Archive for September, 2013

ALLER DE L’AVANT… Recommandations aux décideurs politiques suite au 2ème Atelier international sur l’economie de l’acidification des océans (in French)


Les conclusions et recommandations issues du 2ème Atelier International sur l’Économie de l’Acidification des Océans organisé par le Centre Scientifique de Monaco (CSM) et l’Agence Internationale de l’Energie Atomique (AIEA) en novembre 2012 viennent d’être publiée sous la forme d’une brochure synthétique. Cette brochure met en évidence les disparités régionales et la nécessité de prendre des décisions politiques adéquates en dépit des incertitudes. La brochure liste les actions urgentes pour atténuer les conséquences socio-économiques néfastes de l’acidification des océans sur les pêches et l’aquaculture et donc, sur le bien-être de l’humanité. Ces conclusions avaient été présentées lors de la 14ème réunion des Nations-Unies sur les Océans et le Droit de la Mer (UNICPOLOS, New York, 17 – 20 juin 2013).

Continue reading ‘ALLER DE L’AVANT… Recommandations aux décideurs politiques suite au 2ème Atelier international sur l’economie de l’acidification des océans (in French)’

The response of calcifying plankton to climate change in the Pliocene (update)

As a result of anthropogenic pCO2 increases, future oceans are growing warmer and lower in pH and oxygen, conditions that are likely to impact planktic communities. Past intervals of elevated and changing pCO2 and temperatures can offer a glimpse into the response of marine calcifying plankton to changes in surface oceans under conditions similar to those projected for the future. Here we present new records of planktic foraminiferal and coccolith calcification (weight and size) from Deep Sea Drilling Project Site 607 (mid-North Atlantic) and Ocean Drilling Program Site 999 (Caribbean Sea) from the Pliocene, the last time that pCO2 was similar to today, and extending through a global cooling event into the intensification of Northern Hemisphere glaciation (3.3 to 2.6 million years ago). Test weights of both surface-dwelling Foraminifera Globigerina bulloides and thermocline-dwelling Foraminifera Globorotalia puncticulata vary with a potential link to regional temperature variation in the North Atlantic, whereas in the tropics Globigerinoides ruber test weight remains stable. In contrast, reticulofenestrid coccoliths show a narrowing size range and a decline in the largest lith diameters over this interval. Our results suggest no major changes in plankton calcite production during the high pCO2 Pliocene or during the transition into an icehouse world.

Continue reading ‘The response of calcifying plankton to climate change in the Pliocene (update)’

High-resolution carbon budgets on a Palau back-reef modulated by interactions between hydrodynamics and reef metabolism

Diel trends in carbon chemistry and hydrodynamic regimes were measured on a coral-dominated back-reef community in the Republic of Palau, western Pacific. Observed diel ranges over 5 d were pH 7.92–8.09, partial pressure of carbon dioxide 33.4–52.7 Pa, measured total alkalinity 2080–2272 µmol kg−1, total dissolved inorganic carbon 1763–1939 µmol kg−1, aragonite saturation state 2.84–3.98, and calcite saturation state 4.44–5.67. The combination of reef metabolism and hydrodynamic regimes drives this variability. We report net community calcification (NCC) and net community production (NCP) rates of −20.4 (± 7.8) to 41.2 (± 37.7) mmol CaCO3 m−2 h−1 and 77.3 (± 95) to 64 (± 22) mmol C m−2 h−1, respectively. Using a control volume approach, we show that NCC and NCP rate estimates are quite sensitive to the effective control volume dimensions. At this site, tracking vertical mixing of water masses within the control volume shows that active water mixing is often confined to a region 2–3 m above the corals. Vertical carbon mass fluxes into and out of the benthic environment were unexpectedly large for the slow current flow rates observed, suggesting that coral morphology or reef rugosity may affect mass transport of carbon and nutrients. The ranges of NCC and NCP values highlight the need for additional field work on various reefs to tune and optimize the control volume approach to achieve its full potential for reef metabolism monitoring.

Continue reading ‘High-resolution carbon budgets on a Palau back-reef modulated by interactions between hydrodynamics and reef metabolism’

Long-term legacy of massive carbon input to the Earth system: Anthropocene versus Eocene

Over the next few centuries, with unabated emissions of anthropogenic carbon dioxide (CO2), a total of 5000 Pg C may enter the atmosphere, causing CO2 concentrations to rise to approximately 2000 ppmv, global temperature to warm by more than 8°C and surface ocean pH to decline by approximately 0.7 units. A carbon release of this magnitude is unprecedented during the past 56 million years—and the outcome accordingly difficult to predict. In this regard, the geological record may provide foresight to how the Earth system will respond in the future. Here, we discuss the long-term legacy of massive carbon release into the Earth’s surface reservoirs, comparing the Anthropocene with a past analogue, the Palaeocene–Eocene Thermal Maximum (PETM, approx. 56 Ma). We examine the natural processes and time scales of CO2 neutralization that determine the atmospheric lifetime of CO2 in response to carbon release. We compare the duration of carbon release during the Anthropocene versus PETM and the ensuing effects on ocean acidification and marine calcifying organisms. We also discuss the conundrum that the observed duration of the PETM appears to be much longer than predicted by models that use first-order assumptions. Finally, we comment on past and future mass extinctions and recovery times of biotic diversity.

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Effects of ocean acidification on toxicity of heavy metals in the bivalve Mytilus edulis L

The anthropogenic release of carbon dioxide into the atmosphere leads to an increase in the CO2 partial pressure in the ocean, which may reach 950 μatm by the end of the 21st century. An experiment was performed to test the effects of increased sea water concentrations of CO2 combined with heavy metals on mortality rates, metallothionein, immune funtion, and uptake kinetics of the bivalve Mytilus edulis L. As a result, the mortality rates of Mytilus edulis L fluctuated with pH variety in all heavy metals (Cd, Pb, Cu) test seawater treatments compared to control group. It was demonstrated that in vivo Cd-, Pb-, or Cu pretreatment under acidifications can alleviate metallothionein by in vitro Cd, Pb, and Cu in soft tissues and suggested that acidification can aggravate heavy metals pollution and toxicity for marine organisms. Moreover, the fraction of eosinophilic cells increased over the 21 days period for Cd exposure, then decreased with 28 and 35 days incubation, the fraction of eosinophilic cells increased similar with Cd exposure and pH 8.2. The fraction of eosinophilic cells significantly increased from 32% to 53% of the hemocyte population over the 35-day period for Pb exposure and pH8.2, the fraction of eosinophilic cells increased from 35% to 58% of the hemocyte population over the 35-day period for Pb exposure and pH 6.2. Phagocytosis levels declined with increasing exposure time for Cd alone and phagocytosis levels declined with decreasing pH (from 8.2 to 6.2) with Cd exposure on 35 days. Mytilus edulis L in Pb with reduced pH (6.2) treatments also decreased their phagocytosis levels on 35 days. Further, phagocytosis decreased bigger than that of Pb with pH 8.2. At steady state equilibrium, CF of 109Cd was significantly higher at pH 6.2 and pH 7.7 than at pH 8.2, the accumulation of 203Pb was significantly higher at the lowest pH 6.2 level than at the two exposure levels (pH 7.7 and pH 8.2). Similarly, the lower the seawater pH 6.2, the more 63Cu was accumulated in the hemolymph of Mytilus edulis L. The results indicate that future reductions in pH caused by increased CO2 concentrations in the sea may have an impact on Mytilus edulis L combined with heavy metals pollution.

Continue reading ‘Effects of ocean acidification on toxicity of heavy metals in the bivalve Mytilus edulis L’

Direct and indirect effects of high pCO2 on algal grazing by coral reef herbivores from the Gulf of Aqaba (Red Sea)

Grazing on marine macroalgae is a key structuring process for coral reef communities. However, ocean acidification from rising atmospheric CO2 concentrations is predicted to adversely affect many marine animals, while seaweed communities may benefit and prosper. We tested how exposure to different pCO2 (400, 1,800 and 4,000 μatm) may affect grazing on the green alga Ulva lactuca by herbivorous fish and sea urchins from the coral reefs in the northern Gulf of Aqaba (Red Sea), either directly, by changing herbivore behaviour, or indirectly via changes in algal palatability. We also determined the effects of pCO2 on algal tissue concentrations of protein and the grazing-deterrent secondary metabolite dimethylsulfoniopropionate (DMSP). Grazing preferences and overall consumption were tested in a series of multiple-choice feeding experiments in the laboratory and in situ following exposure for 14 d (algae) and 28 d (herbivores). 4,000 μatm had a significant effect on the biochemical composition and palatability of U. lactuca. No effects were observed at 1,800 relative to 400 μatm (control). Exposure of U. lactuca to 4,000 μatm resulted in a significant decrease in protein and increase in DMSP concentration. This coincided with a reduced preference for these algae by the sea urchin Tripneustes gratilla and different herbivorous fish species in situ (Acanthuridae, Siganidae and Pomacanthidae). No feeding preferences were observed for the rabbitfish Siganus rivulatus under laboratory conditions. Exposure to elevated pCO2 had no direct effect on the overall algal consumption by T. gratilla and S. rivulatus. Our results show that CO2 has the potential to alter algal palatability to different herbivores which could have important implications for algal abundance and coral community structure. The fact that pCO2 effects were observed only at a pCO2 of 4,000 μatm, however, indicates that algal-grazer interactions may be resistant to predicted pCO2 concentrations in the near future.

Continue reading ‘Direct and indirect effects of high pCO2 on algal grazing by coral reef herbivores from the Gulf of Aqaba (Red Sea)’

Understanding the threats of ocean acidification to coral reefs

The Moorea Coral Reef Long Term Ecological Research program affords a unique opportunity to study the implications of ocean acidification (OA) for coral reefs, as ongoing ecological and physical monitoring there provides a context in which the patterns of community change attributed to OA can be detected. We used mesocosms to study the impacts of OA on corals and calcified algae, and conducted experiments to compare multiple species and evaluate how they are affected by changing concentrations of the different forms of dissolved inorganic carbon. Our results reveal taxonomic variation in the response to OA, with some corals and algae showing signs of resistance to OA conditions. This discovery is informing an urgent debate over the form in which coral reefs will survive (if at all) in the future.

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Communicating ocean acidification

Participation in a study circle through the National Network of Ocean and Climate Change Interpretation (NNOCCI) project enabled staff at the California Academy of Sciences to effectively engage visitors on climate change and ocean acidification topics. Strategic framing tactics were used as staff revised the scripted Coral Reef Dive program, which resulted in positive engagement on the topic of ocean acidification, including self-reported awareness, understanding and receptivity to the Academy’s specific asks, including to support and use public transportation as an alternative to driving and to consider green energy alternatives such as solar panels.

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The gorgeous shapes of sea butterflies

Ocean acidification has taken up an unlikely mascot: the shelled pteropod. While “charismatic megafauna,” the large creatures that pull at our heartstrings, are typically the face of environmental problems—think polar bears on a shrinking iceberg and oil-slicked pelicans—these tiny sea snails couldn’t be more different. They don’t have visible eyes or anything resembling a face, diminishing their cute factor. They can barely be seen with the human eye, rarely reaching one centimeter in length. And the changes acidification has on them are even harder to see: the slow disintegration of their calcium carbonate shells.

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Ocean acidification in the IPCC WGI AR5 “Climate Change 2013: The Physical Science Basis” Summary for Policymakers

The summary of the Working Group 1 contribution to the IPCC Fifth Assessment Report is now available. Ocean acidification is mentioned several times.

Continue reading ‘Ocean acidification in the IPCC WGI AR5 “Climate Change 2013: The Physical Science Basis” Summary for Policymakers’

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Ocean acidification in the IPCC AR5 WG II

OUP book