The Fourth International Symposium on the Ocean in a High-CO2 World is underway in Hobart, Australia. While the venue is at the opposite end of Australia from the Great Barrier Reef, the event occurred in the shadow of the largest example we have witnessed of the consequences of unrestrained carbon emissions on a marine environment. Unfortunately, as talk after talk emphasized, this is just a foretaste of what is to come.
This year's unprecedented coral reef destruction is primarily driven by high temperatures induced by greenhouse gases. However, it is rising acidity that presents the greatest threat to the reefs' recovery, and the dangers extend far beyond the tropics. Although the oceans are still slightly alkaline, the acidity – measured by the concentration of H+ ions – has risen by around 30 percent since the start of the Industrial Revolution, mostly as a result of carbon dioxide absorbed from the atmosphere.
“We're seeing marine ecosystem shifts in many places," Dr. Bronte Tilbrook of Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) told IFLScience. "It can be hard to distinguish acidification from other pressures such as pollution and warming. However, what we are seeing is a window into what we can expect with more acidic oceans if carbon emissions continue.”
Although Tilbrook added that “some species are more resilient than others,” the reports presented at the conference brought overwhelmingly bad news. Laboratory experiments show that many species struggle to grow in relatively acidic conditions, while long-standing natural experiments around volcanic vents reveal few signs of adaptation, and reefs from Papua New Guinea to the Galapagos Islands are being displaced by seaweed.
Attendees are tweeting what they are hearing at #OHCO2W, and in a rare moment of light relief, Professor Steve Widdicombe of Plymouth University tweeted: “High CO2 makes squid more likely to run away and less likely to stand their ground or attack. Prepare for cowardly cephalopods.”
Most other reports were much grimmer. University of Queensland Ph.D. candidate Jasmine Lee reported that “ocean acidification could cost us $1 trillion/yr by 2100 in lost coral reef services.” Others noted acidic environments cause fish to lose direction, and that the rate at which acidity is rising is 10 times faster than any period in the last 66 million years.
Clownfish lose the capacity to evade predators in acidic waters, making it easier to find Nemo and eat him. Suwat Sirivutcharungchit/Shutterstock
Some regions are particularly exposed. Off the northwest coast of the U.S., upwelling deep waters often bring bursts of acidic waters. Tilbrook explained to IFLScience that it was the combination of such a natural event with the human-induced increased background acidity that caused what he called “a crisis” in the shellfish industry of the area at one point. “Oysters find it harder to settle and start building their shells in an acidic environment,” Tilbrook said.
On a local level, solutions do exist. Seaweed forests reduce carbon dioxide concentrations in nearby waters, and could be promoted around sensitive areas. Tilbrook noted that shellfish hatcheries have experimented with changing local chemistry with some success, but added that even where this is done, “it still puts a stress on the system and may lead to slower growth.” Moreover, such efforts are defeated by the scale of the natural marine environment.
A rare piece of good news came in the extent with which the issue is starting to gain awareness, which has long been the obscure cousin of global warming. A community event summarizing the conference's talks for non-scientists was packed out.
The Sun may be setting on oyster hatcheries as acidifying oceans make it harder for them to settle and make shells. Naturalmen and Mountain/Shutterstock