Archive for August, 2012

Net community production and stoichiometry of nutrient consumption in a pelagic ecosystem of a northern high latitude fjord: mesocosm CO2 perturbation study

Net community production (NCP) and ratios of carbon to nutrient consumption were studied during a large-scale mesocosm experiment on ocean acidification in Kongsfjorden, West Spitsbergen, during June–July 2010. Nutrient-deplete fjord water with natural phyto- and bacteriaplankton assemblages, enclosed in nine mesocosms of ~ 50 m3 volume, was exposed to pCO2levels ranging from 185 to 1420 μatm on initial state. Mean values of pCO2 levels during experiment ranged from 175 to 1085 μatm in different mesocosms. Phytoplankton growth was stimulated by nutrient addition. In this study NCP is estimated as a cumulative change in dissolved inorganic carbon concentrations. Stoichiometric couping between inorganic carbon and nutrient is shown as a ratio of a cumulative NCP to a cumulative change in inorganic nutrients. Three peaks of chlorophyll a concentration occurred during the experiment. Accordingly the experiment was divided in three phases. Overall cumulative NCP was similar in all mesocosms by the final day of experiment. However, NCP varied among phases, showing variable response to CO2 perturbation. Carbon to nitrogen (C : N) and carbon to phosphorus (C : P) uptake ratios were estimated only for the period after nutrient addition (post-nutrient period). For the total post-nutrient period ratios were close to Redfield proportions, however varied from it in different phases. The response of C : N and C : P uptake ratios to CO2 perturbation was different for three phases of the experiment, reflecting variable NCP and dependence on changing microbial community. Through the variable NCP, C : N and C : P uptake ratios for 31 days of the experiment we show a flexibility of biogeochemical response establishing a strong microbial loop in Kongsfjorden under different CO2 scenarios.

Continue reading ‘Net community production and stoichiometry of nutrient consumption in a pelagic ecosystem of a northern high latitude fjord: mesocosm CO2 perturbation study’

Ocean acidification faster and greater than expected

The oceans are becoming acidic faster and to a greater extent than expected, according to research carried out by scientists at Utrecht university with their international colleagues.

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A Cenozoic record of the equatorial Pacific carbonate compensation depth

Atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carbon input from volcanic and metamorphic outgassing and its removal by weathering feedbacks; these feedbacks involve the erosion of silicate rocks and organic-carbon-bearing rocks. The integrated effect of these processes is reflected in the calcium carbonate compensation depth, which is the oceanic depth at which calcium carbonate is dissolved. Here we present a carbonate accumulation record that covers the past 53 million years from a depth transect in the equatorial Pacific Ocean. The carbonate compensation depth tracks long-term ocean cooling, deepening from 3.0–3.5 kilometres during the early Cenozoic (approximately 55 million years ago) to 4.6 kilometres at present, consistent with an overall Cenozoic increase in weathering. We find large superimposed fluctuations in carbonate compensation depth during the middle and late Eocene. Using Earth system models, we identify changes in weathering and the mode of organic-carbon delivery as two key processes to explain these large-scale Eocene fluctuations of the carbonate compensation depth.

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Ocean acidification (video)

Focus on the increasing acidification of the world’s oceans as World Water Week in Stockholm concentrates on the issue of water and food security.

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L’acidification des océans (video; in French)

La Semaine internationale de l’eau (World Water Week) s’est ouverte lundi à Stockholm avec des appels à la mobilisation pour améliorer la sécurité alimentaire. Face aux pollutions et aux difficultés d’accès qui compromettent la production mondiale de denrées alimentaires, l’agriculture doit “être plus efficace et équitable”, a déclaré le directeur général de l’organisation de l’ONU pour l’alimentation et l’agriculture (FAO).

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Diel variability in seawater pH relates to calcification and benthic community structure on coral reefs

Community structure and assembly are determined in part by environmental heterogeneity. While reef-building corals respond negatively to warming (i.e. bleaching events) and ocean acidification (OA), the extent of present-day natural variability in pH on shallow reefs and ecological consequences for benthic assemblages is unknown. We documented high resolution temporal patterns in temperature and pH from three reefs in the central Pacific and examined how these data relate to community development and net accretion rates of early successional benthic organisms. These reefs experienced substantial diel fluctuations in temperature (0.78°C) and pH (>0.2) similar to the magnitude of ‘warming’ and ‘acidification’ expected over the next century. Where daily pH within the benthic boundary layer failed to exceed pelagic climatological seasonal lows, net accretion was slower and fleshy, non-calcifying benthic organisms dominated space. Thus, key aspects of coral reef ecosystem structure and function are presently related to natural diurnal variability in pH.

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Ocean acidification toolkit for GA teachers

Through funding from the National Science Foundation (NSF award #1041034), UGA Marine Sciences Department, Dr. Brian Hopkinson, three Georgia formal educators and COSEE SE staff developed state aligned lessons for students in grades 3-12 focused on carbon, ocean acidification, and pH.

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Biological monitoring for carbon capture and storage – a review and potential future developments

Effective monitoring of carbon capture and storage (CCS) projects is essential, but detection of leaks and subsequent subtle changes in the surrounding environment are difficult to assess. New tools are being developed for this purpose, yet biological monitoring methods have been under valued; this is surprising given the rapid technological expansion in the field of microbial ecology over the last decade. A review of biological monitoring for CCS shows a number of techniques such as plant surveys, bacterial counts and DNA fingerprinting that have been applied to natural analogues or shallow injection sites. The results of the monitoring potential of these methods vary, perhaps explaining the limited research and adoption of biological monitoring for CCS projects. However, new tools such as microarrays provide rapid throughput that can characterise microbial populations and functional genes that may change due to CO2 leakage and subsequent effects. These tools are not the whole answer for CCS monitoring, but they open new opportunities in this area and should lead to the development of simple biosensors and an expansion of the monitoring toolkit. Comparisons to other fields of research, such as tracing contaminants plumes of BTEX, demonstrate how the techniques reviewed can be developed and applied to CCS monitoring.

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Phenotypic plasticity and evolutionary demographic responses to climate change: taking theory out to the field

  1. Rapid climate change both imposes strong selective pressures on natural populations – potentially reducing their growth rate and causing genetic evolution – and affects the physiology and development of individual organisms. Understanding and predicting the fates of populations under global change, including extinctions and geographical range shifts, requires analysing the interplay of these processes, which has long been a grey area in evolutionary biology.
  2. We review recent theory on the interaction of phenotypic plasticity, genetic evolution and demography in environments that change in time or space. We then discuss the main limitations of the models and the difficulties in testing theoretical predictions in the wild, notably regarding changes in phenotypic selection, the evolution of (co)variances of reaction norm parameters, and transient dynamics.
  3. We use two landmark examples of physiological responses to climate change –trees facing drier climate and extreme temperatures, and marine phytoplankton under rising CO2– to highlight relatively neglected questions and indicate the theoretical and empirical challenges that they raise. These examples illustrate notably that age-specific patterns of plasticity and selection on the one hand, and changes in community interactions and functioning on the other hand, need to be further investigated theoretically and empirically for a better understanding of evolutionary demographic responses to climate change in the wild.

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Mineral fine structure of the American lobster cuticle

A major role of lobster integument is protection from microbes. Calcite and amorphous calcium carbonate are the most abundant and most acid vulnerable of the cuticle minerals. We propose that calcite is invested in neutralizing an acidifying environment modulated by the epicuticle. A minor cuticle component is carbonate apatite (CAP), proposed to play critical roles in the integument’s structural protective function. The CAP of lobster exhibits a flexible composition; its least soluble forms line the cuticular canals most exposed to the environment. A trabecular CAP structure illustrates efficient use of a sparse phosphate resource, cooperating in the hardness of the inner exocuticle. A schematic model of the cuticle emphasizes structural and chemical diversity. A thin outer calcite layer provides a dense microbial barrier that dissolves slowly through the epicuticle, providing an external, alkaline, unstirred layer that would be inhibitory to bacterial movement and metabolism. Injury to the epicuticle covering this mineralized surface unleashes an immediate efflux of carbonate, accentuating the normal alkalinity of an antimicrobial unstirred layer. The trabecular CAP inner exocuticle provides rigidity to prevent bending and cracking of the calcite outer exocuticle. The combined mineral fine structure of lobster cuticle supports antimicrobial function as well as plays a structural protective role.

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Ocean acidification in the IPCC AR5 WG II

OUP book