Archive for June, 2012

Influence of CO2-induced acidification on the reproduction of a key Arctic copepod Calanus glacialis

The Arctic Ocean is facing rapid changes in seawater carbonate chemistry due to the uptake of atmospheric carbon dioxide (CO2). In the current study, the effects of different seawater pH levels (8.2, 7.6 and 6.9) on the reproduction of Calanus glacialis, an Arctic shelf-water copepod, have been quantified. Results indicated that CO2-induced seawater acidification had no significant effect on C. glacialis egg production. However, a reduction in pH to 6.9 significantly delayed hatching and possibly reduced overall hatching success. The results of the current study are in agreement with previous studies on other copepod species and would indicate that copepods, as a group, may be well equipped to deal with the chemical changes associated with ocean acidification. However, all previous studies have been over relatively short exposure periods and most have only considered the isolated impacts of elevated CO2. Long-term exposures examining the synergistic effects of ocean acidification with other climate stressors, particularly warming on population viability and success, have yet to be conducted.

Continue reading ‘Influence of CO2-induced acidification on the reproduction of a key Arctic copepod Calanus glacialis’

The likelihood and potential impact of future change in the large-scale climate-earth system on ecosystem services

This article reviews the level of current scientific understanding regarding the impact of future change in the large-scale climate-earth system on ecosystem services. Impacts from sea level rise, ocean acidification, increases in ocean temperature, potential collapse of the thermohaline circulation; failure of the South Asia monsoon; the melting of sea ice, the Greenland Ice Sheet and the West Antarctic Ice Sheet; changes in water availability; and Amazonia forest dieback, are considered. The review highlights that while a number of uncertainties remain in understanding, there is evidence to suggest that climate change may have already affected some ecosystem services. Furthermore, there is considerable evidence to show that future climate change could have impacts on biodiversity, as well as secondary impacts on issues important to human society, including; habitability; land productivity and food security; water security; and potential economic impacts.

Continue reading ‘The likelihood and potential impact of future change in the large-scale climate-earth system on ecosystem services’

Flourishing seaweed

Macroalgae (seaweed) form an important component of rocky shore ecosystems, so an understanding of their sensitivity to ocean acidification is important for understanding the wider ocean acidification impacts on coastal ecosystems.

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The benthic foraminiferal community in a naturally CO2-rich coastal habitat in the southwestern Baltic Sea

It is expected that the calcification of foraminifera will be negatively affected by the ongoing acidification of the oceans. Compared to the open oceans, these organisms are subjected to much more adverse carbonate system conditions in coastal and estuarine environments such as the southwestern Baltic Sea, where benthic foraminifera are abundant. This study documents the seasonal changes of carbonate chemistry and the ensuing response of the foraminiferal community with bi-monthly resolution in Flensburg Fjord. In comparison to the surface pCO2, which is close to equilibrium with the atmosphere, we observed large seasonal fluctuations of pCO2 in the bottom and sediment pore waters. The sediment pore water pCO2 was constantly high during the entire year ranging from 1244 to 3324 μatm. Nevertheless, in contrast to the bottom water, sediment pore water was slightly supersaturated with respect to calcite as consequence of higher alkalinity (AT) for the most time of the year. Foraminiferal assemblages were dominated by two calcareous species, Ammonia aomoriensis and Elphidium incertum, and the agglutinated Ammotium cassis. The one year-cycle was characterized by seasonal community shifts. Our results revealed that there is no dynamic response of foraminiferal population density and diversity to elevated sediment pore water pCO2. Surprisingly, the fluctuations of sediment pore water undersaturation (Ωcalc) co-vary with the population densities of living Ammonia aomoriensis. Further, we observed that most of the tests of living calcifying specimens were intact. Only Ammonia aomorienis showed dissolution and recalcification structures on the tests, especially at undersaturated conditions. Therefore, the benthic community is subjected to constantly high pCO2 and tolerates elevated levels as long as sediment pore water remains supersaturated. Model calculations inferred that increasing atmospheric CO2 concentrations will finally lead to a perennial undersaturation in sediment pore waters. Whereas benthic foraminifera indeed may cope with a high sediment pore water pCO2, the steady undersaturation of sediment pore waters would likely cause a significant higher mortality of the dominating Ammonia aomoriensis. This shift may eventually lead to changes in the benthic foraminiferal communities in Flensburg Fjord, as well as in other regions experiencing naturally undersaturated Ωcalc levels.

Continue reading ‘The benthic foraminiferal community in a naturally CO2-rich coastal habitat in the southwestern Baltic Sea’

L’acidification des océans en grandeur nature au fond de la Méditerranée (in French)

Villefranche-sur-mer (Alpes-Maritimes) – Sortir du laboratoire pour aller constater in vivo, au fond de la Méditerranée, comment réagissent coquillages et plantes aquatiques face à l’acidification des océans due au CO2: une simulation inédite en Europe est en préparation près de Nice.

Des chercheurs vont déposer au fond de la rade de Villefranche-sur-mer une sorte d’aquarium rectangulaire en plexiglas où ils maintiendront, pendant plusieurs mois, les niveaux d’acidité attendus pour 2050 et pour 2100.

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Underwater aquarium

Late last year, after six years of design and testing, California’s Monterey Bay Aquarium Research Institute conducted the first controlled biological experiment on deep-sea animals using a Free-Ocean Carbon Dioxide Enrichment experiment. Ocean chemist Peter Brewer talks to Nature Climate Change about the project.

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Benthic invertebrates in a high-CO2 world

Ocean acidification (OA), whereby increases in atmospheric carbon dioxide (cO2) over the past 200 years have led to a decline in the pH and carbonate ion availability of the oceans, has emerged as one of the major drivers of twenty- first century marine scientific research. Here we describe the current understanding of OA effects on benthic marine invertebrates, in particular the calcifiers thought to be most sensitive to altered carbonate chemistry. We describe the responses of benthic invertebrates to OA conditions predicted up to the end of the century, examining individual organism response through to ecosystem- level impacts. Research over the past decade has found great variability in the physiological and functional response of different species and communities to OA, with further variability evident between life stages. Over both geological and recent timescales, the presence and calcification rates of marine calcifiers have been inextricably linked to the carbon chemistry of the oceans. Under short-term experimentally enhanced cO2 conditions, many organisms have shown trade-offs in their physiological responses, such as reductions in calcification rate and reproductive output. In addition, carry-over effects from fertilization, larval and juvenile stages, such as enhanced development time and morphological changes, highlight the need for broad- scale studies over multiple life stages. These organism- level responses may propagate through to altered benthic communities under naturally enhanced cO2 conditions, evident in studies of upwelling regions and at shallow- water volcanic cO2 vents. Only by establishing which benthic invertebrates have the ability to acclimate or adapt, via natural selection, to changes from OA, in combination with other environmental stressors, can we begin to predict the consequences of future climate change for these communities.

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Oceanography: plankton in an acidified ocean

The pH of the ocean is expected to drop 0.3 units in the next century. This change is well within the pH range that plankton experience at present, but research suggests that changes in acidity near their cell surface could be larger.

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Early developmental gene regulation in Strongylocentrotus purpuratus embryos in response to elevated CO2 seawater conditions

Ocean acidification, or the increased uptake of CO2 by the ocean due to elevated atmospheric CO2 concentrations, may variably impact marine early life history stages, as they may be especially susceptible to changes in ocean chemistry. Investigating the regulatory mechanisms of early development in an environmental context, or ecological development, will contribute to increased understanding of potential organismal responses to such rapid, large-scale environmental changes. We examined transcript-level responses to elevated seawater CO2 during gastrulation and the initiation of spiculogenesis, two crucial developmental processes in the purple sea urchin, Strongylocentrotus purpuratus. Embryos were reared at the current, accepted oceanic CO2 concentration of 380 microatmospheres (μatm), and at the elevated levels of 1000 and 1350 μatm, simulating predictions for oceans and upwelling regions, respectively. The seven genes of interest comprised a subset of pathways in the primary mesenchyme cell gene regulatory network (PMC GRN) shown to be necessary for the regulation and execution of gastrulation and spiculogenesis. Of the seven genes, qPCR analysis indicated that elevated CO2 concentrations only had a significant but subtle effect on two genes, one important for early embryo patterning, Wnt8, and the other an integral component in spiculogenesis and biomineralization, SM30b. Protein levels of another spicule matrix component, SM50, demonstrated significant variable responses to elevated CO2. These data link the regulation of crucial early developmental processes with the environment that these embryos would be developing within, situating the study of organismal responses to ocean acidification in a developmental context.

Continue reading ‘Early developmental gene regulation in Strongylocentrotus purpuratus embryos in response to elevated CO2 seawater conditions’

Decadal changes in the CaCO3 saturation state along 179°E in the Pacific Ocean

To assess degrees of ocean acidification, we mainly investigated decadal changes in the saturation state of seawater with respect to aragonite (Ωarg), which is a more vulnerable mineral form of CaCO3, along the 179°E meridian (WOCE P14N) in the Pacific Ocean. We found a maximum decrease of Ωarg of −0.48 (−0.034 a−1) at 200–300 dbar (isopycnal surfaces of 24.0–25.8 kg m−3) at 20°N. Between 1993 and 2007, the saturation horizon rose by 17 dbar (1.2 dbar a−1) at latitudes 10°N–50°N. Although ΔΩarg mostly reflected changes in normalized dissolved inorganic carbon (ΔnCT), it was larger than could be explained by anthropogenic CO2 storage alone. Decomposition of ΔnCT revealed that ΔΩarg was enhanced by approximately 50% by a non-anthropogenic CO2 contribution represented by changes in apparent oxygen utilization. Our results suggest that ocean acidification can be temporarily accelerated by temporal changes in oceanic conditions.

Continue reading ‘Decadal changes in the CaCO3 saturation state along 179°E in the Pacific Ocean’

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Ocean acidification in the IPCC AR5 WG II

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