Archive for August, 2012

Research project: Southern Ocean acidification

Summary: The overall goal of this project is to better predict the rate of Southern Ocean carbon uptake over the next several decades to centuries. This will require a thorough understanding of the variable and changing carbonate chemistry of the Southern Ocean, including better constraints on the present-day mean state and seasonal cycle, quantification of past variability, and characterization of key processes driving change in the future.

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Ocean Acidification Pteropod Study (OAPS) blog

First Post of a New Cruise
Gareth here. Welcome back to the Charismatic Microfauna Blog. Today our team set sail on the Scripps Institution of Oceanography’s Research Vessel New Horizon for a 25-day cruise to the northeast Pacific. This is the second cruise in our Ocean Acidification Pteropod Study (OAPS), in which we’re trying to understand how pteropods, a group of shell-forming plankton also known as sea butterflies, will respond to ocean acidification — the process by which the ocean is becoming more acidic as a consequence of the oceans absorbing excess CO2 released into the atmosphere through the burning of fossil fuels.

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Response of bacterioplankton community structure to an artificial gradient of pCO2 in the Arctic Ocean

The influences of ocean acidification on bacterial diversity were investigated using DNA fingerprinting and clone library analysis of bacterioplankton samples collected from the largest CO2 manipulation mesocosm study that had been performed thus far. Terminal restriction fragment length polymorphism analysis of the PCR amplicons of the 16S rRNA genes revealed that bacterial diversity, species richness and community structure varied with the time of incubation but not the degree of ocean acidification. The phylogenetic composition of the major bacterial assemblage after a 30-day incubation under various pCO2 concentrations did not show clear effects of pCO2 levels. However, the maximum apparent diversity and species richness which occurred during incubation differed in the high and low pCO2 treatments, in which different bacterial community structure harbored. In addition, total alkalinity was one of the contributing factors for the temporal variations in bacterial community structure observed during incubation. A negative relationship between the relative abundance of Bacteroidetes and pCO2 levels was observed for samples at the end of the experiment. Our study suggested that ocean acidification affected the development of bacterial assemblages and potentially impacts the ecological function of the bacterioplankton in the marine ecosystem.

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Ocean acidification and pacific fish

Since the 1970s many people have become familiar with the concept of acid rain and its negative effects on the environment, but fewer are aware of the impacts of fossil fuels on the chemistry of the ocean and the potential consequences on valuable fisheries resources. Ocean acidification is the common term for several chemical reactions that occur when carbon dioxide (CO2) released into the atmosphere is absorbed by seawater. The reactions reduce the carbonate ion concentration and increase the hydrogen ion concentration, making the seawater more acidic. The concentration of carbonate ions in the ocean determines the precipitation of calcium carbonate minerals (e.g., aragonite and calcite), which are used by marine organisms such as oysters and clams, to form their shells or skeletons through calcification. Most ocean surface waters are supersaturated in calcium carbonate minerals, but at lower pH, waters can be undersaturated with these vital minerals.

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Ocean acidification (video)

In this 1:42 video produced by World Ocean Observatory and Compass Light Productions, Dr. Carol Turley of the Plymouth Marine Laboratory will talk about the ocean acidification and the known impacts on marine organisms whose hightened sensitivity offers a stark example of the impacts of ocean acidification. Produced by World Ocean Observatory and Compass Light Productions.

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Relationships between bottom water carbonate saturation and element/Ca ratios in coretop samples of the benthic foraminifera Oridorsalis umbonatus (update)

Elemental ratios in benthic foraminifera have been used to reconstruct bottom water temperature and carbonate saturation (Δ[CO32−]). We present elemental data for the long-ranging benthic foraminiferaOridorsalis umbonatus from sediment core tops that span a narrow range of temperatures and a wide range of saturation states. B/Ca, Li/Ca, Sr/Ca and Mg/Ca ratios exhibit positive correlations with bottom water carbonate saturation. The sensitivity of individual element/calcium ratios to bottom water Δ[CO32−] varies considerably, with B/Ca being most sensitive and Sr/Ca the least sensitive. The empirically derived sensitivity of B/Ca, Li/Ca, Mg/Ca and Sr/Ca to bottom water Δ[CO32−] are 0.433 ± 0.053 and 0.0561 ± 0.0084 μmol mol−1 μmol kg−1 and 0.0164 ± 0.0015 and 0.00241 ±0.0004 mmol mol−1μmol kg−1, respectively. To assess the fidelity of these relationships and the possibility of applying these relationships to earlier periods of Earth history, we examine the mechanisms governing elemental incorporation into foraminiferal calcite. Empirical partition coefficients for Li and Sr are consistent with Rayleigh fractionation from an internal pool used for calcification. For O. umbonatus and other benthic species, we show that the fraction of Ca remaining in the pool is a function of bottom water Δ[CO32−], and can be explained by either a growth rate effect and/or the energetic cost of raising vesicle pH at the site of calcification. Empirical partition coefficients for Mg and B may also be controlled by Rayleigh fractionation, but require that either the fractionation factor from the internal pool is smaller than the inorganic partition coefficient and/or additional fractionation mechanisms. O. umbonatus element ratio data may also be consistent with fractionation according to the surface entrapment model and/or the presence of discrete high- and low-Mg calcite phases. However, at present we are limited in our ability to assess these mechanisms. The new X/Ca data for O. umbonatusprovide constraints to test the role of these mechanisms in the future.

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Response of bacterioplankton activity in an Arctic fjord system to elevated pCO2: results from a mesocosm perturbation study

The effect of elevated seawater carbon dioxide (CO2) on the activity of a natural bacterioplankton community in an Arctic fjord system was investigated by a mesocosm perturbation study in the frame of the European Project on Ocean Acidification (EPOCA). A pCO2 range of 175–1085 μatm was set up in nine mesocosms deployed in the Kongsfjorden (Svalbard). The bacterioplankton communities responded to rising chlorophyll a concentrations after a lag phase of only a few days with increasing protein production and extracellular enzyme activity and revealed a close coupling of heterotrophic bacterial activity to phytoplankton productivity in this experiment. The natural extracellular enzyme assemblages showed increased activity in response to moderate acidification. A decrease in seawater pH of 0.5 units roughly doubled rates of β-glucosidase and leucine-aminopeptidase. Activities of extracellular enzymes in the mesocosms were directly related to both seawater pH and primary production. Also primary production and bacterial protein production in the mesocosms at different pCO2 were positively correlated. Therefore, it can be suggested that the efficient heterotrophic carbon utilization in this Arctic microbial food web had the potential to counteract increased phytoplankton production that was achieved under elevated pCO2 in this study. However, our results also show that the transfer of beneficial pCO2-related effects on the cellular bacterial metabolism to the scale of community activity and organic matter degradation can be mitigated by the top-down control of bacterial abundances in natural microbial communities.

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Oyster industry struggles to adapt to climate change

Ocean acidification has reduced some oyster yields by 80% or more.

Oysters on the half shell may be a delicacy, but oysters need their shells to grow and thrive in the first place. Unfortunately, increasing levels of ocean acidification caused by carbon-dioxide emissions and climate change threaten the integrity of oyster shells — and therefore the tasty mollusks themselves — and the oyster industry around the world is struggling to adapt.

Oyster hatcheries and nurseries in the Pacific Northwest started seeing the effect of ocean acidification in the middle of the last decade when oyster larvae started dying after their shells were corroded, NPR station WRVO recently reported. The region’s oyster farms saw a 60 percent drop in production in 2008 and another 80 percent drop the following year. The cause, as determined by National Oceanic and Atmospheric Administration research scientist Richard Feely, was increased anthropogenic CO2 in the ocean water.

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WHOI hosts ocean science forum

WHOI scientists highlighted the issue of ocean acidification.

The Woods Hole Oceanographic Institution hosted a public forum at Redfield Auditorium Wednesday evening, highlighting the serious but little-discussed issue of ocean acidification. The event shed light on the causes and consequences of acidification through an outdoor expo featuring exhibits and demonstrations, and presentations by WHOI scientists.

President and Director Susan Avery began the program by summarizing acidification, calling it “one of the greatest problems facing our ocean and our planet.”

Acidification is a byproduct of carbon dioxide emissions, largely the result of the mass burning of fossil fuels. When carbon dioxide is released into the atmosphere, some it remains there—to contribute to global warming—some is absorbed by the land, and some—about a quarter of the total—comes to rest in the earth’s oceans.

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Op-ed: how we can fight ocean acidification, protect marine life

We must embrace ocean conservation and management strategies to fight ocean acidification.

THOSE of us who care about the health of our coastal and marine resources recently received yet another wake-up call. A longtime oyster grower in Willapa Bay has moved a portion of its operation to Hawaii because of concerns over ocean acidification impacts on hatchery production.

Is the failure of tiny oyster larvae in Northwest coastal waters akin to the death of canaries in coal mines, warning us of imminent threats to our health and livelihoods? Perhaps. As a scientist, I look for the best evidence to support a statement of impending risk.

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BIOS study: climate change, ocean bacteria

When it comes to climate change, few people think about potential impacts on bacteria, but that’s just what a team of researchers from the Bermuda Institute of Ocean Sciences [BIOS] and Princeton University did in a recent study chosen as the feature article in the current issue of Aquatic Microbial Ecology.

Led by Dr. Michael Lomas, PI of the Phytoplankton Ecology Lab at BIOS, the team investigated the short-term responses of photosynthetic bacteria populations to a series of treatments that mimic ocean acidification trends from the last glacial minimum [120,000 years ago] to projected year 2100.

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Effect of ocean acidification on cyanobacteria in the subtropical North Atlantic

Cyanobacteria make significant contributions to global carbon and nitrogen cycling, particularly in the oligotrophic subtropical and tropical gyres. The present study examined short-term (days) physiological and acclimation responses of natural cyanobacterial populations to changes in pH/pCO2 spanning the last glacial minimum, ~8.4/~150 ppm, to projected year 2100 values of ~7.8/~800 ppm. Fe- and P-replete colonies of Trichodesmium increased N2-fixation rates (nmol N colony−1 h−1) at pH 7.8 by 54% (range 6 to 156%) over ambient pH/pCO2 conditions, while N2-fixation at pH/pCO2 8.4 was 21% (range 6 to 65%) lower than at ambient pH/pCO2; a similar pattern was observed when the rates were normalized to colony C. C-fixation rates were on average 13% (range −72 to 112%) greater at low pH than at ambient pH and 37% (−53 to 23%) greater than at high pH. Whole community assemblages dominated by Prochlorococcus and Synechococcus (47 to 95% of autotrophic biomass), whether nutrient-replete or P-limited, did not show a clear response of C-fixation rates to changes in pH/pCO2. Comparison of initial and final C-fixation responses across pH/pCO2 treatments suggests rapid acclimation of cellular physiology to new pH/pCO2 conditions. Changes in cell size and pigment content for Prochlorococcus and Synechococcus were minor and did not vary in a consistent manner with changes in pH/pCO2. These results for natural populations of all 3 cyanobacteria concur with previous research and suggest that one important response to changes in ocean pH and pCO2 might be an increase in N2 and C fixation by Trichodesmium under nutrient-replete conditions. The response of single-cell cyanobacteria to changes in pH/pCO2 will likely be indirect and controlled by the response to other variables, such as nutrients.

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Ocean’s rising acid levels threaten sea life

Skeletons, shells becoming thinner

A thinning of the protective cases of mussels, oysters, lobsters and crabs is likely to disrupt marine food chains by making the creatures more vulnerable to predators. This could reduce human sources of seafood.

“The results suggest that increased acidity is affecting the size and weight of shells and skeletons, and the trend is widespread across marine species,” the British Antarctic Sur-vey (BAS) said in a statement of the findings.

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Gonsalves: hard sell for hard shells

Just in time for football season, the big news in science over the weekend was the Martian touch-down scored by the robotic explorer Curiosity.

For the next two years, Curiosity will search for microscopic life on the red planet, which is why NASA chose a landing site near the Gale Crater — thought to be rich in minerals, remnants of ancient seas.

As scientists have long known, water is an ideal biosolvent uniquely suited to support life. So this new Mars mission is exciting stuff.

Meanwhile, closer to home, the big (though not quite as sexy) news this week in Earth ocean science is the Woods Hole Oceanographic Institution’s science expo on Wednesday. Called Ocean’s Acid Test, it’s designed as a public crash course in the very real global problem of ocean acidification.

Big deal, you say? I’ll let WHOI marine chemist Sarah Cooley tell you why it’s a big deal, especially for those whose livelihood or quality of life is tied to shellfish.

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Ocean acidification (audio)

Iosefa Percival recently joined Conservation Internationals Pacific Islands Program (CI – PIP) as an intern to research the likely impacts of ocean acidification in the Pacific Islands.

Born and raised in Tiapapata, Iosefa Percival recently returned to Samoa from Brandeis University in Boston, USA for an internship with Conservation International. In this interview Iosefa discusses Ocean Acidification, his research plans in Samoa and why this information is so important for our region.

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Ocean acidification threatens global shellfish stocks (video)

Global shellfish populations are under increasing pressure brought about by ocean acidification. Scientists from the British Antarctic Survey say that oysters, mussels and crabs are finding it more difficult to develop their shells, making them vulnerable to predators and an overall decline that could impact other parts of the ecosystem. Jim Drury reports.

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Spatiotemporal variability and long-term trends of ocean acidification in the California Current System

Due to seasonal upwelling, the upper ocean waters of the California Current System (CCS) have a naturally low pH and aragonite saturation state (Ωarag), making this region particularly prone to the effects of ocean acidification. Here, we use the Regional Oceanic Modeling System (ROMS) to conduct preindustrial and transient (1995–2050) simulations of ocean biogeochemistry in the CCS. The transient simulations were forced with increasing atmospheric pCO2 as projected by the NCAR CSM 1.4 model run under either the IPCC SRES A2 or B1 scenarios. Using ROMS, we investigate the timing of transition decades during which pH and Ωarag depart from their modeled preindustrial (1750) and present-day (2011) variability envelopes. We report these transition decades by noting the midpoint of the ten-year transition periods. In addition, we also analyze the timing of near permanent aragonite undersaturation in the upper 100 m of the water column. Our results show that an interplay of physical and biogeochemical processes create large seasonal variability in pH (∼ 0.14) and Ωarag (∼ 0.2). Despite this large variability, we find that present-day pH and Ωarag have already moved out of their preindustrial variability envelopes due to the rapidly increasing concentrations of atmospheric CO2. The simulations following the A2 emissions scenario suggest that nearshore surface pH of the northern and central CCS will move out of their present-day variability envelopes by 2045 and 2037, respectively. However, surface Ωarag of the northern and central CCS subregions are projected to depart from their present-day variability envelopes sooner, by 2030 and 2035, respectively. By 2025, the aragonite saturation horizon of the central CCS is projected to shoal into the upper 75 m for the duration of the annual cycle, causing near permanent undersaturation in subsurface waters. Overall, our study shows that the CCS joins the Arctic and Southern Oceans as one of only a few known ocean regions presently approaching this dual threshold of undersaturation with respect to aragonite and a departure from its variability envelope. In these regions, organisms may be forced to rapidly adjust to conditions that are both inherently chemically challenging and also substantially different from prior conditions.

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The ramifications of ocean acidification – a warning

The coming changes in ocean pH may well occur too rapidly for some marine species to adapt to and survive – warns Professor Lloyd Peck

The perceived big problem that past and predicted ocean acidification has for marine animals is that it makes extracting calcium carbonate from seawater to make skeletons more difficult. Many experiments have shown that exposure to reduced pH has negative consequences for most, if not all marine groups. The problems with the vast majority of studies is that they are perforce short-term and do not replicate the slower natural rates of change seen – and to come in the world’s oceans.

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Shellfish decreasing in size from global warming

Scientists from the British Antarctic Survey (BAS) and the National Oceanography Centre (NOC), together with colleagues from Australia’s James Cook and Melbourne Universities and the National University of Singapore reported the latest results of the effect of global warming on shellfish in the journal Global Change Biology on August 5, 2012. The research was reviewed at the Eureka Alert web site the same day. Continue reading ‘Shellfish decreasing in size from global warming’

Biological and physical forcing of carbonate chemistry in an upwelling filament off northwest Africa: results from a Lagrangian study

The Mauritanian upwelling system is one of the most biologically productive regions of the world’s oceans. Coastal upwelling transfers nutrients to the sun-lit surface ocean, thereby stimulating phytoplankton growth. Upwelling of deep waters also supplies dissolved inorganic carbon (DIC), high levels of which lead to low calcium carbonate saturation states in surface waters, with potentially adverse effects on marine calcifiers. In this study an upwelled filament off the coast of northwest Africa was followed using drifting buoys and sulphur hexafluoride to determine how the carbonate chemistry changed over time as a result of biological, physical and chemical processes. The initial pHtot in the mixed layer of the upwelled plume was 7.94 and the saturation states of calcite and aragonite were 3.4 and 2.2, respectively. As the plume moved offshore over a period of 9 days, biological uptake of DIC (37 μmol kg−1) reduced pCO2 concentrations from 540 to 410 μatm, thereby increasing pHtot to 8.05 and calcite and aragonite saturation states to 4.0 and 2.7 respectively. The increase (25 μmol kg−1) in total alkalinity over the 9 day study period can be accounted for solely by the combined effects of nitrate uptake and processes that alter salinity (i.e., evaporation and mixing with other water masses). We found no evidence of significant alkalinity accumulation as a result of exudation of organic bases by primary producers. The ongoing expansion of oxygen minimum zones through global warming will likely further reduce the CaCO3 saturation of upwelled waters, amplifying any adverse consequences of ocean acidification on the ecosystem of the Mauritanian upwelling system.

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