Archive for March, 2012

Effects of CO2 and their modulation by light in the life-cycle stages of the coccolithophore Emiliania huxleyi

The effects of ocean acidification on the life-cycle stages of the coccolithophore Emiliania huxleyi and their modulation by light were examined. Calcifying diploid and noncalcifying haploid cells (Roscoff culture collection strains 1216 and 1217) were acclimated to present-day and elevated CO2 partial pressures (PCO2; 38.5 vs. 101.3 Pa, i.e., 380 vs. 1000 µatm) under low and high light (50 vs. 300 µmol photons m-2 s−1). Growth rates as well as cellular quotas and production rates of C and N were measured. Sources of inorganic C for biomass buildup were determined using a 14C disequilibrium assay. Photosynthetic O2 evolution was measured as a function of dissolved inorganic C and light by means of membrane-inlet mass spectrometry. The diploid stage responded to elevated PCO2 by shunting resources from the production of particulate inorganic C toward organic C yet keeping the production of total particulate C constant. As the effect of ocean acidification was stronger under low light, the diploid stage might be less affected by increased acidity when energy availability is high. The haploid stage maintained elemental composition and production rates under elevated PCO2. Although both life-cycle stages involve different ways of dealing with elevated PCO2, the responses were generally modulated by energy availability, being typically most pronounced under low light. Additionally, PCO2 responses resembled those induced by high irradiances, indicating that ocean acidification affects the interplay between energy-generating processes (photosynthetic light reactions) and processes competing for energy (biomass buildup and calcification). A conceptual model is put forward explaining why the magnitude of single responses is determined by energy availability.

Continue reading ‘Effects of CO2 and their modulation by light in the life-cycle stages of the coccolithophore Emiliania huxleyi’

IMOS observations for ocean acidification research

Australia’s Integrated Marine Observing System (IMOS) was established in 2007 under the National Collaborative Research Infrastructure Strategy (NCRIS), and extended under the Education Investment Fund (EIF) in 2009.  It has successfully deployed a range of observing equipment in the oceans around Australia, making all of the data freely and openly available through the IMOS Ocean Portal ( for the benefit of Australian marine and ocean-climate science as a whole.

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New Watson fellows will pursue interests around the globe

Two Davidson seniors have been awarded $25,000 from the Thomas J. Watson Foundation to pursue a full year of independent, purposeful exploration and travel. Audrey Gyurgyik will explore a holistic approach to actor training, a form that incorporates the body, soul and mind. Alexis Valauri-Orton will explore ocean acidification and how the threat of oceanic carbon dioxide pollution is perceived by different marine-dependent cultures.

The two were among 40 graduating seniors selected to receive Watson Fellowships from a pool of over 700 applicants nationwide. The foundation began sponsoring the program in 1968 in hopes that the experience would enhance the fellows’ resourcefulness and leadership, and promote their humane and effective participation in the world community.

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Variable production of transparent exopolymeric particles by haploid and diploid life stages of coccolithophores grown under different CO2 concentrations

The production of transparent exopolymeric particles (TEP) by the coccolithophores, Emiliania huxleyi, Calcidiscus leptoporus and Syracosphaera pulchra was investigated in batch cultures. The abundance, size spectra and carbon content of TEP were examined during the exponential growth phase of both haploid and diploid life stages grown under ambient (400 µatm) and elevated (760 µatm) CO2 partial pressure (pCO2) conditions. Results showed species- and life stage-specific differences in TEP production rate (day−1) derived from abundance and carbon content of TEP. At 400 µatm, TEP production rate was the highest in the diploid stage of S. pulchra and E. huxleyi, while TEP carbon content per cell was the highest in the diploid stage of C. leptoporus. At 760 µatm, TEP production rate increased in almost all species and was closely related to the cell growth rates (except in the diploid stage of C. leptoporus), while the slope values δ of the regression lines between TEP size distribution and concentration decreased. This means that the contribution of smaller size TEP was relatively more important than larger TEP in the high pCO2 treatment. Elevated pCO2 is potentially able to alter TEP size distribution. TEP-C content cell−1 generally decreased with increasing pCO2. TEP-C accounted for 1–24% of the cell particulate organic carbon production and was inversely related to increasing pCO2. TEP production by C. leptoporus and S. pulchra has not previously been documented. The amount of organic carbon released as TEP by these coccolithophores is comparable to and may even exceed TEP production by some diatoms.

Continue reading ‘Variable production of transparent exopolymeric particles by haploid and diploid life stages of coccolithophores grown under different CO2 concentrations’

Morphological and physiological effects in Proboscia alata (Bacillariophyceae) grown under different light and CO2 conditions of the modern southern ocean

The combined effects of different light and aqueous CO2 conditions were assessed for the Southern Ocean diatom Proboscia alata  (Brightwell) Sundström in laboratory experiments. Selected culture conditions (light and CO2(aq)) were representative for the natural ranges in the modern Southern Ocean. Light conditions were 40 (low) and 240 (high) μmol photons·m−2·s−1. The three CO2(aq) conditions ranged from 8 to 34 μmol·kg−1 CO2(aq) (equivalent to a pCO2 from 137 to 598 μatm, respectively). Clear morphological changes were induced by these different CO2(aq) conditions. Cells in low [CO2(aq)] formed spirals, while many cells in high [CO2(aq)] disintegrated. Cell size and volume were significantly affected by the different CO2(aq) concentrations. Increasing CO2(aq) concentrations led to an increase in particulate organic carbon concentrations per cell in the high light cultures, with exactly the opposite happening in the low light cultures. However, other parameters measured were not influenced by the range of CO2(aq) treatments. This included growth rates, chlorophyll aconcentration and photosynthetic yield (FV/FM). Different light treatments had a large effect on nutrient uptake. High light conditions caused an increased nutrient uptake rate compared to cells grown in low light conditions. Light and CO2 conditions co-determined in various ways the response of P. alata to changing environmental conditions. Overall P. alata appeared to be well adapted to the natural variability in light availability and CO2(aq) concentration of the modern Southern Ocean. Nevertheless, our results showed that P. alata is susceptible to future changes in inorganic carbon concentrations in the Southern Ocean.
Continue reading ‘Morphological and physiological effects in Proboscia alata (Bacillariophyceae) grown under different light and CO2 conditions of the modern southern ocean’

Changes in coral microbial communities in response to a natural pH gradient

Surface seawater pH is currently 0.1 units lower than pre-industrial values and is projected to decrease by up to 0.4 units by the end of the century. This acidification has the potential to cause significant perturbations to the physiology of ocean organisms, particularly those such as corals that build their skeletons/shells from calcium carbonate. Reduced ocean pH could also have an impact on the coral microbial community, and thus may affect coral physiology and health. Most of the studies to date have examined the impact of ocean acidification on corals and/or associated microbiota under controlled laboratory conditions. Here we report the first study that examines the changes in coral microbial communities in response to a natural pH gradient (mean pHT 7.3–8.1) caused by volcanic CO2 vents off Ischia, Gulf of Naples, Italy. Two Mediterranean coral species, Balanophyllia europaea and Cladocora caespitosa, were examined. The microbial community diversity and the physiological parameters of the endosymbiotic dinoflagellates (Symbiodinium spp.) were monitored. We found that pH did not have a significant impact on the composition of associated microbial communities in both coral species. In contrast to some earlier studies, we found that corals present at the lower pH sites exhibited only minor physiological changes and no microbial pathogens were detected. Together, these results provide new insights into the impact of ocean acidification on the coral holobiont.

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Meeting information: Review of the national ocean acidification research plan

Review of the National Ocean Acidification Research Plan
March 29, 2012 – March 29, 2012

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Ocean acidification video by NIWA

Vodpod videos no longer available.

The oceans are an important sink for atmospheric CO2, but as they take up increasing amounts of CO2 they are becoming more acidic. This has knock-on effects on some marine organisms and on the ocean’s ability to sequester carbon. NIWA oceanographer Dr Cliff Law explains the impacts of ocean acidification on organisms that use carbonates to build their shells, and on bacteria. Effects on bacteria may reduce the ocean’s ability to take up atmospheric CO2, creating a positive feedback loop, whereas organisms that use carbonate may find it more difficult to form and maintain their shells.

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Southeast fisheries investigate, anticipate ocean acidification

Will the carbon output of a growing world economy transform the oceans into an environment that — thanks to basic chemistry — is hostile to Alaska’s famed salmon? Or will Alaskans find ways to mitigate the expected drop in ocean pH?

Ocean acidification coincides with certain mass extinction events in the past, according to Jeremy Mathis, professor of chemical oceanography at the University of Alaska Fairbanks.

Fishers, shellfish grower and harvesters and non-profit organizations have met at recent roundtable meetings to discuss ocean acidification in Alaska.

Anthropologist Rachel Donkersloot is releasing a report on ocean acidification and these roundtable meetings. She conducted the study as fisheries program director of the Coastal Voices on Ocean Acidification Project for the Alaska Marine Conservation Council.

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Calcification of Calcidiscus leptoporus under nitrogen and phosphorus limitation

The coccolithophore Calcidiscus leptoporus was grown in batch culture under nitrogen (N) as well as phosphorus (P) limitation. Growth rate, particulate inorganic carbon (PIC), particulate organic carbon (POC), particulate organic nitrogen (PON), and particulate organic phosphorus (POP) production were determined and coccolith morphology was analysed. While PON production decreased by 70% under N-limitation and POP production decreased by 65% under P-limitation, growth rate decreased by 33% under N- as well as P-limitation. POC as well as PIC production (calcification rate) increased by 27% relative to the control under P-limitation, and did not change under N-limitation. Coccolith morphology did not change in response to either P or N limitation. While these findings, supported by a literature survey, suggest that coccolith morphogenesis is not hampered by either P or N limitation, calcification rate might be. The latter conclusion is in apparent contradiction to our data. We discuss the reasons for this inference.

Continue reading ‘Calcification of Calcidiscus leptoporus under nitrogen and phosphorus limitation’

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Ocean acidification in the IPCC AR5 WG II

OUP book