Archive for April, 2014

Towards international cooperation on the management of data on the biological response to ocean acidification: OA-ICC expert meeting held at the IAEA Environment Laboratories in Monaco

IMG_5512The IAEA Ocean Acidification International Coordination Centre (OA-ICC) organized an expert meeting on the management of ocean acidification biological response data at the IAEA Environment Laboratories in Monaco, 23-24 April 2014. The meeting brought together ocean acidification scientists and data managers from 10 countries, with a common goal to work towards improved data management practices in order to enhance access, integration and inter-comparison of ocean acidification data and to foster global scientific collaboration.

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L’acidification des océans menace la vie marine (in French)

« Nous avons la quasi-certitude que l’acidité moyenne des océans sera multipliée par trois d’ici 2100. Le pH de l’eau pourrait ainsi s’abaisser de 8,1 à 7,8, voire 7,7, avec un impact majeur sur tous les organismes marins (plantes et animaux) qui possèdent un squelette, une coquille ou une structure calcaire, car ils seront dissous par l’acidification. » Spécialiste mondial de l’acidification des océans, dont la réalité est apparue au milieu des années 90, Jean- Pierre Gattuso, directeur de recherche CNRS au Laboratoire d’Océanographie de Villefranche-sur-Mer, est catégorique : « Il n’y a qu’un seul remède à ce phénomène : la diminution des quantités de CO2 rejetées dans l’atmosphère. Le réchauffement climatique et le processus d’acidification ont en effet en commun d’être provoqués par la même cause, les océans absorbant environ un quart du CO2 émis dans l’atmosphère. » Mais quelle relation y a-t-il entre absorption de CO2 et acidification des océans ? Pendant longtemps les chercheurs ont pensé que la dissolution de CO2 dans l’eau de mer n’aurait aucun impact majeur. Jusqu’au jour où ils ont constaté qu’il n’en était rien : la baisse du pH entraîne, notamment, une diminution de la quantité d’ions carbonates, un élément constitutif de la structure calcaire dont nombre d’organismes marins (coraux, huitres, moules, etc.) ont besoin pour exister.

Continue reading ‘L’acidification des océans menace la vie marine (in French)’

Combined effects of warming and ocean acidification on coral reef Foraminifera Marginopora vertebralis and Heterostegina depressa

Warming and changes in ocean carbonate chemistry alter marine coastal ecosystems at an accelerating pace. The interaction between these stressors has been the subject of recent studies on reef organisms such as corals, bryozoa, molluscs, and crustose coralline algae. Here we investigated the combined effects of elevated sea surface temperatures and pCO2 on two species of photosymbiont-bearing coral reef Foraminifera: Heterostegina depressa (hosting diatoms) and Marginopora vertebralis (hosting dinoflagellates). The effects of single and combined stressors were studied by monitoring survivorship, growth, and physiological parameters, such as respiration, photochemistry (pulse amplitude modulation fluorometry and oxygen production), and chl a content. Specimens were exposed in flow-through aquaria for up to seven weeks to combinations of two pCO2 (~790 and ~490 µatm) and two temperature (28 and 31 °C) regimes. Elevated temperature had negative effects on the physiology of both species. Elevated pCO2 had negative effects on growth and apparent photosynthetic rate in H.depressa but a positive effect on effective quantum yield. With increasing pCO2, chl a content decreased in H. depressa and increased in M. vertebralis. The strongest stress responses were observed when the two stressors acted in combination. An interaction term was statistically significant in half of the measured parameters. Further exploration revealed that 75 % of these cases showed a synergistic (= larger than additive) interaction between the two stressors. These results indicate that negative physiological effects on photosymbiont-bearing coral reef Foraminifera are likely to be stronger under simultaneous acidification and temperature rise than what would be expected from the effect of each of the stressors individually.

Continue reading ‘Combined effects of warming and ocean acidification on coral reef Foraminifera Marginopora vertebralis and Heterostegina depressa’

The Global Ocean Health program launches new web site on ocean acidification

The Global Ocean Health program, a joint initiative of the Sustainable Fisheries Partnership and National Fisheries Conservation Center, has just gone online with their new website, globaloceanhealth.org. There is an active media stream, a good resource library of video, print, and web resources, their own publications (including the Ocean Acidification Report), and a section to learn more about the successes they have already made in fighting ocean acidification. Based in the Pacific Northwest, where the affects of ocean acidification have hit hardest, Global Ocean Health has stories from the front lines of solving this growing threat to fisheries.

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River sources of dissolved inorganic carbon in the Gulf of Trieste (N Adriatic): stable carbon isotope evidence

River inputs can significantly affect carbon dynamics in the costal ocean. Here, we investigate the influence of four rivers (Isonzo/Soča, Timavo/Reka, Rižana, and Dragonja) on inorganic carbon (C) in the Gulf of Trieste in the northern Adriatic Sea using stable isotope signatures of dissolved inorganic carbon (δ13CDIC). In 2007, rivers exported 1.03 × 1011 g C in the form of dissolved inorganic carbon (DIC) to the Gulf of Trieste with the lowest export observed in the Dragonja and the highest in the Isonzo/Soča. River plumes were associated with higher total alkalinity (TA) and pCO2 values compared with Gulf of Trieste waters, but their inputs showed high spatial variability. The δ13CDIC values and the isotopic mass balance suggested that river input during the spring of 2007 represented about 16 % of DIC at our study site VIDA, located in the southeastern part of the Gulf of Trieste. During autumn of 2007, the riverine contribution of DIC was less pronounced (3 %) although the river export of C was higher relative to the spring season. Convective mixing with the Gulf of Trieste waters and bora wind events appear to reduce the riverine contribution to the DIC system. Our results suggest that river plumes play an important role in C cycling in the Gulf of Trieste by direct inputs of higher riverine DIC and by increased biological uptake of DIC promoted by the supply of riverine nutrients.

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A new ocean acidification website launched

Ocean-acidification.net is a new website launched by the International Geosphere-Biosphere Programme and its collaborating partners. For the science community, the website offers immediate access to current information on the topic of ocean acidification in a variety of print formats and visual media. The up-to-date content published online about changes in ocean acidification worldwide is designed to help those working in various areas of science, education and decision-making. (…)

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Differential response of two Mediterranean cold-water coral species to ocean acidification

Cold-water coral (CWC) reefs constitute one of the most complex deep-sea habitats harboring a vast diversity of associated species. Like other tropical or temperate framework builders, these systems are facing an uncertain future due to several threats, such as global warming and ocean acidification. In the case of Mediterranean CWC communities, the effect may be exacerbated due to the greater capacity of these waters to absorb atmospheric CO2 compared to the global ocean. Calcification in these organisms is an energy-demanding process, and it is expected that energy requirements will be greater as seawater pH and the availability of carbonate ions decrease. Therefore, studies assessing the effect of a pH decrease in skeletal growth, and metabolic balance are critical to fully understand the potential responses of these organisms under a changing scenario. In this context, the present work aims to investigate the medium- to long-term effect of a low pH scenario on calcification and the biochemical composition of two CWCs from the Mediterranean, Dendrophyllia cornigera and Desmophyllum dianthus. After 314 d of exposure to acidified conditions, a significant decrease of 70 % was observed in Desmophyllum dianthus skeletal growth rate, while Dendrophyllia cornigera showed no differences between treatments. Instead, only subtle differences between treatments were observed in the organic matter amount, lipid content, skeletal microdensity, or porosity in both species, although due to the high variability of the results, these differences were not statistically significant. Our results also confirmed a heterogeneous effect of low pH on the skeletal growth rate of the organisms depending on their initial weight, suggesting that those specimens with high calcification rates may be the most susceptible to the negative effects of acidification.

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Online lessons on ocean acidification

pg1Have you started hearing the term “ocean acidification”? This unit will explain what ocean acidification means, so that you will be able to explain it to others! It is split into two lessons. Lesson one is a refresher about the pH scale, acids and bases. Lesson two focuses on the chemical process of ocean acidification, and how the pH of the ocean is being lowered by an excess of carbon dioxide in the water. (…)

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Ocean acidification as an emerging issue (box on ocean acidification in book chapter)

Since the industrial revolution and the increase in the anthropogenic carbon dioxide emissions, surface ocean pH has on average dropped by 0.1 units, from 8.25 to 8.14, equal to a 30% increase in acidity. Rising global CO2 emissions could result in average ocean pH falling by 0.5 units by 2100. Acidification could then reach a level that has not been seen for millions of years, with potential impacts on sea life and all the goods and services ocean provides. (…)

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Interactive effects of elevated temperature and pCO2 on early-life-history stages of the giant kelp Macrocystis pyrifera

Rising atmospheric CO2 is expected to increase global temperatures and partial pressure of CO2 in surface waters, causing ocean warming and acidification. These changes may have important consequences for the physiological performance of early life-history stages of marine organisms. In this study we investigated the potential for interactive effects of ecologically relevant levels of temperature and pCO2 on germination, dormancy and mortality of zoospores of the giant kelp Macrocystis pyrifera, a foundation species of temperate reef ecosystems. Newly settled kelp spores were cultured in the laboratory for seven days in a factorial design with temperature (13 °C and 18 °C) and pCO2 (~ 370 and ~ 1800 μatm) as experimental factors. The two levels of temperature and the low-pCO2 treatment in our design were consistent with present-day environmental conditions in the kelp forest as measured by autonomous temperature and pH sensors, while the high-pCO2 treatment reflects an extreme, future acidification scenario. Our results revealed that the combined effects of increased temperature and pCO2 can significantly decrease germination rates and increase the mortality of kelp spores. Interactive effects of temperature and pCO2 were detected on spore mortality and dormancy. Spore mortality only differed between pCO2 treatments at high temperature. In contrast, spore dormancy was higher in the treatment with low temperature and high pCO2, which is similar to the environmental conditions experienced during upwelling events in southern California. Our results highlight the importance of considering multiple stressors to understand how the early-stages of foundation species such as M. pyrifera will be affected by global change.

Continue reading ‘Interactive effects of elevated temperature and pCO2 on early-life-history stages of the giant kelp Macrocystis pyrifera’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book

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