Organic matter exudation by Emiliania huxleyi under simulated future ocean conditions

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.

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

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.

Chemical oceanography PhD position

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.

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

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.

Coral and mollusc responses to acidified ocean

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.

Ocean acidification study clarifies effects of CO2

Might a penguin’s next meal be affected by the exhaust from your tailpipe? The answer may be yes, when you add your exhaust fumes to the total amount of carbon dioxide lofted into the atmosphere by humans since the Industrial Revolution. One-third of that carbon dioxide is absorbed by the world’s oceans, making them more acidic and affecting marine life.

A UC Santa Barbara marine scientist and a team of 18 other researchers have reported results of the broadest worldwide study of ocean acidification to date. Acidification is known to be a direct result of the increasing amount of greenhouse gas emissions. The scientists used sensors developed at Scripps Institution of Oceanography at UC San Diego to measure the acidity of 15 ocean locations, including seawater in the Antarctic, and in temperate and tropical waters.

As oceans become more acidic, with a lower pH, marine organisms are stressed and entire ecosystems are affected, according to the scientists. Gretchen E. Hofmann, an eco-physiologist and professor in UC Santa Barbara’s Department of Ecology, Evolution & Marine Biology, is lead author of the recent article in PLoS ONE that describes the research.

“We were able to illustrate how parts of the world’s oceans currently have different pH, and thus how they might respond to climate changes in the future,” said Hofmann. “The sensors allowed us to capture that.” The sensors recorded at least 30 days of continuous pH values in each area of the study.