Dr Donna Roberts, an Australian scientist from the University of Tasmania, is head of the FOCE Antarctic project. In partnership with the Monterey Bay Aquarium Research Institute (MBARI) in California, she wants to evaluate the effects of the acidification of polar waters on marine organisms. A real challenge since the drop in pH, which is twice as rapid as elsewhere, could prefigure the future of the other oceans. She talks about her procedure.
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Le Dr Donna Roberts, scientifique australienne de l’Université de Tasmanie, est à la tête du projet Antarctic FOCE. En partenariat avec le Monterey Bay Aquarium Research Institute (MBARI), en Californie, elle veut évaluer les effets de l’acidification des eaux polaires sur les organismes marins. Un véritable enjeu car la baisse du pH, qui y est deux fois plus rapide qu’ailleurs, pourrait préfigurer le futur des autres océans. Elle revient sur sa démarche.
No matter where you live, if you go outside and start walking north, at some point you’ll reach the Arctic Ocean. A vast expanse at the northern reaches of the planet, the Arctic Ocean supports a dizzying array of ocean wildldife, including the charismatic – and much threatened – polar bear. Most readers of The Blog Aquatic know that summer sea ice has been rapidly melting, caused by human-induced climate change from our ever rising global carbon emissions. Indeed, the concentration of carbon dioxide in the global atmosphere just broke a new record high.
But more poorly understood is that carbon dioxide is beginning to undermine the Arctic ocean itself through a process called ocean acidification. No less than 10 key scientific findings can be found in a just-released assessment of ocean acidification undertaken by an international group of independent scientists.
By Dr. Lizzie Mcleod, Climate Adaptation Scientist for the Nature Conservancy, Asia Pacific Region
As if the long list of threats to coral reefs weren’t enough, we can now add ocean acidification to the list.
Perhaps you’ve seen the gloomy headlines like “Ocean Acidification: ‘Evil Twin’ Threatens World’s Oceans, Scientists Warn.”
Perhaps it is no wonder that folks think coral reef scientists are never finished “crying wolf” about the next global challenge threatening to wipe out coral reef ecosystems.
How serious is this threat and what can we do to address it? To answer these questions, we decided to enlist the help of some global acidification experts. But first, we have to understand the problem.
The chemistry of the ocean is changing. Most climate change discussion focuses on the warmth of the air, but around one-quarter of the carbon dioxide we release into the atmosphere dissolves into the ocean. Dissolved carbon dioxide makes seawater more acidic—a process called ocean acidification—and its effects have already been observed: the shells of sea butterflies, also known as pteropods, have begun dissolving in the Antarctic.
Tiny sea butterflies are related to snails, but use their muscular foot to swim in the water instead of creep along a surface. Many species have thin, hard shells made of calcium carbonate that are especially sensitive to changes in the ocean’s acidity. Their sensitivity and cosmopolitan nature make them an alluring study group for scientists who want to better understand how acidification will affect ocean organisms. But some pteropod species are proving to do just fine in more acidic water, while others have shells that dissolve quickly. So why do some species perish while others thrive?
Ocean acidification has gained attention recently due to the possibility that it may put marine ecosystems at risk, including those that are vital resources for human populations. Willapa Bay, an estuary made up of shallow areas of tidal flats with a deep central channel, is home to various seagrass, bivalve, invertebrate, fish and seabird species, and oyster farming is a dominant economic activity in the region. In this investigation, we gathered existing pH and temperature data and upwelling from 1991-2012 for the Nahcotta Channel, located in Willapa Bay to explore the relationship between ocean pH, upwelling, temperature and ENSO events We analyzed temporal trends of pH levels, temperature and upwelling indices. These trends were analyzed in light of recent El Niño and La Niña events. It was observed that pH and upwelling tends to increase during strong ENSO events while temperature is not affected.
Today at the Arctic Ocean Acidification conference: the chemistry and urgency of acidification
During the opening day of the conference on Arctic Ocean Acidification, I was bombarded by technical vocabulary like omega aragonites, fracturation in alkalinity and biogeochemical cycling. The whole day was dedicated to explaining the changing chemistry of the Arctic Ocean. By changing the amount of CO2 in the atmosphere, we are actually increasing the acidity of the ocean without fully understanding the future impacts on Arctic marine ecosystems.
Many international bodies are enhancing their efforts to understand ocean acidification and there is a growing interest amongst decision-makers.
The MedSeA oceanographic cruise along the Mediterranean Sea is an essential part of the European project “Mediterranean Sea Acidification in a changing climate – MEDSEA” (medsea-project.eu), within the FP7 Cooperation program. The European project MedSeA assesses uncertainties, risks and thresholds related to Mediterranean Sea acidification and warming, at organismal, ecosystem, and socio-economic impact scales. This is the first expedition studying at the basin scale the impact of elevated CO2 on the Mediterranean Sea biogeochemistry and target endemic organisms.
The research cruise has two legs from Cadiz to Heraklion and from Heraklion to Barcelona (May 2, 2013 – June 2 – 2013). The major campaign objective is to conduct a comprehensive water column sampling from each of the basins of the Mediterranean Sea. There will be sediment core sampling, plankton tows and aereosol collectors. Four bioArgo floats will also be deployed. The MedSeA campaign is also part of an international program GEOTRACES that aims to characterize and study the seawater dissolved elements.
Since the start of the industrial revolution, the ocean has silently absorbed roughly 30% of the carbon dioxide that people generate through industry and agriculture. Now ocean chemistry of the seawater is rapidly changing in a process known as ocean acidification. These changes in seawater chemistry affect animal growth, survival and behavior, and they are depleting the ocean of calcium carbonate, a nutrient vital for shellfish to build shells. Marine organisms with calcium carbonate shells or skeletons – such as corals, oysters, clams, and mussels – can be affected by small changes in acidity. That’s important, because shelled organisms are essential throughout the marine food chain. They are also vital to our economy, as shellfish hatcheries on the brink of collapse just a few years ago, struggle to adapt.
Many people are familiar with sea level rise and ocean warming, but ocean acidification?
Just as carbon dioxide from the burning of fossil fuels ends up in our atmosphere, it also ends up in our oceans, resulting in a process called ocean acidification. The carbon dioxide (CO2) dissolving in our ocean combines with seawater (H2O) to make carbonic acid (H2CO3) (see illustration).
Ocean chemistry is changing fast. The measure of the acid-alkaline balance is pH, from 0, extremely acidic, to 14, extremely alkaline (7 is neutral). On this scale, an increase or decrease of 1 unit is a tenfold change. The current ocean pH is around 8.0 but surface pH has decreased by 0.1 since 1750, and a further decrease of 0.3-0.4 units is projected to occur by 2100. While these may seem like small changes, the reality is that ocean pH normally changes extremely slowly over vast periods of time, giving organisms time to evolve. This rate of change means that by 2050, the ocean could be more acidic than at any point over the last 20 million years.