The World Meteorological Organization (WMO) reports that the amounts of atmospheric greenhouse gases reached a new high in 2013, driven by rapidly rising levels of carbon dioxide.
The news is consistent with trends in fossil fuel consumption. But what comes as more of a surprise is the WMO’s revelation that the current rate of ocean acidification, which greenhouse gases (GHGs) help to cause, appears unprecedented in at least the last 300 million years.
The details of growing GHG levels are in the annual Greenhouse Gas Bulletin, published by the WMO—the United Nations specialist agency that plays a leading role in international efforts to monitor and protect the environment.
They show that between 1990 and 2013 there was a 34 percent increase in radiative forcing—the warming effect on our climate—because of long-lived greenhouse gases such as carbon dioxide (CO2), methane and nitrous oxide.
Complex interactions
The Bulletin reports on atmospheric concentrations—not emissions—of greenhouse gases. Emissions are what go into the atmosphere, while concentrations are what stay there after the complex system of interactions between the atmosphere, biosphere (the entire global ecological system) and the oceans.
About a quarter of total emissions are taken up by the oceans and another quarter by the biosphere, cutting levels of atmospheric CO2.
In 2013, the atmospheric concentration of CO2 was 142 percent higher than before the Industrial Revolution started, in about 1750. Concentrations of methane and nitrous oxide had risen by 253 percent and 121 percent respectively.
The observations from WMO’s Global Atmosphere Watch network showed that CO2 levels increased more from 2012 to 2013 than during any other year since 1984. Scientists think this may be related to reduced CO2 absorption by the Earth’s biosphere, as well as by the steady increase in emissions.
Although the oceans lessen the increase in CO2 that would otherwise happen in the atmosphere, they do so at a price to marine life and to fishing communities—and also to tourism. The Bulletin says the oceans appear to be acidifying faster than at any time in at least the last 300 million years.
“We know without any doubt that our climate is changing and our weather is becoming more extreme due to human activities such as the burning of fossil fuels,” said the WMO's secretary-general, Michel Jarraud.
Running out of time
“The Greenhouse Gas Bulletin shows that, far from falling, the concentration of carbon dioxide in the atmosphere actually increased last year at the fastest rate for nearly 30 years. We are running out of time. The laws of physics are non-negotiable.
“The Bulletin provides a scientific base for decision-making. We have the knowledge and we have the tools for action to try to keep temperature increases within 2°C to give our planet a chance and to give our children and grandchildren a future. Pleading ignorance can no longer be an excuse for not acting.”
Wendy Watson-Wright, executive secretary of the Intergovernmental Oceanographic Commission of UNESCO, said: “It is high time the ocean, as the primary driver of the planet’s climate and attenuator of climate change, becomes a central part of climate change discussions.
“If global warming is not a strong enough reason to cut CO2 emissions, ocean acidification should be, since its effects are already being felt and will increase for many decades to come.”
The amount of CO2 in the atmosphere reached 396.0 parts per million (ppm) in 2013. At the current rate of increase, the global annual average concentration is set to cross the symbolic 400 ppm threshold within the next two years.
More potent
Methane, in the short term, is a far more powerful greenhouse gas than CO2—34 times more potent over a century, but 84 times more over 20 years.
Atmospheric methane reached a new high of about 1,824 parts per billion (ppb) in 2013, because of increased emissions from human sources. Since 2007, it has started increasing again, after a temporary period of levelling-off.
Nitrous oxide’s atmospheric concentration in 2013 was about 325.9 ppb. Its impact on climate, over a century, is 298 times greater than equal emissions of CO2. It also plays an important role in the destruction of the ozone layer that protects the Earth from harmful ultraviolet solar radiation.
The oceans currently absorb a quarter of anthropogenic CO2 emissions—about 4kg of CO2 per day per person. Acidification will continue to accelerate at least until mid-century, according to projections from Earth system models.
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The waters off the U.S. state of Alaska are some of the best fishing grounds anywhere, teeming with salmon and with shellfish such as crab.
But a new study, funded by the U.S. National Oceanic and Atmospheric Administration (NOAA), says growing acidification of Alaska’s waters, particularly those off the southern coast, threatens the state’s whole economy—largely dependent on the fishing industry.
The study, which appears in the journal Progress in Oceanography, says that not only will the state’s commercial fishing sector be badly hit by a growth in acidification, but it will also affect subsistence fisherpeople whose diet mainly consists of the catch from local waters.
Forming acid
The oceans act as a “carbon sink,” absorbing vast amounts of carbon dioxide. Acidification occurs when amounts of carbon dioxide are dissolved into seawater, where it forms carbolic acid.
Scientists say the oceans are now 30 percent more acidic than they were at the beginning of the industrial revolution about 250 years ago.
Among the sea species most vulnerable to acidification are shellfish, because a build-up of acid in waters prevents species developing their calcium shells. Alaska’s salmon stocks are also at risk as one of the main ingredients of a salmon diet are pteropods, small shell creatures.
Jeremy Mathis, an NOAA oceanographer and a lead author of the study, told the Alaska Dispatch News that whereas past reports had focused on the consequences of increased acidification on ocean species, the aim of this one was designed to examine the wider economic impact.
“This is an economic-social study,” Mathis said. “It focuses on food security, employment opportunity and the size of the economy.”
Mathis said acidification is more likely in Alaskan waters than in many other parts of the world. He explained: “It’s all about geography. The world’s ocean currents end their cycles here, depositing carbon dioxide from elsewhere. The coastal waters of Alaska sit right at the end of the ocean conveyor belt.”
Elsewhere, acidification is already having a serious impact on fishing and shellfish industries.
Oysters dying
The New York Times reports that billions of baby oysters—known as spat—are dying off the coast of Washington state in the north-western U.S.
In May this year, the U.S. government’s major report on climate change, the National Climate Assessment, said that waters off the north-west of the country are among the world’s most acidic.
Jay Inslee, Governor of Washington, says an industry worth US$270 million is at risk. “You can’t overstate what this means to Washington,” he says.
Inslee and many others in Washington state are fighting plans by the coal industry to build large coal ports in the region in order to export to China and elsewhere in Asia.
Climate scientists say greenhouse gas emissions resulting from coal burning are a main cause of global warming.
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Our power plants and cars have pumped so much carbon dioxide into the atmosphere that the oceans are becoming more acidic. Something like a quarter of our carbon dioxide pollution dissolves into the seas, where it reacts with water:
CO2 (aq) + H2O 
H2CO3 HCO3− + H+ CO32− + 2 H+
Illustration by Perry Shirley
Those leftover hydrogen ions at the right of the equation add up. The hydrogen ion concentration at the surface of the world’s oceans has increased by 26 percent since pre-industrial times, leading to a pH decline of 0.1. That might not sound like much, but it has been enough to kill off billions of farmed shellfish and punch holes in the shells of wild sea snails.
Shellfish and corals are especially vulnerable to ocean acidification because they rely on calcium carbonate to make their shells and skeletons. Ocean acidification increases concentrations of bicarbonate ions while decreasing concentrations of carbonate ions—and these animals need calcium carbonate to produce their protective body parts.
Fish, meanwhile, are thought to be suffering neurological effects of acidifying oceans, while vast mats of algae are expected to flourish.
The good news is that populations of animals naturally adapt to changes in their environments—and evolutionary changes to help some species cope with ocean acidification are already underway. The bad news is that changes in oceanic pH levels might be happening too quickly for animals to adapt, threatening scores of marine species with extinction.
I asked Ryan Kelly, an assistant professor at the University of Washington’s School of Marine and Environmental Affairs, and a coauthor of a recent BioScience paper about acidification that I wrote about for Pacific Standard, whether we could do anything to help species accelerate the rate with which they evolve needed adaptations.
“‘Accelerating’ species’ evolutionary adaptations to acidification would mean either tweaking the heritability of traits—and it’s unclear whether this is desirable, or how to do it; or increasing the strength of selection—which would mean making the selective impacts of acidification worse than they already are,” Kelly said. “So I’m thinking that, in an evolutionary sense, you don’t want to accelerate adaptation.”
Is there anything that we can do?
“What you do want to do, in order to protect marine ecosystems as we know them, is to preserve the adaptive capacity of the species that make up those ecosystems. That means preserving the genetic diversity that exists within those species, so that when the selective pressures of acidification happen, there will be some variability in those species’ responses. When there’s no genetic diversity, you get no variability in response to selective pressure, and natural selection and evolution doesn’t really work.”
Which means that we need to expand and improve the globe’s network of marine reserves, banning fishing in some places, and giving species the best possible shot of surviving the storm of acidity that’s building around them.
“From a conservation perspective, measures that preserve existing genetic diversity safeguard the adaptive capacity of species and ecosystems. This means working to maintain large population sizes and not fragmenting habitats, which are common conservation measures.”
As U.S. Secretary of State John Kerry led workshops in June dealing with ocean acidification and other ocean health issues, President Barack Obama’s administration proposed sweeping expansions of marine reserves surrounding remote Pacific Ocean atolls. The move would limit fishing for tuna and other species, helping to protect top predators that are critical for ecosystem health, while also protecting smaller species that are killed as bycatch.
“This is an important step in trying to maintain the health of this region and, as a result, the surrounding areas in the Pacific,” said Lance Morgan, president of Marine Conservation Institute. “It will give us more resilience into the future. We’ll have to replicate this and do more work in other areas as well, but it is an important step.”
Meanwhile, the National Oceanic and Atmospheric Administration is planning to expand the boundaries of Gulf of the Farallones National Marine Sanctuary and Cordell Bank National Marine Sanctuary, both of which lie off the West Coast, where strong upwelling leads to especially severe rates of ocean acidification. Meanwhile, Kiribati recently announced that it would close an area the size of California to fishing to help wildlife recover.
Ocean acidification is not a major consideration in the creation of marine reserves, but it’s a growing threat against which the reserves can help populations of wildlife evolve natural defenses.
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Acidic ocean water blunts the sense of smell in fish, making them bolder—perhaps recklessly so, according to a new study offering a glimpse of the oceans of the future.
The findings suggest that, if greenhouse gas emissions continue unabated, fish could suffer debilitating behavioral effects.
"If reef fish behavior does not adapt to rising [carbon dioxide] CO2 levels over coming generations, there could be serious consequences for the structure and function of future reef communities," the authors wrote in the study published in Nature Climate Change.
The researchers, however, were surprised to find fish populations near the carbon seeps about as diverse and abundant as the fish from normal reefs.
The researchers studied young fish living near reefs in Papua New Guinea where CO2 venting from volcanic seeps make the water more acidic. Compared to fish from reefs without seeps, the fish in acidic waters were more attracted to their predator's smell, didn't distinguish between different habitats' odors and were bolder, emerging from shelter at least six times faster after a disturbance.
The findings build on laboratory and field studies suggesting that increasing ocean acidification will impair fish behavior and gravely affect creatures like coral and shellfish that depend on calcium for a shell.
Buffer for Emissions
The oceans have absorbed about one-third of humanities' greenhouse gas emissions, buffering the atmosphere. But as oceans absorb the carbon dioxide —some 530 billion tons to date—seawater becomes more acidic. The water's pH, a measurement of acidity, remained stable at 8.2 for roughly 300 million years before industrialization. Today it is near 8.1, a drop of 25 percent on the logarithmic scale.
Seawater pH near the seeps in Papua New Guinea is about 7.8—the same pH that ocean surface waters will reach by 2100, according to climate models assessed by the Intergovernmental Panel on Climate Change.
"This is the first time people have been able to test what would happen in 100 years," said Danielle Dixson, an assistant professor at Georgia Tech University and co-author of the study, which was led by Australian researchers.
The differences are striking, said Karl Castillo, an assistant professor of marine sciences at the University of North Carolina who was not involved with the research.
'Strong Study'
"This is a strong study," Castillo said. "There's no doubt there is something happening here due to acidification."
Most animals on coral reefs, including fish, rely on chemical cues to know if they should hide or eat or mate with something, Dixson explained. Acidity dulls the ability to detect those cues, and the impacts could cascade through the entire reef.
"Not being able to recognize a predator is one of the most dangerous things for any animal," Dixson added.
Given the behavior differences, it's not clear why there wasn't more difference in species composition and richness between the seep reefs and the normal reefs, Dixson said.
The study is just the latest example of why ocean acidification needs to be addressed, said Emily Jeffers, a staff attorney with the Center for Biological Diversity. The Center for Biological Diversity has petitioned the U.S. government to list certain species of corals and reef dependent fish as endangered to offer some protection from acidification.
In 2010, the U.S. Environmental Protection Agency passed a ruling that water impacted by ocean acidification should be listed as impaired under the Clean Water Act. However, no state has listed water as such yet.
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A few weeks from now, in the waters off the Tasmanian coast, marine ecologist Jonny Stark of the Australian Antarctic Division and a team of biologists and technicians will piece together an underwater laboratory. Once they get the technology hooked up and running, they will promptly disassemble the hoses, instruments, pumps and plastic panels and crate it all up. This is merely a dress rehearsal, and in much kinder conditions than those anticipated for the performance later this year in Antarctica.
Their mission?
“We’re going to build a bio-dome on the sea floor with a future ocean inside it,” declares project co-leader Donna Roberts, a marine biologist with Australia’s Antarctic Climate and Ecosystems Cooperative Research Center.
Within the chambers of their laboratory, which will be dropped 20 meters below the frozen crust of a little Antarctic bay just south of the Australian government’s Casey Station, Roberts, Stark and their colleagues will introduce a selection of plants and animals from the local seafloor community to the more acidic seawater conditions anticipated by 2100. In the ensuing four months, the scientists will maintain the artificial conditions in the chambers via an umbilical system fed through a hole bored in three-meter-thick ice. The results of their experiment will help illuminate a key question about future climate change: what will be the impact of dramatically changing seawater chemistry on ocean biology?
The Australian research project is one of a handful being conducted by scientists in Antarctica and the Arctic, where the reality of ocean acidification—the so-called other carbon dioxide (CO2) problem—is expected to be felt first, soon, and hard. That’s because colder ocean waters inhale and retain more carbon dioxide from the atmosphere than warmer waters. This creates higher levels of acidity and threatens a host of creatures—from tiny zooplankton to sea urchins and sea stars—that may have difficulty building shells or reproducing in waters with a lower pH.
Scientists say that frigid polar seas are on the front line of the most dramatic shift in ocean chemistry in millions of years.
“In both the Arctic and the Southern Ocean the change is happening very quickly,” says Richard Bellerby of the Norwegian Institute for Water Research, chairman of the recent Arctic Monitoring and Assessment Program acidification summary and leader of a pending acidification study in the Southern Ocean. According to Bellerby, the Arctic report documents that “we’ve already crossed some important geochemical and biological thresholds in the Arctic” These include areas at the floor of the Arctic shelf that are now inhospitable for some marine organisms due to higher acidity and lower oxygen levels, he said. Together with shifts in ice cover and ocean freshening from ice sheet melting, they have led to changing species diversity in many regions.
“The challenge is to understand the baseline, the natural workings of the ecosystems,” says Bellerby. “Because we are now observing a system undergoing rapid change, it is crucial that we get the knowledge as soon as possible. The earlier we get that, the more robust our understanding for future management to preserve these already sensitive regions.”
About one-third of the CO2 produced by human activity over 200 years of intensive fossil fuel burning has so far been swallowed up by the oceans, resulting in a 0.1 unit drop in the pH of seawater, according to the Intergovernmental Panel on Climate Change. A major summary report published by the International Council for Science last November observed that CO2 absorption by the oceans has thus far translated to a 26 percent increase in ocean acidity in the industrial era. By 2100, the shift is expected to rise to 170 percent if humanity continues on the current emissions path. As atmospheric concentrations of carbon dioxide reach levels not seen in millions of years, the world’s oceans will soon hold fewer carbonate ions, a crucial building block for marine organisms assembling their calcium carbonate shells and skeletons.
Arctic specialists warn that 10 percent of northern polar surface waters will be corrosive for aragonite, a form of calcium carbonate, by 2018, and that these hostile conditions will spread over the entire Arctic Ocean by the end of the century. The same has been anticipated in winter in parts of the Southern Ocean by the 2030s.
In Nov. 2012, the British Antarctic Survey published the first evidence that change is already affected marine organisms. Samples collected on a research cruise back in 2008 revealed that the shells of tiny marine snails—pteropods—were being dissolved by ocean acidification occurring in pockets of the Southern Ocean where natural upwelling created more corrosive conditions.
“We’re only talking in terms of 10 to 20 years that surface waters at the poles will be undersaturated”—that is, lacking in the carbonate ions used to build aragonite, says Stark. “These are the conditions where aragonite might be vulnerable and might start dissolving. There’s not a lot of research on which organisms will feel it—it’s still early days, but pteropods are one. Polar ecosystems might be the canary for what happens in other parts of the ocean.”
Maybe creatures will survive, but with damaged or weaker shells, says Stark. “For a developed animal growing, trying to extract aragonite from the water, it would take more energy,” he notes, “so it has less energy for reproduction and survival, for growth and development.”
Bellerby reckons that some species, like the pteropods, will be “outcompeted—shunted out of particular ecosystems,” with profound implications for the marine food web. Others may survive and thrive, like the mussels and other bivalves known to do well in lower pH water.
“So we have this interplay, these multi-stressors,” says Bellerby. “How will productivity change? How will warming, circulation, the timing and extent of ice cover influence the food supply? It’s just not as simple as crossing a particular acidification threshold—you have to look at the whole package.”
To date, the constraints of laboratory aquaria have hobbled efforts to grasp the big picture. Artificial conditions can never emulate the intricacies of complex marine ecosystems—the untested tolerance and adaptability of various species; the efficiency of natural buffers, such as seafloor sediment, in absorbing and offsetting change; the lottery of which populations will win and which will lose in the new scenarios.
The experiment under the sea ice at Casey Station is part of a vanguard of initiatives to conquer these obstacles by taking “the lab to the ecosystem, instead of taking the ecosystem to the lab,” says Roberts. “We want to see how the entire community responds. Our hypothesis is that things that need calcium carbonate [to build and maintain shells or skeletons] will do poorly, but plants will be stimulated. The interesting thing is what the sum of responses means to the community at large.”
Scientists in the north have also broken out of the laboratory, launching a series of giant, floating enclosures, called mesocosms, into fjords in Norway, Finland and Sweden within which they examine how more acidic conditions affect the wider marine community. One of their initial findings is that tiny plankton capitalize and thrive in the new conditions, but do so at the expense of larger species, a change that alone could throw marine ecosystems out of kilter.
Donna Roberts’ Antarctic project is the latest in an evolving family of in situ experiments using Free Ocean CO2 Enrichment (FOCE)technology developed by California’s Monterey Bay Aquarium Research Institute. While there are FOCE experiments now running at three other marine sites—off the California coast, in the Mediterranean, and in the coral shallows of Australia’s Great Barrier Reef—the fledgling Antarctic project (“antFOCE”) is the most ambitious effort yet, given the formidable challenges of working in the polar environment.
To build the laboratory, Stark and seven other divers will plunge through the ice to work in near-freezing water—about 1.5 degrees Celsius—in hour-long shifts four times a day, about the limit anyone can safely endure the punishing environment.
They will construct four, coffee table-sized polycarbonate chambers and fix them to the sea floor. Two of the chambers will function as controls, tracking natural conditions, primarily the pH level. Meanwhile the two active chambers are constantly dosed by seawater mixed with CO2 at the levels expected in the atmosphere by the turn of the century—around 900 parts per million, a rate that assumes humanity continues to do little to reduce the current high emissions trajectory.
The 2100 chemical scenario translates as about 7.8 pH—0.4 pH units lower than today’s ambient ocean pH, with the chamber technology constantly calibrating and adjusting to maintain the projected future acidity. As pH 7.8 happens to be the tipping point identified for the viability of shelled organisms in naturally lower-pH waters around volcanic vents on the sea floor, “it is going to be interesting to see what happens,” says Roberts.
In a Swedish fjord, European researchers are conducting an ambitious experiment aimed at better understanding how ocean acidification will affect marine life. Ultimately, these scientists hope to determine which species might win and which might lose in a more acidic ocean.
Filters will stop bigger fish getting in, but the chambers are otherwise porous, washed with a flow of natural light, seawater, nutrients and tiny creatures, and sitting upon undisturbed sediment, which some experts have theorized might provide a buffer against the effects of higher acidity.
Conducting these experiments in an environment that captures the natural physical and biological conditions is critical to gaining meaningful insight into how to manage the future, says Bellerby. But “it makes it much more challenging to weed out results,” he says. “You lose a certain amount of control, but that is part of the rapid learning curve.”
It’s complex, logistically fraught, expensive science. The Casey Station experiment will cost roughly $5.5 million, including transport and logistics to support the team in Antarctica. One passing iceberg and the latest experiment could be wiped out. “We’re very excited,” says Roberts. “Some of the highest reward science has some of the highest risk.”
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Without deep cuts in carbon dioxide emissions, the planet’s coral reefs could be in serious trouble. In a world in which humans continue to burn fossil fuels unchecked, ocean conditions will become ultimately inhospitable, according to U.S. scientists.
Katharine Ricke and Ken Caldeira of the Carnegie Institution in Washington and colleagues make their sombre prediction in Environmental Research Letters. Their argument on the face of it seems inconsistent with other recent research on reef response to climate change, which in one case suggests that some corals could vanish, and in another that some corals might adapt, very slowly.
But the debate in all three cases is about the rate of warming, the levels of carbon dioxide in the atmosphere and the ultimate impact of changes in the pH levels of the seas.
Ricke and Caldeira looked not so much at the warming of the seas–tropical corals are very sensitive to temperature–nor at the levels of acidification as such (because rain dissolves carbon dioxide to form a weak carbonic acid and inevitably affects the ocean’s pH levels), but at the chemical circumstances in which crystals of aragonite can form.
All fossil reefs and shell and bone sediments are ultimately calcium carbonate in the form of limestone or chalk. However, calcium carbonate, or CaCO3, exists in two crystal structures, calcite and aragonite, and these fossilized sediments must once have been mostly aragonite.
That is because marine life, in the form of corals, fish and mollusc shells, mainly begins with aragonite. The biochemical availability of aragonite depends on the pH values of the water.
An End to Dumping
Ricke and Caldeira used computer models to calculate ocean chemical conditions under a range of carbon dioxide scenarios, looking for the necessary conditions to support aragonite formation and shell and bone growth, and set a potential aragonite saturation threshold.
In pre-industrial times, 99.9 percent of the oceans that washed over coral reefs were comfortably above this threshold. Under the notorious business-as-usual threshold, in which fossil fuel use continues to grow, ultimately the water surrounding the 6,000 coral reefs they used as a database for their research would be significantly below the threshold.
There would be a point at which the resilience and capacity to adapt that must be inherent in corals would be overwhelmed. The conclusion is a bleak one.
“Our results show that if we continue on our current emissions path, by the end of the century there will be no water left in the ocean with the chemical properties that have supported coral reef growth in the past. We can’t say with 100 percent certainty that all shallow water coral reefs will die, but it is a pretty good bet,” said Ricke.
“To save coral reefs, we need to transform our energy system into one that does not use the atmosphere and ocean as waste dumps for carbon dioxide pollution,” Caldeira added.
Visit EcoWatch’s WATER and BIODIVERSITY pages for more related news on this topic.
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