of Montana and enlisted the help of her colleague Assistant Professor Robert Shriver, a plant ecologist, for both research projects to complete the biomass growth modeling. Blaszczak, Shriver, and Lowman all conduct research as part of the College'sDepartment of Natural Resources & Environmental Science, as well as the College'sExperiment Stationresearch unit. The College's faculty often take interdisciplinary approaches to meet research challenges, Blaszczak said.

Expanding out to a continental scale

Blaszczak wanted to delve further by applying this approach to more rivers over a longer period of time to shed light on how various factors may be influencing both a river's thresholds for flood disturbance and its resilience to floods. Thus, she recruited Lowman to embark on the second, more extensive study. Lowman's research examined landscape and river characteristics that affected the rivers' resiliency to floods.

"We've never had such great insight into the resilience of rivers, and because of the amount of data and our modeling, we now understand the natural variation in resilience, and that the widest rivers without dams upstream recover the most quickly," Lowman said.

The fact that wide rivers without dams recover more quickly than wide rivers with dams upstream was not immediately obvious, she said, and is one example of how rivers can be affected and/or managed by our actions. Most of the rivers Lowman researched had three to four years of data, with some having as much as nine years, and a handful having less than a year.

"Having three to four years' worth of data is way more than we've ever been able to use before," Lowman said. "And, we used rivers of various sizes with various climates and land characteristics."

Besides wider rivers without dams being more resilient, Lowman said those rivers that had more frequent floods also tended to recover more quickly.

"It could be that they have had a long history of frequent flooding, so their algae and plant communities have developed the ability to adapt to more frequent disturbance," she said.

Overall, Lowman said the new model results are consistent with other previous approaches. But, she said that some sites took much longer, a month or more, to recover from floods than other sites, regardless of river size.

"It might be the composition of the algal and plant communities, the structure of the river bed, or other factors," she said. "The thresholds and recovery times are very likely partially dependent on the slope, the grain size of the sediment, and possibly other factors that aren't as well documented. Those are some next steps for future research."

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Complex green organisms emerged a billion years ago

Of all the organisms that photosynthesize, land plants have the most complex bodies. How did this morphology emerge? A team of scientists led by the University of Göttingen has taken a deep dive into the evolutionary history of morphological complexity in streptophytes, which include land plants and many green algae. Their research allowed them to go back in time to investigate lineages that emerged long before land plants existed. Their results revise the understanding of the relationships of a group of filamentous algal land colonizers much older than land plants. Using modern gene sequencing data, researchers pinpoint the emergence of multicellularity to almost a billion years ago. The results were published in the journal Current Biology.

The study focused on Klebsormidiophyceae, a class of green algae known for its ability to colonize diverse habitats worldwide.

The team of researchers conducted extensive sampling, investigating habitats ranging from streams, rivers, and lake shores to bogs, soil, natural rocks, tree bark, acidic post-mining sites, sand dunes, urban walls, and building façades.

"It's really fascinating that these tiny robust little organisms have such a high diversity in their morphology and also are extremely well adapted to live in sometimes very harsh environments," says Dr Tatyana Darienko, University of Göttingen's Institute for Microbiology and Genetics.

This comprehensive sampling aimed to create a global distribution map for Klebsormidiophyceae, emphasizing their adaptability, ecological significance, and hidden diversity.

Based on genetic data calibrated by fossils, the researchers performed "molecular clock analyses."

While delving into the complex evolutionary history of Klebsormidiophyceae, the researchers faced challenges in resolving phylogenetic relationships using traditional markers.

To overcome this, they employed hundreds of genes obtained from the transcriptomes of 24 isolates from different continents and habitats.

"Our approach, known as phylogenomics, was to reconstruct the evolutionary history taking into account whole genomes or large fractions of genomes," explains Dr Iker Irisarri, Leibniz Institute for the Analysis of Biodiversity Change.

"This extremely powerful method can reconstruct evolutionary relationships with very high precision."

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Despite intensive scientific analyses, this centaur head remains a mystery

At the National Museum in Copenhagen, Denmark, there is a marble head that was once part of the ancient Greek Parthenon temple on the Acropolis in Athens. The head originally belonged to a centaur figure and was part of a scene depicting the Greek mythological Lapiths' battle against the centaurs (mythical creatures that were half-horse, half-human).

For reasons that have yet to be explained, parts of the centaur head are coated with a thin brown film, as are several other marble fragments from the Parthenon.

The mysterious brown film was first examined by the British Museum in 1830.

Back then, attempts were made to determine if the color originated from ancient paint, but it was eventually concluded that it might be a result of a chemical reaction between the marble and the air, or that the marble contained iron particles that had migrated to the surface, coloring it brown.

Oxalic acid, algae and fungi

"There have been many attempts to explain the peculiar brown film. In 1851, German chemist, Justus von Liebig, performed the first actual scientific investigation and determined that the brown film contained oxalates -- salts of oxalic acid. This has been confirmed by later analyses, but the origin of the oxalates has remained a mystery," says Professor emeritus Kaare Lund Rasmussen, an expert in chemical analyses of historical and archaeological artifacts, Department of Physics, Chemistry and Pharmacy, University of Southern Denmark.

Along with University of Southern Denmark colleagues Frank Kjeldsen and Vladimir Gorshkov from the Department of Biochemistry and Molecular Biology, Bodil Bundgaard Rasmussen, former head of the Antiquities Collection at the National Museum of Denmark, Thomas Delbey from Cranfield University in England, and Ilaria Bonaduce from the University of Pisa, Italy, he has published a scientific article describing the results of their investigations into the brown-colored centaur head from the National Museum.

The article is published in Heritage Science, and you can find it here.

"We especially wanted to examine whether the brown film could have been formed by some biological organism, such as lichen, bacteria, algae, or fungi. This theory had been suggested before, but no specific organism had been identified. The same goes for the theory that it could be remnants of applied paint -- perhaps to protect or tone the marble surface," says Kaare Lund Rasmussen.

For their investigations, the research team was allowed to take five small samples from the back of the centaur head.

These samples underwent various analyses in SDU's laboratories, including protein analysis and so-called Laser Ablation Inductively Coupled Plasma Mass Spectrometry.

"We found no traces of biological matter in the brown layers -- only from our own fingerprints and perhaps a bird egg that broke on the marble in ancient times. This doesn't prove that there never was a biological substance, but it significantly reduces the probability, making the theory of a biological organism less probable now," says Kaare Lund Rasmussen.

Similarly, it is now less probably that the marble surface was painted or preserved, according to the researchers, who also specifically searched for traces of paint.

Ancient paints were typically based on natural products such as eggs, milk, and bones, and no traces of such ingredients were found in the brown stain alone.

The mystery remains

Through their investigations, the research team also discovered that the brown film consists of two separate layers.

These two layers are approximately equally thick, around 50 micrometers each, and they differ in terms of trace element composition.

However, both layers contain a mixture of the oxalate minerals weddellite and whewellite.

The fact that there are two distinct layers argues against the theory that they were created by the migration of material, such as iron particles, from the interior of the marble.

It also contradicts the theory that they resulted from a reaction with the air.

Air pollution is also unlikely for another reason; the centaur head has been indoors in Copenhagen since before the modern industrialization began in the 18th century.

In fact, this makes the heads at the National Museum particularly valuable compared to the marble pieces on the Acropolis, of which some have only recently been brought indoors.

"As there are two different brown layers with different chemical compositions, it is likely that they have different origins. This could suggest that someone applied paint or a conservation treatment, but since we haven't found traces of such substances, the brown color remains a mystery," concludes Kaare Lund Rasmussen.

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Study identifies key algae species helping soft corals survive warming oceans

Scleractinian corals, or hard corals, have been disappearing globally over the past four decades, a result of climate change, pollution, unsustainable coastal development and overfishing. However, some Caribbean octocorals, or soft corals, are not meeting the same fate.

During a two-year survey of soft corals in the Florida Keys, Mary Alice Coffroth, professor emerita of geology at the University at Buffalo, along with a small team of UB researchers, identified three species of octocorals that have survived heat waves. While the coral animal itself may be heat tolerant, Coffroth said that her team concluded that the symbiotic algae inside the coral serve as a protector of sorts.

"The resistance and resilience of Caribbean octocorals offers clues for the future of coral reefs," Coffroth said.

A recent paper outlining their research, "What makes a winner? Symbiont and host dynamics determine Caribbean octocoral resilience to bleaching," was published on Nov. 22, in Science Advances by the American Association for the Advancement of Science (AAAS).

Coffroth is the lead author on the study she conducted between 2015 and 2017 with graduate student Louis Buccella, undergraduates Katherine Eaton and Alyssa Gooding and technician Harleena Franklin. Howard Lasker, professor emeritus in the departments of Environment and Sustainability and Geology, also contributed to the study.

Algae helps corals survive heat waves

Both hard and soft coral depend on a nutritional symbiosis with single-celled algae living within their tissues. Warmer waters can cause the symbiosis to break down, resulting in a loss of the algal symbionts, which turns the corals white, a phenomenon known as bleaching.

"Bleaching can lead to coral death," said Coffroth, who has studied coral reefs in the Florida Keys since 1998, including a more recent study in 2020-21. "It's unclear if the algae leave or are ejected from the coral.

"In this study, we examined possible mechanisms that contribute to the heightened resistance and resilience of three octocoral species in the face of the recurring marine heat waves leading to bleaching events," Coffroth said, noting that this is the first study that follows both symbiont genetic makeup and density in Caribbean octocorals before, during and after a major heat wave.

By and large, Caribbean octocorals harbor symbionts within the genus Breviolum, she said. And this symbiont is helping to make the octocoral better able to handle the rising heat.

"The Breviolum densities declined during the heatwaves but recovered quickly," she explained. "Octocoral mortality was low compared to their scleractinian relatives."

2014 El Niño prompted research

When Coffroth saw bleached corals during the 2014 El Niño and knew that a similar event was predicted for the following summer, she applied for a Rapid Response Research (RAPID) grant from the National Science Foundation. She was awarded $56,305 and with her master's student, Buccella, conducted the study in the Keys, following the fate of the octocorals and their symbionts for 28 months.

She and other members of the team made trips to the Keys Marine Lab at the Florida Institute of Oceanography to study the octocorals in the spring and fall of 2015 and 2016 and spring and summer of 2017, recording coral coloration and taking samples to study density of the symbionts and their genetic identity.

"We knew it was critical to follow individual colonies across an event with long-term monitoring of both host and symbiont responses," she said, "and to examine the response at least at the level of symbiont species, if not the genotype, to identify potentially resilient species."

Climate change moving faster than coral evolution

Although the study began almost a decade ago, Coffroth said the findings are extremely relevant because they mirror what is happening right now, with the continuing warming of ocean waters, increased storms and major bleaching events across the globe.

"There is evidence that corals are withstanding higher temperature now than they did in the 1960s," she said. "That signals evolution, but the problem is that climate change is moving too fast, faster than evolution."

In addition to their beautiful aesthetics, coral reefs provide many benefits to the planet and its inhabitants, including barriers to coastal regions that are susceptible to hurricanes and other tropical storms; habitat for large fish such as grouper and snapper; a tourist destination for snorkeling, fishing and diving; and a source for bioactive compounds used in drugs to treat inflammation and certain kinds of cancer.

"If you a see picture of coral reefs when I started diving in the 1970s and compare it with one now, it makes you want to cry," she said. "The change is just amazing."

While she noted that this study has some important observations, further study is needed to better understand what is happening to the ecosystem.

"I'm seeing species bleach that have never bleached before but also ones showing more resilience," she said. "There is a lot of variation within both the animal and symbiont genera. We need to understand the variation."

The hope is to continue research into coral reef relationships and the durability of the symbiotic algae while also taking steps to halt the damage to the environment by human action, such as overfishing and the burning of fossil fuels.

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Heat tolerant coral may trade fast growth for resilience

Algae living within the soft tissue of coral supply much of the energy needed by their hosts, and some symbiotic algae help coral withstand warmer water better than others. In a recently published study led by the University of Hawai'i at Manoa, researchers found that there was a tradeoff for corals dominated by the thermally sensitive algae -- they have higher growth, but only in cooler water.

"As the ocean continues to warm, understanding how symbionts and environmental factors affect coral growth and health will help predict reef futures and inform conservation interventions where coral stocks are selected for specific traits or symbionts," said Shayle Matsuda, a doctoral student at the Hawai'i Institute of Marine Biology in the UH Mānoa School of Ocean and Earth Science and Technology at the time of the research.

The study was co-led by Matsuda, now a postdoctoral fellow at the Shedd Aquarium, and Mariah Opalek, who conducted the experiment for her undergraduate thesis at UH Mānoa. The research team investigated whether rice corals hosting symbiotic algae that can tolerate warmer water may grow more slowly, which could impact survivorship and competition for space on the reef, compared to coral hosting symbionts that are more susceptible to bleaching when ocean waters warm.

Over a two-month study period, the researchers measured the growth of rice corals dominated by heat tolerant or heat sensitive symbiotic algae. Additionally, they tested growth across decreasing light levels to see if the tradeoff between growth and tolerance to warm water would be affected by light, which is a major driver of the distribution of these symbionts in Kāneʻohe Bay, Hawai'i.

"This research shows us the complexity of coral growth on a reef," said Opalek, who is now a grant support assistant at Kaua'i Community. "A coral's competitive advantage could be lost in a matter of a few degrees depending on what type of symbiont they associate with."

During the first month, when water temperatures were warmer, the symbiont present did not affect growth. However, over the cooler second month, corals with heat sensitive algae grew up to 77% faster than corals dominated by heat tolerant algae, and this growth advantage increased in higher light treatments, which correlates to shallower depths on a reef.

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Bizarre new fossils shed light on ancient plankton

A scientist from the University of Leicester has discovered a new type of fossil that reveals life in the oceans half a billion years ago.

The tiny organisms, detailed in a new study in the journal Proceedings of the Royal Society B, resemble modern-day algae and might also give scientists an insight into the climate changes that affected our oceans.

The fossils are microscopic and look like spiny balls connected together. The study's author Dr Tom Harvey, from the University of Leicester School of Geography, Geology and the Environment, said: "When I first saw them, I had no idea what they were. I wondered if they could be animal eggs, or some new type of organism. There's nothing quite like them, living or extinct."

But as further specimens came to light, Dr Harvey identified similarities with modern green algae that live floating in the plankton of ponds and lakes. He explains: "The fossils have the same sort of colonial structure as the modern algae, with cells linking together, explaining their neat, geometric arrangements. Surprisingly, though, the fossil examples lived in the sea, giving a rare glimpse of the early marine plankton."

The importance of the fossils lies in their immense age. They lived around the time when animals were first evolving, during the Cambrian 'explosion' of life -- and this is probably no coincidence. In today's world, phytoplankton provides the fundamental food source for almost all life in the oceans. However, the modern groups of phytoplankton evolved relatively recently, and we do not know which groups inhabited the Cambrian oceans.

Dr Harvey explains: "When we look at modern plankton, we see that algae develop colonies when animals are trying to eat them. It's a defence mechanism. So, the existence of colonial algae in the Cambrian Period suggests that early animals were evolving to feed in the plankton, starting a predator-prey relationship that has continued ever since.

"Considering that the plankton underpins life in the oceans, and fossil plankton helps us build ancient climate models, these small fossils have a big role in telling the history of life on Earth."

The new discovery will prompt a re-think on other early microfossils. For years, scientists have thought that the spiny balls found individually were the dormant cysts of single-celled life.

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Polar experiments reveal seasonal cycle in Antarctic sea ice algae

In the frigid waters surrounding Antarctica, an unusual seasonal cycle occurs. During winter, from March to October, the sun barely rises. As seawater freezes it rejects salts, creating pockets of extra-salty brine where microbes live in winter. In summer, the sea ice melts under constant daylight, producing warmer, fresher water at the surface.

This remote ecosystem is home to much of the Southern Ocean's photosynthetic life. A new University of Washington study provides the first measurements of how sea-ice algae and other single-celled life adjust to these seasonal rhythms, offering clues to what might happen as this environment shifts under climate change.

The study, published Sept. 15 in the International Society for Microbial Ecology's ISME Journal, contains some of the first measurements of how sea-ice microbes respond to changing conditions.

"We know very little about how sea-ice microbes respond to changes in salinity and temperature," said lead author Hannah Dawson, a UW postdoctoral researcher who did the work while pursuing her doctorate in oceanography at the UW. "And until now we knew almost nothing about the molecules they produce and use in chemical reactions to stay alive, which are important for supporting higher organisms in the ecosystem as well as for climate impacts, like carbon storage and cloud formation."

The polar oceans play an important role in global ocean currents and in supporting marine ecosystems. Microbes form the base of the food web, supporting larger life forms.

"Polar oceans make up a significant portion of the world's oceans, and these are very productive waters," said senior author Jodi Young, a UW assistant professor of oceanography. "These waters support big swarms of krill, the whales that come to feed on those krill, and either polar bears or penguins. And the start of that whole ecosystem are these single-celled microscopic algae. We just know so little about them."

The tiny organisms are also important for the climate, since they quietly perform photosynthesis and soak up carbon from the atmosphere. Polar algae are especially good at producing sulfur-containing molecules that give beaches their distinctive smell and, when lofted into the air in sea spray, promote formation of clouds that can reduce penetration of solar rays.

Antarctic sea ice, though long stable, is at an all-time record low this year.

In other oceans, satellite instruments can capture dramatic seasonal phytoplankton blooms from space -- but that isn't possible for microbes hidden under sea ice. And Antarctic waters are particularly challenging to visit, leaving researchers with almost no measurements in winter.

In late 2018, Dawson and co-author Susan Rundell traveled to Palmer Station, a U.S. research station on the West Antarctic Peninsula. They used a small boat to sample seawater and sea ice at the same nearby sites every three days.

Back on shore, the two graduate students performed 10-day experiments in tanks to see which microbes grew as temperature and salinity were adjusted to mimic sea-ice formation and melt. They also shipped samples back to Seattle for more complex measurements of the samples' genetics and metabolites, the small organic molecules produced by the cell.

Results revealed how single-celled algae deal with their fluctuating environments. As temperatures drop, the cells produce cryoprotectants, similar to antifreeze, to prevent their cellular fluid from crystallizing. Many of the most common cryoprotectant molecules were the same across different microbial lifeforms.

As salinity changes, to avoid either bursting in freshening waters or becoming desiccated like raisins in salty conditions, the cells change the concentration of salt-like organic molecules. Many such molecules serve a dual role as cryoprotectants, to balance conditions inside and outside the cell to maintain water balance.

The results show that under short-term temperature and salinity changes, community structure in each sample remained stable while adjusting the production of protective molecules. Different microbe species showed consistent responses to changing conditions. This should simplify modeling future responses to climate change, Young said.

Results also hint that the production of omega-3 fatty acids may decline in lower-salinity environments. This would be bad news for consumers of krill oil supplements, and for the marine ecosystem that relies on those algae-derived nutrients. Future research now underway by the UW group aims to confirm that result -- especially with the prospect of increasing freshwater input from melting sea ice and glaciers.

"We're interested in how these sea-ice algae contend with changes in temperature, salinity and light under normal conditions," Dawson said. "But then we also have climate change, which is completely remodeling the landscape in terms of when sea ice is forming, how much sea ice forms, how long it stays before it melts, as well as the quantity of freshwater input from glaciers. So we're both trying to capture what's happening now, and also asking how that can inform what might happen in the future."

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Remains of an extinct world of organisms discovered

Newly discovered biomarker signatures point to a whole range of previously unknown organisms that dominated complex life on Earth about a billion years ago. They differed from complex eukaryotic life as we know it, such as animals, plants and algae in their cell structure and likely metabolism, which was adapted to a world that had far less oxygen in the atmosphere than today. An international team of researchers, including GFZ geochemist Christian Hallmann, now reports on this breakthrough for the field of evolutionary geobiology in the journal Nature.

The previously unknown "protosteroids" were shown to be surprisingly abundant throughout Earth´s Middle Ages. The primordial molecules were produced at an earlier stage of eukaryotic complexity -- extending the current record of fossil steroids beyond 800 and up to 1,600 million years ago. Eukaryotes is the term for a kingdom of life including all animals, plants and algae and set apart from bacteria by having a complex cell structure that includes a nucleus, as well as a more complex molecular machinery. "The highlight of this finding is not just the extension of the current molecular record of eukaryotes," Hallmann says: "Given that the last common ancestor of all modern eukaryotes, including us humans, was likely capable of producing 'regular' modern sterols, chances are high that the eukaryotes responsible for these rare signatures belonged to the stem of the phylogenetic tree."

Unprecedented glimpse of a lost world

This "stem" represents the common ancestral lineage that was a precursor to all still living branches of eukaryotes. Its representatives are long extinct, yet details of their nature may shed more light on the conditions surrounding the evolution of complex life. Although more research is needed to evaluate what percentage of protosteroids may have had a rare bacterial source, the discovery of these new molecules not only reconciles the geological record of traditional fossils with that of fossil lipid molecules, but yields a rare and unprecedented glimpse of a lost world of ancient life. The competitive demise of stem group eukaryotes, marked by the first appearance of modern fossil steroids some 800 Million years ago, may reflect one of the most incisive events in the evolution of increasingly complex life.

"Almost all eukaryotes biosynthesise steroids, such as cholesterol that is produced by humans and most other animals" adds Benjamin Nettersheim from the University of Bremen, first author of the study -- "due to potentially adverse health effects of elevated cholesterol levels in humans, cholesterol doesn't have the best reputation from a medical perspective. However, these lipid molecules are integral parts of eukaryotic cell membranes where they aid in a variety of physiological functions. By searching for fossilised steroids in ancient rocks, we can trace the evolution of increasingly complex life."

What the Nobel laureate thaught impossible...

Nobel laureate Konrad Bloch had already speculated about such a biomarker in an essay almost 30 years ago. Bloch suggested that short-lived intermediates in the modern biosynthesis of steroids may not always have been intermediates. He believed that lipid biosynthesis evolved in parallel with changing environmental conditions throughout Earth history. In contrast to Bloch, who did not believe that these ancient intermediates could ever be found, Nettersheim started searching for protosteroids in ancient rocks that were deposited at a time when those intermediates could actually have been the final product.

But how to find such molecules in ancient rocks? "We employed a combination of techniques to first convert various modern steroids to their fossilised equivalent; otherwise we wouldn't have even known what to look for," says Jochen Brocks, professor at the Australian National University who shares the first-authorship of the new study with Nettersheim. Scientists had overlooked these molecules for decades because they do not conform to typical molecular search images. "Once we knew our target, we discovered that dozens of other rocks, taken from billion-year-old waterways across the world, were oozing with similar fossil molecules."

The oldest samples with the biomarker are from the Barney Creek Formation in Australia and are 1.64 billion years old. The rock record of the next 800 Million years only yields fossil molecules of primordial eukaryotes before molecular signatures of modern eukaryotes first appear in the Tonian period. According to Nettersheim "the Tonian Transformation emerges as one of the most profound ecological turning points in our planet's history." Hallmann adds that "both primordial stem groups and modern eukaryotic representatives such as red algae may have lived side by side for many hundreds of millions of years." During this time, however, the Earth's atmosphere became increasingly enriched with oxygen -- a metabolic product of cyanobacteria and of the first eukaryotic algae that would have been toxic to many other organisms. Later, global "Snowball Earth" glaciations occurred and the protosterol communities largely died out. The last common ancestor of all living eukaryotes may have lived 1.2 to 1.8 billion years ago. Its descendants were likely better able to survive heat and cold as well as UV radiation and displaced their primordial relatives.

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Global macrogenetic map of marine habitat-forming species

Species known as marine habitat-forming species -- gorgonians, corals, algae, seaweeds, marine phanerogams, etc. -- are organisms that help generate and structure the underwater landscapes. These are natural refuges for other species, and provide biomass and complexity to the seabeds. But these key species in marine ecosystems are currently threatened by climate change and other perturbations derived from human activity. Now, a study published in the journal Global Ecology and Biogeography warns that even in the marine protected areas (MPAs) the genetic diversity of structural species is not protected, although it is essential for the response and adaptation of populations to changes that alter the natural environment.

The study was carried out by Laura Figuerola-Ferrando, Cristina Linares, Ignasi Montero-Serra and Marta Pagès-Escolà, from the Faculty of Biology of the University of Barcelona and the Biodiversity Research Institute of the UB (IRBio); Jean-Baptiste Ledoux and Aldo Barreiro, from the Interdisciplinary Centre of Marine and Environmental Research (CIIMAR) in Portugal, and Joaquim Garrabou, from the Institute of Marine Sciences (ICM-CSIC).

Genetic diversity is also a component of biodiversity

Traditionally, marine biodiversity management and conservation plans have considered factors such as species richness. Genetic diversity -- another major component of biodiversity -- reflects the genetic variation that exists among organisms of the same species and is a determining factor in the adaptive capacity of populations and their survival. Despite its importance, genetic diversity has so far been overlooked in management and conservation plans.

"Genetic diversity plays a key role in enhancing the ability of species, populations and communities to adapt to rapid environmental changes resulting from climate change and thus increase their resilience," says researcher Laura Figuerola-Ferrando, first author of the study.

"However, -- she continues -- so far, the vast majority of marine protected areas are implemented based on the presence of several species and habitats, without considering their genetic diversity. Another example would be the red list of the International Union for Conservation of Nature (IUCN), which does not consider genetic diversity either."

"In recent years, the need to focus conservation efforts on the protection of genetic diversity has been reinforced. Technological progress in the massive development of different techniques to determine genetic diversity (for example, through the use of microsatellites or small DNA fragments), as well as their affordable cost, can help to include genetic diversity in management and conservation plans," says the researcher from the Department of Evolutionary Biology, Ecology and Environmental Sciences of the UB.

From the northwest Atlantic to the Gulf of Guinea

The study applies macrogenetic techniques to identify general genetic patterns of diverse marine species at large spatial scales. The authors have analyzed data from a global database containing genetic diversity information (based on microsatellites) for more than 9,300 populations of 140 species in different marine regions around the globe.

The results outline a reference scenario of genetic patterns in marine habitat-forming species (corals, macroalgae, marine phanerogams, etc.) of potential interest for improving marine life management and conservation plans.

The northwest Atlantic provinces and the Bay of Bengal are the regions where the highest genetic diversity in marine landscape species has been identified. Quite high values (above the global average) have also been identified in the Mediterranean. In contrast, the marine provinces with the lowest values of genetic diversity are the Gulf of Guinea and the southwest Atlantic.

The findings also indicate a positive correlation between genetic diversity and species richness of both animal and plant marine habitat-forming species. However, the paper warns of a worrying result: the Network of Marine Protected Areas (RAMP) in the large oceanic ecoregions does not preserve areas where the genetic diversity of marine habitat-forming species is highest.

"What we have seen is that what is not being protected in MPAs is genetic diversity. In the study, the initial hypothesis was that within these areas there would be greater genetic diversity, but this has not been the case. In fact, we have seen, at a global level, that there are no differences in genetic diversity between inside and outside the MPAs," notes Laura Figuerola-Ferrando, who is doing her doctoral thesis under the supervision of Cristina Linares (UB) and Joaquim Garrabou (ICM-CSIC).

A new pattern of equatorial biodiversity at the poles

The authors have also identified a specific pattern in the distribution of genetic diversity of the marine habitat-forming species that differs from the traditional models known to date. "This is a bimodal latitudinal pattern: it is a complex biogeographic model and it implies that if we model how the genetic diversity of these species varies with latitude, we find two peaks in temperate zones and a small dip in genetic diversity at the equator," notes the ICREA Academia professor Cristina Linares (UB-IRBio), one of the coordinators of the study together with Jean-Baptiste Ledoux (CIIMAR).

This scientific discovery is relevant because until a few decades ago it was considered that the distribution of biodiversity on the planet followed a unimodal pattern, that is, it had maximum values at the equator and decreased towards the poles. "This is not always the case, especially in terms of species diversity in marine ecosystems. For example, in the case of benthic species, this pattern is biomodal rather than unimodal in terms of both species richness and genetic diversity," explains Cristina Linares.

"In our study, the bimodal latitudinal pattern is influenced by taxonomy: in the used model, we found statistically significant differences between animal species (more genetic diversity) and plant species (less genetic diversity). Furthermore, if we explore the latitudinal pattern separating animal and plant species, we can see that a bimodal pattern continues to be observed in animals, but the same cannot be said for plants," adds researcher Jean-Baptiste Ledoux (CIIMAR).

Genetic diversity: improving conservation management plans

The conclusions of the work recall the need to include the genetic diversity of populations in biodiversity management and conservation plans on the planet. "The importance of having genetic diversity in biodiversity management and conservation plans has just been reinforced with the 'Kunming-Montreal Global Biodiversity Framework' within the Convention on Biological Diversity (CBD/COP/15/L25, 2022). In this context, we believe that the baseline on genetic diversity patterns in marine habitat-forming species defined as our work can be very relevant," notes Jean-Baptiste Ledoux.

This study also reveals that the Mediterranean and Atlantic regions are among the most present in the scientific literature used in this work on macrogenetic patterns of deep-sea structural species.

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Algae in Swedish lakes provide insights to how complex life on Earth developed

By studying green algae in Swedish lakes, a research team, led by Lund University in Sweden, has succeeded in identifying which environmental conditions promote multicellularity. The results give us new clues to the amazing paths of evolution.

The evolution of multicellular life has played a pivotal role in shaping biological diversity. However, we have up until now known surprisingly little about the natural environmental conditions that favour the formation of multicellular groups.

The cooperation between cells within multicellular organisms has enabled eyes, wings and leaves to evolve. The predominant explanation for why multicellularity evolves is that being in a group enables species to better cope with environmental challenges -- where being in a large group can, for instance, protect cells against being eaten.

"Our results challenge this idea, showing that multicellular groups form, not because they are inherently beneficial, but rather as a by-product of single-celled strategies to reduce environmental stress. In particular, cells produce a range of substances to protect themselves from the environment and these substances appear to prevent daughter cells from dispersing away from their mother cell," says Charlie Cornwallis, biology researcher at Lund University.

To understand how and why single-celled organisms evolve to be multicellular, the scientists experimented on green algae where some species are always single-celled, some are single-celled but become multicellular under certain conditions, while others are always multicellular containing thousands of cells.They could then identify the environmental conditions that promote multicellularity and find out the benefits and costs for organisms. The researchers then combined data with information on the environments that single-celled and multicellular green algae are adapted to across the whole of Sweden.

"I was surprised that there were no benefits or costs to living in multicellular groups. The conditions that individual cells experience can be extremely different when swimming around on their own, to being stuck to other cells and having to coordinate activities. Imagine you were physically tied to your family members, I think it would have quite an effect on you," says Charlie Cornwallis.

The study was conducted in Swedish lakes, and it not only provides information on which green algae occur where, and why -- it also helps us understand the origins of biological diversity that shape the world around us.

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Geoscientists shed a light on life's evolution 800 million years ago

Is nitrate responsible for algae, flowers, and even your neighbors?

A team of Virginia Tech geoscientists have unearthed evidence that may indicate yes.

The team's findings, recently published in Science Advances, reveal an increase in biologically available nitrogen during the time that marine eukaryotes -- organisms whose cells have a nucleus -- became dominate. Complex eukaryotic cells evolved into multicellular organisms and are credited for ushering in a whole new era for life on Earth, including animals, plants, and fungi.

"Where we sit today, with life as it is on the planet, is the sum total of all the events that happened in the past," said Ben Gill, an associate professor of sedimentary geochemistry and co-author on the paper. "And this is a key event where we shift from dominantly prokaryotic ecosystems -- cells that are much simpler than the ones in our bodies -- to eukaryotes. If that did not happen, we would not be here today."

Previous research focused on phosphorus' role in the rise of eukaryotes, but Junyao Kang, a doctoral student in the Department of Geosciences and lead author of the paper, was curious about the part nitrogen played in this event.

"This data is unique because nitrogen isotope data are virtually nonexistent from the early Neoproterozoic time period, or between a billion and 800 million years ago," said Kang.

Collaborating with the Nanjing University in Najing, China, Kang has spent two years working to understand what drove the rise of eukaryotes through nitrogen isotope analysis of rock samples from the North China Craton. Home to rocks dating back 3.8 billion years ago, the region was once covered by an ocean.

"We had some rough ideas of when eukaryotes became ecologically successful," said Shuhai Xiao, professor of geobiology and a paper co-author. "They had been there for a long time in a low-key status until about 820 million years ago, when they became abundant."

Kang decided he wanted to learn why. He took the data from the rock samples, entered it into a larger database, and analyzed it across a longer time scale that spanned different geographic locations.

"Once we did this kind of integration and put it into a big picture, we saw the rise of nitrates through time, which happened around 800 million years ago," said Kang.

Solid collaboration

A collaborative, international approach was key to connecting this new data with biological events, mostly notably, the rise of eukaryotes.

Gill and Rachel Reid, also a College of Science geochemist and co-author of the paper, provided critical analyses through resources, including the mass spectrometer in the Geoscience Stable Isotope Lab at Virginia Tech. An elemental analyzer coupled to the mass spectrometer allowed the researchers to extract pure nitrogen gas from the samples for analysis.

Gill specializes in reconstructing present and past chemical cycles on our planet. He collaborates with paleontologists to study the record of life preserved in the geological record and examines what potential environmental drivers might have enabled changes in life through history.

Reid, who generally focuses her research on Earth's more recent events, had a special opportunity to offer her nitrogen isotope expertise to these ancient fossils.

Feifei Zhang, a geochemist at Nanjing University, was the paper's fourth co-author. Zhang provided insights on how much oxygen would have been available in the oceans during the time when nitrate increased in abundance.

All of the Virginia Tech authors are affiliated members of the Fralin Life Sciences Institute's Global Change Center, with Kang serving as a Ph.D. fellow in the Interfaces of Global Change graduate program. The center brings together experts from diverse disciplines to solve these complex global challenges and train the next generation of leaders.

Past, present, and future

Xiao, who has helped excavate and study some of the most ancient fossils from around the world, said this type of study gives him hope for future discoveries. The team members look forward to collaborating with NASA on future grants, such as the exobiology program supporting their current research.

He also credits University Libraries at Virginia Tech for its support of open-access publications, such as Science Advances, to provide a vetted selection of research, freely available to readers.

"We can link the dots from the nitrogen isotopic compositions in the ancient past and then go to the next step and infer how much nitrate was available for organisms," said Xiao. "And then we tie that with the fossil data to show that there's a relationship."

While ancient oceans are long gone, what happened in ancient oceans are recorded in rocks, and studying these rocks provides a link from our Earth's history to the present and to the future.

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Coral reefs in the Eastern Pacific could survive into the 2060s

Scientists at the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science found that some reefs in the tropical Pacific Ocean could maintain high coral cover into the second half of this century by shuffling the symbiotic algae they host. The findings offer a ray of hope in an often-dire picture of the future of coral reefs worldwide.

While global warming is causing the loss of coral reefs globally, scientists believe that some corals are increasing their tolerance to heat by changing the symbiotic algae communities they host, which through photosynthesis provide them with the energy they need to live.

"Our results suggest that some reefs in the eastern tropical Pacific, which includes the Pacific coasts of Panama, Costa Rica, Mexico, and Colombia, might be able to maintain high coral cover through the 2060s," said coral biologist Ana Palacio-Castro, lead author of the study, alumna of the Rosenstiel School, and a postdoctoral associate at the school's Cooperative Institute for Marine and Atmospheric Studies. "However, while this may be seen as good news for these reefs, their survival may not continue past that date unless we reduce global greenhouse gas emissions and curtail global warming on a larger scale."

Shallow coral reefs in the eastern tropical Pacific Ocean are predominantly built by branching corals in the genus Pocillopora, which are extremely important for the reefs in the region. The microscopic algae they host in their tissue harvest light to help the coral produce energy to grow. The loss of these symbiotic algae causes the coral to turn white, or bleach, and the coral struggles to meet their energy needs, which can often prove fatal.

To better understand how corals improved their tolerance to heat stress, the researchers examined over 40 years' worth of coral reef-monitoring data from Panama, one of the longest datasets of its kind in the world. They analyzed temperature, coral cover, bleaching and mortality data spanning three ocean heatwaves -- in 1982-1983, 1997-1998, and 2015-2016 -- along with data on algal symbiont community data during the last two.

The analysis showed that the 1982-83 heatwave significantly reduced coral cover on the reef, but the effects of the 1997-98 and 2015-16 El Niño were milder, especially for corals in the genus Pocillopora -- sometimes known as cauliflower coral -- the predominant reef-building coral in the eastern tropical Pacific. They also confirmed that during strong ocean heatwaves, the heat-tolerant alga Durusdinium glynnii becomes increasingly common in this particular lineage of corals, allowing them to better withstand periods of elevated temperatures. When combined with climate projections of future heat stress, the reefs that were predominantly composed of Pocillopora corals and that hosted this heat-tolerant alga were found to be better equipped to survive and maintain high levels of coral cover well into the second half of the current century, indicating that some reef systems may be more resilient to warming than previously thought.

"This study shows that there are some unusual reefs that may be able to survive for several decades as a result of their ability to shuffle symbionts," said Andrew Baker, professor of marine biology and ecology at the Rosenstiel School, and senior author of the study. "While we don't think that most reefs will be able to survive in this way, it does suggest that vestiges of our current reefs may persist for longer than we previously thought, although potentially with many fewer species. Coral reefs are incredibly valuable natural assets, providing coastal protection and fisheries benefits, and supporting many local communities. We can still make a difference by protecting them."

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Palau's Rock Islands harbor heat-resistant corals

Ocean warming is driving an increase in the frequency and severity of marine heatwaves, causing untold damage to coral reefs. Tropical corals, which live in symbiosis with tiny single celled algae, are sensitive to high temperatures, and exhibit a stress response called bleaching when the ocean gets too hot. In the last 4 decades, marine heatwaves have caused widespread bleaching, and killed millions of corals. Because of this, a global search is underway for reefs that can withstand the heat stress, survive future warming, and act as sources of heat-tolerant coral larvae to replenish affected areas both naturally and through restoration.

Now, scientists studying reefs in Palau, an archipelago in the western tropical Pacific, have identified genetic subgroups of a common coral species that exhibit remarkable tolerance to the extreme heat associated with marine heatwaves. Further, the scientists found evidence that larvae from these corals are traveling from their birthing grounds deep in Palau's lagoons, to the outer reef, where they survive and grow, and maintain their heat tolerance.

Understanding both the underlying mechanisms that facilitate heat tolerance of these corals, as well as the dispersal capabilities of their larvae will go a long way toward enhancing coral reef conservation and restoration efforts in the 21st century ocean, according to scientists at the Woods Hole Oceanographic Institution (WHOI) who led the research.

In Palau's main lagoon, a network of very ancient, fossilized reefs has been uplifted to form a series of mountains known as the Rock Islands. These formations slow water flow in and around them, creating localized environments in which the water temperatures are consistently higher than other areas of Palau's reefs.

Scientists sampled the keystone coral species Porites lobata (lobe coral) across Palau, including the Rock Islands. They took skeletal biopsies and examined the cores for stress bands, which are telltale signs of bleaching, a stress response corals have to high temperatures. They found corals from the Rock Islands bleached less during the intense 1998 heatwave than corals from other areas of the reef, indicating enhanced thermal tolerance.

Scientists then investigated the genetics of the corals and discovered four distinct lineages within the same species. Within the warmer Rock Islands, certain lineages, designated as "LB" and "RD" lineages, were much more common. The scientists were able to match the genetics of each coral with its own bleaching history and found that fewer individuals from the "LB" and "RD" lineages bleached during 1998, indicating enhanced thermal tolerance.

Remarkably, the scientists found the LB lineage was not restricted to the Rock Islands. They found some LB colonies also living on the cooler outer reefs. An examination of the bleaching histories of these colonies again revealed fewer stress bands, indicating that they maintained the thermal tolerance characteristic of their relatives in the Rock Islands.

"This suggests that the Rock Islands provide naturally tolerant larvae to neighboring areas," the scientists write in the paper titled "Palau's warmest reefs harbor thermally tolerant corals that thrive across different habitats," published in Communications Biology, a journal published by Nature. "Finding and protecting such sources of thermally-tolerant corals is key to reef survival under 21st century climate change."

"As oceans worldwide continue to warm, corals derived from extreme habitats will be at a competitive advantage and may enable the survival of otherwise vulnerable reefs," the authors continue. "Identifying and safeguarding natural breeding grounds of environmentally tolerant corals that can thrive under future climate conditions will be fundamental to the persistence of coral reef ecosystems worldwide in the coming decades."

"We found that some of Palau's reefs with the highest temperatures have corals that are more tolerant than one would expect," said the paper's lead author Hanny Rivera, a graduate of the MIT-WHOI Joint Program. Rivera, who conducted this work as part of her Ph.D. and postdoctoral research, is currently an associate director of business development at Ginko Bioworks. "In addition, they are genetically distinct from the same corals found in other parts of Palau, which suggests that there has been natural selection for hardier corals in these regions.."

Paper co-author Michael Fox added that the study is particularly exciting because it combines coral genetics with historical records of bleaching preserved in their skeletons to shed light on how corals from extreme habitats with high temperature tolerance can be dispersed across a reefscape. "This integrated perspective is essential for improving projections of coral communities in a warming ocean," said Fox, who was a postdoctoral scholar at WHOI during the research for this paper. He currently is an assistant research professor in the Red Sea Research Center at King Abdullah University of Science and Technology in Thuwal, Saudi Arabia.

The Palau research is directly related to the Super Reefs initiative WHOI launched with The Nature Conservancy and Stanford University to locate coral communities that can withstand marine heat waves, and work with local communities and governments to protect them.

"This work is the scientific basis for the Super Reefs initiative," said paper co-author Anne Cohen, a scientist at WHOI and Rivera's advisor on the study. "The Palau research demonstrates that Super Reefs exist and also provides actionable science knowledge that can be used to support their protection."

Cohen noted that there are other coral reefs, not just in Palau, where coral communities have not bleached as severely as scientists predicted based on the levels of thermal stress. "When we find the coral communities that are heat-tolerant or bleaching-resistant, and we protect them from other stresses that can kill them -- like dynamiting, overfishing, or coastal development -- they will produce millions of larvae that will travel on the currents, outside of their places of origin as we see on Palau, and they will repopulate reefs that have been devastated by heatwaves," she said. "Nature is amazing. Our job with the Super Reefs initiative is to protect these thermally resilient reefs and let nature do the rest."

Rivera added she is in awe of the immense appreciation, respect, and stewardship that the Palauan people have for their environment.

"They have been one of the pioneering countries in promoting marine conservation and ecological protection. It is wonderful to know that these special reefs are in such good hands," Rivera said. "It is my greatest hope that our research will further support the Palauan people in their efforts to maintain a healthy marine ecosystem."

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Shedding light on photosynthesis at sea

Plants that live on land, such as spinach, grow by using sunlight to perform photosynthesis. How, then, do algae photosynthesize in the deep sea, an environment where only a little light reaches them?

Land plants mainly absorb red and blue light from the sun and use it for photosynthesis. However, only weak blue-green light reaches the ocean floor. Therefore, macroalgae growing in the ocean have developed a protein, a so-called photosynthetic antenna, that efficiently utilizes this blue-green light. The photosynthetic antenna of marine macroalgae is very similar to that of land plants but differs in the structure of the pigments bound to it. Land plants have two types of pigments bound to their photosynthetic antennae, namely carotenoids and chlorophylls. In the marine green macroalga Codium fragile, the major carotenoids are substituted with siphonaxanthin while some chlorophyll a molecules are replaced by chlorophyll b molecules. Siphonaxanthin and chlorophyll b are known to contribute to increased absorption of green light and blue-green light, respectively, but the mechanism has not yet been fully understood.

Responding to this gap, a research team led by Associate Professor Ritsuko Fujii, from the Research Center for Artificial Photosynthesis (ReCAP) at Osaka Metropolitan University, and graduate student Soichiro Seki, from the Graduate School of Science at Osaka City University, used cryogenic electron microscopy to investigate the structures and binding environments of pigments bound to the photosynthetic antenna of C. fragile. The results allow for the elucidation of the molecular mechanism by which blue-green light -- the only light available in deep seawater -- is efficiently utilized for photosynthesis. Their findings were published in BBA Advances on November 11, 2022.

High-resolution analysis by cryogenic electron microscopy showed that siphonaxanthin in C. fragile is greatly distorted and forms hydrogen bonds with the surrounding protein at two locations. This structural feature is deemed a key factor in siphonaxanthin's ability to absorb green light. Additionally, the researchers successfully detected the difference between chlorophyll a and chlorophyll b, and they clarified several chlorophyll molecule substitution sites. When the substitution occurs, the adjacent region of chlorophyll b clusters becomes wider, enabling better absorption of blue-green light. In other words, the team was able to obtain information on the pigment coordinates, contributing to a better understanding of the mechanism of more efficient photosynthesis.

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World's oldest meal helps unravel mystery of our earliest animal ancestors

The contents of the last meal consumed by the earliest animals known to inhabit Earth more than 550 million years ago has unearthed new clues about the physiology of our earliest animal ancestors, according to scientists from The Australian National University (ANU).

Ediacara biota are the world's oldest large organisms and date back 575 million years. ANU researchers found the animals ate bacteria and algae that was sourced from the ocean floor. The findings, published in Current Biology, reveal more about these strange creatures, including how they were able to consume and digest food.

The scientists analysed ancient fossils containing preserved phytosterol molecules -- natural chemical products found in plants -- that remained from the animals' last meal. By examining the molecular remains of what the animals ate, the researchers were able to confirm the slug-like organism, known as Kimberella, had a mouth and a gut and digested food the same way modern animals do. The researchers say it was likely one of the most advanced creatures of the Ediacarans.

The ANU team found that another animal, which grew up to 1.4 metres in length and had a rib-like design imprinted on its body, was less complex and had no eyes, mouth or gut. Instead, the odd creature, called Dickinsonia, absorbed food through its body as it traversed the ocean floor.

"Our findings suggest that the animals of the Ediacara biota, which lived on Earth prior to the 'Cambrian Explosion' of modern animal life, were a mixed bag of outright weirdos, such as Dickinsonia, and more advanced animals like Kimberella that already had some physiological properties similar to humans and other present-day animals," lead author Dr Ilya Bobrovskiy, from GFZ-Potsdam in Germany, said.

Both Kimberella and Dickinsonia, which have a structure and symmetry unlike anything that exists today, are part of the Ediacara biota family that lived on Earth about 20 million years prior to the Cambrian Explosion -- a major event that forever changed the course of evolution of all life on Earth.

"Ediacara biota really are the oldest fossils large enough to be visible with your naked eyes, and they are the origin of us and all animals that exist today. These creatures are our deepest visible roots," Dr Bobrovskiy, who completed the work as part of his PhD at ANU, said.

Study co-author Professor Jochen Brocks, from the ANU Research School of Earth Sciences, said algae are rich in energy and nutrients and may have been instrumental for Kimberella's growth.

"The energy-rich food may explain why the organisms of the Ediacara biota were so large. Nearly all fossils that came before the Ediacara biota were single-celled and microscopic in size," Professor Brocks said.

Using advanced chemical analysis techniques, the ANU scientists were able to extract and analyse the sterol molecules contained in the fossil tissue. Cholesterol is the hallmark of animals and it's how, back in 2018, the ANU team was able to confirm that Ediacara biota are among our earliest known ancestors.

The molecules contained tell-tale signatures that helped the researchers decipher what the animals ate in the lead up to their death. Professor Brocks said the difficult part was differentiating between the signatures of the fat molecules of the creatures themselves, the algal and bacterial remains in their guts, and the decaying algal molecules from the ocean floor that were all entombed together in the fossils.

"Scientists already knew Kimberella left feeding marks by scraping off algae covering the sea floor, which suggested the animal had a gut. But it was only after analysing the molecules of Kimberella's gut that we were able to determine what exactly it was eating and how it digested food," Professor Brocks said.

"Kimberella knew exactly which sterols were good for it and had an advanced fine-tuned gut to filter out all the rest.

"This was a Eureka moment for us; by using preserved chemical in the fossils, we can now make gut contents of animals visible even if the gut has since long decayed. We then used this same technique on weirder fossils like Dickinsonia to figure out how it was feeding and discovered that Dickinsonia did not have a gut."

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Learning to better understand the language of algae

Communication is everything -- and that applies for algae, too. However, their chemical language and its significance in aquatic ecosystems remain largely unknown. A research duo from the Helmholtz Centre for Environmental research (UFZ) and the Plymouth Marine Laboratory (PML) have published a corresponding review in Biological Reviews. This summarizes the current state of knowledge and identifies new approaches for future research in the language of algae and their ecological relationships.

Can algae talk? "Well, although they don't have any mouth or ears, algae still communicate with their own kind and with other organisms in their surroundings. They do this with volatile organic substances they release into the water," says Dr. Patrick Fink, a water ecologist at the UFZ's Magdeburg site. These chemical signals are known as BVOCs (biogenic volatile organic compounds) and are the equivalent of odours in the air with which flowering plants communicate and attract their pollinators. When under attack by parasites, some plant species release odours that attract the parasites' natural enemies to them. "Algae also employ such interactions and protective mechanisms," says Fink. "After all, they are among the oldest organisms on Earth, and chemical communication is the most original form of exchanging information in evolutionary history. However, our knowledge in this area still remains very fragmentary."

Patrick Fink is the corresponding author of the article recently appearing in Biological Reviews, where he has summarized the current status of research in the chemical communication of algae. "For example, we know from laboratory investigations that some species of cyanobacteria keep water fleas at bay by releasing BVOCs in the water. This signal apparently acts as a repellent and has a true added value for the algae, namely that of effective grazing protection," says Fink. In contrast, it is not yet understood why some freshwater algae growing as biofilms on rocks or shellfish shells, for example, release BVOCS on grazing by pond snails. Because: These chemical signals attract more snails. "The pond snails very clearly use the BVOCs to their advantage -- but it remains unknown what function they actually serve for the algae," says Fink. An example from the ocean: A diatom bloom represents a true feast for copepods. This rich offering of nutrients should ensure that their population subsequently grows. However, this is not the case. "Although the copepods are well nourished, their spawn that they carry with them in their egg sack is at serious risk. Because the BVOCS from the diatoms impede cell division and thus disrupt embryonic development," Fink explains "In this way, the diatoms prevent excessive predation on their descendants -- thereby ensuring the preservation of their kind."

The language of algae was first detected in investigations of macroalgae in the early 1970s. "Macroalgae -- such as the bladder wrack also known from the coasts of Germany -- reproduce by releasing gametes into the water. The male and female gametes each release pheromones so that they can also find each other in the vastness of the ocean," explains Dr. Mahasweta Saha, marine chemical ecologist at the Plymouth Marine Laboratory (PML) in Great Britain. "This was the first indication that algae communicate via chemical signals, and that they fulfil important ecological functions."

In their publication, the author duo references the presumably significant effect of BVOCS within aquatic ecosystems, identifies gaps in knowledge and indicates possible future research areas such as coevolutionary processes between signal senders and receivers or the consequences of changes in the environment caused by humans on aquatic ecosystems. "As the primary producers, algae form the basis of life of all aquatic food webs," says Fink. "It is therefore important that we learn to better understand the chemical communication of algae and their basic functional relationships in aquatic ecosystems."

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Fossil algae, dating from 541 million years ago, offer new insights into the plant kingdom's roots

Paleontologists have identified a new genus and species of algae called Protocodium sinense which predates the origin of land plants and modern animals and provides new insight into the early diversification of the plant kingdom.

Discovered at a site in China, this 541-million-year-old fossil is the first and oldest green alga from this era to be preserved in three dimensions, enabling the researchers to investigate its internal structure and identify the new specimen with unprecedented accuracy. The study is published today in BMC Biology, opening a window into a world of evolutionary puzzles that scientists are just beginning to unravel.

"Protocodium belongs to a known lineage of green algae and has a surprisingly modern architecture, showing that these algae were already well diversified before the end of the Ediacaran period," says co-author Cédric Aria, postdoctoral fellow in the Department of Ecology & Evolutionary Biology in the Faculty of Arts & Science at the University of Toronto and based at the Royal Ontario Museum (ROM). "Its discovery touches the origin of the entire plant kingdom and puts a familiar name on the organisms that preceded the Cambrian explosion over half a billion years ago, when the world's first modern ecosystems emerged."

The newly discovered Protocodium fossils were found by a team led by Hong Hua, professor of geology, and including Shu Chai, postdoctoral researcher, both of Northwest University, Xi'an, China. It is part of the Gaojiashan biota, the name given to a significant group of exceptionally well-preserved fossils, at the Dengying Formation in the southern Shaanxi Province. In the past 20 years, this geological formation has yielded important fossil species documenting the end of the Ediacaran Period 541-million-years ago.

Organisms and their parts that do not originally absorb minerals -- unlike shells or bones -- require exceptional conditions to be preserved. In this case, the whole fossils and their fine cellular details were preserved in three dimensions due to the replacement of the original organic material by phosphate. This mode of preservation allowed the researchers to use various electron and X-ray microscopy techniques to virtually slice the fossil, unveil its internal structure with precision and ultimately identify it as a close relative of the modern Codium alga, a type of seaweed.

Protocodium fossils are small spheres half a millimetre wide, like large grains of pollen, covered by a multitude of smaller domes. Thanks to the 3D examination, the researchers determined the domed surface to be part of a complex, single cell that contains thin strands called siphons. This morphology is typical of certain modern single-celled seaweeds that contain many nuclei.

The discovery of Protocodium would call for caution when identifying generic spherical Ediacaran fossils and may imply that organisms like Codium are in fact much older and widespread. The famous Doushantuo fossil embryos, also from China and preserved in 3D, have

been at the heart of debates about the deep origin of certain animal groups. Specific stages of some of these animal-like embryos resemble the unicellular Protocodium on the outside, but 3D slicing reveals how they are comprised of many cells. On the other hand, numerous 2D, round fossils of uncertain algal or other affinity are also known from the Ediacaran and older periods, but in less detail.

"We know that seaweed-like fossils are at least one billion-years-old," says Chai, the study's first author. "But until now, flat, grainy two-dimensional preservation has made it challenging to recognize more than general morphological structures."

Green algae are photosynthetic organisms, which means they convert light and carbon dioxide into sugars and oxygen. They were therefore likely important foundations of Earth's early ecosystems, and the study suggests green algae were already established in the world's shallow waters as carbon dioxide recyclers and oxygen producers before the Cambrian explosion.

Apart from its smaller size, Protocodium appears surprisingly identical to the modern Codium, a type of green algae found in many seas worldwide. Certain types of this seaweed are notoriously invasive -- such as Codium fragile subspecies tomentosoides, dubbed "dead man's fingers" for its appearance, and spread along with commercially farmed shellfish. From an evolutionary perspective, green algae like the ancient Protocodium and land plants share a common ancestor that was thought to be about one billion to one billion and a half years old, but now likely older -- the assignment of Protocodium so close to a modern group pushes back in time the history of the entire plant kingdom.

"It's very telling that such an organism has remained practically unchanged over at least 540 million years," says Aria. "By the Ediacaran, evolution had driven it towards a stable adaptive zone -- it's been comfortable there since, and more than that, quite successful. So much so, in fact, that nowadays Codium takes advantage of global trade to easily outcompete other algal species."

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No glacial fertilization effect in the Antarctic Ocean

Changes in the concentration of atmospheric carbon dioxide (CO2) are considered to be the main cause of past and future climate change. A long-standing debate centers on whether the roughly 30 percent lower CO2 content of the ice-age atmosphere was caused by iron fertilization. It is argued that iron-rich dust is carried into the ocean by wind and water, where it stimulates the growth of algae that absorb more CO2. As the algae die and then sink permanently into the depths of the ocean, the CO2 also remains there like in a trap. Although there is clear evidence that dust input increased during the ice ages, the fertilization effect is controversial, at least for the Antarctic Ocean.

In a recent study, an international team of 38 researchers from 13 countries led by Dr. Michael Weber from the Institute for Geosciences at the University of Bonn investigated this question. As part of the Integrated Ocean Discovery Program (IODP), the team traveled to the Scotia Sea on the drillship "JOIDES Resolution" and spent two months in 2019 bringing up cores from the seafloor at depths of 3,000 to 4,000 meters. Weber: "We collected the highest-resolution and longest climate archive ever obtained near Antarctica and its main dust source, Patagonia."

1.5 million years of climate history

In the 200-meter-long deep-sea core U1537, the climate history of the last 1.5 million years was recorded in detail. This allows the reconstruction of the dust input to be nearly doubled, since Antarctic ice cores only cover the last 800,000 years. Current records from the deep ocean show that dust deposition during the ice ages was actually five to 15 times higher. This is also reflected in the ice cores.

However, the researchers found no evidence of a fertilization effect from dust in the Antarctic Ocean during the ice ages. Rather, the production of algae, for example, and thus carbon CO2 sequestration, was high only during warm periods when dust input into the Scotia Sea was low. This means that during cold periods, other processes prevented the CO2 captured in the ocean from escaping into the atmosphere and triggering warming. The main factors here are much more extensive sea ice cover, more intense stratification in the ocean, and reduced dynamics of the current systems, which contributed to a reduction in the CO2 content of the atmosphere during cold periods.

The opposing trends in dust deposition and oceanic productivity during the ice ages and interglacial periods of the Pleistocene are accompanied by long-term, gradual changes in the climate system in the southern polar region. Bioproductivity was particularly high during the interglacial periods of the last 400,000 years, but during the mid-Pleistocene transition 1.2 million to 700,000 years ago, it differed little from that during cold periods. As the transition progressed, the dust input covered larger and larger areas in the Southern Hemisphere. Abrupt changes continued to occur 900,000 years ago, indicating greater glaciation of Antarctica.

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Mystery of photosynthetic algae evolution finally solved

 An evolutionary mystery that had eluded molecular biologists for decades may never have been solved if it weren't for the COVID-19 pandemic.

"Being stuck at home was a blessing in disguise, as there were no experiments that could be done. We just had our computers and lots of time," says Professor Paul Curmi, a structural biologist and molecular biophysicist with UNSW Sydney.

Prof. Curmi is referring to research published this month in Nature Communications that details the painstaking unravelling and reconstruction of a key protein in a single-celled, photosynthetic organism called a cryptophyte, a type of algae that evolved over a billion years ago.

Up until now, how cryptophytes acquired the proteins used to capture and funnel sunlight to be used by the cell had molecular biologists scratching their heads. They already knew that the protein was part of a sort of antenna that the organism used to convert sunlight into energy. They also knew that the cryptophyte had inherited some antenna components from its photosynthetic ancestors -- red algae, and before that cyanobacteria, one of the earliest lifeforms on earth that are responsible for stromatolites.

But how the protein structures fit together in the cryptophyte's own, novel antenna structure remained a mystery -- until Prof. Curmi, PhD student Harry Rathbone and colleagues from University of Queensland and University of British Columbia pored over the electron microscope images of the antenna protein from a progenitor red algal organism made public by Chinese researchers in March 2020.

Unravelling the mystery meant the team could finally tell the story of how this protein had enabled these ancient single-celled organisms to thrive in the most inhospitable conditions -- metres under water with very little direct sunlight to convert into energy.

Prof. Curmi says the major implications of the work are for evolutionary biology.

"We provide a direct link between two very different antenna systems and open the door for discovering exactly how one system evolved into a different system -- where both appear to be very efficient in capturing light," he says.

"Photosynthetic algae have many different antenna systems which have the property of being able to capture every available light photon and transferring it to a photosystem protein that converts the light energy to chemical energy."

By working to understand the algal systems, the scientists hope to uncover the fundamental physical principles that underlie the exquisite photon efficiency of these photosynthetic systems. Prof. Curmi says these may one day have application in optical devices including solar energy systems.

EATING FOR TWO

To better appreciate the significance of the protein discovery, it helps to understand the very strange world of single-celled organisms which take the adage "you are what you eat" to a new level.

As study lead author, PhD student Harry Rathbone explains, when a single-celled organism swallows another, it can enter a relationship of endosymbiosis, where one organism lives inside the other and the two become inseparable.

"Often with algae, they'll go and find some lunch -- another alga -- and they'll decide not to digest it. They'll keep it to do its bidding, essentially," Mr Rathbone says. "And those new organisms can be swallowed by other organisms in the same way, sort of like a matryoshka doll."

In fact, this is likely what happened when about one and a half billion years ago, a cyanobacterium was swallowed by another single-celled organism. The cyanobacteria already had a sophisticated antenna of proteins that trapped every photon of light. But instead of digesting the cyanobacterium, the host organism effectively stripped it for parts -- retaining the antenna protein structure that the new organism -- the red algae -- used for energy.

And when another organism swallowed a red alga to become the first cryptophyte, it was a similar story. Except this time the antenna was brought to the other side of the membrane of the host organism and completely remoulded into new protein shapes that were equally as efficient at trapping sunlight photons.

EVOLUTION

As Prof. Curmi explains, these were the first tiny steps towards the evolution of modern plants and other photosynthetic organisms such as seaweeds.

"In going from cyanobacteria that are photosynthetic, to everything else on the planet that is photosynthetic, some ancient ancestor gobbled up a cyanobacteria which then became the cell's chloroplast that converts sunlight into chemical energy.

"And the deal between the organisms is sort of like, I'll keep you safe as long as you do photosynthesis and give me energy."

One of the collaborators on this project, Dr Beverley Green, Professor Emerita with the University of British Columbia's Department of Botany says Prof. Curmi was able to make the discovery by approaching the problem from a different angle.

"Paul's novel approach was to search for ancestral proteins on the basis of shape rather than similarity in amino acid sequence," she says.

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