The Bottom Line
Corals are very narrowly adapted to their environment. While urchins have adapted to the pulses of acidic water washing up from the deeper Pacific, coral larvae will only flourish in water that fits into a narrow band of pH and temperature. Thanks to the SeaFET sensors, researchers now know that the pH of coral reefs is diurnal.
Ocean acidification is not just a pollution problem: it’s an economic and food security problem. This rings true for Hofmann, her research lab, members of the consortium — and people who run fisheries, urchin harvesters, or tour operators. “Global-change biologists talk about four outcomes when environments start to change,” Hofmann explains. “One option is that the organism can migrate — change its range, go somewhere else where conditions are most hospitable to them. They can also acclimate or climatize, use their plasticity and their flexibility to stay where they live and keep functioning. Or, they can truly adapt, come up with a new genetic solution to the problem. And the fourth option is extinction. Populations that are less able to adapt or climatize are very vulnerable to extinction.”
This means that the pH of the water in a coral reef is regulated by the respiration of the Symbiodinium — the algae that are symbionts in the cells of the invertebrate coral — on a daily basis. Coral reefs are therefore among the only places in the world where the pH of the water is not due to outside forces, such as upwelling on the Pacific coast or the extreme temperatures of the Southern Ocean. Hofmann points out, “Out there on the reef, it’s biology driving the exchange of carbon in the water.”
The same set of choices might be what’s in store for human beings. Economically, says Hofmann, when changes due to acidification start to happen “the intensity of the impact will be local, really focal and intense.” Bleached or algaecovered corals will translate to less revenue for people who rely on tourism or fishing, and more acidic waters will stunt or exterminate the larvae of pteropods, urchins, and corals.
This “diurnal signature of respiration” in coral reefs is significant not only because it creates its own pH levels, but because coral reefs are, in a certain sense, the lungs of the ocean. The massive exchange of CO2 between reefs and the atmosphere is hugely important for the health of the atmosphere, as well as the oceans. Hofmann reminds us, “You could also argue that coral reefs are economically important, too, because a lot of nations are dependant upon the health of coral reefs for their economy.” Besides being home to nearly a quarter of the entire world’s marine species, tropical coral reefs are major tourist attractions. Globally, travel and recreation associated with tropical coral reefs is valued at over 100 billion dollars. As with urchin harvesting and oyster farming, Hofmann feels that the degradation of tropical reefs by ocean acidification could mean economic disaster for people who depend on the biodiversity there not just for food, but for tourism, too. “The Maldives and little island nations are in big, big trouble,” said Hofmann. The people of these nations rely on the ocean for their economy.” Despite their small carbon footprint, people in small island nations like French Polynesia, New Guinea, or Indonesia could have their whole lives upended by the effects of ocean acidification.
“If ocean acidification is allowed to take hold, people who depend on the ocean for their livelihood might have to give up and move away. Further down the line, people who love seafood might have to adapt to a world with fewer options and less food security. It’s not an exaggeration to say,” she warns, “that there could be some things that aren’t around in a hundred years that used to be around. If things get bad enough, important seafood will be really challenged.” The question of future food security is just one way Hofmann and her team make the threat of anthropogenic ocean acidification real for the public. In Hofmann’s experience, “I haven’t heard a lot of skepticism about it. When I talk to people, it clicks really quickly. People love the oceans, and ocean acidification is basic chemistry.” “That’s how I explain ocean acidification to the average person. And it resonates.”
VIDEO EXTRA Watch the research team dive deep below icebergs to place SeaFET sensors. convergence.ucsb.edu Video produced by Henry Kaiser
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