Tag Archives: acidification

Ocean acidification may turn on the lights for some glow-in-the-dark species

Credit: Pixnio.

The oceans are becoming increasingly acidic as humans dump more carbon into the atmosphere, with potentially devastating consequences for marine life. We know, for instance, that water with low pH bleaches coral, potentially destroying beloved reefs. But some of the consequences of ocean acidity can be wildly unpredictable. Case in point, a new study found some bioluminescent marine creatures may glow brighter, while others may have their lights dimmed as a result of increasing acidity.

Most people are familiar with fireflies, which are perhaps the most famous bioluminescent creatures in the animal kingdom. However, bioluminescence — which is the production of cold light by animals through a series of chemical reactions or host bacteria that do so — is actually most common in the ocean.

In fact, in the ocean, glowing is the norm. A staggering 76% of all ocean animals are bioluminescent, which shouldn’t be consumed with biofluorescence, the process by which blue light hitting the surface of a creature is reemitted as a different color, such as orange, red, or green.

These animals use their luminescence like built-in flashlights to attract or find food. Some species also use it in order to communicate to predators that they should stay away because they are poisonous — or it might just be a bluff, but will the predator take the chance?

You know that a trait is definitely prized by evolution if it can enhance survival — and bioluminescence has appeared more than 90 times in different species. It has evolved 27 times among ray-finned fishes alone, which represent a huge group that makes up half of all vertebrate species alive today.

However, not all species glow in the same way. Some marine plankton can really put on a light show. For instance, dinoflagellates are known to cluster in the millions and create a stunning shimmering effect, turning the undulating water blue under the moonlight.

But as average ocean pH levels are expected to drop from 8.1 to 7.7 by 2100, scientists wanted to know how bioluminescence may be affected. Researchers at the University of Hawaii at Manoa performed a review of 49 studies on bioluminescence that involved animals across nine different phyla, including Bacteria, Dinoflagellata, Cnidaria, Mollusca, Arthropoda, Ctenophora, and Chordata.

The findings suggest that bioluminescence is indeed affected by ocean acidity, but not necessarily in one particular way. For some species, such as the sea pansy (Renilla reniformis), the pH drop expected by the end of the century should lead to a twofold increase in light production. Other species like the firefly squid (Watasenia scintillans) may experience the opposite effect, as scientists expect a 70% decrease in light production.

Because marine life uses bioluminescence for a wide variety of purposes, the impact increasing acidity will have is difficult to gauge. What’s certain is that it will be felt and may negatively affect certain species. “The rapid (in an evolutionary timescale) increase in light intensity would have a multitude of knock-on effects for the sensory ecology of marine communities,” the authors wrote in the abstract of their study, which was presented at The Society for Integrative and Comparative Biology Annual Meeting.

A new model developed to estimate how ocean acidity evolves over time

A new mathematical model developed at the University of Colorado at Boulder could allow us to accurately forecast ocean acidity levels up to five years in advance.

A pteropod shell submerged in seawater adjusted to an ocean chemistry projected for the year 2100. It dissolved in 45 days.
Image credits NOAA.

Ocean acidification is driven by CO2 gas in the atmosphere, levels of which are increasing sharply due to human activity. The acid in question is carbonic acid which, although a relatively weak acid, can impact the health and wellbeing of marine life by messing with their metabolism and calcification processes (i.e. with their ability to form and maintain shells).

The authors hope that their model can be used to insulate coastal communities from the economic and nutritional impacts of ocean acidification while helping researchers and policymakers develop adequate conservation methods for marine environments.

Not the acid we were looking for

“We’ve taken a climate model and run it like you would have a weather forecast, essentially — and the model included ocean chemistry, which is extremely novel,” said Riley Brady, lead author of the study, and a doctoral candidate in the Department of Atmospheric and Oceanic Sciences.

The team says that their model is the first to allow for acidity predictions over such a long time period, as previous attempts could only reliably predict up to a few months of data.

For the study, the team focused on the California Current System (CCS), which is one of the four major coastal upwelling systems in the world, running from the tip of Baja California in Mexico all the way up into the Canadian coast. The CCS supports fishing grounds that yield around a billion dollars in fishing catches every year in the U.S. alone. It’s also particularly vulnerable to ocean acidification, the team explains, as it pushes deeper waters (which acidic and denser, so they settle near the bottom) to the surface. The extra acidification we’re causing could push its fragile ecosystems over the edge.

The team used a climate model developed at the National Center for Atmospheric Research to generate ‘forecasts’ for past changes in acidity levels and compared those to real-world data — finding that they fit recorded changes very well. Another advantage this model has over localized ones that it can factor in events with global effects, such as El Niño.

However, while the results were quite exciting, our ability to deploy such models is still limited. These tools still require an immense amount of computational power, data, manpower, and time to implement and run, so they can’t really be used around the clock to generate acidification forecasts.

But we do know that they would be useful. It’s estimated that around 30% to 40% of the CO2 emissions from human activity are absorbed by the world’s waters and react to form carbonic acid, which makes them more acidic. The effect is only going to increase in the future, and researchers are expecting that large swaths of the ocean are going to become completely corrosive to the shells of certain organisms within decades.

“The ocean has been doing us a huge favor,” said study co-author Nicole Lovenduski, associate professor in atmospheric and oceanic sciences and head of the Ocean Biogeochemistry Research Group at INSTAAR.

But now, “ocean acidification is proceeding at a rate 10 times faster today than any time in the last 55 million years.”

Communities who rely on ocean resources for food or tourism will undoubtedly be affected by acidification, the team notes.

The paper “Skillful multiyear predictions of ocean acidification in the California Current System” has been published in the journal Nature.

Asteroid that wiped out the dinosaurs triggered a sharp rise in ocean acidity

A long-held theory about the last great mass extinction event in history and how it affected Earth’s oceans was just confirmed by a new study by Yale University, which may also answer questions about how marine life eventually recovered.

Credit Wikimedia Commons

The researches argued this is the first direct evidence that the Cretaceous-Paleogene extinction event 66 million years ago coincided with a sharp drop in the pH levels of the oceans—which indicates a rise in ocean acidity.

The Cretaceous-Paleogene die-off occurred when an asteroid slammed into Earth at the end of the Cretaceous period. The impact and its aftereffects killed roughly 75% of the animal and plant species on the planet.

“For years, people suggested there would have been a decrease in ocean pH because the meteor impact hit sulfur-rich rocks and caused the raining-out of sulphuric acid, but until now no one had any direct evidence to show this happened,” said lead author Michael Henehan.

Researchers looked at the foraminifera, tiny plankton that grow a calcite shell and have an amazingly complete fossil record going back hundreds of millions of years. An analysis of the chemical composition of foraminifera fossils from before, during and after the event produced a wealth of data about changes in the marine environment.

Previous research of the die-off had shown that some marine calcifiers—animal species that develop shells and skeletons from calcium carbonate—were disproportionately wiped out in the mass extinction. This new study showed higher ocean acidity may have prevented the calcifiers from creating the shells.

This was important, according to the researchers, because these calcifiers made up an important part of the first rung on the ocean food chain, supporting the rest of the ecosystem.

“The ocean acidification we observe could easily have been the trigger for mass extinction in the marine realm,” said senior author Pincelli Hull, assistant professor of geology and geophysics at Yale.

The team’s boron isotope analysis and modeling techniques may have reconciled some competing theories and puzzling facts relating to ocean life after the die-off event. One theory, for example, argued that for a time after the die-off event, the ocean was essentially dead, and the normal carbon cycle just stopped.

Another popular theory called the “Living Ocean” suggested that the die-off killed off larger plankton species, disrupting the carbon cycle by making it harder for organic matter to sink to the deep sea, but allowed for some marine life to survive.

The new study splits the difference. It says the oceans had a major, initial loss of species productivity—by as much as 50% —followed by a transitional period in which marine life began to recover.

“In a way, we reconciled both of these ‘Strangelove’ and ‘Living Ocean’ scenarios,” Henehan said. “Both of them were partially right; they just happened in sequence.”

CO2 in the atmosphere heralds imminent food chain collapse — and it’s gonna start in the oceans

The first global analysis of how marine environments react to the ever-increasing levels of CO2 that humanity is pumping into the atmosphere does not bode well at all for tomorrow’s would-be fishers. Published today in the journal Proceedings of the National Academy of Sciences (PNAS), the work of the University of Adelaide’s marine ecologists states that the warming and expected ocean acidification is likely to produce a reduction in diversity and numbers of various key species that underpin marine ecosystems around the world.

Image via onearth

“This ‘simplification’ of our oceans will have profound consequences for our current way of life, particularly for coastal populations and those that rely on oceans for food and trade,” says Associate Professor Ivan Nagelkerken, Australian Research Council (ARC) Future Fellow with the University’s Environment Institute.

Associate Professor Negelkerken and fellow University of Adelaide marine ecologist Professor Sean Connell went through the data from 632 published experiments focusing on waters from all types of climate and ecosystems, from tropical to arctic, and ranging from coral reefs to forests of kelp or open oceans.

“We know relatively little about how climate change will affect the marine environment,” says Professor Connell. “Until now, there has been almost total reliance on qualitative reviews and perspectives of potential global change. Where quantitative assessments exist, they typically focus on single stressors, single ecosystems or single species.

“This analysis combines the results of all these experiments to study the combined effects of multiple stressors on whole communities, including species interactions and different measures of responses to climate change.”

The researchers found that there would be “limited scope” for acclimation to warmer waters and acidification. There aren’t that many species that can escape or adapt fast enough to keep pace with the effects of increasing CO2 levels, and the researchers expect a large reduction in both species diversity and abundance across the globe. Interestingly enough, not all species will feel the blow — microorganisms are actually expected to increase in number and diversify.

We will feel the effects too — even if primary production (plankton) is expected to increase in the warmer waters, it’s doubtful that this will translate into secondary production (zooplankton and smaller fish) due to the more acidic environment, so the amount of food we can pull out of the ocean will be dramatically reduced.

“With higher metabolic rates in the warmer water, and therefore a greater demand for food, there is a mismatch with less food available for carnivores—the bigger fish that fisheries industries are based around,” says Associate Professor Nagelkerken. “There will be a species collapse from the top of the food chain down.”

The analysis also showed that with warmer waters or increased acidification or both, there would be deleterious impacts on habitat-forming species — coral, oysters and mussels for example. Any slight change in the health of habitats would have a broad impact on a wide range of species these reefs house.

Another alarming finding was that acidification would lead to a decline in dimethylsulfide gas (DMS) production by ocean plankton which helps cloud formation and therefore in controlling the Earth’s heat exchange.

Northern shrimp hauled aboard a shrimp boat. Credit: Wikimedia

Shrimps become less tastier as a result of climate change

The effects of climate change on food stock quality is well documented, yet a new study suggests that climate change might not only affect survival rates of marine life, but also how it tastes too. The findings came after an international team of researchers sought to see how high water acidity affects the sensory quality of shrimp.

Northern shrimp hauled aboard a shrimp boat. Credit: Wikimedia

Northern shrimp hauled aboard a shrimp boat. Credit: Wikimedia

Carbon is stored not only in trees, but also in the world’s oceans and sea which act like huge carbon sinks. As more and more carbon is being absorbed, this causes the water to become more acidic, a process called ocean acidification. Marine animals  interact in complex food webs that may be disrupted by ocean acidification due to losses in key species that will have trouble creating calcium carbonate shells in acidified waters. Some species of calcifying plankton that are threatened by ocean acidification form the base of marine food chains and are important sources of prey to many larger organisms. With coral and plankton gone, most marine species will follow, thus acidification is a huge concern. But if you’re not that interested in the fate of marine life, maybe you’d be more considerate of how it tastes.

The researchers put hundreds of northern shrimps (Pandalus borealis) into tanks that mimic a projected 2100 ocean acidification level of pH 7.5, while a control group was put in tanks of pH 8.0, the current average level in the waters. In addition, the water was heated to 11 degrees Centigrade, or roughly the extreme of the shrimps’ temperature tolerance, so that the animals would be more stressed and make acidification stand out more. After three weeks, the shrimps were put out of the tanks and served to 30 connoisseurs for a taste test.

Shrimp from less acidic waters were 3.4 times as likely to be judged the tastiest, while those from more acidic waters were 2.6 times as likely to be rated the worst tasting, according to the paper published in the Journal of Shellfish Research. Not to be neglected is that decreased pH increased mortality significantly, by 63%. Does this mean that the shrimp industry is doomed? It’s hard to tell, but what the study shows is that the effects of climate change extend well beyond food supply, but also quality. I’ve yet to find something similar, but it may be likely that the same might be said about other marine food stocks, like tuna.

Regarding terrestrial food, a University of California, Davis study found that  rising CO2 levels are inhibits plants’ ability to assimilate nitrates into nutrients, altering their quality for the worse. Thus, it’s expected that crops in the future will contain less nutrients than they do today.