Archive for January, 2016

Ocean acidification: investigation and presentation of the effects of elevated carbon dioxide levels on seawater chemistry and calcareous organisms

Ocean acidification refers to the process by which seawater absorbs carbon dioxide from the atmosphere, producing aqueous carbonic acid. Acidic conditions increase the solubility of calcium carbonate, threatening corals and other calcareous organisms that depend on it for protective structures. The global nature of ocean acidification and the magnitude of its potential impact on marine ecosystems and the industries they support make it an important and engaging topic to explore in the undergraduate laboratory. In this multiweek experiment, designed for second year analytical and environmental chemistry courses, artificial seawater samples containing pieces of seashell or coral were prepared. One sample was pressurized with carbon dioxide and stirred for 1 week, while the other was stirred without carbonation. Mass and pH measurements and carbonate, bicarbonate, calcium(II), and magnesium(II) titrations were performed on samples before and after treatment. Through data analysis and a rigorous consideration of the acid–base and solubility equilibria involved, students concluded that carbonation significantly decreased seawater pH and caused appreciable seashell and coral dissolution, which raised the bicarbonate and calcium(II) concentrations. Minimal change in the seawater chemistry or carbonaceous material was observed for the noncarbonated sample. Overall, the experience provided a meaningful experimental context for titration analyses and a practical application of the conceptual treatment of a multiequilibrium system. In addition to the experiment, a corresponding oral presentation assignment is presented, in which students produced a video designed to educate a general audience on the topic of ocean acidification by using their experimental results as support. Through this assignment, students reflected on the broader ecological and societal ramifications of ocean acidification and developed the ability to communicate scientific knowledge to a nonscientific audience, a critical collaborative skill for addressing such multifaceted issues.

Continue reading ‘Ocean acidification: investigation and presentation of the effects of elevated carbon dioxide levels on seawater chemistry and calcareous organisms’

Effect of ocean acidification and elevated fCO2 on trace gas production by a Baltic Sea summer phytoplankton community

The Baltic Sea is a unique environment as the largest body of brackish water in the world. Acidification of the surface oceans due to absorption of anthropogenic CO2 emissions is an additional stressor facing the pelagic community of the already challenging Baltic Sea. To investigate its impact on trace gas biogeochemistry, a large-scale mesocosm experiment was performed off Tvärminne Research Station, Finland in summer 2012. During the second half of the experiment, dimethylsulphide (DMS) concentrations in the highest fCO2 mesocosms (1075–1333 μatm) were 34 % lower than at ambient CO2 (350 μatm). However the net production (as measured by concentration change) of seven halocarbons analysed was not significantly affected by even the highest CO2 levels after 5 weeks exposure. Methyl iodide (CH3I) and diiodomethane (CH2I2) showed 15 % and 57 % increases in mean mesocosm concentration (3.8 ± 0.6 pmol L−1 increasing to 4.3 ± 0.4 pmol L−1 and 87.4 ± 14.9 pmol L−1 increasing to 134.4 ± 24.1 pmol L−1 respectively) during Phase II of the experiment, which were unrelated to CO2 and corresponded to 30 % lower Chl-ɑ concentrations compared to Phase I. No other iodocarbons increased or showed a peak, with mean chloroiodomethane (CH2ClI) concentrations measured at 5.3 (± 0.9) pmol L−1 and iodoethane (C2H5I) at 0.5 (± 0.1) pmol L−1. Of the concentrations of bromoform (CHBr3; mean 88.1 ± 13.2 pmol L−1), dibromomethane (CH2Br2; mean 5.3 ± 0.8 pmol L−1) and dibromochloromethane (CHBr2Cl, mean 3.0 ± 0.5 pmol L−1), only CH2Br2 showed a decrease of 17 % between Phases I and II, with CHBr3 and CHBr2Cl showing similar mean concentrations in both Phases. Outside the mesocosms, an upwelling event was responsible for bringing colder, high CO2, low pH water to the surface starting on day t16 of the experiment; this variable CO2 system with frequent upwelling events implies the community of the Baltic Sea is acclimated to regular significant declines in pH caused by up to 800 μatm fCO2. After this upwelling, DMS concentrations declined, but halocarbon concentrations remained similar or increased compared to measurements prior to the change in conditions. Based on our findings, with future acidification of Baltic Sea waters, biogenic halocarbon emissions are likely to remain at similar values to today, however emissions of biogenic sulphur could significantly decrease from this region.

Continue reading ‘Effect of ocean acidification and elevated fCO2 on trace gas production by a Baltic Sea summer phytoplankton community’

Physiological responses of a Southern Ocean diatom to complex future ocean conditions

A changing climate is altering many ocean properties that consequently will modify marine productivity. Previous phytoplankton manipulation studies have focused on individual or subsets of these properties. Here, we investigate the cumulative effects of multi-faceted change on a subantarctic diatom Pseudonitzschia multiseries by concurrently manipulating five stressors (light/nutrients/CO2/temperature/iron) that primarily control its physiology, and explore underlying reasons for altered physiological performance. Climate change enhances diatom growth mainly owing to warming and iron enrichment, and both properties decrease cellular nutrient quotas, partially offsetting any effects of decreased nutrient supply by 2100. Physiological diagnostics and comparative proteomics demonstrate the joint importance of individual and interactive effects of temperature and iron, and reveal biased future predictions from experimental outcomes when only a subset of multi-stressors is considered. Our findings for subantarctic waters illustrate how composite regional studies are needed to provide accurate global projections of future shifts in productivity and distinguish underlying species-specific physiological mechanisms.

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Ocean acidification (effects on marine plants: phytoplankton – coccolithophores): summary

(Please see the important comment below!)

Coccolithophores are single-celled algae and protists that are found throughout the surface euphotic zones of the world’s oceans. They contain chlorophyll, conduct photosynthesis and possess special plates or scales known as coccoliths, which they create via the process of calcification. This summary briefly reviews the results of several studies investigating how coccolithophores may be affected by ocean acidification in a CO2-enriched world of the future. As indicated below, the findings of these several works challenge the alarmist view of ocean acidification espoused by the IPCC and others. Instead of experiencing great harm in response to future declines in oceanic pH predicted for the future, coccolithophores will likely adapt and possible even thrive under such changes.

Introducing this complex subject of global change research, over a decade ago Riebesell (2004) wrote that a doubling of present-day atmospheric CO2 concentrations “is predicted to cause a 20-40% reduction in biogenic calcification of the predominant calcifying organisms, the corals, coccolithophorids, and foraminifera.” On the other hand, he noted that “a moderate increase in CO2 facilitates photosynthetic carbon fixation of some phytoplankton groups,” including “the coccolithophorids Emiliania huxleyi and Gephyrocapsa oceanica.” And in what constituted a major challenge to the model-based claim that atmospheric CO2 enrichment will harm such marine organisms, Riebesell went on to suggest that “CO2-sensitive taxa, such as the calcifying coccolithophorids, should therefore benefit more from the present increase in atmospheric CO2 compared to the non-calcifying diatoms.” (…)

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Dense water flow and carbonate system in the southern Adriatic: A focus on the 2012 event

The active deep overturning circulation of the Mediterranean is emerging as one of the most effective mechanisms in transporting the atmospheric imprint on the carbon cycle to the interior of the basin. There is growing evidence that sites of dense water formation over the continental shelf, such as the Northern Adriatic Sea, play a key role in this process. Nevertheless, little is known about the inorganic carbon chemistry of the Adriatic sea, and CO2 absorption and its fate.

The winter of 2012 experienced peculiar meteorological conditions with an extended period of cold weather with strong winds that triggered, in February, a massive formation of an extremely cold and dense (potential density anomaly > 30.00 kg m− 3) Northern Adriatic Dense Water (NAdDW) water mass. This event provided a unique opportunity to study this process at sub-basin scale taking into account CO2 adsorption within the NAdDW source area (the Gulf of Trieste in the northern Adriatic), and its spreading over the shelf and into the Southern Adriatic Pit.

The northern Adriatic and the Gulf of Trieste, during winter, act as a CO2 sink. The average air-sea CO2 flux of 60 mmol m− 2 d− 1 estimated during the exceptional 2012 event was at least 3 times higher than the flux measured in winter 2008 when dense water was produced through the same mechanism but under less extreme conditions. In winter 2012, absorbed CO2 resulted in the decrease of pHT25 down to 7.907 (− 0.034 pHT units) and the strong evaporation induced by wind-increased total alkalinity (TA) to 2673 (+ 16 μmol kg− 1).

Following its formation in the North, the NAdDW plume entering the Southern Adriatic, observed in March 2012, exhibited significantly modified values. The plume was characterized by colder temperature (~ 10 °C), lower pHT25 (7.947 pHT units) and higher alkalinity (2635 μmol kg− 1) than the surrounding water masses along the western Adriatic shelf. However, the signal of atmospheric CO2 enrichment was weaker than in the northern Adriatic source region, as well as positive apparent oxygen utilization (AOU) values (~ 20 μmol kg− 1) were recorded. This is suggestive of oxygen consumption in the water mass.

Observed changes in both physical and biogeochemical properties were similar to those observed in 2008, suggesting that mixing with Levantine Intermediate Waters (LIW) was the main driver modulating the changes of AOU and inorganic carbon chemistry in both winters. The rising of pHT25 and AOU due to the mixing indicates that NAdDW, at its origin, was richer in atmospheric CO2 than the LIW was, thus confirming the relevance of the Northern Adriatic Sea for CO2 adsorption.

The study provides the first characterization of inorganic carbon chemistry, including carbonate minerals saturation states (ΩAr and ΩCa), in the bottom waters both on the slope and along the expected pathways of dense water cascading in the Adriatic Sea. Therefore, it can represent a baseline to improve the knowledge on the acidification process and impacts as well as being useful for comparison with other benthic environments.

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Science Café- Ocean acidification, 10 March 2016, Elizabeth City, North Carolina

Date & time: 10 March 2016 | 7:00 pm – 9:00 pm

Venue: Island Breeze Grill, 220 Poindexter St, Elizabeth City, NC 27909

Port Discover Science Educator, Ashley Emley, will be discussing the effects of ocean acidification in our oceans and steps we can take to slow the process.

A science program just for the local adult community. Science Café is typically on the second Thursday of every month, starts at 7:00 pm, and is free. It is a chance for participants to learn about and discuss science topics presented by local experts. In an informal, casual restaurant setting, participants will be able to add to the conversation and ask questions.

Further information.


Ocean acidification: states taking action

Screen-Shot-2016-01-27-at-11_blogOcean acidification is one of those big, scary problems that scientists have been warning us about for years.  Carbon emissions are being absorbed by the ocean, turning it more acidic – spelling trouble for oysters, clams, mussels, as well as corals, salmon and even sharks. We know that reducing global carbon emissions is key to solving ocean acidification.  The UN Climate Meeting in December was a resounding success, but what can people and states do, today, that will make a difference to their communities and businesses impacted by acidification?  Turns out, quite a lot.

There is no one size fits all approach, but my colleagues and I have been tracking the efforts underway, and have noticed that many states are sitting up and taking action.  In seeking to make local actions more achievable in other locations, we’ve complied and analyzed these efforts in a paper that was published today in Frontiers in Marine Policy.

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Ocean acidification catches State Senate attention (audio)

Climate change is taking a toll on the oceans, making them more acidic, and threatening ocean habitats as well as economies that rely on threatened fisheries. The state Senate held its first ever hearing on the issue of ocean acidification, what some call “the evil twin of climate change.” Christopher Martinez reports from Sacramento.

Christopher Martinez, The Pacifica Evening News, 26 January 2016. Audio.

New octopus and science/beer events on central Oregon coast, 28 January 2016, Newport, Oregon

(…)The OSU Hatfield Marine Science Center and the Union of Concerned Scientists will host a reception and panel discussion on the environmental and economic impacts of ocean acidification on our coastal communities. The event is from 5-7 pm this Thursday, January 28 in the HMSC Visitor Center’s Hennings Auditorium.

Expert panelists will discuss the science of ocean acidification, local impacts and potential solutions with community members and elected officials. The aspects most relevant to the Oregon coast include how it affects oyster growers, shellfish, how it interacts with hypoxia (ocean dead zones) and more.

Panelists include: Dr. George Waldbusser, Assistant Professor, OSU College of Earth, Ocean and Atmospheric Science; Alan Barton, Whiskey Creek Shellfish Hatchery; Dr. Francis Chan, Associate Professor and Senior Researcher, OSU College of Science; Emily Heffling, Western States Outreach Coordinator, Union of Concerned Scientists.

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California lawmakers urged to tackle ocean acidity

SACRAMENTO, Calif. (CN) – Humans are changing the chemical makeup of the world’s oceans and causing dangerous acidity levels that threaten California’s coastal ecosystems, scientists warned a state Senate committee Tuesday.

A panel of scientists studying ocean acidification and hypoxia – dubbed “the evil twin of global warming” – told California state senators that increased acidity levels in the Pacific Ocean are a “generational” threat and already damaging California’s 840 miles of coastline.

During the first-ever California legislative hearing on ocean acidification, scientists urged the state Senate Natural Resources and Water Committee to increase their role in raising public and political awareness of the global phenomenon they claim is intertwined with climate change.

“This is a huge problem that is going to be very difficult to stop and slow down, and this problem is going to affect our children and grandchildren,” Dr. Alexandria Boehm, Stanford scientist and chair of the West Coast Ocean Acidification Hypoxia Science Panel, said. “It’s the problem that’s going to define a generation.”

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Ocean acidification in the IPCC AR5 WG II

OUP book