Our Common Future Under Climate Change

International Scientific Conference 7-10 JULY 2015 Paris, France

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Wednesday 8 July - 17:30-19:00 UPMC Jussieu - Amphi 15

2207 - Ocean Change: Understanding and projecting the impacts of warming and acidification on natural and human systems

Parallel Session

Lead Convener(s): J.P. Gattuso (CNRS and Université Pierre et Marie Curie, Villefranche-sur-mer, France), O. Hoegh-Guldberg (University of Queensland, Brisbane, Australia)

17:30

Ecological challenges for life in a rapidly changing ocean

J.-P. Gattuso (CNRS and Université Pierre et Marie Curie, Villefranche-sur-mer, France), T. Ocean 2015 Initiative (Institut du développement durable et des relations internationales, Paris, France)

Abstract details
Ecological challenges for life in a rapidly changing ocean

JP. Gattuso (1) ; T. Ocean 2015 Initiative (2)
(1) CNRS and Université Pierre et Marie Curie, Laboratoire d'Océanographie de Villefranche, Villefranche-sur-mer, France; (2) Institut du développement durable et des relations internationales, Paris, France

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Ocean warming and acidification share the same primary cause, which is the increase in atmospheric CO2. The fossil record indicates that the rate and magnitude of the present, human-generated carbon perturbation leads to changes potentially unparalleled in the last 300 My of Earth history. Ocean warming and acidification are two key global environmental drivers that challenge marine organisms and ecosystems. Responses can be influenced, often exacerbated by other drivers, such as hypoxia, eutrophication, habitat loss and overexploitation of resources.

A large range of approaches are used to assess the present impacts and project future risks: paleo-observations, observations in natural gradients and around CO2 vents, perturbation experiments in the laboratory and in the field, as well as modelling. All approaches indicate that the effects of ocean warming and acidification on individual organisms are or will be widespread, and that they propagate at the ecosystem level. Warming induces shifts in the abundance, geographic distribution, migration patterns, and timing of seasonal activities of species, generating changes in the composition of ecosystems. Such distributional shifts will continue in the coming decades, increasing species richness at mid- and high latitudes and decreasing it at tropical latitudes. This will result in a global redistribution of catch potential for fishes and invertebrates, with implications for food security. A wide range of sensitivities to projected rates of ocean acidification exists within and across diverse groups of organisms, with a trend for greater sensitivity in early life stages. A pattern of positive and negative impacts emerges. The rate of calcification decreases in most, but not all, sea floor calcifiers such as reef-building corals, coralline algae, bivalves, and gastropods, reducing the competitiveness with non-calcifiers. The combined effects of ocean warming and acidification have resulted and will further result in changing interactions between species, including competition, predation and pathogen dynamics.

A considerable number of biological, chemical, and physical processes act at enormous ranges of space and time scales to control ecosystem properties. Few of these processes and interactions are understood because most studies are short-term, organism-centric and examined just one driver at a time. Gaps in our understanding and uncertainty in future projections therefore remain. Coral reefs are the main ecosystem which already exhibits prominent signs of the impact of climate-related variables but it must be pointed out that seemingly stable ecosystems maintained by feedback mechanisms can be subject to abrupt ecological shifts. Taken together, these observations as well as the fossil record confirm links between ocean warming and acidification and responses of ocean ecosystems. There are no plausible alternatives to immediate, deep reduction of greenhouse gases emissions for limiting future ecological challenges and maintaining ocean services. It should be emphasised that reducing CO2 emissions to address ocean acidification will simultaneously address climate change but reducing emissions of other greenhouse gases to limit warming will not necessarily address ocean acidification.

The Oceans 2015 Initiative comprises 17 experts (D. Allemand, R. Billé, L. Bopp, W. Cheung, M. Colombier, S. R. Cooley, J.-P. Gattuso, O. Hoegh-Guldberg, F. Joos, R. Kelly, D. Laffoley, A. Magnan, H.-O. Pörtner, A. Rogers, T. Spencer, C. Turley and S. Treyer). It is supported by the Prince Albert II of Monaco Fondation, Ocean Acidification International Coordination Centre, and BNP Paribas Foundation.

17:45

Climate change and the Ocean: regional challenges and opportunities

O. Hoegh-Guldberg (University of Queensland, Brisbane, Australia), T. Ocean 2015 Initiative (Institut du développement durable et des relations internationales, Paris, France)

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Climate change and the Ocean: regional challenges and opportunities

O. Hoegh-Guldberg (1) ; T. Ocean 2015 Initiative (2)
(1) University of Queensland, Global Change Institute, Brisbane, Australia; (2) Institut du développement durable et des relations internationales, Paris, France

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Earth’s ocean plays a central role in its climate, absorbing 93% of the extra heat from the enhanced greenhouse effect, and approximately 30% of the CO2 emitted by the burning of fossil fuels and landuse change.  While these contributions play an important role in reducing the rate of change in the average global temperature, they have come at a price in terms of shifts in ocean temperature and chemistry, and consequently a wide range of other key variables such as surface salinity, wind, pH, carbonate chemistry, stratification, ocean currents, nutrient availability, and oxygen content. According to AR5 of the IPCC we are now seeing changes in ocean conditions that are unprecedented, which in the case of ocean acidification, are “unprecedented within the last 65 Ma (high confidence) if not the last 300 Ma (medium confidence).” 

These rapid changes within the Ocean are affecting the distribution and abundance of organisms and ecosystems, with important consequences for the goods and services that the Ocean provides to communities and nations worldwide.  Fisheries and ocean-related livelihoods play important role in the lives of at least 3 billion people globally, with many nations receiving more than half of the protein requirements from the Ocean.  While often overlooked in terms of national accounts, contributions by the ocean to key issues such as food security, employment, health, and coastal protection are large and are only likely to become more important over coming decades. Consequently, understanding the regional challenges posed by a changing ocean is critically important in terms of adaptation challenges and opportunities.

A regional analysis of climate change reveals a range of responses by ocean ecosystems.  Recent changes to wind and ocean mixing are influencing the transfer of organic carbon to deep regions, which has had knock-on effect of stimulating microbial respiration and reducing oxygen levels.  There is considerable evidence and agreement that fisheries in regions such as the High Latitude Spring Bloom Systems (HLSBS) in the North-Eastern Atlantic are changing in response to warming and ice retreat, with both positive and/or negative implications depending on the particular HLSBS fishery.  Other fisheries are relocating at a high rate, placing stress on regional management. 

Equatorial upwelling systems (EUS) which support highly productive fisheries off Equatorial Africa and South America, have warmed significantly over the past 60 years.  While warming is consistent with changes in upwelling intensity, more work is needed to understand how EUS will change in response to warming over time.  The risks, however, a significant given the importance of these changes for ecosystems, fisheries and communities.  Coastal ecosystems such as coral reefs mangroves are under significant pressure from climate change, along with local stresses. Elevated sea temperatures are driving impacts such as mass coral bleaching and mortality, with models projecting that coral-dominated reef systems will have disappeared from most regions by 2050.  Given that an estimated 500 million people depend on coral reefs for food and livelihoods, addressing this growing source of exposure for some of the least resourced nations must be a priority going forward.

The regional analysis of climate change for ocean systems reveals an important yet poorly understood source of risk and vulnerability for the world’s nations.  As a consequence, there is a major need to address these information gaps, and pursue otherwise poorly developed adaptation options, especially in terms of building socio-ecological resilience for the large number of exposed nations.  Establishing communities of practice, knowledge and solutions platforms, as well as creating an alliance of nations around the challenges posed by a rapidly changing ocean will only grow in importance over the coming decades and century.

The Oceans 2015 Initiative comprises 17 experts (D. Allemand, R. Billé, L. Bopp, W. Cheung, M. Colombier, S. R. Cooley, J.-P. Gattuso, O. Hoegh-Guldberg, F. Joos, R. Kelly, D. Laffoley, A. Magnan, H.-O. Pörtner, A. Rogers, T. Spencer, C. Turley and S. Treyer). It is supported by the Prince Albert II of Monaco Fondation, Ocean Acidification International Coordination Centre, and BNP Paribas Foundation.

18:00

Climate sensitivity across marine domains of life: limits to evolutionary adaptation shape species interactions

D. Storch (Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, Germany), L. Menzel, (Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, Germany), S. Frieckenhaus (Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, Germany), H.-O. Pörtner (Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany)

Abstract details
Climate sensitivity across marine domains of life: limits to evolutionary adaptation shape species interactions

D. Storch (1) ; L. Menzel, (1) ; S. Frieckenhaus (2) ; HO. Pörtner (3)
(1) Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Integrative Ecophysiology, Bremerhaven, Germany; (2) Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Scientific computing, Bremerhaven, Germany; (3) Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany

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Organisms in all domains, Archaea, Bacteria, and Eukarya will respond to climate change with differential vulnerabilities resulting in shifts in species distribution, coexistence, and interactions. The identification of unifying principles of organism functioning across all domains would facilitate a cause and effect understanding of such changes and their implications for ecosystem shifts. For example, the functional specialization of all organisms in limited temperature ranges leads us to ask for unifying functional reasons. Organisms also specialize in either anoxic or various oxygen ranges, with animals and plants depending on high oxygen levels. Here, we identify thermal ranges, heat limits of growth, and critically low (hypoxic) oxygen concentrations as proxies of tolerance in a meta-analysis of data available for marine organisms, with special reference to domain-specific limits. For an explanation of the patterns and differences observed, we define and quantify a proxy for organismic complexity across species from all domains. Rising complexity causes heat (and hypoxia) tolerances to decrease from Archaea to Bacteria to uni- and then multicellular Eukarya. Within and across domains, taxon-specific tolerance limits likely reflect ultimate evolutionary limits of its species to acclimatization and adaptation. We hypothesize that rising taxon-specific complexities in structure and function constrain organisms to narrower environmental ranges. Low complexity as in Archaea and some Bacteria provide life options in extreme environments. In the warmest oceans, temperature maxima reach and will surpass the permanent limits to the existence of multicellular animals, plants and unicellular phytoplankter. Smaller, less complex unicellular Eukarya, Bacteria, and Archaea will thus benefit and predominate even more in a future, warmer, and hypoxic ocean.

18:15

Differential synergistic adverse effect of increased sea temperature and acidity on corals

F. Prada (University of Bologna, Bologna, Italy), E. Caroselli, (University of Bologna, Bologna, Italy), B. Capaccioni, (University of Bologna, Bologna, Italy), S. Mengoli, (University of Bologna, Bologna, Italy), P. Fantazzini, (Centro Fermi and University of Bologna, Bologna, Italy), L. Pasquini, (University of Bologna, Bologna, Italy), O. Levy, (Bar–Ilan University, Ramat–Gan, Israel), J. C. Weaver, (Harvard University, Cambridge, United States of America), K. E. Fabricius, (Australian Institute of Marine Science, Townsville, Australia), Z. Dubinsky, (Bar–Ilan University, Ramat–Gan, Israel), G. Falini, (University of Bologna, Bologna, Italy), S. Goffredo, (University of Bologna, Bologna, Italy)

Abstract details
Differential synergistic adverse effect of increased sea temperature and acidity on corals

F. Prada (1) ; E. Caroselli, (1) ; B. Capaccioni, (2) ; S. Mengoli, (3) ; P. Fantazzini, (4) ; L. Pasquini, (5) ; O. Levy, (6) ; JC. Weaver, (7) ; KE. Fabricius, (8) ; Z. Dubinsky, (6) ; G. Falini, (9) ; S. Goffredo, (1)
(1) University of Bologna, Marine science group, dep of biological, geol and environmental sciences, section of biology, Bologna, Italy; (2) University of Bologna, Department of biological, geological and environmental sciences, section of geology, Bologna, Italy; (3) University of Bologna, Department of management, Bologna, Italy; (4) Centro Fermi and University of Bologna, Department of Physics and Astronomy, Bologna, Italy; (5) University of Bologna, Department of physics and astronomy, Bologna, Italy; (6) Bar–Ilan University, The mina and everard goodman faculty of life sciences, Ramat–Gan, Israel; (7) Harvard University, Wyss institute for biologically inspired engineering, Cambridge, United States of America; (8) Australian Institute of Marine Science, Pmb 3, Townsville, Australia; (9) University of Bologna, Department of chemistry “g. ciamician”, Bologna, Italy

Abstract content

Global climate change is predicted to affect marine organisms and ecosystems reliant on the accumulation of calcium carbonate structures, as coral reefs, potentially reducing the socioeconomic benefits these habitats provide. In the marine realm, two of the main stressors causing significant changes are ocean warming and ocean acidification.

Projections of future climatic change estimate a 0.6-2.0°C average increase in surface ocean temperature by the end of 2100, posing a major threat for marine organisms. In temperate areas, the effect of warming is expected to be even greater. The Mediterranean Sea is already showing warming rates three times higher than the global ocean. Increased seawater temperature in the Mediterranean Sea has determined longer stratification periods associated with mass mortality events. The first well-documented Mediterranean multispecies mass mortality events were during the summers 1999 and 2003. In both years, a positive correlation was observed between mortality rates and exposure to heat stress, indicating that shallow water corals are living, at least in the North Mediterranean, near their upper thermal limits during summer. Since the frequency of abnormally warm summers is expected to increase in the next century, as a result of climate change, such mortality events in summer may also become more frequent as a direct response to elevated temperatures.

Also ocean acidification is a global phenomenon which impact varies locally. The Mediterranean Sea has experienced a pH decrease of up to 0.14 units since the pre-industrial era, larger than the global average surface ocean pH decrease. Hence, understanding how enhanced acidity has already affected and how it will likely affect Mediterranean Sea ecosystems and their key taxa is urgent and crucial.

Given the projected decrease of seawater pH, the mass mortality events could be exacerbated by the combination of high temperatures and low pH. Studies like this one, assessing the synergistic interaction between low pH and elevated temperatures, are essential to detect possible interactions between multiple stressors and establish to which extent corals inhabiting shallower ranges will be threatened by climate change.

Here we assessed the combined effects of in situ exposure to different acidity and seasonal temperatures on the mortality and growth rates of three Mediterranean scleractinian corals; the solitary zooxanthellate Balanophyllia europaea, the solitary azooxanthellate Leptopsammia pruvoti and the colonial azooxanthellate Astroides calycularis. The corals were transplanted and observed in different seasonal conditions in proximity to a volcanic vent where water is naturally acidified to levels matching different future Intergovernmental Panel on Climate Change scenarios.

The results suggest differential synergistic adverse effects of increased sea temperature and acidity and different levels of resilience/resistance to climate change among temperate coral species, probably related to different modes of nutrition and/or biomineralization processes, making symbiotic species relatively less sensitive due to the increased photosynthesis at high CO2. 

Acknowledgements: The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement n° 249930 – CoralWarm: Corals and global warming: the Mediterranean versus the Red Sea.

18:25

Rising reef carbonate dissolution due to bioeroding microflora under climate change - an overlooked buffer process?

A. Tribollet (IRD, Paris, France), P. Cuet (Université de la Réunion, Saint Denis, La Réunion, France), J. Grange (UPMC, Paris, France), H. Rybarczyk (UPMC, Paris, France), A. Chauvin (Université de la Réunion, Saint Denis, La Réunion, France), M. Atkinson (HIBM, Kaneohe, United States of America)

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Rising reef carbonate dissolution due to bioeroding microflora under climate change - an overlooked buffer process?

A. Tribollet (1) ; P. Cuet (2) ; J. Grange (3) ; H. Rybarczyk (4) ; A. Chauvin (2) ; M. Atkinson (5)
(1) IRD, Ipsl-locean, Paris, France; (2) Université de la Réunion, Entropie, Saint Denis, La Réunion, France; (3) UPMC, Ipsl-locean, Paris, France; (4) UPMC, Borea, Paris, France; (5) HIBM, Kaneohe, United States of America

Abstract content

Since the industrial era, the atmospheric partial pressure of CO2 (pCO2) has been rising. Consequently, the world’s ocean is getting warmer and acidified. By the end of the century, IPCC models in the worst case scenario predict an increase of sea surface temperature of 4°C and a decrease of seawater pH estimated at 0.3-0.4 pH-units. As a consequence, the saturation state of surface seawater (Ω) with respect to calcium carbonate minerals (CaCO3) will also decrease. All these climatic factors are expected to affect calcification and dissolution processes, putting for instance in jeopardy coral reef ecosystems which are entirely made of carbonates. Among those processes, biogenic dissolution of carbonates due to bioeroding microflora (or euendoliths), which comprise cyanobacteria, algae and fungi, has been the most overlooked process and is currently not taken into account in biogeochemical models. So far, rates of biogenic dissolution were estimated by quantifying the volume of calcium carbonate removed by bioeroding filaments using microscopy observations. Although those rates are significant (up to 1.1 kg CaCO3 dissolved per m² per year in coral reefs), the question is how much alkalinity bioeroding microflora are able to release in the ocean, and how they are influenced by climate change (pH and temperature). In addition, all experiments recently carried out which highlighted the positive effects of ocean warming and acidification on biogenic dissolution, were realized under controlled conditions (mesocosms) in tropical regions over short periods of time (2-3 months). The long term dynamics of the process of biogenic dissolution under natural conditions remains poorly known. Here we present results of five experiments carried out in tropical (Hawaii, New Caledonia reefs) and temperate regions (Ischia in Italy) at different time scales (a few hours up to 4 years), to show that (1) the amount of alkalinity produced by bioeroding microflora is significant (as high as 71 mequiv m-2 d-1  which converts to a CaCO3 dissolution rate of  1.3 kg m-2 y-1 under constant light conditions in tropical regions), (2) biogenic dissolution can occur under various saturation states (0.8 < Ω ≤ 5 both in temperate and tropical regions) and increases under rising pCO2 (by 50% to 250% depending on conditions) as long as the saturation state is above 1 (otherwise carbonate dissolution due to chemical conditions limits euendolith development and thus, biogenic dissolution), and (3) biogenic dissolution is more efficient (x2.7) when new carbonate substrates become available for colonization by microboring communities in the summer season (higher temperature, light intensities, etc…) than in the winter season in tropical regions as colonization by the main agents of biogenic dissolution is faster in summer than in winter. These results suggest that at least in coral reef systems, global warming and ocean acidification will most probably stimulate the process of carbonate bioegenic dissolution due to microboring flora, accelerating the transition from a net coral reef accretion towards net coral reef dissolution. We estimate that today, at ambient temperature and pH in coral reef ecosystems, at most 20% of produced carbonates are dissolved by bioeroding microflora. By 2100, these organisms may be responsible for the dissolution of up to 70% of reef carbonates that are expected to be produced. If all dissolution processes are taken into account, i.e. chemical dissolution driven by water chemistry and bacteria metabolic activity, biogenic dissolution by bioeroding flora and biogenic dissolution by macroborers (such as boring sponges), reef carbonate budget may become negative much earlier than 2100. The capacity of carbonate biogenic dissolution due to bioeroding flora in buffering seawater remains however, unknown and needs to be investigated in order to better understand carbon biogeochemical cycles and to improve predictions of the fate of carbonate coastal systems.  

18:35

From natural science to management: Pteropods as sentinel species for OA waters status assessments

N. Bednarsek (University of Washington, Seattle, WA, 98105, United States of America), T. Klinger, (Universtiy of Washington, Seattle, WA, 98105, United States of America), R. Feely, (Pacific Marine Environmental Laboratory, Seattle, WA, 98115, United States of America)

Abstract details
From natural science to management: Pteropods as sentinel species for OA waters status assessments

N. Bednarsek (1) ; T. Klinger, (2) ; R. Feely, (3)
(1) University of Washington, School of marine and environmental affairs, Seattle, WA, 98105, United States of America; (2) Universtiy of Washington, School of marine and environmental affairs, Seattle, WA, 98105, United States of America; (3) Pacific Marine Environmental Laboratory, Noaa, Seattle, WA, 98115, United States of America

Abstract content

Pteropods are ubiquitously distributed pelagic marine zooplankton of importance in productive upwelling and high-latitude systems, where they represent an important prey item for variety of economically, ecologically, and culturally important fish species. Because of their extreme sensitivity to ocean acidification (OA) conditions, pteropods can be used to establish cause and effect relationships between OA status and biological condition. As a result, pteropods can be used as a robust bioindicator for use in OA assessment. To demonstrate this utility, newly developed methods were used to determine and quantify pteropod responses in the natural environment. Biological responses, such as shell dissolution, shell calcification, changes in vertical distribution, and survival success were assessed to establish pteropod condition under a variety of OA conditions. We used modelling to estimate population survival rates based on future regional ocean acidification scenarios and to determine the level of sampling required to make confident predictions. We found that pteropods provide a repeatedly quantifiable measure that can be used as a rapid and cost-effective biomarker to monitor biological response to ocean acidification conditions across scales of time and space of relevance to managers. 

18:45

Ocean acidification and its relevance to the United Nations Framework Convention on Climate Change in Paris in December 2015

C. Turley (Plymouth Marine Laboratory, Plymouth, United Kingdom), P. Williamson (University of East Anglia, Norwich, United Kingdom), D. Herr, (International Union for Conservation of Nature, Bonn, Germany), K. Isensee (IOC-UNESCO, Paris, France), E. Harrould-Kolieb (University of Melbourne, Melbourne, VIC, Australia)

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Ocean acidification and its relevance to the United Nations Framework Convention on Climate Change in Paris in December 2015

C. Turley (1) ; P. Williamson (2) ; D. Herr, (3) ; K. Isensee (4) ; E. Harrould-Kolieb (5)
(1) Plymouth Marine Laboratory, Plymouth, United Kingdom; (2) University of East Anglia, School of Environmental Sciences, Norwich, United Kingdom; (3) International Union for Conservation of Nature, Bonn, Germany; (4) IOC-UNESCO, Ocean Science Section, Paris, France; (5) University of Melbourne, School of Geography, Melbourne, VIC, Australia

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Ocean acidification is a relatively recently recognised phenomenon, with recognition of its importance growing rapidly over the last few years. It is caused by anthropogenic carbon dioxide emissions and it has the potential for widespread, damaging effects on marine ecosystems that will also impact human society. It therefore must be part of the debate on emissions reduction at the United Nations Framework Convention on Climate Change Conference of the Parties (COP-21) in Paris in December 2015. Ocean acidification brings additional arguments for encouraging national governments to rapidly reduce CO2 emissions and accelerate the transformation to a carbon-free economy, thereby reducing the impact of both climate change and ocean acidification.  Emission pathways to stay within the 2oC global warming target are under discussion by nations. However, ocean acidification impacts at the CO2 equivalent of a mean global temperature increase of 2οC would already be substantial for some regions and ecosystems.  To bring this important issue fully into the discussion, recognizing that ocean acidification is a major threat to societies worldwide, there would be considerable merit in the UNFCCC process formally embracing the ocean acidification issue in its COP-21 text and post 2015 agenda.  Thus the UNFCCC could promote the mitigation of ocean acidification, and adaptation to its impacts, in all relevant policy documents and regulation instruments.