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    In one lake deep under Antarctica’s ice, microbes feast on ancient carbon

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    How microbes survive in lakes far beneath Antarctica’s ice sheet has been a mystery. Now scientists have figured out what’s on the menu for microbes in one buried lake in West Antarctica.

    The lake’s bacteria and other microbial inhabitants get by on carbon that seawater left behind thousands of years ago, researchers report in the April AGU Advances. The find adds to existing evidence that, during a period of warming about 6,000 years ago, the ice sheet in West Antarctica was smaller than it is today. That allowed seawater to deposit nutrients in what is now a lake bed buried under hundreds of meters of ice.

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    This study is among the first to provide evidence from beneath the ice that the ice sheet was smaller in the not-so-distant past, geologically speaking, before growing back to its modern size, says Greg Balco, a geochemist at the Berkeley Geochronology Center in California.

    Understanding how the ice sheet changed during past periods of warming is crucial to predicting Antarctica’s future as the world continues to warm due to human-caused climate change, says Balco, who was not involved in the new study.

    Hundreds of lakes pool under Antarctica’s massive ice sheet, the result of the underside of the ice ever-so-slowly melting due to heat from the Earth’s interior. The lakes tend to be pitch-black, near freezing and are almost all isolated from the outside world.

    These less-than-ideal conditions should make them hostile to life. “If I were a microbe, I wouldn’t want to live in the cold, dark depths where I haven’t seen the sun or a new nutrient in thousands of years,” says Ryan Venturelli, a paleoglaciologist at the Colorado School of Mines in Golden. Yet billions of microbes — and even some animals — have found a way to thrive in these subglacial waterbodies (SN: 4/21/23).

    As the last glacial period came to a close, starting around 15,000 years ago, ice sheets around the world retreated. Computer simulations have predicted that as the climate warmed, the ice sheet in West Antarctica may have shrunk to an even smaller size than it is today. But working out what a smaller ice sheet might have looked like isn’t easy since most of the evidence for it is now locked under ice, Balco says.

    In 2018, Venturelli joined a team of about 30 scientists headed to a remote corner of West Antarctica to drill for the past. The journey took them to Lake Mercer: a body of subglacial water that today sits 150 kilometers from the sea.

    It took the expedition over a week of using a hot-water drill 24 hours a day to pierce through just over a kilometer of ice to reach the lake. “There was a lot of cheering and high-fiving” when the drill finally made it through, Venturelli recalls. Lake Mercer is only the second subglacial lake in the world that scientists have ever managed to reach.

    Paleoglaciologist Ryan Venturelli holds a tube of sediment collected from the bed of Lake Mercer. Carbon in this sediment core reveals that the lake was connected to the ocean 6,000 years ago.Billy Collins

    The team collected and analyzed lake water and sediment samples from the lake bed. This work revealed traces of 6,000-year-old carbon-14, a form of the element that’s made in the atmosphere and then falls to Earth. For that carbon to get past the ice, the lake would have had to have contact with the outside world. 

    The researchers didn’t spot any telltale signs of ancient photosynthesizing plankton, suggesting that the area wasn’t open ocean when the carbon settled in the sediment. Instead, seawater carrying the carbon must have come to the lake. That means that ocean water had to have flowed under the ice about 250 kilometers farther inland than it does today, the researchers say. 

    “There’s no other way to get carbon-14 in there,” Balco says. “You can’t push it through ice. Organisms can’t tunnel through. The only way for it to get it there is for ocean water to get under the ice sheet.”

    Seawater does flow under the ice today — but not as far inland as the lake’s location. So the edge of the ice shelf was probably closer to Lake Mercer several thousand years ago. That suggests, the team says, that the ice sheet over West Antarctica was probably smaller back then.

    Microorganisms living in this area 6,000 years ago would have feasted on the inflow from the ocean. And their descendants still seem to as well. The researchers found traces of carbon-14 in the water samples as well as in the sediment, suggesting the microbes are recycling the ancient carbon deposited in the lake bed as food.

    The new study emphasizes how much information is waiting to be found in Antarctica’s hidden lakes, Venturelli says. “There are about 675 lakes under the ice sheet, and we’ve only sampled two,” she says. “I would very much like to drill into every single one of them.” More

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      in Heart

      A new metric of extinction risk considers how cultures care for species

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      In shallow coastal waters of the Indian and Pacific oceans, a seagrass-scrounging cousin of the manatee is in trouble. Environmental strains like pollution and habitat loss pose a major threat to dugong (Dugong dugon) survival, so much so that in December, the International Union for Conservation of Nature upgraded the species’ extinction risk status to vulnerable. Some populations are now classified as endangered or critically endangered.

      If that weren’t bad enough, the sea cows are at risk of losing the protection of a group who has long looked after them: the Torres Strait Islanders. These Indigenous people off the coast of Australia historically have been stewards of the dugong populations there, sustainably hunting the animals and monitoring their numbers. But the Torres Strait Islanders are also threatened, in part because sea levels are rising and encroaching on their communities, and warmer air and sea temperatures are making it difficult for people to live in the region.

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      This situation isn’t unique to dugongs. A global analysis of 385 culturally important plant and animal species found that 68 percent were both biologically vulnerable and at risk of losing their cultural protections, researchers report January 3 in the Proceedings of the National Academy of Sciences.

      The findings clearly illustrate that biology shouldn’t be the primary factor in shaping conservation policy, says cultural anthropologist Victoria Reyes-García. When a culture dwindles, the species that are important to that culture are also under threat. To be effective, more conservation efforts need to consider the vulnerability of both the species and the people that have historically cared for them, she says.

      “A lot of the people in the conservation arena think we need to separate people from nature,” says Reyes-García, of the Catalan Institution for Research and Advanced Studies and the Autonomous University of Barcelona. But that tactic overlooks the caring relationship many cultural groups – like the Torres Strait Islanders – have with nature, she says.

      “Indigenous people, local communities, also other ethnic groups – they are good stewards of their biodiversity,” says Ina Vandebroek, an ethnobotanist at the University of the West Indies at Mona in Kingston, Jamaica, who was not involved in the work. “They have knowledge, deep knowledge, about their environments that we really cannot overlook.”

      One way to help shift conservation efforts is to give species a “biocultural status,” which would provide a fuller picture of their vulnerability, Reyes-García and colleagues say. In the study, the team used existing language vitality research to determine a culture’s risk of disappearing: The more a cultural group’s language use declines, the more that culture is threatened. And the more a culture is threatened, the more culturally vulnerable its important species are. Researchers then combined a species’ cultural and biological vulnerability to arrive at its biocultural status. In the dugong’s case, its biocultural status is endangered, meaning it is more at risk than its IUCN categorization suggests.

      This intersectional approach to conservation can help species by involving the people that have historically cared for them (SN: 3/2/22). It can also highlight when communities need support to continue their stewardship, Reyes-García says. She hopes this new framework will spark more conservation efforts that recognize local communities’ rights and encourage their participation – leaning into humans’ connection with nature instead of creating more separation (SN: 3/8/22).       More

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      Sea sponges launch slow-motion snot rockets to clean their pores

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      The next time you spot a sea sponge, say “gesundheit!” Some sponges regularly “sneeze” to clear debris from their porous bodies.

      As filter feeders, sponges draw in water through inlet pores — called ostia — and strain it through an internal canal system for nutrients. But there are also inedible bits in the water, like sediment. To prevent the undesirable junk from clogging up their outer pores, a Caribbean tube sponge (Aplysina archeri) uses mucus to trap and sneeze out unwanted particles, Niklas Kornder, a marine biologist at the University of Amsterdam, and colleagues report online August 10 in Current Biology. To the team’s surprise, it found that the sponge expels its snot from the same pores through which it absorbs water.

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      It’s “like someone with a runny nose,” says team member Sally Leys, an evolutionary biologist at the University of Alberta in Edmonton, Canada. “It’s constantly streaming, but it’s going counterflow to the in-current.”

      Researchers knew that sponges used contractions dubbed “sneezing” to move water through their bodies in a one-way flow. Typically, water comes in through numerous ostia and leaves through the osculum, a hole near the sponges’ top.

      But when the team captured time-lapse video of A. archeri, it saw tiny specks of mucus exiting from the ostia, moving against the flow of incoming water. Sneezelike contractions appeared to expel and move the specks along a “mucus highway” across the surface of the sponge to points where they collected in stringy, gooey clumps. Unlike an explosive human sneeze, the sponges slowly and continuously secreted debris-laden mucus from their ostia, with one contraction taking between 20 and 50 minutes, the study finds.

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      The Caribbean tube sponge (Aplysina archeri) uses contractions — called “sneezes” — to help eject mucus from its pores, or ostia. As the time-lapse video zooms in closer, it’s possible to see tiny specks of debris floating out of these pores and traveling along a “mucus highway” where they collect into stringy clumps of goo floating above the surface of the sponge. In real time, this sponge takes between 20 and 50 minutes to complete a sneeze.

      Other sea critters feast on these ocean boogers, like brittle stars and small crustaceans. Scientists view sponges primarily as habitat builders, but the mucus buffet shows they also perform an important function as food providers, says Amanda Kahn, a marine biologist at Moss Landing Marine Labs in California who was not involved with this work.

      “There’s so much to be said for a study that really spends time and watches,” Kahn says. “They let the animals show for themselves what was happening.”

      Most sponges appear to sneeze, so it’s likely not just A. archeri that uses the counterflow technique, Leys says. The team also noted a similar behavior in an Indo-Pacific sponge (Chelonaplysilla sp). But biologists need to dig deeper to figure out how widespread the mechanism is. It’s also unclear exactly what the mucus is or how it’s moving backward through pores. More

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      High altitudes may be a climate refuge for some birds, but not these hummingbirds

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      Cooler, higher locales may not be very welcoming to some hummingbirds trying to escape rising temperatures and other effects of climate change.

      Anna’s hummingbirds live no higher than about 2,600 meters above sea level. If the birds attempt to expand their range to include higher altitudes, they may struggle to fly well in the thinner air, researchers report May 26 in the Journal of Experimental Biology.

      These hummingbirds have expanded their range in the past. Once only found in Southern California, the birds now live as far north as Vancouver, says Austin Spence, an ecologist at the University of California, Davis. That expansion is probably due to climate change and people using feeders to attract hummingbirds, he says.

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      Spence and colleagues collected 26 Anna’s hummingbirds (Calypte anna) from different elevations in the birds’ natural range in California. The team transported the birds to an aviary about 1,200 meters above sea level and measured their metabolic rate when hovering. After relocating the hummingbirds to a field station at 3,800 meters altitude, the researchers let the birds rest for at least 12 hours and then measured that rate again.

      The rate was 37 percent lower, on average, at the higher elevation than the aviary, even though the birds should have been working harder to stay aloft in the thinner air (SN: 2/8/18). At higher altitudes, hovering, which takes a lot of energy compared with other forms of flight, is more challenging and requires even more energy, Spence says. The decrease in metabolic rate shows that the birds’ hovering performance was suffering, he says. “Low oxygen and low air pressure may be holding them back as they try to move upslope.”

      Additional work is needed to see whether the birds might be able to better adjust if given weeks or months to acclimate to the conditions at gradually higher altitudes. More

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      Fungi may be crucial to storing carbon in soil as the Earth warms

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      When it comes to storing carbon in the ground, fungi may be key.

      Soils are a massive reservoir of carbon, holding about three times as much carbon as Earth’s atmosphere. The secret behind this carbon storage are microbes, such as bacteria and some fungi, which transform dead and decaying matter into carbon-rich soil.

      But not all carbon compounds made by soil microbes are equal. Some can last for decades or even centuries in the soil, while others are quickly consumed by microbes and converted into carbon dioxide that’s lost to the atmosphere. Now, a study shows that fungi-rich soils grown in laboratory experiments released less carbon dioxide when heated than other soils.

      The result suggests that fungi are essential for making soil that sequesters carbon in the earth, microecologist Luiz Domeignoz-Horta and colleagues report November 6 in ISME Communications.

      Who is making soil matters, Domeignoz-Horta says.

      The study comes as some scientists warn that climate change threatens to release more carbon out of the ground and into the atmosphere, further worsening global warming. Researchers have found that rising temperatures can lead to population booms in soil microbes, which quickly exhaust easily digestible carbon compounds. This forces the organisms to turn to older, more resilient carbon stores, converting carbon stored away long ago into carbon dioxide.

      With the combined threat of rising temperatures and damage to soil microbe communities from intensive farming and disappearing forests, some computer models indicate that 40 percent less carbon will stick in the soil by 2100 than previous simulations have anticipated (SN: 9/22/16).

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      To see if scientists can coax soils to store more carbon, researchers need to understand what makes soil microbes tick. But that is no simple task. “Some say soil is the most complex matrix on the planet,” says Kirsten Hofmockel, an ecologist at the Pacific Northwest National Laboratory in Richland, Wash., who was not involved in the research.

      To simplify matters, Domeignoz-Horta, of the University of Zurich, and colleagues grew their own dirt in the lab. The researchers separated fungi and bacteria from forest soil and grew five combinations of these communities in petri dishes, including some that were home only to bacteria or fungi. The researchers sustained the microbes on a diet of simple sugar and left them to churn out soil for four months. The team then heated the different soils to see how much carbon dioxide was produced.

      Bacteria were the main drivers behind making soil, but fungi-rich soils produced less carbon dioxide when heated than soils made solely by bacteria, the researchers found. Why is still unclear. One possibility is that fungi could be producing enzymes — proteins that build or break up other molecules — that bacteria aren’t capable of making on their own, Domeignoz-Horta says. These fungi-derived compounds may provide bacteria with different building blocks with which to build soil, which may end up creating carbon compounds with a longer shelf life in soils.

      What happens in lab-grown soil may not play out the same in the real world. But the new research is an important step in understanding how carbon is locked away long-term, Hofmockel says. This kind of information could one day help researchers develop techniques to ensure that more carbon stays in the ground for longer, which could help mitigate the amount of carbon dioxide in the atmosphere.

      “If we can get carbon in the ground for five years, that’s a step in the right direction,” Hofmockel says. “But if we can have stable carbon in the soil for centuries or even millennia, that’s a solution.” More

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      Albatrosses divorce more often when ocean waters warm

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      When it comes to fidelity, birds fit the bill: Over 90 percent of all bird species are monogamous and — mostly — stay faithful, perhaps none more famously than the majestic albatross. Albatross couples rarely separate, sticking with the same breeding partner year after year. But when ocean waters are warmer than average, more of the birds split up, a new study finds.

      In years when the water was warmer than usual, the divorce rate — typically less than 4 percent on average — rose to nearly 8 percent among albatrosses in part of the Falkland Islands, researchers report November 24 in Proceedings of the Royal Society B. It’s the first evidence that the environment, not just breeding failure, affects divorce in wild birds. In fact, the team found that during warmer years, even some females that had bred successfully ditched their partners.

      The result suggests that as the climate changes as a result of human activity, higher instances of divorce in albatrosses and perhaps other socially monogamous animals may be “an overlooked consequence,” the researchers write.

      Albatrosses can live for decades, sometimes spending years out on the ocean searching for food and returning to land only to breed. Pairs that stay together have the benefits of familiarity and improved coordination, which help when raising young. This stability is particularly important in dynamic, marine environments, says Francesco Ventura, a conservation biologist at the University of Lisbon in Portugal.

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      But if breeding doesn’t work out, many birds — mostly females — leave their partner and try to find better luck elsewhere (SN: 3/7/98). Breeding is more likely to fail in years with more difficult conditions, with knock-on effects on divorce rates the following years. Ventura wanted to find out whether the environment also has a direct impact: changing the rate of divorce regardless of whether the breeding had gone well.

      Ventura and his team analyzed data collected from 2004 to 2019 on a large colony of black-browed albatrosses (Thalassarche melanophris) living on New Island in the Falkland Islands. The team recorded nearly 2,900 breeding attempts in 424 females, and tracked bird breakups. Then, accounting for previous breeding success in individual pairs, the researchers checked to see if environmental conditions had any noticeable further impact on pairings.

      Breeding failure, especially early on, was still the main factor behind a divorce: Each female lays just a single egg, and those birds whose eggs didn’t hatch were over five times as likely to separate from their partners as those who succeeded, or those whose hatched chicks didn’t survive. In some years, the divorce rate was lower than 1 percent.

      Yet this rate increased in line with average water temperatures, reaching a maximum of 7.7 percent in 2017 when waters were the warmest. The team’s calculations revealed that the probability of divorce was correlated with rising temperatures. And surprisingly, females in successful breeding pairs were more likely to be affected by the harsher environment than males or females that either didn’t breed, or failed. When ocean temperatures dropped again in 2018 and 2019, so did divorce rates.

      Warmer water means fewer nutrients, so some birds may be fueling up out at sea for longer, delaying their return to the colony or turning up bedraggled and unappealing. If members of pairs return at different times, this can lead to breakups (SN: 10/6/04).

      What’s more, worse conditions one year might raise stress-related hormones in the birds too, which can affect mate choice. A bird may incorrectly attribute its stress to its partner, rather than the harsher environment, and separate even if hatching was successful, the researchers speculate.

      Such misreading between cues and reality could make separation a less-effective behavior, suggests Antica Culina, an evolutionary ecologist at the Netherlands Institute of Ecology in Wageningen who was not involved in the study. If animals divorce for the wrong reason and do worse the following season, that can lead to lower breeding success overall and possibly population decline.

      Similar patterns could be found in other socially monogamous animals, including mammals, the researchers suggest. “If you imagine a population with a very low number of breeding pairs … this might have much more serious repercussions,” Ventura says. More

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      Neon colors may help some corals stage a comeback from bleaching

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      For some corals, going bright may be part of their fight against bleaching. Higher-than-normal ocean temperatures can cause some corals to bleach and lose the beneficial algae that dwell within their cells. Those algae help feed the corals and give them their color, so bleached corals can become bone white, and may struggle to survive […] More

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      The Great Barrier Reef is suffering its most widespread bleaching ever recorded

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      Australia’s Great Barrier Reef is currently experiencing its third mass bleaching in just five years — and it is the most widespread bleaching event ever recorded. Results from aerial surveys conducted along the 2,000-kilometer-long reef over nine days in late March, and released April 7, show that 25 percent of 1,036 individuals reefs surveyed were […] More