Archive for August, 2010

Acidifying oceans spell bleak marine biological future ‘by end of century’, Mediterranean research finds

A unique ‘natural laboratory’ in the Mediterranean Sea is revealing the effects of rising carbon dioxide levels on life in the oceans. The results show a bleak future for marine life as ocean acidity rises, and suggest that similar lowering of ocean pH levels may have been responsible for massive extinctions in the past.

The scientists, from the University of Plymouth and the University of Santa Catarina, Brazil, studied a single celled organisms called Foraminifera around volcanic carbon dioxide vents off Naples in Italy. The study, published in the September issue of the Journal of the Geological Society, found that increasing CO2 levels caused foram diversity to fall from 24 species to only 4.

‘Previous studies have shown a reduction in diversity of 30%, but this is even bigger for forams’, said Dr Jason Hall-Spencer, one of the study’s co-authors. ‘A tipping point occurs at mean pH 7.8. This is the pH level predicted for the end of this century’.

Rising carbon dioxide levels acidify the ocean, which has a particularly devastating effect on organisms that have calcium carbonate shells, like Foraminifera.

‘Forams are well preserved in the fossil record, which is why we chose to study them’, says Dr Hall-Spencer. ‘We knew the results were likely to show a decline in foram diversity but we weren’t expecting such a seismic shift’.
Continue reading ‘Acidifying oceans spell bleak marine biological future ‘by end of century’, Mediterranean research finds’

Ocean acidification: research on top of the world

The oceans currently absorb approximately one-third of total emissions of carbon dioxide (CO2) generated by fossil-fuel combustion. As CO2 is absorbed by the ocean, it forms carbonic acid and lowers the slightly alkaline (basic) pH of seawater. This suite of chemical changes is known collectively as ocean acidification. Lowered ocean pH alters the ability of many calcifying marine organisms to produce calcium carbonate skeletons and shells. Ocean acidification is an emerging global problem because, as CO2 emissions continue, so will the lowering of ocean pH that may cause profound changes in marine food webs and global ecosystems. (See related Sound Waves articles “Impacts of Ocean Acidification on Coral Growth: Historical Perspectives from Core-Based Studies,” “Research Cruises Collect Measurements on the West Florida Shelf for Modeling Climate Change and Ocean Acidification,” and “Coral-Reef Builders Vulnerable to Ocean Acidification.”)

The U.S. Geological Survey (USGS), along with other federal agencies, is working with the international scientific community to help standardize and compile information that adequately describes ocean chemistry trends and analyzes relations between these trends and carbon sources, cycles, and human activities. The USGS has been pioneering work to improve capabilities in measuring marine carbonate species and metabolic cycles that affect carbon compounds (http://coastal.er.usgs.gov/flash/), as well as characterizing CO2 concentrations in a wide variety of marine environments (http://coastal.er.usgs.gov/crest/).
Continue reading ‘Ocean acidification: research on top of the world’

Monitoring ocean acidification (audio)

Changes in the chemistry of the world’s oceans, due to an excess of atmospheric carbon dioxide, creates higher acidity in the oceans.

For more than 3 decades, scientists at the U.S. Department of Commerce’s National Oceanic and Atmospheric Administration, or NOAA, have been studying a growing global problem: changes in the chemistry of the world’s oceans due to an excess of atmospheric carbon dioxide which make the oceans more acidic. The process is called “ocean acidification” and researchers are now finding evidence of this change in U.S. coastal waterways.

Approximately 30 percent of all carbon dioxide released into the atmosphere is absorbed by the ocean. While this removes some of this greenhouse gas from the atmosphere, there is a problem: When carbon dioxide reacts with seawater, it forms carbonic acid, which changes ocean chemistry in 2 fundamental ways. First, carbonic acid releases hydrogen ions, making the ocean more acidic. Changes in the ocean’s acidity will have profound effects on both individual organisms and ecosystems, many of which will be unpredictable and irreversible on any meaningful timeframe. Second, the acid produced by carbonic acid removes carbonate ions, an essential building block for the shells of many marine organisms such as corals, marine plankton, and shellfish. Combined, these changes stand to have fundamental affects on marine food webs.
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UAF establishes ocean acidification research center

The University of Alaska Fairbanks has created a new research center dedicated to studying ocean acidification in Alaska.

Jeremy Mathis, assistant professor of chemical oceanography and an ocean acidification expert, will be the director of the center.

Ocean acidification is a term to describe increasing acidity in the world’s oceans. The ocean absorbs carbon dioxide from the air. As the ocean absorbs more carbon dioxide, seawater becomes more acidic. Scientists estimate that the ocean is 25 percent more acidic today than it was 300 years ago. According to Mathis, ocean acidification is happening more rapidly, and more severely, in Alaska waters. 
Continue reading ‘UAF establishes ocean acidification research center’

Limiting ocean acidification under global change

Emissions of carbon dioxide are causing ocean acidification as well as global warming. Scientists have previously used computer simulations to quantify how curbing of carbon dioxide emissions would mitigate climate impacts. New computer simulations have now examined the likely effects of mitigation scenarios on ocean acidification trends. They show that both the peak year of emissions and post-peak reduction rates influence how much ocean acidity increases by 2100. Changes in ocean pH over subsequent centuries will depend on how much the rate of carbon dioxide emissions can be reduced in the longer term.

Largely as a result of human activities such as the burning of fossil fuels for energy and land-use changes such deforestation, the concentration of carbon dioxide in the atmosphere is now higher that it has been at any time over the last 800,000 years. Most scientists believe this increase in atmospheric carbon dioxide to be an important cause of global warming.

“The oceans absorb around a third of carbon dioxide emissions, which helps limit global warming, but uptake of carbon dioxide by the oceans also increases their acidity, with potentially harmful effects on calcifying organisms such as corals and the ecosystems that they support,” explained Dr Toby Tyrrell of the University of Southampton’s School of Ocean and Earth Science (SOES) based at the National Oceanography Centre, Southampton.

“Increased ocean acidification is also likely to affect the biogeochemistry of the oceans in ways that we do not as yet fully understand,” he added.
Continue reading ‘Limiting ocean acidification under global change’

Erratum to the “Guide to Best Practices for Ocean Acidification Research and Data Reporting”

An error was found in the maximum pH value reported in table 3.1. All calculations have been checked, and the table and its legend corrected. The pdf files of the full guide and chapter 3 have been corrected on 26 August 2010. Files downloaded before that date must take into account the revised table and legend available here.

Impact of ocean acidification on energy metabolism of oyster, Crassostrea gigas—changes in metabolic pathways and thermal response

Climate change with increasing temperature and ocean acidification (OA) poses risks for marine ecosystems. According to Pörtner and Farrell [1], synergistic effects of elevated temperature and CO2-induced OA on energy metabolism will narrow the thermal tolerance window of marine ectothermal animals. To test this hypothesis, we investigated the effect of an acute temperature rise on energy metabolism of the oyster, Crassostrea gigas chronically exposed to elevated CO2 levels (partial pressure of CO2 in the seawater ~0.15 kPa, seawater pH ~ 7.7). Within one month of incubation at elevated PCO2 and 15 °C hemolymph pH fell (pHe = 7.1 ± 0.2 (CO2-group) vs. 7.6 ± 0.1 (control)) and PeCO2 values in hemolymph increased (0.5 ± 0.2 kPa (CO2-group) vs. 0.2 ± 0.04 kPa (control)). Slightly but significantly elevated bicarbonate concentrations in the hemolymph of CO2-incubated oysters ([HCO3]e = 1.8 ± 0.3 mM (CO2-group) vs. 1.3 ± 0.1 mM (control)) indicate only minimal regulation of extracellular acid-base status. At the acclimation temperature of 15 °C the OA-induced decrease in pHe did not lead to metabolic depression in oysters as standard metabolism rates (SMR) of CO2-exposed oysters were similar to controls. Upon acute warming SMR rose in both groups, but displayed a stronger increase in the CO2-incubated group. Investigation in isolated gill cells revealed a similar temperature-dependence of respiration between groups. Furthermore, the fraction of cellular energy demand for ion regulation via Na+/K+-ATPase was not affected by chronic hypercapnia or temperature. Metabolic profiling using 1H-NMR spectroscopy revealed substantial changes in some tissues following OA exposure at 15 °C. In mantle tissue alanine and ATP levels decreased significantly whereas an increase in succinate levels was observed in gill tissue. These findings suggest shifts in metabolic pathways following OA-exposure. Our study confirms that OA affects energy metabolism in oysters and suggests that climate change may affect populations of sessile coastal invertebrates such as mollusks.
Continue reading ‘Impact of ocean acidification on energy metabolism of oyster, Crassostrea gigas—changes in metabolic pathways and thermal response’

Deep sea to get louder with climate change

As carbon dioxide continues to build up in Earth’s atmosphere, it will also accumulate in her oceans. This rise in CO2 has already made the upper ocean more acidic and the same is expected to happen even in the lower depths in the coming century.

Physicists from the Woods Hole Oceanographic Institution now say that these changes will make some far flung reaches of the ocean more noisy. In a paper published last week in the Journal of the Acoustical Society of America, the team modeled ambient shipping noise for the deep ocean, incorporating forecasts for ocean pH levels and shipping noise in the coming century.

Any first year physics student knows the thickness of a fluid is important in considering how well sound waves propagate, but also of crucial importance in sea water is the concentration of boric acid and other chemicals. Boron ions help filter out low frequency waves, but as the ocean gets increasingly acidic, the amount of boron ions will decrease and these low frequency sound waves will penetrate into deeper waters.
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Ocean acidification Old Spice


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Feedbacks and responses of coral calcification on the Bermuda reef system to seasonal changes in biological processes and ocean acidification (update)

Despite the potential impact of ocean acidification on ecosystems such as coral reefs, surprisingly, there is very limited field data on the relationships between calcification and seawater carbonate chemistry. In this study, contemporaneous in situ datasets of seawater carbonate chemistry and calcification rates from the high-latitude coral reef of Bermuda over annual timescales provide a framework for investigating the present and future potential impact of rising carbon dioxide (CO2) levels and ocean acidification on coral reef ecosystems in their natural environment. A strong correlation was found between the in situ rates of calcification for the major framework building coral species Diploria labyrinthiformis and the seasonal variability of [CO32-] and aragonite saturation state Ωaragonite, rather than other environmental factors such as light and temperature. These field observations provide sufficient data to hypothesize that there is a seasonal “Carbonate Chemistry Coral Reef Ecosystem Feedback” (CREF hypothesis) between the primary components of the reef ecosystem (i.e., scleractinian hard corals and macroalgae) and seawater carbonate chemistry. In early summer, strong net autotrophy from benthic components of the reef system enhance [CO32-] and Ωaragonite conditions, and rates of coral calcification due to the photosynthetic uptake of CO2. In late summer, rates of coral calcification are suppressed by release of CO2 from reef metabolism during a period of strong net heterotrophy. It is likely that this seasonal CREF mechanism is present in other tropical reefs although attenuated compared to high-latitude reefs such as Bermuda. Due to lower annual mean surface seawater [CO32-] and Ωaragonite in Bermuda compared to tropical regions, we anticipate that Bermuda corals will experience seasonal periods of zero net calcification within the next decade at [CO32-] and Ωaragonite thresholds of ~184 μmoles kg−1 and 2.65. However, net autotrophy of the reef during winter and spring (as part of the CREF hypothesis) may delay the onset of zero NEC or decalcification going forward by enhancing [CO32-] and Ωaragonite. The Bermuda coral reef is one of the first responders to the negative impacts of ocean acidification, and we estimate that calcification rates for D. labyrinthiformis have declined by >50% compared to pre-industrial times.
Continue reading ‘Feedbacks and responses of coral calcification on the Bermuda reef system to seasonal changes in biological processes and ocean acidification (update)’


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