Fuente: Futurity.org
Expuesto el: miércoles, 03 de julio de 2013 17:16
Autor: Robert Perkins-USC
Asunto: Climate change's biggest loser: Tiny ocean bacteria
Carbon dioxide in the atmosphere is expected to have significant consequences for tiny bacteria, like this colony of Trichodesmium bacteria roughly the size of the head of a pin. (Credit:Eric Webb) USC (US) — Climate change may be weeding out the bacteria that form the base of the ocean's food chain, selecting only certain strains for survival, a new study finds. In climate change, as in everything, there are winners and losers. As atmospheric carbon dioxide levels and temperature rise globally, scientists increasingly want to know which organisms will thrive and which will perish in future environments. The answer to this question for nitrogen-fixing cyanobacteria (bacteria that obtain energy through photosynthesis, or "blue-green algae") turns out to have implications for every living thing in the ocean. Nitrogen-fixing is when certain special organisms like cyanobacteria convert inert—and therefore unusable—nitrogen gas from the air into a reactive form that the majority of other living beings need to survive. Without nitrogen fixers, life in the ocean could not survive for long.
"Our findings show that CO2 has the potential to control the biodiversity of these keystone organisms in ocean biology, and our fossil fuel emissions are probably responsible for changing the types of nitrogen fixers that are growing in the ocean," says David Hutchins, professor of marine environmental biology at the University of Southern California (USC). "This may have all kinds of ramifications for changes in ocean food chains and productivity, even potentially for resources we harvest from the ocean such as fisheries production." For the study, published in Nature Geosciences, Hutchins and colleagues studied two major groups of nitrogen-fixing cyanobacteria: Trichodesmium, which forms large floating colonies big enough to see with the naked eye and makes vast "blooms" in the open ocean, and Crocosphaera, which is also very abundant but is a single-celled, microscopic organism. Previous research showed that these two types of cyanobacteria should be some of the biggest "winners" of climate change, thriving in high CO2 levels and warmer oceans. However, those previous studies only examined one or two strains of the organisms. Using USC's culture library of strains and species of organisms assembled by associate professor Eric Webb, the team was able to show that some strains grow better at CO2 levels not seen since the start of the Industrial Revolution, while others will thrive in the future "greenhouse" Earth. "It's not that climate change will wipe out all nitrogen fixers; we've shown that there's redundancy in nature's system. Rather, increasing atmospheric carbon dioxide changes specifically which nitrogen fixers are likely to thrive," Hutchins says. "And we're not entirely certain how that will change the ocean of tomorrow." The National Science Foundation funded the research. Source: USC
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