Important: vote for the future you want

In the lead up to Rio+20, 10 topics of the Sustainable Development Dialogues, or Rio+20 Dialogues, were identified, each containing 10 recommendations. One item is of interest to the ocean acidification community: “Monitor and promote international coordinated research on ocean acidification and its effects on marine life and ecosystems”

Seawater acidification by CO2 in a coastal lagoon environment: effects on life history traits of juvenile mussels Mytilus galloprovincialis

The carbonate chemistry of seawater from the Ria Formosa lagoon was experimentally manipulated, by diffusing pure CO₂, to attain two reduced pH levels, by − 0.3 and − 0.6 pH units, relative to unmanipulated seawater. After 84 days of exposure, no differences were detected in terms of growth (somatic or shell) or mortality of juvenile mussels Mytilus galloprovincialis. The naturally elevated total alkalinity of the seawater (≈ 3550 μmol kg^− 1) prevented under-saturation of CaCO₃, even under pCO₂ values exceeding 4000 μatm, attenuating the detrimental effects on the carbonate supply-side. Even so, variations in shell weight showed that net calcification was reduced under elevated CO₂ and reduced pH, although the magnitude and significance of this effect varied among size-classes. Most of the loss of shell material probably occurred as post-deposition dissolution in the internal aragonitic nacre layer. Our results show that, even when reared under extreme levels of CO₂-induced acidification, juvenile M. galloprovincialis can continue to calcify and grow in this coastal lagoon environment. The complex responses of bivalves to ocean acidification suggest a large degree of interspecific and intraspecific variability in their sensitivity to this type of perturbation. Further research is needed to assess the generality of these patterns and to disentangle the relative contributions of acclimation to local variations in seawater chemistry and genetic adaptation.

Calcification acidifies the microenvironment of a benthic foraminifer (Ammonia sp.)

Calcareous foraminifera are well known for their CaCO₃ shells. Yet, CaCO₃ precipitation acidifies the calcifying fluid. Calcification without pH regulation would therefore rapidly create a negative feedback for CaCO₃ precipitation. In unicellular organisms, like foraminifera, an effective mechanism to counteract this acidification could be the externalization of H⁺ from the site of calcification. In this study we show that a benthic symbiont-free foraminifer Ammonia sp. actively decreases pH within its extracellular microenvironment only while precipitating calcite. During chamber formation events the strongest pH decreases occurred in the vicinity of a newly forming chamber (range of gradient ~ 100 μm) with a recorded minimum of 6.31 (< 10 μm from the shell) and a maximum duration of 7 h. The acidification was actively regulated by the foraminifera and correlated with shell diameters, indicating that the amount of protons removed during calcification is directly related to the volume of calcite precipitated. The here presented findings imply that H⁺ expulsion as a result of calcification may be a wider strategy for maintaining pH homeostasis in unicellular calcifying organisms.

Relationship between CO2-driven changes in extracellular acid–base balance and cellular immune response in two polar echinoderm species

Anthropogenic CO₂ emissions are acidifying the world’s oceans. A growing body of evidence demonstrates that ocean acidification can impact survival, growth, development and physiology of marine invertebrates. However, little is known on the impact of elevated pCO₂ on immune-response. Here we investigate the impact of short-term (5–7 days) exposure to elevated pCO₂ (1275 μatm compared to 350 μatm in the control) on extracellular pH (pHe) and cellular immune response in two polar echinoderm species, the green sea urchin Strongylocentrotus droebachiensis and the seastar Leptasterias polaris. Both species experienced extracellular acidosis following short term exposure to elevated pCO₂. While this acidosis remained uncompensated within 7 days for L. polaris, pHe was fully compensated after 5 days for S. droebachiensis. For both species, coelomic fluid acidosis was associated with an increase in total coelomocyte number and a reduction in vibratile cells in S. droebachiensis. A relationship between pHe and phagocyte numbers was observed in S. droebachiensis suggesting a direct link between pHe and cellular immune-response. Further studies would require the coordinated effort of ecologists and immunologists to understand the role of elevated pCO₂ on the host–pathogen interactions that are involved in the stability of ecosystems.

Calcification and photobiology in symbiont-bearing benthic foraminifera and responses to a high CO2 environment

The present study investigates impacts of ocean acidification on calcification rates and light responses of large benthic foraminifera (LBF). Studies were conducted on diatom-bearing Amphistegina radiata and Heterostegina depressa and dinoflagellate-bearing Marginopora vertebralis in controls and manipulated seawater pCO₂ conditions (467–1925 μatm pCO₂). In a six week experiment, calcification and photobiology were investigated for all three species. Additionally, short-term experiments were carried out on H. depressa and M. vertebralis to determine photosynthetic rates in several pCO₂ environments and impacts of elevated pCO₂ in increasing light intensities (photosynthesis irradiance “P–I” curves) on M. vertebralis. In the long-term experiment, positive growth (inferred through cross-sectional surface area) was measured in all control and acidification conditions but growth rates of A. radiata and H. depressa were not affected by increased pCO₂ (linear models, p > 0.05). However, M. vertebralis displayed significantly (planned comparison t = 2.61, p < 0.05) increased calcification rates (63%) in elevated pCO₂ regimes. Increased pCO₂ did not affect maximum quantum yield (measured by pulse amplitude modulation “PAM” fluorometry) and chlorophyll a content in any species investigated. Photosynthetic measurements (oxygen evolution) on H. depressa and M. vertebralis revealed positive net production under experimental light conditions (10 and 29 μmol photons m^− 2 s^− 1, respectively), however no significant effect of elevated pCO₂ on net production and dark respiration after both long- and short-term exposure was observed. M. vertebralis measured under nine different light conditions displayed typical P–I curves with light saturation points of app. 500 μmol photons m^− 2 s^− 1. However, P_max, α and E_k did not vary under different pCO₂ conditions (496 and 1925 μatm). Thus, foraminiferal species investigated in the present study did not show negative effects in exposures up to 1925 μatm pCO₂. However, previous field studies from natural CO₂ vents showed that LBF disappear at pCO₂ conditions predicted for the near future (pH_Total < 7.9). This indicates that the short term ability of the holobiont or symbiont to cope or even benefit from elevated pCO₂ is no guarantee for their survival in the long-term.

A hypothesis linking sub-optimal seawater pCO2 conditions for cnidarian-Symbiodinium symbioses with the exceedence of the interglacial threshold (>260 ppmv) (update)

Most scleractinian corals and many other cnidarians host intracellular photosynthetic dinoflagellate symbionts (“zooxanthellae”). The zooxanthellae contribute to host metabolism and skeletogenesis to such an extent that this symbiosis is well recognised for its contribution in creating the coral reef ecosystem. The stable functioning of cnidarian symbioses is however dependent upon the host’s ability to maintain demographic control of its algal partner. In this review, I explain how the modern envelope of seawater conditions found within many coral reef ecosystems (characterised by elevated temperatures, rising pCO₂, and enriched nutrient levels) are antagonistic toward the dominant host processes that restrict excessive symbiont proliferation. Moreover, I outline a new hypothesis and initial evidence base, which support the suggestion that the additional “excess” zooxanthellae fraction permitted by seawater pCO₂ levels beyond 260 ppmv significantly increases the propensity for symbiosis breakdown (“bleaching”) in response to temperature and irradiance extremes. The relevance of this biological threshold is discussed in terms of historical reef extinction events, glacial-interglacial climate cycles and the modern decline of coral reef ecosystems.

NODC ocean acidification scientific data stewardship

The Federal Ocean Acidification Research and Monitoring (FOARAM) Act of 2009 mandates that NOAA establishes a monitoring and research program to document ocean acidification (OA) impacts. In general terms, ocean acidification refers to the net changes in seawater chemistry, including decreases in seawater pH, due to the ocean’s absorption of atmospheric carbon dioxide (see what is ocean acidification?). A consensus research strategy has been developed for NOAA to advance the understanding of the impacts of ocean acidification and to address related challenges to local and national ecosystems and communities (NOAA Ocean Acidification Steering Committee, 2010). The NOAA Ocean Acidification Program was formally established in May 2011 to integrate and fund efforts across and external to NOAA that address Ocean Acidification (NOAA Ocean Acidification Program Director, Libby Jewett, Ph.D.).

Climate change indicators in the United States – ocean acidity

This indicator shows acidity levels in the ocean, which are strongly affected by the amount of carbon dioxide in the water.

Key Points

• Measurements made over the last few decades have demonstrated that ocean carbon dioxide levels have risen, accompanied by an increase in acidity (that is, a decrease in pH) (see Figure 1).
• Modeling suggests that over the last few centuries, ocean acidity has increased globally (meaning pH has decreased), most notably in the Atlantic (see Figure 2).
• Direct observations show that pH levels fluctuate more frequently in some areas of the ocean than in others. ³ More measurements are needed to better understand the links between these natural fluctuations and long-term changes in ocean acidity.

Stanford researchers help predict the oceans of the future with a mini-lab

Scientists from Stanford and elsewhere joined to create a mini-lab in Australia’s Great Barrier Reef. The device can simulate predicted future ocean conditions – such as rising carbon dioxide levels – and their effects on ecosystems such as coral.

Stanford researchers have helped open a new door of possibility in the high-stakes effort to save the world’s coral reefs.

Working with an international team, the scientists – including Stanford Woods Institute for the Environment Senior Fellows Jeff Koseff, Rob Dunbar and Steve Monismith – found a way to create future ocean conditions in a small lab-in-a-box in Australia’s Great Barrier Reef.

Protecting lobsters, oysters and seafood one person at a time

Do you enjoy eating lobster, oysters, seafood, or walking along the seashore and picking-up seashells? If so, then the state of our oceans is going to curtail at least one of your pleasures.

Burning over 82 million metric tons of greenhouse gases, daily, on our planet is significantly disrupting the climate and all wild ecosystems whether they are under the sea or on mountaintops.

As rising levels of CO2 are absorbed by the oceans’ phytoplankton — which account for about 30 percent of Earth’s natural CO2 processing — they are becoming acidic (as CO2 is absorbed carbonic acid is released). The oceans are now acidifying faster than any time over the past 300 million years. Furthermore, as ocean currents warm, upwelling which carries essential nutrients are prevented, and 40 percent of Earth’s phytoplankton — the base of the entire ocean food chain — is missing.

According to Professor Jean-Pierre Gattuso of the National Center for Scientific Research in France the Arctic Ocean is becoming so acidic it will dissolve shells of sea creatures within 10 years.