8/17/2023 0 Comments Dead cells map chartsAs our world warms, the surface waters of our oceans lose oxygen, in addition to other dissolved gases. First, the laws of physics dictate that warmer water can hold less dissolved gas than cooler water (this is why a warm soda is less fizzy than a cold one). The oxygen drop is driven by a few factors. According to the Interngovernmental Panel on Climate Change's (IPCC) 2019 special report on the oceans, from 1970 to 2010, the volume of "oxygen minimum zones" in the global oceans – where big fish can't thrive but jellyfish can – increased by between 3% and 8%. Some patches are worse than others – the top of the north-east Pacific has lost more than 15% of its oxygen. Oxygen levels in the world's oceans have already dropped more than 2% between 19, and they are expected to decline up to 7% below the 1960 level over the next century. "If you run out of oxygen, the other problems are inconsequential." Fish, like other animals, need to breathe. "That's not so surprising," says Wilco Verberk, an eco-physiologist at Radboud University in the Netherlands. But when researchers take the time to compare the three effects - warming, acidification, and deoxygenation - the impacts of low oxygen are the worst. That's obviously not good for marine life. Just this April, for example, headlines screamed that global surface waters were hotter than they have ever been - a shockingly balmy average of 21C (70F). Researchers complain that the oxygen problem doesn't get the attention it deserves, with ocean acidification and warming grabbing the bulk of both news headlines and academic research. The tropics will empty as fish move to more oxygenated waters, says Pauly, and those specialist fish already living at the poles will face extinction. Our future ocean – warmer and oxygen-deprived – will not only hold fewer kinds of fish, but also smaller, stunted fish and, to add insult to injury, more greenhouse-gas producing bacteria, scientists say. "Deoxygenation is a big problem," Pauly summarises. Lack of ecosystem diversity means lack of resilience. Researchers expect many places to experience a decline in species diversity, ending up with just those few species that can cope with the harsher conditions. ![]() As the atmosphere warms, oceans around the world are becoming ever more deprived of oxygen, forcing many species to migrate from their usual homes. But the influx provides a peek at a bleak future for China and for the planet as a whole. The boom is making some people happy, since Bombay duck is perfectly edible. Fish species that can't cope with less oxygen have fled, while the Bombay duck, part of a small subset of species that is physiologically better able to deal with less oxygen, has moved in. The reason for this mass invasion, says Pauly, is extremely low oxygen levels in these polluted waters. ![]() "It's monstrous," says University of British Columbia fisheries researcher Daniel Pauly of the explosion in numbers. When research ships trawl the seafloor off that coast, they now catch upwards of 440lb (200kg) of the gelatinous fish per hour - a more than tenfold increase over a decade ago. Off the coast of south-east China, one particular fish species is booming: the oddly named Bombay duck, a long, slim fish with a distinctive, gaping jaw and a texture like jelly.
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