Ocean acidification

Ocean acidification monitoring buoy installed at Cheeca Rocks

Jean-Pierre Gattuso — Wed, 01 Feb 2012 07:03:37 +0000

Visitors to Florida Keys National Marine Sanctuary may notice a recent addition to the reef near Cheeca Rocks: a sophisticated new monitoring buoy. NOAA scientists from the Atlantic Oceanographic and Meteorological Laboratory and partners from the University of Miami’s Cooperative Institute for Marine and Atmospheric Studies deployed the buoy in December 2011 under permit from the sanctuary. The large yellow ‘MApCO2’ buoy sits roughly three feet above the waterline and along with subsurface instruments, simultaneously measures the concentrations of carbon dioxide in the atmosphere and ocean. Divers and boaters are asked to keep clear of the buoy.

Ocean researchers are studying ocean acidification — changes in ocean chemistry resulting from rising levels of carbon dioxide in the atmosphere then absorbed by the ocean. The Cheeca Rocks buoy is part of the Atlantic Ocean Acidification Test Bed,funded by NOAA’s Coral Reef Conservation Program.

This test bed includes studies of coral community productivity and calcification rates,along with coral growth and bioerosion rates, and tests advanced technologies for monitoring ocean acidification and the impacts to coral reef ecosystems. Understanding how coral reef communities interact with the surrounding chemical environment is critical towards improving understanding of how ocean acidification unfolds within local ecosystems.

Florida Keys National Marine Sanctuary, 24 January 2011. Web site.

L’acidification menace les écosystèmes marins (in French)

Jean-Pierre Gattuso — Tue, 31 Jan 2012 07:13:57 +0000

Une part importante du dioxyde de carbone libéré dans l’atmosphère par la combustion des énergies fossiles se retrouve dans l’océan, où il augmente l’acidité de l’eau. Les organismes marins en souffriront.

Doney SC, 2011. L’acidification menace les écosystèmes marins. Dossier Pour la Science 73. Article (subscription required).

Primordial soup or vinaigrette: did the RNA world evolve at acidic pH?

Jean-Pierre Gattuso — Tue, 31 Jan 2012 07:05:01 +0000

Background
The RNA world concept has wide, though certainly not unanimous, support within the origin-of-life scientific community. One view is that life may have emerged as early as the Hadean Eon 4.3-3.8 billion years ago with an atmosphere of high CO2 producing an acidic ocean of the order of pH 3.5-6. Compatible with this scenario is the intriguing proposal that life arose near alkaline (pH 9-11) deep-sea hydrothermal vents like those of the ‘Lost City’, with the interface with the acidic ocean creating a proton gradient sufficient to drive the first metabolism. However, RNA is most stable at pH 4-5 and is unstable at alkaline pH, raising the possibility that RNA may have first arisen in the acidic ocean itself (possibly near an acidic hydrothermal vent), acidic volcanic lake or comet pond. As the Hadean Eon progressed, the ocean pH is inferred to have gradually risen to near neutral as atmospheric CO2 levels decreased.

Presentation of the hypothesis
We propose that RNA is well suited for a world evolving at acidic pH. This is supported by the enhanced stability at acidic pH of not only the RNA phosphodiester bond but also of the aminoacyl-(t)RNA and peptide bonds. Examples of in vitro-selected ribozymes with activities at acid pH have recently been documented. The subsequent transition to a DNA genome could have been partly driven by the gradual rise in ocean pH, since DNA has greater stability than RNA at alkaline pH, but not at acidic pH.

Testing the hypothesis
We have proposed mechanisms for two key RNA world activities that are compatible with an acidic milieu: (i) non-enzymatic RNA replication of a hemi-protonated cytosine-rich oligonucleotide, and (ii) specific aminoacylation of tRNA/hairpins through triple helix interactions between the helical aminoacyl stem and a single-stranded aminoacylating ribozyme.

Implications of the hypothesis
Our hypothesis casts doubt on the hypothesis that RNA evolved in the vicinity of alkaline hydrothermal vents. The ability of RNA to form protonated base pairs and triples at acidic pH suggests that standard base pairing may not have been a dominant requirement of the early RNA world.

Reviewers: This article was reviewed by Eugene Koonin, Anthony Poole and Charles Carter (nominated by David Ardell).

Bernhardt, HS & Tate WP, 2012. Primordial soup or vinaigrette: did the RNA world evolve at acidic pH? Biology Direct 7:4, doi:10.1186/1745-6150-7-4. Article.

Sea cucumbers may save Great Barrier Reef

Jean-Pierre Gattuso — Mon, 30 Jan 2012 06:44:38 +0000

Tropical sea cucumbers and their faeces could save coral reefs from the harmful impacts of climate change, scientists have found.
Scientists at One Tree Island, the University of Sydney’s research station on the Great Barrier Reef, say sea cucumbers reduce the impact of ocean acidification on coral growth.
“When they ingest sand, the natural digestive processes in the sea cucumber’s gut increases the pH levels of the water on the reef where they defecate,” Tree Island director professor Maria Byrne said.
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This works to counter the negative effects of ocean acidification.
One of the by-products when sea cucumbers digest sand is also calcium carbonate (CaCO3), which is a key component of coral.
“To survive, coral reefs must accumulate CaCO3 at a rate greater than or equal to the CaCO3 that is eroded from the reef,” Professor Byrne said.
“The research at One Tree Island showed that, in a healthy reef, dissolution of calcium carbonate sediment by sea cucumbers and other bioeroders appears to be an important component of the natural calcium carbonate turnover.”
The ammonia waste produced when sea cucumbers digest sand also serves to fertilise the surrounding area, providing nutrients for coral growth.
Sea cucumbers are among the largest invertebrates found on tropical reefs.
About 30 species are commercially harvested by the fishery industry along the Great Barrier Reef and throughout the tropics.
“We urgently need to understand the impact of removing sea cucumbers and other invertebrates on reef health and resilience at a time when reefs face an uncertain future,” Professor Byrne said.

The Sydney Morning Herald, 30 January 2012. Article.

Oyster shell dissolution rates in estuarine waters: effects of pH and shell legacy

Jean-Pierre Gattuso — Mon, 30 Jan 2012 05:10:45 +0000

Oyster shell is a crucial component of healthy oyster reefs. Shell planting has been a main component of oyster restoration efforts in many habitats and has been carried out on scales from individual and grassroots efforts to multiagency efforts across entire estuaries. However, the cycling and lifetime of the shell that makes up the bulk of an oyster reef has only recently received attention, and most of the work to date has focused on the role of epi- and endobionts on shell degradation. Here we report findings from a laboratory study in which we manipulated pH in a flow-through control system using water from the mesohaline mouth of the Patuxent River to measure dissolution rates of intact oyster shell. Shells from the Eastern oyster (Crassostrea virginica Gmelin 1791) with three different legacies were exposed to 4 levels of pH that encompass a range typical of the mesohaline waters of the Chesapeake Bay (7.2–7.9 on the NBS scale). Mass loss over a 2-wk period was used to measure dissolution rate on 3 shell legacies: fresh, weathered, and dredged. We found that pH and shell legacy had significant effects on shell dissolution rate, with lower pH increasing dissolution rate. Fresh shell had the highest dissolution rate, followed by weathered then dredged shell. Dissolution rates were significantly different among all 4 pH treatments, except between the lowest (7.2) and the next lowest (7.4); however, shells lost mass even under noncorrosive conditions (7.9). We discuss the implications of our findings to ongoing efforts to understand shell budgets and cycling in oyster reef habitat, the interaction of biological and geochemical agents of shell degradation, and the complexity associated with shell carbonate cycling in the unique milieu of the oyster reef.

Waldbusser GG, Steenson RA & Green MA, 2011. oyster shell dissolution rates in estuarine waters: effects of ph and shell legacy. Journal of Shellfish Research 30(3), 659-669. Article (subscription required).

Organic matter exudation by Emiliania huxleyi under simulated future ocean conditions

Anne-Marin Nisumaa — Fri, 27 Jan 2012 15:57:01 +0000

Emiliania huxleyi (strain B 92/11) was exposed to different growth, CO₂ and temperature conditions in phosphorous controlled chemostats, to investigate effects on organic carbon exudation, and partitioning between the pools of particulate organic carbon (POC) and dissolved organic carbon (DOC). ¹⁴C incubation measurements for primary production (PP) and for extracellular release (ER) were performed. Chemical analysis included amount and composition of high molecular weight dissolved combined carbohydrates (>1 kDa, HMW-dCCHO), particulate combined carbohydrates (pCCHO) and the carbon content of transparent exopolymer particles (TEP-C). Applied CO₂ and temperature conditions were 300, 550 and 900 μatm pCO₂ at 14 °C, and additionally 900 μatm pCO₂ at 18 °C simulating a greenhouse ocean scenario. A reduction in growth rate from μ =0.3 d⁻¹ to μ =0.1 d⁻¹ induced the most profound effect on the performance of E. huxleyi, relative to the effect of elevated CO₂ and temperature. At μ =0.3 d⁻¹, PP was significantly higher at elevated CO₂ and temperature. DO¹⁴C production correlated to PO¹⁴C production in all cultures, resulting in similar percentages of extracellular release (DO¹⁴C/PP × 100; PER) of averaged 3.74 ± 0.94%. At μ =0.1 d⁻¹, PO¹⁴C decreased significantly, while exudation of DO¹⁴C increased, thus leading to a stronger partitioning from the particulate to the dissolved pool. Maximum PER of 16.3 ± 2.3% were observed at μ =0.1 d⁻¹ at greenhouse conditions. Concentrations of HMW-dCCHO and pCCHO were generally higher at μ =0.1 d⁻¹ compared to μ =0.3 d⁻¹. At μ =0.3 d⁻¹, pCCHO concentration increased significantly along with elevated CO₂ and temperature. Despite of high PER, the percentage of HMW-dCCHO was smallest at greenhouse conditions. However, highest TEP-formation was observed under greenhouse conditions, together with a pronounced increase in pCCHO concentration, suggesting a stronger partitioning of PP from DOC to POC by coagulation of exudates. Our results imply that greenhouse condition will enhance exudation processes in E. huxleyi and may affect organic carbon partitioning in the ocean due to an enhanced transfer of HMW-dCCHO to TEP by aggregation processes.

Borchard C., & Engel A., 2012. Organic matter exudation by Emiliania huxleyi under simulated future ocean conditions. Biogeosciences Discussions 9(1):1199-1236. Article.

Global decline in ocean ventilation, oxygenation, and productivity during the Paleocene-Eocene Thermal Maximum: Implications for the benthic extinction

Anne-Marin Nisumaa — Fri, 27 Jan 2012 07:41:10 +0000

The prominent global warming event at the Paleocene-Eocene boundary (55 Ma), referred to as the Paleocene-Eocene Thermal Maximum (PETM), was characterized by rapid temperature increase and changes in the global carbon cycle in <10,000 yr, and a major extinction of benthic foraminifera. We explore potential causes of this extinction in response to environmental changes linked to a massive carbon injection by comparing sedimentary records with results from a comprehensive climate–carbon cycle model, and infer that an increase in oceanic vertical temperature gradients and stratification led to decreased productivity and oxygen depletion in the deep sea. Globally, productivity diminished particularly in the equatorial zone by weakening of the trades and hence upwelling, leading to a decline in food supply for benthic organisms. In contrast, near the Ross Sea, export of organic matter into the deep sea was enhanced due to increased near-surface mixing related to a positive salinity anomaly caused by a rise in wind-driven vertical mixing, contributing to the depletion of the deep-sea oxygen concentration, combined with a sluggish deep-sea circulation. The extinction of deep-sea benthic foraminifera at the PETM thus was probably caused by multiple environmental changes, including decreased carbonate saturation and ocean acidification, lowered oxygen levels, and a globally reduced food supply, all related to a massive carbon injection.

Winguth A. M. E., Thomas E., & Winguth C., in press. Global decline in ocean ventilation, oxygenation, and productivity during the Paleocene-Eocene Thermal Maximum: Implications for the benthic extinction. Geology doi:10.1130/G32529.1. Article (subscription required).

Chemical oceanography PhD position

Anne-Marin Nisumaa — Fri, 27 Jan 2012 07:38:20 +0000

The Ocean Acidification Research Center (OARC) at the University of Alaska Fairbanks (UAF) is seeking a graduate student to conduct a fully funded project in the western Arctic Ocean to better understand the controls on carbonate mineral saturation states and ocean acidification in the region. Funding includes full stipend, tuition, health insurance and travel support for one annual meeting. The ideal applicant will have a background (either undergraduate or preferably M.S.) in marine chemistry or a closely related field. The project will require extensive fieldwork in the Arctic Ocean and the applicant must be able to start by June 1, 2012.

For more information please visit www.sfos.uaf.edu/oarc or contact Professor Jeremy Mathis jmathis@sfos.uaf.edu.
Applications can be submitted at http://www.sfos.uaf.edu/.

University of Alaska Fairbanks, Ocean Acidification Research Center, Web site.

Ocean acidification and coral reefs: Eat, think, and be merry science cafe

Anne-Marin Nisumaa — Fri, 27 Jan 2012 07:33:57 +0000

Date/Time: On January 31, 2012 from 7:00 pm to 9:00 pm
Location: Luna Star Cafe

Remy Okazaki is a doctoral candidate in the University of Miami Rosentiel School of Marine and Atmospheric Science (RSMS) studying how corals from various environments respond to ocean acidification. As the first guest lecturer of the spring 2012 Eat, Think, and Be Merry Science Cafe, Okazaki will present his research entitled, “Ocean Acidification and Coral Reefs”.

The Eat, Think, and Be Merry Science Cafe, held at the Luna Star Cafe in North Miami, gives students and the community the opportunity to discuss timely scientific issues with researchers in a relaxed conversational setting. The event will begin at 7:00 p.m. on Tuesday, Jan. 31 at the Luna Star Cafe in North Miami. For more information, please follow the link below.

Contact: Elaine Pritzker
Email: epritzke@fiu.edu
Phone: (305) 919-5861
Url: http://casgroup.fiu.edu/SEAS/events.php?id=2045

Florida International University, Web site.

Coral and mollusc responses to acidified ocean

Anne-Marin Nisumaa — Fri, 27 Jan 2012 07:26:51 +0000

Coral and mollusc species with an outer layer of protective tissue are more able to withstand acidic seawater than some other species, according to a recent study. However, higher temperatures projected under climate change are likely to worsen the impact of ocean acidification on coral and molluscs, even affecting those that are otherwise resistant to higher levels of acidity.

The increasing atmospheric concentrations of CO2 are making the oceans more acidic. Seawater absorbs some of the CO2 from the atmosphere, and it is thought that by 2100, this will increase the acidity of surface ocean waters by 0.3-0.5 pH units. Acidity reduces the amount of available carbonate used by some marine organisms, such as corals and molluscs, to form shells and skeletons out of calcium carbonate. Previous studies suggest different species of marine organisms that form shells and skeletons vary in their sensitivity to ocean acidification. It
is thought that an outer layer of living tissue on these organisms protects the skeleton or shell from dissolving in more acidic seawater.

Partly funded under the EU MedSeA project, the researchers compared the rates at which they form shells and skeletons (a process known as calcification) and lost (a process known as dissolution) in samples of the corals Balanophyllia europaea (which has a protective outer layer of tissue) and Cladocora caespitose (which does not have a protective layer); and in samples of the molluscs Mytilus galloprovincialis (a mussel with an outer layer protecting the shell) and Patella caerulea, (a limpet with no protective layer).

Samples of the corals and molluscs were transplanted into water off the Island of Ischia in Italy. Volcanic activity from nearby Mount Vesuvius causes CO2 to bubble up from the ocean floor, creating naturally occurring acidified seawater with a range of different pH conditions. Currently, normal seawater is pH 8.1, but by 2100, it is projected to be 7.8 (lower pH denotes more acidity). In waters of pH 7.8 at the test site, corals and molluscs were able to continue calcifying, in some cases at faster than normal rates. However, as the water became more acidic, the rate at which shells and skeletons dissolved increased. How much dissolved depended on the amount of protective tissue covering the shells or skeletons.
Living molluscs and limpets transplanted to the acidic waters continued to calcify at pH 8.1 (normal seawater) and pH 7.4. Mussels were able to increase the rate of calcification even at pH 7.2. Limpets living in highly acidic areas of the sea (pH 6.5) were able to increase their rate of calcification, possibly in response to the higher rates of dissolution of the shells.

Both species of coral in the test area were able to continue calcifying, although this rate decreased by 30% at pH 7.4 for C. caespitose, in contrast to B. europaea, which exhibited an increased rate of calcification at higher levels of acidity. The corrosive action of the seawater was evident on C. caespitose, whereas B. europaea was unaffected and protected by an outer layer of tissue.

However, coral and molluscs were more susceptible to the effects of ocean acidification under higher temperatures. Under unusually high temperatures in September 2009, for example, B. europaea samples in water of pH 8.0 continued to calcify normally, but almost stopped at pH 7.4. A warming Mediterranean Sea is likely to worsen the impact of ocean acidification, affecting even those organisms that were resistant to higher levels of acidity.

Source: Rodolfo-Metalpa, R., Houlbrèque, F., Tambutté É. et al. (2011) Coral and mollusc resistance to ocean acidification adversely affected by warming. Nature Climate Change. 1:308-312.
Contact: riccardo@rodolfo-metalpa.com
Theme(s): Climate change and energy, Marine ecosystems

Science for Environment Policy, DG Environment News Alert Service, 19 January 2012. Article.