Climate change could have impact on ocean food chain

Climate change may affect the evolution of bacteria at the base of the ocean's food chain, selecting certain strains for survival, a U.S. study indicates. As atmospheric carbon dioxide levels and temperature rise globally, scientists at the University of Southern California have been looking at the effects on nitrogen-fixing cyanobacteria "blue-green algae," that obtain energy through photosynthesis. Nitrogen-fixing organisms like cyanobacteria convert inert -- and therefore unusable -- nitrogen gas from the air into a reactive form the majority of other living beings need to survive, they said. "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," marine environmental biology Professor David Hutchins said. Certain types of cyanobacteria could be some of the biggest "winners" in climate change, thriving in high CO2 levels and warmer oceans, the researchers said. "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 said. "And we're not entirely certain how that will change the ocean of tomorrow."