Mounting concerns over ocean acidification—a consequence of CO2 emissions—has accelerated research funding aimed at understanding the process potentially endangering marine life in ocean waters all across the earth.
In early October, the National Science Foundation awarded over $24 million dollars to 22 projects through a new grant program targeted to study how ocean acidification affects marine environments. While the NSF has funded ocean acidification in the past, it is the first time the agency has created a special program aimed at the field of study.
As CO2 concentrations in the atmosphere increase, much of the gas is absorbed by the oceans, where it dissolves in the water. As a result, the oceans are getting more acidic over time. However, the long-term effects of the process are poorly understood.
“There are serious concerns about ocean acidification, and that's why this research is being conducted," Phillip Taylor, Head of the Ocean Section in NSF's Ocean Sciences Division, told SolveClimate News. “There are many who think this is going to have an impact on important animals in the sea that are instrumental in driving the productivity of ocean waters.”
Ocean acidification threatens the growth of corals, clams and other organisms at the bottom of the food chain. These changes could trigger a domino effect throughout the oceanic ecosystem.
The funded projects investigate a variety of topics, such as modeling the rate of future acidification, studying how organisms behave in lowered pH and looking at earth history to understand how current trends may progress.
What the Science Says So Far
One recipient of the new grants was Bärbel Hönisch, a paleoceanographer and assistant professor at Columbia University. Hönisch is using boron isotopes to reconstruct how the oceans' pH has changed with time; she hopes that past trends will shed light on the changes to come.
"All of [this funding] is meant to get a better idea of what's going to happen in the ocean—what can be expected for the ecology and economy," she said.
The pH of the modern oceans is 8.1. Since the Industrial Revolution, the oceans' pH has dropped by 0.1 and is expected to drop another 0.2-0.3 by 2100, said Hönisch.
Those changes may not sound like a lot, but pH is measured on a logarithmic scale, so a 0.1 difference is equivalent to a 30% change in acidity or alkalinity. "When you change the pH of water, it has very clear and potentially immediate affects on the physiology of organisms," Taylor said.
One effect of ocean acidification is to decrease the availability of carbonate ions in the water, an important compound for organisms like corals, shellfish and foraminifera that use carbonate to build their calcium carbonate shells. These shells are part of the organisms' body structure; they provide shape, size and protection against predators.
“There are serious questions about what the food chain impacts will be," said Taylor. In particular, pteropods—a major food source for salmon—depend on calcium carbonate shells. The larvae of sea urchins, mussels and crabs could also be affected.
Study: Lower Survival Rates
A paper published Oct. 5 in the science journal Proceedings of the National Academy of Sciences showed just how serious the consequences could be. The first examination of how ocean acidification of the past 200 years has affected marine shellfish, the study revealed that bivalve shellfish larvae survive to become juvenile shellfish about half as frequently in water with current CO2 levels as they do in water with preindustrial CO2 levels.
Christopher Gobler, an associate professor in the School of Marine and Atmospheric Sciences at Stony Brook University, and his colleagues raised two species of bivalve shellfish larvae in different CO2 concentrations. One group was placed in water with 250 parts per million of dissolved CO2 to mimic preindustrial conditions, and another group was grown in concentrations of 390 ppm, or present-day levels. A third were placed in water with CO2 concentrations of 1500 parts per million—an extreme case.
Over the 40-day experiment, the organisms grew from shell-less embryos to juveniles with actual calcium carbonate shells. The ones that grew in lower CO2 concentrations ended up with larger, thicker shells. Shellfish survival rates under 250 ppm were nearly double that of 390 ppm. Very few shellfish survived in 1500 ppm waters.
The larval stage is particularly important because that's when the shellfish are most sensitive, said Gobler: "It looks like even small changes in the availability of carbonate has a big impact at [the larval] stage."
The next step is to see how the shellfish might adapt, said Gobler. When animals are faced with stress, they can move, adapt or die out. Since ocean acidification is a global phenomenon, changing habitat isn't an option. Shellfish will either adapt to higher CO2 levels or go extinct.
A Need for Speed
To survive, they’ll have to adapt fast. Many modern shellfish evolved about 20 million years ago, four million years after the last time atmospheric CO2 levels were as high as they are today.
"There is a possibility [the shellfish] can adapt quickly,” Gobler said. “We just don't know."
While there have been times in Earth's past when atmospheric CO2 reached current concentrations, those changes happened over thousands of years. Today's aquatic organisms have much less time to adjust.
"In many ways you can say climate change is happening all the time, and species are changing constantly," said Columbia’s Hönisch. "It's just happening so quickly right now."
An executive order signed into action in July mirrors this increasing awareness of the need to monitor ocean health. The policy for the Stewardship of the Ocean, Coasts and Great Lakes aims to improve ocean management through integrated, ecosystem-based planning for conservation and multiple-use areas.
"[I think the new policy] is an indication that people in the science realm and policy makers and the public think this is a serious problem," said NSF's Taylor. "I think we'll see [ocean acidification] elevated in priority very soon."