Archive for December, 2010

Unshelled abalone and corrupted urchins: development of marine calcifiers in a changing ocean

The most fragile skeletons produced by benthic marine calcifiers are those that larvae and juveniles make to support their bodies. Ocean warming, acidification, decreased carbonate saturation and their interactive effects are likely to impair skeletogenesis. Failure to produce skeleton in a changing ocean has negative implications for a diversity of marine species. We examined the interactive effects of warming and acidification on an abalone (Haliotis coccoradiata) and a sea urchin (Heliocidaris erythrogramma) reared from fertilization in temperature and pH/pCO2 treatments in a climatically and regionally relevant setting. Exposure of ectodermal (abalone) and mesodermal (echinoid) calcifying systems to warming (+2°C to 4°C) and acidification (pH 7.6–7.8) resulted in unshelled larvae and abnormal juveniles. Haliotis development was most sensitive with no interaction between stressors. For Heliocidaris, the percentage of normal juveniles decreased in response to both stressors, although a +2°C warming diminished the negative effect of low pH. The number of spines produced decreased with increasing acidification/pCO2, and the interactive effect between stressors indicated that a +2°C warming reduced the negative effects of low pH. At +4°C, the developmental thermal tolerance was breached. Our results show that projected near-future climate change will have deleterious effects on development with differences in vulnerability in the two species.

Continue reading ‘Unshelled abalone and corrupted urchins: development of marine calcifiers in a changing ocean’

A tipping-elements expedition in the footsteps of Alexander von Humboldt

When Alexander von Humboldt set out to explore the American continent, he came across terrestrial and marine (eco-)systems that are considered tipping elements today. Small perturbations linked to climate change may trigger abrupt and/or irreversible change in these systems. If Alexander von Humboldt had undertaken his expedition in modern times, he might have studied potential tipping behavior of the marine biological carbon pump, the Amazon rainforest, coral reefs in the Caribbean Sea, and the El Niño-Southern Oscillation (one of the major oceanic/atmospheric circulation modes on Earth). Likewise, when he later travelled across the vast plains of Russia, he might have been most interested in signs of approaching tipping points in boreal forests, permafrost soils, Tibetan glaciers, and marine methane hydrates off the Siberian coast. Here, we follow Alexander von Humboldt on a mental journey. We present recent scientific findings on tipping elements that are located along his expedition routes. To conclude, we sketch a research agenda whose successful completion would provide society with the knowledge and tools required to handle the risks arising from tipping elements.
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Project Manager of the FP7 Mediterranean Sea Acidification in a changing climate (MedSeA) project

Project Manager of the FP7 Mediterranean Sea Acidification in a changing climate (MedSeA) project coordinated at the Universitat Autònoma de Barcelona (UAB)

MedSeA is a medium-scale FP7 research project addressing ecologic and economic impacts from the combined influences of ocean acidification and anthropogenic warming. Increases of atmospheric CO2 and associated decreases in seawater pH and carbonate ion concentration this century and beyond are likely to have wide impacts on marine ecosystems, including those of the Mediterranean Sea. MedSeA will forecast environmental changes and evaluate their socio-economical impacts driven by increases in CO2 and other greenhouse gases, while focusing on the combined impacts of acidification and warming on marine shell building, productivity, and food webs. The project will involve an international partnership of 16 research groups. These experts will provide science-based projections of Mediterranean acidification under the influence of climate change as well as associated economic impacts. The scientific advances will enable the best advice to policymakers who must develop regional strategies for adaptation and mitigation.

The project manager will assist the Project Coordinator in the day-to-day project management.

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MEDUSA: a new intermediate complexity plankton ecosystem model for the global domain

The ongoing, anthropogenically-driven changes to the global ocean are expected to have significant consequences for plankton ecosystems in the future. Because of the role that plankton play in the ocean’s “biological pump”, changes in abundance, distribution and productivity will likely have additional consequences for the wider carbon cycle. Just as in the terrestrial biosphere, marine ecosystems exhibit marked diversity in species and functional types of organisms. Predicting potential change in plankton ecosystems therefore requires the use of models that are suited to this diversity, but whose parameterisation also permits robust and realistic functional behaviour. In the past decade, advances in model sophistication have attempted to address diversity, but have been criticised for doing so inaccurately or ahead of a requisite understanding of underlying processes. Here we introduce MEDUSA (Model of Ecosystem Dynamics, nutrient Utilisation, Sequestration and Acidification), a new “intermediate complexity” plankton ecosystem model that expands on traditional nutrient-phytoplankton-zooplankton-detritus (NPZD) models, and remains amenable to global-scale evaluation. MEDUSA includes the biogeochemical cycles of nitrogen, silicon and iron, broadly structured into “small” and “large” plankton size classes, of which the “large” phytoplankton class is representative of a key phytoplankton group, the diatoms. A full description of MEDUSA’s state variables, differential equations, functional forms and parameter values is included, with particular attention focused on the submodel describing the export of organic carbon from the surface to the deep ocean. MEDUSA is used here in a multi-decadal hindcast simulation, and its biogeochemical performance evaluated at the global scale.

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Elevated level of carbon dioxide affects metabolism and shell formation in oysters Crassostrea virginica

Estuarine organisms are exposed to periodic strong fluctuations in seawater pH driven by biological carbon dioxide (CO2) production, which may in the future be further exacerbated by the ocean acidification associated with the global rise in CO2. Calcium carbonate-producing marine species such as mollusks are expected to be vulnerable to acidification of estuarine waters, since elevated CO2 concentration and lower pH lead to a decrease in the degree of saturation of water with respect to calcium carbonate, potentially affecting biomineralization. Our study demonstrates that the increase in CO2 partial pressure (pCO2) in seawater and associated decrease in pH within the environmentally relevant range for estuaries have negative effects on physiology, rates of shell deposition and mechanical properties of the shells of eastern oysters Crassostrea virginica (Gmelin). High CO2 levels (pH ~7.5, pCO2 ~3500 µatm) caused significant increases in juvenile mortality rates and inhibited both shell and soft-body growth compared to the control conditions (pH ~8.2, pCO2 ~380 µatm). Furthermore, elevated CO2 concentrations resulted in higher standard metabolic rates in oyster juveniles, likely due to the higher energy cost of homeostasis. The high CO2 conditions also led to changes in the ultrastructure and mechanical properties of shells, including increased thickness of the calcite laths within the hypostracum and reduced hardness and fracture toughness of the shells, indicating that elevated CO2 levels have negative effects on the biomineralization process. These data strongly suggest that the rise in CO2 can impact physiology and biomineralization in marine calcifiers such as eastern oysters, threatening their survival and potentially leading to profound ecological and economic impacts in estuarine ecosystems.

Continue reading ‘Elevated level of carbon dioxide affects metabolism and shell formation in oysters Crassostrea virginica’

Growing seaweed can solve acidification

Large-scale cultivation of sea lettuce can help reduce acidification of the oceans. And help solve the global food supply problem to boot.

This idea, presented by Wageningen biologist Ronald Osinga, came as a surprise to delegates at the international coral symposium held in Wageningen last week. The symposium was an initiative by the International Society for Reef Studies (ISRS) and focused on the effects of climate change on coral reefs. Acidification of the oceans is one of the problems, and corals are highly sensitive to it. They become bleached and the calcium they contain dissolves.

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Boron isotopes as pH proxy: a new look at boron speciation in deep-sea corals using 11B MAS NMR and EELS

Dissolved boron in modern seawater occurs in the form of two species, trigonal boric acid B(OH)3 and tetrahedral borate ion B(OH)4. One of the key assumption in the use of boron isotopic compositions of carbonates as pH proxy is that only borate ions, B(OH)4, are incorporated into the carbonate. Here we investigate the speciation of boron in deep-sea coral microstuctures (Lophelia pertusa specimen) by using high field magic angle spinning nuclear magnetic resonance (11B MAS NMR) and electron energy-loss spectroscopy (EELS). We observe both boron coordination species, but in different proportions depending on the coral microstructure, i.e. centres of calcification versus fibres. These results suggest that careful sampling is necessary before performing boron isotopic measurements in deep-sea corals. By combining the proportions of B(OH)3 and B(OH)4 determined by NMR and our previous ion microprobe boron isotope measurements, we propose a new equation for the relation between seawater pH and boron isotopic composition in deep-sea corals.

Continue reading ‘Boron isotopes as pH proxy: a new look at boron speciation in deep-sea corals using 11B MAS NMR and EELS’

Deep-water carbonate concentrations in the southwest Pacific

We have compiled carbonate chemistry and sedimentary CaCO3% data for the deep-waters (>1500 m water depth) of the southwest (SW) Pacific region. The complex topography in the SW Pacific influences the deep-water circulation and affects the carbonate ion concentration ([CO32-]), and the associated calcite saturation horizon (CSH where Ωcalcite =1). The Tasman Basin and the southeast (SE) New Zealand region have the deepest CSH at ~3100 m, primarily influenced by middle and lower Circumpolar Deep Waters (m or lCPDW), while to the northeast of New Zealand the CSH is ~2800 m, due to the corrosive influence of the old North Pacific deep waters (NPDW) on the upper CPDW (uCPDW). The carbonate compensation depth (CCD; defined by a sedimentary CaCO3 content of <20%), also varies between the basins in the SW Pacific. The CCD is ~4600 m to the SE New Zealand, but only ~4000 m to the NE New Zealand. The CaCO3 content of the sediment, however, can be influenced by a number of different factors other than dissolution, therefore we suggest using the water chemistry to estimate the CCD. The depth difference between the CSH and CCD (ΔZCSH-CCD), however, varies considerably in this region and globally. The global ΔZCSH-CCD appears to expand with increasing age of the deep-water, resulting from a shoaling of the CSH. In contrast the depth of the chemical lysocline (Ωcalcite = 0.8) is less variable globally and is relatively similar, or close, to the CCD determined from the sedimentary CaCO3%. Geochemical definitions of the CCD, however, cannot be used to determine changes in the paleo-CCD. Given the range of factors that influence the sedimentary CaCO3%, an independent dissolution proxy, such as the foraminifera fragmentation % (>40% = foraminiferal lysocline) is required to define a depth where significant CaCO3 dissolution has occurred back through time. The current foraminiferal lysocline for the SW Pacific region ranges from 3100-3500 m, which is predictably just slightly deeper than the CSH. This compilation of sediment and water chemistry data provide a CaCO3 dataset for the present SW Pacific for comparison with glacial/interglacial CaCO3 variations in deep-water sediment cores, and to monitor future changes in [CO32-] and dissolution of sedimentary CaCO3 resulting from increasing anthropogenic CO2.

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The EPOCA project office wishes you happy holidays!

The EPOCA project office wishes you happy holidays!
Lina Hansson, Anne-Marin Nisumaa and Jean-Pierre Gattuso

Climate change and ocean acidification: synergies and opportunities within the UNFCCC, discussion paper

Ocean acidification is arguably one of the most serious threats facing the oceans and humans this century. Ocean acidification is not a symptom of climate change; rather, it is a threat concurrent with climate change and caused by a common root problem: ongoing anthropogenic CO2 emissions. It is a serious global challenge of unprecedented scale and importance that requires immediate action.

Preventing further acidification of the oceans will require stabilizing and reducing the level of CO2 in the atmosphere, which is most effectively done through reducing CO2 emissions. The United Nations Framework Convention on Climate Change (UNFCCC) is clearly an appropriate environmental policy regime to deal with the mitigation of ocean acidification, through CO2 reductions. It is also a suitable forum for devising and providing funding for responses to ocean acidification that can be incorporated into national adaptation plans.

Many efforts are underway to raise awareness and inform policy and decision makers about ocean acidification and its potential impacts. So far, however, no concrete recommendations have been made on how ocean acidification could be integrated within the UNFCCC. This paper attempts to address this gap by offering an initial suite of possible ways to address ocean acidification alongside climate change mitigation and adaptation strategies.

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Ocean acidification in the IPCC AR5 WG II

OUP book