October 16, 2013
We often hear about melting sea ice, rising tides and bleached coral reefs, but climate change is poised to reverberate through a broader swath of the marine environment than these headline issues alone might suggest.
According to a new study published in PLoS Biology, “the entire world’s ocean surface will be simultaneously impacted by varying intensities of ocean warming, acidification, oxygen depletion, or shortfalls in productivity.” As the ocean’s biogeochemistry shifts, the paper reports, so too will its habitats and the creatures living there. This could mean hardship for some 470 to 870 million people–many of whom live in poverty–who depend upon the bounty of the sea to support livelihoods and fill dinner plates. And these impacts are not predicted to occur centuries down the road, either: according to the study, they may transpire as soon as 2100.
Nearly 30 scientists from around the world–including climate modelers, ecologists, biogeochemists and social scientists–co-authored the study. They built upon computer models from the Intergovernmental Panel for Climate Change by compiling data from 31 Earth System Models that included at least one ocean parameter. All told, 27,000 years’ worth of data of the various overlapping, aggregated variables were compiled into their new model.
With those data compiled, they then modeled two different future scenarios: one in which atmospheric carbon dioxide concentrations increase to 550 parts per million, and another in which they hit 900 ppm (the planet currently stands at about 400 ppm, as compared to pre-industrial times, when that measurement was 280 ppm). The former model represents values predicted if mitigation efforts are undertaken, while the latter is predicted for a “business-as-usual” scenario where we maintain current levels of greenhouse gas emissions into the future.
Their model predicted changes in temperature, oxygen levels, increased acidity and productivity (the creation of organic compounds by primary producers like phytoplankton) on both the ocean surface and the sea floor under those two future scenarios. Nearly across the board on the ocean’s surface, they found, their models predicted a continued warming and rise in acidity accompanied by a decline in oxygen and productivity. The only exception was in a small fraction of the sea in polar regions, where the sea surface would experience increased oxygen and productivity. The magnitude of these predicted changes, they write, will be greater than any comparable shifts over the past 20 million years.
“When you look at the world ocean, there are few places that will be free of changes; most will suffer the simultaneous effects of warming, acidification, and reductions in oxygen and productivity,” Camilo Mora, a geographer at the University of Hawaii at Mānoa, said in a press release.
The most drastic impacts, they found, will occur on the ocean’s surface, but the seafloor will also experience its share of smaller but still significant changes. Seafloor temperature and acidity will change only slightly compared to the surface, but there will be large reductions in the influx of carbon, which provides food for many bottom-dwelling organisms. The drop in dissolved oxygen on the sea floor will be similar to that experienced on the surface.
These changes may be enough to disrupt the ocean floor’s delicate ecosystem. ”Because many deep-sea ecosystems are so stable, even small changes in temperature, oxygen, and acidity may lower the resilience of deep-sea communities,” Lisa Levin, an oceanographer at the University of California, San Diego, and co-author of the paper, said in the release. “This is a growing concern as humans extract more resources and create more disturbances in the deep ocean.”
As for the surface, the magnitude of the projected changes will vary by place. The tropics will experience the smallest changes in acidity; temperate regions will suffer the least significant shifts in temperature and productivity; and the Southern Ocean near Antarctica will be spared the least fluctuations in oxygen. But overall, across the board the ocean surface will suffer significant impacts.
With those data in hand, they then overlaid habitat and biodiversity hot spot information for 32 diverse marine environments around the world to see how these changes would impact ocean flora and fauna. Coral reefs, seagrass beds and other shallow areas will suffer the greatest impacts, they found, while deep ocean seamounts and vents will suffer the least.
Humans will not be spared the repercussions of those changes. In a final analysis, they quantified humanity’s dependence on the ocean by analyzing global jobs, revenues and food that comes from the sea. Most of the up to 870 million people who will be affected most by these changes live in some of the world’s poorest nations, they found.
While these predictions are subject to the same limitations that plague any computer model that attempts to represent a complex natural system and project its future fate, the authors believe that the results are robust enough to strongly support the likelihood that our oceans will be very different places in the not-too-distant future. If carbon dioxide levels continue to rise, they write, “substantial degradation of marine ecosystems and associated human hardships are very likely to occur.”
“It is truly scary to consider how vast these impacts will be,” co-author Andrew Sweetman of the International Research Institute of Stavanger, Norway, emphasized in the press release. “This is one legacy that we as humans should not be allowed to ignore.”
December 18, 2012
Despite covering 70 percent of the earth’s surface, the ocean doesn’t often make it into the news. But when it does, it makes quite a splash (so to speak). Here are the top ten ocean stories we couldn’t stop talking about this year, in no particular order. Add your own in the comments!
2012: The Year of the Squid From the giant squid’s giant eyes (the better to see predatory sperm whales, my dear), to the vampire squid’s eerie diet of remains and feces, the strange adaptations and behavior of these cephalopods amazed us all year. Scientists found a deep-sea squid that dismembers its own glowing arm to distract predators and make a daring escape. But fascinating findings weren’t relegated to the deep: at the surface, some squids will rocket themselves above the waves to fly long distances at top speeds.
James Cameron Explores the Deep Sea Filmmaker James Cameron has never shied away from marine movie plots (See: Titanic, The Abyss), but this year he showed he was truly fearless, becoming the first person to hit the deepest point on the seafloor (35,804 feet) in a solo submarine. While he only managed to bring up a single mud sample from the deepest region, he found thriving biodiversity in the other deep-sea areas his expedition explored, including giant versions of organisms found in shallow water.
Small Fish Make a Big Impact Forage fish—small, schooling fish that are gulped down by predators—should be left in the ocean for larger fish, marine mammals and birds to eat, according to an April report from the Lenfest Forage Fish Task Force. These tiny fish, including anchovies, menhaden, herring and sardines, make up 37% of the world’s catch, but only 10% are consumed by people, with the rest processed into food for farmed fish and livestock. With the evidence mounting that forage fish are worth more as wild fish food, state governments and regional fishery management councils are making moves to protect them from overfishing.
Marine Debris and Plastic Get Around In June, a dock encrusted with barnacles, sea stars, crabs and other sea life washed ashore on the coast of Oregon. It had floated across the Pacific from a Japanese port more than 5,000 miles away—a small piece of the estimated 1.5 million tons of marine debris set afloat by the 2011 Tohoku tsunami. But that’s not the only trash in the sea. Researchers found ten times as much plastic in the “pristine” Antarctic oceans than they expected. Some species are even learning to adapt to the ubiquitous ocean plastic.
Taking Measure of Coral Reef Health Australia’s iconic Great Barrier Reef, so large it can be seen from space, is not doing well. An October study found that since 1986, half of the living coral has died because of warming water, predation and storm damage. And it’s not just Australia: the December Healthy Reefs report gave most Mesoamerican reefs a “poor” rating. It’s hard to escape that gloom, but there were glimmers of hope. Some coral species proved able to adapt to warmer water, and changing circulation caused by the warming ocean may create refuges for coral reef habitat.
Shark Finning Slowing Down? The fishing practice of shark finning—slicing off a shark’s fins before tossing it back in the ocean to slowly sink and suffocate—began its own slow death in 2012. A steady stream of U.S. states have banned the sale of shark fins
ning; the European Union will now require fisherman to land sharks with their fins on; four shark sanctuaries were created in American Samoa, the Cook Islands, Kosrae and French Polynesia; and, in July, China announced that official banquets would be prohibited from serving shark fin soup (although the ban may take up to three years to go into effect).
Arctic Sea Ice Hits All-Time Low On September 16, sea ice extent reached a record low in the Arctic, stretching 3.41 million square kilometers—that’s 49% lower than the 1979-2000 average minimum of 6.7 million square kilometers. What’s more, its melt rate is increasing: 2012 had the largest summer ice loss by more than one million square kilometers. This change is expected to affect ecosystems—from polar bears to phytoplankton—and accelerate warming in the area, eventually melting Greenland’s ice sheet and raising sea level dramatically.
Hurricane Sandy Elevates Awareness of Sea-Level Rise This year certainly opened our eyes to the severity of climate change and sea-level rise. The east coast of the U.S., where scientists project sea-level will rise three to four times faster than the global average, got a glimpse of its effects when Hurricane Sandy caused $65 billion in damage, took at least 253 lives, and flooded Manhattan’s subways in October. The disaster inspired The Economist, Bloomberg Businessweek and other major news sources to take a closer look at climate change and what it means for us all.
Counting Ocean Animals from Space Scientists took advantage of satellite technology this year to learn more about ocean wildlife. The first satellite-driven census of an animal population discovered that there are twice as many emperor penguins in Antarctica as previously thought, including seven new colonies of the large flightless birds. A second study tracked the travels of sea turtles by satellite, which could help researchers get a better idea of where they might interact with fisheries and accidentally end up caught in a net.
The Ocean Gets a Grade The first tool to comprehensively assess ocean health was announced in August 2012—and the ocean as a whole received a score of 60 out of a possible 100. This tool, the Ocean Health Index, is novel in that it considered ten ways the ocean supports people, including economies, biodiversity, and recreation. The U.S. scored a 63, ranking 26th globally, while the uninhabited Jarvis Island took home an 86, the top grade of the 171 rated countries.
–Hannah Waters, Emily Frost and Amanda Feuerstein co-wrote this post
November 8, 2012
Corals are constantly under attack. Sea stars and other predators would love to take a bite, coral diseases lie waiting to take them out and many human-caused stresses persist in the water they inhabit, such as pollution, warming temperatures and rising acidity.
One of the first signs of a sick reef is the takeover of seaweeds, which continually threaten even healthy corals. However, corals aren’t alone in the fight against greenery, according to new research published in Science. When attacked, some corals send out chemical signals to their bodyguards—small goby fish—who scrape off or eat the coral-choking seaweeds.
Turtle weed (Chlorodesmis fastigiata) threatens corals because, upon contact, it releases a noxious chemical that disrupts their food source, the photosynthetic algae (zooxanthellae) that live inside their cells, ultimately leading to coral bleaching. Although most fish don’t have a palate for such toxic seaweed, authors Mark Hay and Danielle Dixson from the Georgia Institute of Technology observed coral gobies—small fish that spend their lives living in a single coral colony—eating it, and they wondered if there was more to this behavior than taste.
Hay and Dixson placed turtle weed on small staghorn coral (Acropora nasuta), a common reef-building coral found in the Pacific and Indian oceans, while in the presence of two goby species. The gobies cleaned up quickly: Within three days, 30% of the turtle weed was gone, and coral bleaching dropped by 70-80% compared to a goby-less seaweed invasion.
“These little fish would come out and mow the seaweed off so it didn’t touch the coral,” said Hay in a press release. “This takes place very rapidly, which means it must be very important to both the coral and the fish.”
In a series of experiments, the researchers worked out how the coral contacts the gobies to let them know that they need their hedges trimmed. Once the coral gets hit with chemicals from the invading turtle weed, it releases its own chemical signal—an emergency call to gobies—within 15 minutes. And, within another 15 minutes or less, gobies receive the message and swoop in to nibble away at the encroaching foliage.
What are the gobies getting out of this arrangement? The broad-barred goby (Gobiodon histrio) got a boost in its own defenses. It produces its own poisonous mucus to deter predators and, after eating the noxious turtle weed, this mucus impaired their predators’ swimming ability more than twice as fast, the researchers found. But the other goby species—the redhead goby (Paragobiodon echinocephalus)—doesn’t eat the seaweed, simply shearing it off the coral. What is its benefit?
“The fish are getting protection in a safe place to live and food from the coral,” Hay said. “The coral gets a bodyguard in exchange for a small amount of food. It’s kind of like paying taxes in exchange for police protection.”
This kind of chemical signaling system is the first observed in coral reef organisms—but it surely isn’t the only one. Many coral reef organisms are interdependent, relying on one or two other species for food or habitat, which means that the loss of just a few species can accelerate the disappearance of many others. For example, if these coral-cleaning gobies were overfished, say for the aquarium trade, the reef would be threatened by seaweed takeover, which could then degrade the entire community.
“Who would have thought that such a small, seemingly insignificant fish might play such a large role in keeping corals from being killed by seaweeds?” said coral reef biologist Nancy Knowlton from the Smithsonian National Museum of Natural History, who did not participate in the research. “It’s a compelling example of why maintaining biodiversity is so important.”
It’s also possible that such subtle chemical signals could be disrupted by ocean acidification. Clownfish and damselfish raised in seawater with the acidity scientists predict we’ll see in the year 2050 have trouble identifying scents in seawater to find their homes or avoid predators. If these gobies have similar problems, the impacts of acidification on reef communities could be greater than expected.
September 17, 2012
Most concerns when it comes to rising greenhouse gas emissions involve changes to aspects of climate: warmer air temperatures, erratic weather patterns and the impacts of these trends on landscapes and agriculture. One of the most immediate dangers to the environment, though, is a drastic change to the chemistry of an ecosystem that covers 71 percent of the planet but many of us rarely see—the ocean.
As we covered previously, higher concentrations of carbon dioxide in the atmosphere result in an increasingly acidic ocean, as roughly a third of the carbon dioxide we emit annually (35 billion metric tons) diffuses into the surface layer of water and is converted into carbonic acid. Scientists have long known that a more acidic ocean poses grave problems for wildlife, especially for creatures associated with coral reefs, which are home to one quarter of all species of life in the oceans.
Scientists have not only been studying how acidic and warmer waters harm ocean life but also how quickly that damage is happening, and they can now put a number on the extent of the potential damage: At least 70 percent of coral reefs are projected to suffer from degradation by 2030 without a dramatic change in how much carbon we emit, according to a study published yesterday in Nature Climate Change. Scientists from the Potsdam Institute for Climate Impact Research and elsewhere arrived at this number by conducting the first comprehensive global survey of the impact of both acidification and climate change on coral reefs.
“Our findings show that under current assumptions regarding thermal sensitivity, coral reefs might no longer be prominent coastal ecosystems if global mean temperatures actually exceed 2 degrees Celsius above the pre-industrial level,” says lead author Katja Frieler of the Potsdam Institute. Many prominent climatologists now believe that there is “little to no chance” of avoiding a 2 degrees Celsius (3.5 degrees Fahrenheit) increase and view it as a realistic best-case scenario even if we begin curtailing greenhouse gas emissions immediately.
To calculate just how many reefs would be damaged by climate change and acidification, the researchers looked at 2,160 coral reefs around the globe and modeled what would happen to them under a number of different greenhouse gas emissions scenarios, ranging from the most optimistic to the most dire. They used 19 separate climate models, simulating 32,000 years in total, allowing for the widest possible range of outcomes.
The 70 percent figure might seem dire, but even that occurred under what the researchers termed “an ambitious mitigation scenario” for greenhouse gas emissions. Without any mitigation—a “plan” we’re currently pursuing—they found that all reefs would be subject to degradation. The reason for this staggering degree of damage is that corals are doubly harmed by greenhouse gases—they’re severely affected by both warmer waters (an effect of climate change as a whole) and ocean acidification.
Warming harms coral reefs through a process called bleaching. Reefs are actually inert physical structures created by living animals called corals, which in turn obtain most of their energy through a symbiotic relationship with microscopic algae. This symbiotic process, though, breaks down in the presence of unusually warm waters, causing the corals to die and the reefs to bleach, turning a pale white color. Although corals can survive brief periods of warm water, extended heat stress kills them en masse, something seen in 1998, when a prolonged period of unusual warmth tied to El Niño killed an estimated 16 percent of shallow-water reefs worldwide.
When coral reefs are already stressed by bleaching, acidification can be deadly. Just as shellfish use naturally-occurring calcium carbonate in the water to construct their shells, corals use it to build reefs, their external skeletons. More acidic water, though, directly reduces the amount of calcium carbonate available for construction. Most previous models for estimating potential damage to reefs by warming, the researchers say, neglected to take in the exacerbating damage done by acidification.
Furthermore, the particular life traits of corals make it much less likely that they will be able to adapt to warmer and more acidic waters. “Corals themselves have all the wrong characteristics to be able to rapidly evolve new thermal tolerances,” says co-author Ove Hoegh-Guldberg, a marine biologist at the University of Queensland in Australia. “They have long life cycles of five to 100 years and they show low levels of diversity due to the fact that corals can reproduce by cloning themselves.” This means that advantageous traits that would allow them to tolerate the conditions they’ll face in the future are much less likely to spread within the timeframe necessary.
This is especially unfortunate because of how valuable coral reefs are, in terms of both biodiversity and services to humans. Coral reef ecosystems cover less than 1 percent of the world’s ocean area yet are home to about 25 percent of all marine species. Moreover, the value of the ecosystem services they provide—in terms of shoreline protection, tourism and fisheries—is estimated to be $375 billion annually.
All this is likely to be gone within decades, though, if we don’t quickly change our carb0n emission habits. “The window of opportunity to preserve the majority of coral reefs, part of the world’s natural heritage, is small,” says study co-author Malte Meinshausen of the Postdam Institute. “We close this window if we follow another decade of ballooning global greenhouse-gas emissions.”
July 18, 2012
Since the Industrial Revolution, ocean acidity has risen by 30 percent as a direct result of fossil-fuel burning and deforestation. And within the last 50 years, human industry has caused the world’s oceans to experience a sharp increase in acidity that rivals levels seen when ancient carbon cycles triggered mass extinctions, which took out more than 90 percent of the oceans’ species and more than 75 percent of terrestrial species.
Rising ocean acidity is now considered to be just as much of a formidable threat to the health of Earth’s environment as the atmospheric climate changes brought on by pumping out greenhouse gases. Scientists are now trying to understand what that means for the future survival of marine and terrestrial organisms.
In June, ScienceNOW reported that out of the 35 billion metric tons of carbon dioxide released annually through fossil fuel use, one-third of those emissions diffuse into the surface layer of the ocean. The effects those emissions will have on the biosphere is sobering, as rising ocean acidity will completely upset the balance of marine life in the world’s oceans and will subsequently affect humans and animals who benefit from the oceans’ food resources.
The damage to marine life is due in large part to the fact that higher acidity dissolves naturally-occurring calcium carbonate that many marine species–including plankton, sea urchins, shellfish and coral–use to construct their shells and external skeletons. Studies conducted off Arctic regions have shown that the combination of melting sea ice, atmospheric carbon dioxide and subsequently hotter, CO2-saturated surface waters has led to the undersaturation of calcium carbonate in ocean waters. The reduction in the amount of calcium carbonate in the ocean spells out disaster for the organisms that rely on those nutrients to build their protective shells and body structures.
The link between ocean acidity and calcium carbonate is a directly inverse relationship, which allows scientists to use the oceans’ calcium carbonate saturation levels to measure just how acidic the waters are. In a study by the University of Hawaii at Manoa published earlier this year, researchers calculated that the level of calcium carbonate saturation in the world’s oceans has fallen faster in the last 200 years than has been seen in the last 21,000 years–signaling an extraordinary rise in ocean acidity to levels higher than would ever occur naturally.
The authors of the study continued on to say that currently only 50 percent of the world’s ocean waters are saturated with enough calcium carbonate to support coral reef growth and maintenance, but by 2100, that proportion is expected to drop to a mere five percent, putting most of the world’s beautiful and diverse coral reef habitats in danger.
In the face of so much mounting and discouraging evidence that the oceans are on a trajectory toward irreparable marine life damage, a new study offers hope that certain species may be able to adapt quick enough to keep pace with the changing make-up of Earth’s waters.
In a study published last week in the journal Nature Climate Change, researchers from the ARC Center of Excellence for Coral Reef Studies found that baby clownfish (Amphiprion melanopus) are able to cope with increased acidity if their parents also lived in higher acidic water, a remarkable finding after a study conducted last year on another clownfish species (Amphiprion percula) suggested acidic waters reduced the fish’s sense of smell, making it likely for the fish to mistakenly swim toward predators.
But the new study will require further research to determine whether or not the adaptive abilities of the clownfish are also present in more environmentally-sensitive marine species.
While the news that at least some baby fish may be able to adapt to changes provides optimism, there is still much to learn about the process. It is unclear through what mechanism clownfish are able to pass along this trait to their offspring so quickly, evolutionarily speaking. Organisms capable of generation-to-generation adaptations could have an advantage in the coming decades, as anthropogenic emissions push Earth to non-natural extremes and place new stresses on the biosphere.