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    • Plankton are the backbone of the ocean – and may not survive what’s to come
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    Plankton are the backbone of the ocean – and may not survive what’s to come

    Pabio Posted on

    Dino Grandoni
    | Washington Post

    They drift aimlessly at sea, absorbing sunlight from the sky and nutrients from the depths. Often invisible to the naked eye, these tiny invertebrates form the hidden backbone of ocean ecosystems. Everything from the smallest fish to the largest whale depends on them for food.

    Yet these tiny organisms – called plankton – may be unable to thrive in rapidly warming oceans, according to two new studies. The decline of these microscopic creatures will put huge swaths of marine life at risk in coming decades if nothing is done to curb human-caused climate change.

    “If the little things disappear, the food disappears — for small fish, then for larger fish, for marine mammals and for us,” said Daniela Schmidt, a climate scientist at the University of Bristol in England, who co -writes one of the two articles published Wednesday in the journal Nature.

    Each of the two studies takes a different approach, but they come to the same surprising conclusion: Plankton, much of which forms the basis of marine food chains, is under siege. The research highlights one of many ways oceans are increasingly under attack, with potentially disastrous consequences for humans who rely on the seas for food.

    Any drop in plankton levels will have “cascading effects on marine ecosystems”, said Kerrie Swadling, an ecologist at the University of Tasmania who was not involved in the research.

    —

    To assess the future impacts of warming waters on plankton, Schmidt and his colleagues looked to ancient changes. The team analyzed numerous fossils of a type of plankton called foraminifera, which leave behind tiny shells that fall to the seafloor when they die.

    While many plankton have become accustomed to the increase in temperature since the peak of the last ice age 20,000 years ago, plankton biomass will decline by more than 10% if the The world warms by 3 degrees Celsius above pre-industrial levels by the end of the century. , the researchers discovered.

    That’s a rate of warming that plankton simply can’t withstand, researchers say. “The last deglaciation lasted several thousand years,” Schmidt said. “The same amount of warming is currently occurring over 100 years. »

    The decline of plankton is already underway.

    In the second study published in Nature, plankton ecologist Sonia Chaabane and colleagues combed through eight decades of plankton data collected using nets, traps and other instruments around the world.

    By scrutinizing nearly 200,000 samples, the team found that the abundance of foraminifera had already declined by almost a quarter since the 1940s, with many species migrating away from the equator and moving deeper into the water column to survive.

    “We are not sure that migration would be enough for them,” Chaabane said. “The change is very, very huge, very rapid – and we think it will continue to be,” she added.

    Michal Kucera, a micropaleontologist at the University of Bremen who was not involved in both papers, noted that understanding plankton has many challenges. Foraminifera, for example, are just one type of plankton, and the methods researchers use to collect them have evolved over time.

    However, he added that the results should be taken seriously. “No matter where or how we look, today’s plankton is not what it used to be,” he said.

    —

    Climate change threatens plankton in different ways. Warming stifles ocean circulation that brings nutrients from the depths to the surface. The buildup of dissolved carbon dioxide in water makes the oceans more acidic, making it harder for foraminifera to build their shells.

    Unlike sharks or squid, plankton cannot propel themselves through water, making it difficult to migrate to cooler habitats. “They can float,” Chaabane said, “but they can’t swim against the current.”

    According to Schmidt, a drop of just 10% in plankton could cause a domino effect leading to a decline in populations of fish and other larger sea creatures throughout the food chain. “It would just be brutal,” she said. “That doesn’t seem like much, 10 percent. But it’s a vast change.

    Although seafood is a luxury in many places, she added, “there are some areas of the world where food from the ocean is the primary source of protein.”

    Even for those who forgo eating fish, plankton is crucial to preventing climate change from getting even worse. When foraminifera form their shell, they bind carbon to calcium to make their building material. After they die, the shells fall to the seafloor, locking this carbon out of the atmosphere for eons.

    Plankton isn’t the only marine creature in danger. More than 40 percent of reef-building corals are at risk of disappearing, according to a report also released Wednesday by the International Union for Conservation of Nature.

    As temperatures rise, corals turn ghostly white after expelling the symbiotic algae that provide them with food. Reefs from Fiji to the Florida Keys have recently been devastated by a massive global bleaching event.

    “They can’t run away,” said Beth Polidoro, a conservation scientist at Arizona State University who coordinated the coral work. “They’re stuck to the ground.”

    The surge in research into marine life comes as diplomats gather this month in Azerbaijan for a United Nations climate summit. The negotiations aim to keep countries on track to keep temperature rises below 1.5 degrees Celsius by the end of the century. Countries can curb warming by reducing greenhouse gas pollution.

    But currently, the world is far from achieving this goal.

    “Limiting emissions is really the only way to reverse warming,” Swadling said.

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