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One of the more serious impacts of human-caused climate disruption occurs when seawater absorbs excess carbon dioxide from the atmosphere. When this occurs, the carbon dioxide reacts with the water to form carbonic acid, which then ultimately reduces its pH level. For much of the marine life in the oceans, the consequences of this will be dire.

“Animals that have a calcium carbonate shell such as, corals, coralline algae, pteropods, bivalves and gastropods are negatively affected by ocean acidification,” said Richard Feely, a senior scientist with the National Oceanic and Atmospheric Administration’s (NOAA) Pacific Marine Environmental Laboratory. “In some cases, their shells are weakened or actually dissolve while the animal is still alive. Fish behavior is also impacted by ocean acidification such that some species lose their ability to navigate or avoid predators.”

Acidifying oceans have already killed valuable oysters within the Pacific Northwest where Feely lives. “Oyster larvae are dying in the shellfish hatcheries along the West Coast,” he said.

Feely, who also holds an affiliate full professor faculty position at the University of Washington School of Oceanography, has been studying ocean acidification for nearly half a century. He moved to Seattle in 1974 and started a chemical oceanography program at NOAA. Feely ultimately went on to become one of the first scientists to measure how seawater was storing excess carbon dioxide and has, from the beginning, been one of the leading scientists studying ocean acidification.

The pH scale measures acidity, and 7.0 is neutral, whereas higher readings are more “basic” and lower readings are more “acidic.” Historically, Earth’s oceans averaged a pH of 8.2, but this is predicted to fall by as much as 0.4 by 2100. Since the pH scale is logarithmic, one pH unit represents a tenfold change. The ocean’s pH level has already dropped from 8.2 to 8.1, which represents a 25 percent drop within just the past century.

As oceans absorb increasing amounts of our industrial emissions of CO2, their pH is expected to drop to a staggering 7.7 pH by 2100, according to professor of marine chemistry Aleck Wang at the Woods Hole Oceanographic Institution. Wang told National Geographic that by 2100, “you are going to start seeing calcium carbonate shells dissolve. It’s not going to be that far away.”

Most scientists studying the impacts of ocean acidification agree that by killing off the types of organisms Feely mentioned (corals, oysters, types of phytoplankton, etc.), major portions of the oceanic food chain could be greatly impacted.

Feely told Truthout that key marine organisms and ecosystem services face contrasting risks from the combined effects of ocean acidification, warming and sea level rise, and that even under the most stringently controlled CO2 emissions scenario, warm water corals and mid-latitude bivalves “are considered to be at high risk by 2100.”

“Under our current rate of CO2 emissions, most marine organisms are expected to have very high risk of impacts by 2100 and many by 2050,” Feely said. “These results are consistent with evidence of biological responses during high-CO2 periods in the geological past. Impacts to the ocean’s ecosystem services follow a parallel trajectory.”

Ecosystem Impacts

Seiji Nakaya is a coral biologist who coordinated and recently completed the Palau International Coral Reef Center’s research program on climate disruption’s impacts on coral reefs. Now working back in Japan, Nakaya shared with Truthout his concerns about ocean acidification’s impact on global fisheries.

Nakaya explained several ways the impact will be felt. “Acidification will inhibit growth of … organisms that have calcium carbonate skeleton such as shellfish, crustaceans and sea urchins,” he said. “It will impact fisheries by inhibiting growth of planktons with calcium carbonate, such as pteropods, [which] are bases of food chains to sustain fish populations, and acidification will inhibit growth of corals, damaging the dimensional structure of coral reefs that fish or prey of fishery-target species inhabit.”

Feely shared similar concerns and pointed out how corals, bivalves and other organisms are negatively affected by acidification, as it also reduces their competitiveness with non-calcifiers. He added how in some parts of the ocean that already have naturally low pH — like upwelling areas, the polar regions and in mid/deep waters — ocean acidification can even result in the “net dissolution of carbonate shells and skeletons (i.e. cold-water coral reefs) and loss of associated habitat.”

Feely pointed out there are some positive impacts from acidification — species like blue crabs, lobsters and shrimp actually grow thicker shells that could make them more resistant to predators, according to one study — and that some biological responses can be exacerbated by other factors like oceanic warming, deoxygenation and metal pollution.

“As a result, many uncertainties remain in our understanding of the impacts of ocean acidification on organisms, life histories and ecosystem responses,” he said.

But Feely has been concerned about the negative impacts for a long time.

“Over the past 20 million years, ocean ecosystems have evolved in a very stable pH environment,” Feely told Climate.gov in 2009. “I’m worried that if concentrations of carbon dioxide continue to rise, the ocean could undergo large and rapid changes in pH.”

In 2004, Feely had published two critically important articles in the journal Science that showed the ocean had already absorbed roughly one-third of the carbon dioxide emitted by humans, and had caused changes in the seawater.

According to Feely, high latitude and upwelling regions of the oceans are already “seriously affected by ocean acidification,” and he said that he and his colleagues are “already observing dissolution of pteropod shells in the Arctic and Southern Oceans, and also upwelling regions along the West Coast of North America.”

Rich Childers is the Ocean Acidification Policy Lead for the Washington State Department of Fish and Wildlife, where he monitors ocean acidification’s impacts on wild stock populations in Washington’s marine waters. To Childers, acidification’s impacts on global fisheries is “the million-dollar question” that resource managers and researchers are struggling with.

“Of great concern to resource managers is how ocean acidification is and will impact planktonic species (both plant and animal) that are key organisms in marine primary production and large-scale food webs,” Childers told Truthout. “A likely scenario is that future impacts to marine life from ocean acidification will result in ‘winners’ and ‘losers’ at the organism level, and a resulting change in marine community structures.”

Similar to Feely and Nakaya, Childers described acidification’s impact of reducing the carbonate ion and other essential minerals utilized by calcifying marine organisms to produce shells as a “great concern to resource managers and ecologists.”

Childers told Truthout that, beginning in 2005, “Pacific Northwest oyster hatcheries in Washington and Oregon experienced oyster seed production failures resulting from arrival of low-pH (more acidic) seawater. This low-pH seawater was corrosive to shell-forming organisms, including the young oysters being produced in the hatchery.”

Increasing Concerns

Nakaya told Truthout one of his most serious concerns about acidification’s impacts was that it could cause a negative feedback by “reducing the capacity of seawater that can absorb atmospheric CO2 by affecting CO2 fixing organisms, which in turn increases atmospheric CO2. This may intensify climate change.”

Nakaya pointed out that there is no way to reverse acidification quickly, “except for reducing emission of CO2, and we don’t know how serious the impact of ocean acidification will be in future.”

Childers pointed out that ocean acidification has the potential to “seriously influence survival of marine wild stock populations and compromise and/or change marine ecosystems on both large and small scales.”

He said that while the end results are unclear at this time, “Clearly, ocean acidification will have negative impacts to some marine species and potentially to large-scale ecosystems.”

Feely believes that successful management of the impacts of ocean acidification entails the reduction of human-caused CO2 emissions and “societal adaptation by reducing the consequences of past and future ocean acidification.”

The latter of these entails the direct mitigation of acidification by reduction of atmospheric CO2 emissions, which he sees as also the least risky.

Feely addressed the idea of climate geo-engineering techniques based on solar radiation management and said that these efforts “will not directly abate ocean acidification since CO2 levels would continue to increase” anyway.

He went on to add, “Techniques to remove CO2 from the atmosphere, by either biological, geochemical or chemical means, could directly address the problem, but are not yet well-developed.” And of those, “They seem likely to have additional environmental consequences, or may be very costly, or may be limited by the lack of CO2 storage capacity.”

Feely’s deepest concerns about ocean acidification are that so many ecosystem processes that humans depend on for food and survival are already impacted by both oceanic warming and acidification, and the risks of these impacts to these services only increases with continued CO2 emissions, which currently show little signs of slowing down.

“[The impacts] are predicted to remain moderate for the next several decades for most services under stringent emission reductions,” Feely said. “But the business-as-usual scenario would put all ecosystem services at high or very high risk over the same time frame.”

A 2015 study warned that ocean acidification could cause dramatic changes to phytoplankton, the basis of the entire oceanic food web.

According to a 2016 study published in the journal Nature Geoscience, CO2 is being added to the atmosphere at a minimum of 10 times faster than it had during a major warming event roughly 56 million years ago that caused a major planetary extinction event.

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