Archive for July, 2012

The quiet tsunami: the ecological, economic, social, and political consequences of ocean acidification

A large portion of the carbon dioxide emitted into the atmosphere is absorbed by the world’s oceans. They become more acidic as they absorb the gas. This has far-reaching implications for the oceanic food web, biodiversity, and the global economy, particularly fishing and ecotourism industries in developing countries. This article briefly outlines the scientific evidence of ocean acidification and the implications of anthropogenic carbon emissions for marine ecosystems. It then assesses the economic, social, and political ramifications of ocean acidification and suggests a new strategy for the promotion of climate change policy. The “quiet tsunami” of oceanic climate change necessitates a policy shift away from the business-as-usual approach to reducing carbon emissions. The high stakes involved in this looming crisis may prompt unwilling governments to act in order to ensure food security and protect key economic markets around the world.

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Studying evolution with an eye on the future

A conversation with Sinéad Collins

Charles Darwin came to many of his ideas by observing the wild creatures of South America. The biologist Sinéad Collins elaborates on his work by actually creating evolution in her laboratory at the University of Edinburgh. Dr. Collins, 36, sets up experiments to uncover evolution’s basic rules. She then uses the information to help work on solutions to contemporary environmental problems like global warming and marine acidification.

We spoke for two hours at last winter’s annual meeting of the American Association for the Advancement of Science in Vancouver, British Columbia, and then again last month by telephone. An edited and condensed version of the conversations follows.

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Ocean acidification refugia of the Florida Reef Tract

Ocean acidification (OA) is expected to reduce the calcification rates of marine organisms, yet we have little understanding of how OA will manifest within dynamic, real-world systems. Natural CO2, alkalinity, and salinity gradients can significantly alter local carbonate chemistry, and thereby create a range of susceptibility for different ecosystems to OA. As such, there is a need to characterize this natural variability of seawater carbonate chemistry, especially within coastal ecosystems. Since 2009, carbonate chemistry data have been collected on the Florida Reef Tract (FRT). During periods of heightened productivity, there is a net uptake of total CO2 (TCO2) which increases aragonite saturation state (Ωarag) values on inshore patch reefs of the upper FRT. These waters can exhibit greater Ωarag than what has been modeled for the tropical surface ocean during preindustrial times, with mean (± std. error) Ωarag-values in spring = 4.69 (±0.101). Conversely, Ωarag-values on offshore reefs generally represent oceanic carbonate chemistries consistent with present day tropical surface ocean conditions. This gradient is opposite from what has been reported for other reef environments. We hypothesize this pattern is caused by the photosynthetic uptake of TCO2 mainly by seagrasses and, to a lesser extent, macroalgae in the inshore waters of the FRT. These inshore reef habitats are therefore potential acidification refugia that are defined not only in a spatial sense, but also in time; coinciding with seasonal productivity dynamics. Coral reefs located within or immediately downstream of seagrass beds may find refuge from OA.

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Multi-decadal uptake of carbon dioxide into subtropical mode water of the North Atlantic Ocean

Natural climate variability impacts the multi-decadal uptake of anthropogenic carbon dioxide (Cant) into the North Atlantic Ocean subpolar and subtropical gyres. Previous studies have shown that there is significant uptake of CO2 into subtropical mode water (STMW) of the North Atlantic. STMW forms south of the Gulf Stream in winter and constitutes the dominant upper-ocean water mass in the subtropical gyre of the North Atlantic Ocean. Observations at the Bermuda Atlantic Time-series Study (BATS) site near Bermuda show an increase in dissolved inorganic carbon (DIC) of +1.51 ± 0.08 μmol kg−1 yr−1 between 1988 and 2011, but also an increase in ocean acidification indicators such as pH at rates (−0.0022 ± 0.0002 yr−1) higher than the surface ocean (Bates et al., 2012). It is estimated that the sink of CO2 into STMW was 0.985 ± 0.018 Pg C (Pg = 1015 g C) between 1988 and 2011 (70 ± 1.8% of which is due to uptake of Cant). The sink of CO2 into the STMW is 20% of the CO2 uptake in the North Atlantic Ocean between 14°–50° N (Takahashi et al., 2009). However, the STMW sink of CO2 was strongly coupled to the North Atlantic Oscillation (NAO), with large uptake of CO2 into STMW during the 1990s during a predominantly NAO positive phase. In contrast, uptake of CO2 into STMW was much reduced in the 2000s during the NAO neutral/negative phase. Thus, NAO induced variability of the STMW CO2 sink is important when evaluating multi-decadal changes in North Atlantic Ocean CO2 sinks.

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Ocean acidification in the outcome document of Rio+20

Ocean acidification is mentioned in paragraph 166 of the outcome document “The future we want” of the United Nations Conference on Sustainable Development (Rio+20).

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Le fond des mers mis en boîte

On dirait un énorme aquarium de Plexiglas : c’est en fait un prototype de laboratoire sous-marin de deux mètres de long pour un mètre de large.  

C’est la pierre de touche du programme européen Efoce, dédié au suivi à long terme de l’acidification des océans.

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Isotope data improve the predictive capabilities of a marine biogeochemical model

Mesocosm experiments combined with biogeochemical modeling provide a powerful research tool to better understand marine ecosystem processes. Using an extended Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD) model, we investigated the added value of stable isotope tracer additions to constrain biogeochemical transformations within a mesocosm experiment that was designed to study ocean acidification effects on the marine ecosystem. Markov-Chain Monte-Carlo simulations revealed that even when isotope data were available for the majority of the components, not all parameters in the model could be constrained by calibration. However, when isotope tracer data were deliberately excluded from the calibration, the overparameterisation was even stronger. More specifically, it led to unconstrained fluxes through the zooplankton and detritus compartment, and different relative contributions of these two compartments to phytoplankton biomass loss produced equally plausible results. It is concluded that model uncertainty due to overparameterisation can be considerably reduced by explicitly resolving stable isotope dynamics. Therefore, this mesocosm experiment has benefitted substantially from isotope tracer additions to unravel carbon cycling under varying CO2 regimes.

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Oregon oysters & ocean acidification: CO2 turns seas corrosive (radio)

Oregon Oysters! So Popular on Summer Menus! At risk from Carbon Dioxide in the waters off our coast! Ocean Acidification is damaging sea life across the globe, now it’s putting the future of Oregon fisheries at risk. Host, Linda Olson-Osterlund on A Deeper Look is joined by Dr. George Waldbusser of OSU’s College of Earth, Ocean and Atmospheric Sciences. He talks about his recent study that definitively links the increasing acidity of the ocean to the collapse of oyster seed production along the coast. How driving our cars and heating our homes can contribute to killing our seas. He’ll also talk about what steps hatcheries are taking to mitigate the damaged caused by the changing ph level and what we as individual can to to address the broader issue of CO2 emissions.

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Rising acidity brings an ocean of trouble

The burning of fossil fuels emits some 35 billion metric tons of CO2 into the atmosphere every year. That has already begun to change the fundamental chemistry of the world’s oceans, steadily increasing their level of acidity. On page 220 of this week’s issue of Science, scientists report projections from a new high-resolution computer model showing that over the next 4 decades, the combination of deep-water upwelling and rising atmospheric CO2 is likely to have profound impacts on waters off the West Coast of the United States, home to one of the world’s most diverse marine ecosystems and most important commercial fisheries. The new computer model is only one of several recent warning signs. Numerous laboratory and field studies over the past few years underscore rising concerns that ocean acidification could devastate marine ecosystems on which millions of people depend for food and jobs.

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Tracking the impacts of climate change’s evil twin

The ocean may seem timeless and impervious. Yet we are increasingly seeing that in the sea, as in the natural world as a whole, the only thing that is constant is change.

While some changes–like habitat loss or overfishing –have long been studied, we are only just beginning to understand emerging threats like ocean acidification. Sometimes described as “osteoporosis of the sea,” we already know that ocean acidification is impacting the health of shellfish and coral reefs. But we have as many questions as answers about the long-term implications for sea life and people.

Scientists are currently playing catch-up in an effort to understand what acidification, caused by oceans absorbing excess carbon dioxide in the atmosphere, and climate change will mean for the ocean. Over the last decade, the pace at which those factors have triggered changes in ocean conditions is startling.

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Ocean acidification in the IPCC AR5 WG II

OUP book