Arctic Ocean carbon biogeochemistry under climate change and ocean acidification

Published 8 July 2013 Science Leave a Comment
Tags: Arctic, biogeochemistry, biological response, chemistry, community, field, mesocosms, modeling, multiple factors, phytoplankton, primary producation, prokaryotes, regional, temperature

Human-induced CO2 emissions to the atmosphere cause climate change and ocean acidification. The strongest indicators of climate change and ocean acidification are expected to be found in the Arctic Ocean (AO). The AO area is small compared to the world ocean, but the global influence of its carbon biogeochemical system with large spatial and temporal variability is considerable and complex. The AO carbon biogeochemical system is also expected to experience feedback in regard to climate change, and to influence the energy flow throughout the Arctic food web. This thesis investigates the carbon biogeochemical system in the AO: present variability; coupling with processes at the low trophic level; and response to future climate and CO2 scenarios. The study combines differing methodological approaches: (i) in-situ observations, (ii) field perturbation experiments, and (iii) ecosystem modeling. The thesis is based on four separate papers. Paper I describes the natural variability of particulate organic carbon and particulate organic nitrogen in a composition of seston and estimates the carbon to nitrogen (C:N) ratio in the AO seston. The paper is based on 3672 in-situ measurements gathered from sources both published and unpublished. The overall C:N ratio in seston was 7.4, which is significantly higher than the classical Redfield ratio of 6.6. A great regional variability in the seston C:N ratio was found. Paper II introduces the inorganic carbonate system around the Svalbard archipelago in the AO, at present and under future climate and CO2 scenarios. This paper is based on results from a coupled physical-biogeochemical ecosystem model forced by SRES A1B scenario, as well as on results of a CO2 perturbation study on the natural community conducted in an Arctic fjord. The results presented in this paper suggest that seawater pCO2 in the area around Svalbard at the end of the 21st century will be 300 μatm higher than at present in the Atlantic influenced region, and 400 μatm higher than at present in the Arctic influenced region. As a result, the waters in the Arctic-influenced region will be undersaturated with respect to aragonite, and waters in the Atlantic-influenced region will be close to the undersaturation state. The modeled summer decrease in seawater pCO2, and the increase in pH and aragonite saturation state are all steeper in the future. This was also observed during an experiment on ocean acidification in natural phytoplankton assemblage, which was perturbed with the projected high levels of seawater pCO2. Paper III is based on results from two model simulations, performed with the coupled physical-biogeochemical ecosystem model forced by SRES A1B scenario, parameterized with the constant C:N ratio and with the pCO2 sensitive C:N ratio. The paper demonstrates that more inorganic carbon could be fixed by autotrophs in the future surface Arctic waters if annual primary production increases in response to the pCO2 sensitive C:N ratio. As a result of higher primary production, and consequently higher export production in case of pCO2 sensitive C:N ratio, more carbon is released below the euphotic zone, which leads to lower pH and aragonite saturation states than in case with the constant C:N ratio. Paper IV is based on the results of the large-scale CO2 perturbation experiment, revealing enhanced carbon fixation by autotrophs at high levels of pCO2 when the phytoplankton assemblage was dominated by a smallsized phytoplankton group. The results of the paper suggest that net community production could enhance if small-sized phytoplankton thrives in the future Arctic Ocean.

The introduction to the thesis provides a comprehensive overview of the carbonate system and processes controlling it. The AO carbon biogeochemistry is introduced, with its uniqueness and importance for the earth climate system. The findings of the four papers are summarized and future prospects for carbon biogeochemistry research in the AO are discussed.

Silyakova A., 2013. Arctic Ocean carbon biogeochemistry under climate change and ocean acidification. PhD thesis, University of Bergen, 40 p. Thesis.

Detrimental effects of reduced seawater pH on the early development of the Pacific abalone

Published 8 July 2013 Science Leave a Comment
Tags: biological response, laboratory, mollusks, morphology, North Pacific, reproduction

The hatching process of the Pacific abalone Haliotis discus hannai was prolonged at a pH of 7.6 and pH 7.3, and the embryonic developmental success was reduced. The hatching rate at pH 7.3 was significantly (10.8%) lower than that of the control (pH 8.2). The malformation rates at pH 7.9 and pH 8.2 were less than 20% but were 53.8% and 77.3% at pH 7.6 and pH 7.3, respectively. When newly hatched larvae were incubated for 48 h at pH 7.3, only 2.7% of the larvae settled, while more than 70% of the larvae completed settlement in the other three pH treatments. However, most 24 h old larvae could complete metamorphosis in all four pH treatments. Overall, a 0.3-unit reduction in water pH will produce no negative effect on the early development of the Pacific abalone, but further reduction in pH to the values predicted for seawater by the end of this century will have strong detrimental effects.

Li J., Jiang Z., Zhang J., Qiu J.-W., Du M., Bian D. & Fang J., in press. Detrimental effects of reduced seawater pH on the early development of the Pacific abalone. Marine Pollution Bulletin. Article (subscription required).

A high-throughput system for boron microsublimation and isotope analysis by total evaporation thermal ionization mass spectrometry

Published 8 July 2013 Science Leave a Comment
Tags: chemistry, methods, paleo

RATIONALE
Research on the ocean carbon cycle is vitally important due to the projected impacts of atmospheric CO₂ on global temperatures and climate change, but also on ocean chemistry. The direct influence of this CO₂ rise on the seawater pH can be evaluated from the boron isotopic composition in biogenic carbonates; however, conscientious laboratory techniques and data treatment are vital in obtaining accurate and precise results. A rapid-throughput boron purification and Total Evaporation Thermal Ionization Mass Spectrometry method was developed for high accuracy and precision boron isotopic analysis for small (ng) sample sizes.

METHODS
An improved microsublimation method, in which up to 20 samples can be processed simultaneously under identical temperature conditions, was developed. Several tests have confirmed the viability of this technique. First, seawater and Porites coral samples were processed with H₂O₂ and the results compared with those obtained using microsublimation; second, the impact of various sublimation times was evaluated; and third, quantitative recovery was assessed using standard addition.

RESULTS
Microsublimation provides a valid method for the quantitative recovery and separation of boron from both major elements and organic matter under low-blank conditions. The close agreement of our results with published values validates the accuracy of the measurements. The isotopic ratio for SRM 951a boric acid isotopic standard was 4.0328 ± 0.0054 (2 STD, n = 25). The reproducibility of boron isotopic composition for standards including AE121, IAEA B-1 and an in-house coral standard UM-CP1 was ±0.68‰ (2 STD, n = 15), ±1.12‰ (2 STD, n = 24), and ±1.17‰ (2 STD, n = 14), respectively. The sample sizes were <1 ng for each measurement.

CONCLUSIONS
The developed method for preparing and measuring boron isotopic values in a variety of carbonate materials should facilitate the reconstruction of past ocean pH conditions with decadal-scale resolution.

Liu Y.-W., Aciego S. M., Wanamaker Jr. A. D. & Sell B. K., 2013. A high-throughput system for boron microsublimation and isotope analysis by total evaporation thermal ionization mass spectrometry. Rapid Communications in Mass Spectrometry 27(15): 1705–1714. Article (subscription required).

Morphological changes in branchial mitochondria-rich cells of the teleost Paralichthys olivaceus as a potential indicator of CO2 impacts

Published 8 July 2013 Science Leave a Comment
Tags: biological response, fish, laboratory, morphology, physiology

We studied the morphological and biochemical changes of mitochondria-rich cells (MRCs) of a demersal teleost, Paralichthys olivaceus, during exposure to 0.98, 2.97 and 4.95 kPa pCO₂. The apical opening area of MRCs increased 2.2 and 4.1 times by 24 h exposure to 2.97 and 4.95 kPa pCO₂, respectively, while the cross-sectional area or density of MRCs did not change. Gill Na⁺/K⁺-ATPase activity more than doubled at 72 h and then returned to the pre-exposure level at 168 h in 0.98 kPa pCO₂, while it increased 1.7 times at 24 h at 4.95 kPa. These results indicate that the apical opening area of MRCs and the gill Na⁺/K⁺-ATPase activity may be used as an indicator of acute (up to 72 h), but not chronic, impacts of high (>1 kPa) seawater CO₂ conditions in P. olivacues. Limitations of those parameters as indices of CO₂ impacts are discussed.

Hayashi M., Kikkawa T. & Ishimatsu A., in press. Morphological changes in branchial mitochondria-rich cells of the teleost Paralichthys olivaceus as a potential indicator of CO2 impacts. Marine Pollution Bulletin. Article (subscription required).

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• Bridie Jabour
• guardian.co.uk, Monday 8 July 2013 17.34 AEST

Tony Abbott: ‘Business should not have to run the gauntlet twice.’ Photograph: Stefan Postles/Getty Images

A Coalition government would tie “red tape” reduction targets to senior public servants’ pay, establish a deregulation unit within the prime minister’s office and hand over most environmental regulation responsibilities to the states.

The opposition leader, Tony Abbott, announced the Coalition policy relating to productivity and regulation at KPMG’s Sydney offices on Monday.

In the 28-page document, the Coalition sets a target to reduce “red and green” tape by $1bn a year and will set aside at least two parliamentary sitting days to repeal legislation associated with “counter-productive” regulation.

A deregulation unit would be set up within the prime minister’s office to give ministers targets to reduce regulation within their units, with pay rises and bonuses for senior public servants being linked in part to the outcomes.

Examples in the document of regulation a Coalition government would get rid of include repealing the carbon tax and mining tax – policy already announced by the Coalition.

In a press conference, Abbott emphasised the proposal to create a single process for environmental approvals, abolishing the commonwealth level of approvals and leaving most of the environmental regulation to states.

“Business should not have to run the gauntlet twice,” he said.

“Yes, we do expect high environmental standards, but you shouldn’t have to run the gauntlet twice.

“Once you have demonstrated to one set of officials that you are going to meet high environmental standards, that should be enough.”

The policy document lists examples of “excessive red and green tape” but does not specifically say it will repeal all of the regulations mentioned.

In the examples are childcare laws which will require each worker to have an official qualification from next year, and the newly established Australian Charities and Not-for-Profits Commission which was described in the document as duplicating reporting obligations.

“If we can reduce the burdens on business, we make it easier for them to employ, we make it easier for them to pay the kind of wages that the Australian public are entitled to expect,” Abbott said.

“That’s our job, to make it easier for the businesses of Australia to get on with their business of producing wealth and producing employment for the Australian people.”

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