ReportWire

Tag: the arctic

  • Hidden bacteria beneath the Arctic ice could boost ocean life

    The Arctic Ocean, once locked in a vault of thick, old ice, now is transforming at lightspeed. Temperatures there are increasing at up to four times the rate of the planet overall, melting sea ice that once shielded the ocean surface. With the ice removed, sunlight can penetrate deeper into the water, remodeling the entire marine food web from bacteria to large sea animals.

    One of the surprises from this melting world is that nitrogen, one of the most crucial nutrients in life, can be restored in ways no one previously thought possible. For decades, researchers believed that the Arctic’s frozen, cold waters had nearly zero fixation of nitrogen, which is the process by which certain microbes can convert nitrogen gas into forms that other animals can use. But an international study led by researchers at the University of Copenhagen turned that idea on its head.

    A New Source of Life in the Arctic Ocean

    Nitrogen fixation is microbial alchemy. Certain microorganisms referred to as diazotrophs harvest molecular nitrogen (N₂) out of the air—usually out of reach for most life—and transform it into ammonium, a nutrient that powers the growth of algae and the remainder of the marine food web.

    Measurements of nitrogen fixation in the Arctic Ocean aboard RV Polarstern. (CREDIT: Rebecca Duncan)

    In warmer oceans, cyanobacteria do the work. But in the central Arctic, where things are harsher, researchers found that a whole different set of players is getting the job done: non-cyanobacterial diazotrophs, or NCDs.

    So far, we believed that it was not possible for nitrogen fixation in the sea ice because we believed the conditions were too harsh for the organisms which are responsible for nitrogen fixation. We made a mistake,” said study leader Lisa W. von Friesen, a previous PhD student at the Department of Biology at the University of Copenhagen.

    The discovery shows that not only is nitrogen fixation occurring at the ice edge, where the melting is most intense, but under thick, multiyear ice in the central Arctic Ocean as well. That means nitrogen, until now thought to be in short supply in the Arctic, is being quietly cycled and replenished back into the system even under ice.

    Measuring the Invisible

    The researchers investigated levels of nitrogen fixation within several Arctic settings: the Central Arctic Ocean (CAO), where thick ice remains; the Marginal Ice Zone (MIZ), where melting continues; and shorelines under land-fast ice.

    They measured the daily quantity of nitrogen being fixed, as well as a host of other variables—temperature, salinity, and concentrations of nutrients such as phosphate and nitrate—in an effort to understand what triggers the process.

    Nitrogen fixation is the conversion of molecular nitrogen to bioavailable ammonium by microorganisms called diazotrophs. (CREDIT: Communications Earth & Environment)

    Nitrogen fixation is the conversion of molecular nitrogen to bioavailable ammonium by microorganisms called diazotrophs. (CREDIT: Communications Earth & Environment)

    On the CAO, rates of fixation ranged from around 0.4 to 2.5 nanomoles per liter per day, while in the MIZ, zones were as high as 5.3 nanomoles per liter per day. Even within stable, land-fast ice near Greenland, trace but detectable levels were present—indicating the process is widespread on all sea-ice regimes.

    Dissolved organic carbon (DOC) that was added to certain samples raised nitrogen fixation rates, suggesting that these Arctic microorganisms thrive under conditions with higher amounts of organic matter—typically released by algae. “These non-cyanobacterial diazotrophs seem to feed on the organic matter released by algae, and they pay that back by supplying fixed nitrogen that enables those algae to grow,” von Friesen said.

    Microscopic Architects of the Arctic Food Web

    They are a world away, under the microscope, from their tropical relatives. Instead of cyanobacteria, they mostly belong to groups that scientists classify as Gamma-Arctic1 and Gamma-Arctic2—microorganisms that dominate in multiyear ice conditions and appear especially vigorous where ice is melting or breaking down.

    Quantitative analysis revealed that these microbes were far more abundant and active than anticipated. The scientists found more than 870 forms of genes linked to nitrogen fixation, the majority of which were from these Arctic-specific clades. This strongly indicates that the nitrogen cycle in the Arctic is being dominated to a large extent by non-cyanobacterial microbes.

    Their presence could hold the key to explaining how life continues to flourish in nutrient-poor seas. Algae, the foundation of Arctic sea food webs, are dependent to a great extent upon nitrogen. When nitrogen is in short supply, growth among algae decreases, affecting everything from plankton to fish to sea mammals. But if nitrogen fixation occurs more often than initially suspected, it would help to feed these ecosystems during melting ice.

    Maps of the study region. North-Pole-centred overview of the Central Arctic Ocean (CAO) and the stations sampled during the Synoptic Arctic Survey (SAS) in 2021. (CREDIT: Communications Earth & Environment)

    Maps of the study region. North-Pole-centred overview of the Central Arctic Ocean (CAO) and the stations sampled during the Synoptic Arctic Survey (SAS) in 2021. (CREDIT: Communications Earth & Environment)

    The Ice Edge: A Fertile Frontier

    The highest fixation rates of nitrogen were at the ice margin, where meltwater, light, and nutrients come together to allow very good growing conditions. As sea ice recedes and the melt region expands, scientists expect this location to become a hotbed of microbes.

    Since algae are the primary food for tiny animals such as planktonic crustaceans, which are eaten by small fish, additional algae can have an indirect effect on the whole food chain,” von Friesen stated.

    Her colleague, Professor Lasse Riemann, said that these submicroscopic processes may even influence the rate at which the Arctic Ocean takes up carbon dioxide. “If the productivity of algae increases, the Arctic Ocean will take up more CO₂ because more will be trapped in algal biomass,” he explained. “For the climate and the environment, this is probably good news—but biological systems are extremely complicated, so it is difficult to make definite predictions.

    A New Chapter in Arctic Science

    The significance of this finding is great. Nitrogen is one of the most crucial drivers of marine ecosystem productivity. The discovery that Arctic microorganisms fix nitrogen in the presence of sea ice destroys the long-standing assumption that nitrogen addition in the region is minimal.

    Environmental differences between the study regions. (CREDIT: Communications Earth & Environment)

    Environmental differences between the study regions. (CREDIT: Communications Earth & Environment)

    As the Arctic melts and the ice pulls back, open water area where nitrogen may be fixed will expand explosively. Excess nitrogen means more algae and more to eat for fish and other marine animals. But it might also mean more carbon cycling, and possibly wild swings in ocean chemistry.

    Scientists caution that the full effect is unknown. Nitrogen fixation represents only a fraction—sometimes less than 1 percent—of total nitrogen input in wealthier regions. But in the nutrient-poor Central Arctic, it could represent up to 8 percent of the nitrogen needed for plankton growth. That’s an important percentage for so remote an ecosystem.

    Practical Implications of the Research

    The discovery of nitrogen fixation active under Arctic sea ice changes scientists’ perspectives about nutrient cycling within one of the world’s most rapidly changing ecosystems. It suggests life in the Arctic is perhaps more resilient than predicted, as microbially mediated processes adapt to conditions as ice retreats.

    In practice, this could redefine climate models’ estimation of ocean productivity and carbon sequestration in polar oceans. If nitrogen fixation increases as the ice cover disappears, the Arctic Ocean can absorb more CO₂, countering some warming effects at least regionally.

    The findings also highlight the importance of incorporating microbial activity into future climate predictions. With nitrogen fixation included, models would be able to better calculate the amount of carbon taken in by the Arctic and how alterations in nutrient availability could ripple through the global food web.

    Research findings are available online in the journal Communications Earth & Environment.

    Related Stories

    Like these kind of feel good stories? Get The Brighter Side of News’ newsletter.

    Source link

  • These Climate Hacks to Save the Poles Could Totally Backfire

    Last year, the United Nations predicted that Earth’s average temperature could rise more than 5.4 degrees Fahrenheit (3 degrees Celsius) by 2100 if we don’t reduce global emissions. That level of warming would cause catastrophic, irreversible damage to ecosystems, underscoring the urgent need to slow the pace of climate change.

    Still, the amount of greenhouse gases humans pump into the atmosphere continues to rise. Without sufficient progress on the emissions front, some scientists have suggested another route: artificially counteracting global warming through geoengineering. Many of these controversial solutions aim to mitigate climate breakdown in the polar regions, but a review published Tuesday in Frontiers in Science concludes that even the most widely recognized proposals are likely to cause more harm than good.

    “I find that there’s been confusion between urgency and haste,” co-author Ben Orlove, a professor of international and public affairs at Columbia University, told Gizmodo. “Though we recognize the urgency of action, that should never serve as an excuse for incompletely reviewed proposals moving forward.”

    Polar regions under pressure

    Earth’s polar regions are warming faster than the average global temperature. Experts predict this will lead to severe and irreversible consequences both regionally and globally, such as local ecosystem collapse and sea level rise. Proponents of geoengineering often cite this as a driving force behind efforts to implement such strategies in the Arctic and Antarctic, but none of them are backed by robust, real-world testing at scale.

    For this review, an international team of researchers evaluated five geoengineering concepts designed to slow the pace of ice melt in the polar regions. The ideas include spraying reflective particles into the atmosphere, using giant underwater curtains to shield ice shelves from warm water, artificially thickening or boosting the reflectivity of sea ice, pumping water out from underneath glaciers, and adding nutrients to polar oceans to stimulate blooms of carbon-sequestering phytoplankton.

    More problems than solutions

    The researchers evaluated each proposed solution’s scope of implementation, effectiveness, feasibility, negative consequences, cost, and governance with respect to their deployment at scale. According to their assessment, all five ideas would lead to environmental damages such as the disruption of habitats, migration routes, the ocean’s natural chemical cycle, global climate patterns, and more.

    Additionally, the authors estimate that each proposal would cost at least $10 billion to implement and maintain. This is likely an underestimate, they say, pointing to hidden costs that would undoubtedly arise as environmental and logistical consequences come into play. What’s more, polar regions lack sufficient governance to regulate these projects, necessitating extensive political negotiation and new frameworks before large-scale deployment.

    Even if these tactics offered some benefit, none could scale fast enough to meaningfully address the climate crisis within the limited time available to do so, the researchers concluded.

    “It is clear to us that the assessed approaches are not feasible, and that further research into these techniques would not be an effective use of limited time and resources,” the authors write, emphasizing the importance of focusing on reducing greenhouse gas emissions and conducting fundamental research in the polar regions.

    Not every fix is worth the risk

    Orlove hopes these findings encourage the scientific community and decision-makers to exercise scrutiny before investing time and money in polar geoengineering projects. “One of the things that troubles me is the claim that climate change is so severe that we need to try all possible methods, and blocking any possible solution is an error,” he said.

    “There is a long history in medical research of not undertaking certain experiments on living humans and not attempting extreme cures that just seem unethical,” Orlove said. “But when it comes to experimenting on the planet—and its immediate effect on people—that kind of awareness doesn’t come forward.”

    Ellyn Lapointe

    Source link