Archive for June, 2010

Response of the Arctic pteropod Limacina helicina to projected future environmental conditions

Thecosome pteropods (pelagic mollusks) can play a key role in the food web of various marine ecosystems. They are a food source for zooplankton or higher predators such as fishes, whales and birds that is particularly important in high latitude areas. Since they harbor a highly soluble aragonitic shell, they could be very sensitive to ocean acidification driven by the increase of anthropogenic CO2 emissions. The effect of changes in the seawater chemistry was investigated on Limacina helicina, a key species of Arctic pelagic ecosystems. Individuals were kept in the laboratory under controlled pCO2 levels of 280, 380, 550, 760 and 1020 µatm and at control (0°C) and elevated (4°C) temperatures. The respiration rate was unaffected by pCO2 at control temperature, but significantly increased as a function of the pCO2 level at elevated temperature. pCO2 had no effect on the gut clearance rate at either temperature. Precipitation of CaCO3, measured as the incorporation of 45Ca, significantly declined as a function of pCO2 at both temperatures. The decrease in calcium carbonate precipitation was highly correlated to the aragonite saturation state. Even though this study demonstrates that pteropods are able to precipitate calcium carbonate at low aragonite saturation state, the results support the current concern for the future of Arctic pteropods, as the production of their shell appears to be very sensitive to decreased pH. A decline of pteropod populations would likely cause dramatic changes to various pelagic ecosystems.
Continue reading ‘Response of the Arctic pteropod Limacina helicina to projected future environmental conditions’

Examining possible effects of seawater pH decline on foraminiferal stable isotopes during the Paleocene-Eocene Thermal Maximum

A large body of paleoceanographic data for the Paleocene-Eocene Thermal Maximum (PETM) is based on foraminiferal stable carbon and oxygen isotope composition (δ13C and δ18O). However, the proxy records could be biased due to a “pH effect” on stable isotopes during times when the ocean became more acidic, as has been demonstrated for modern planktonic foraminifera. In this paper, we calculate the possible ranges of the pH effect on δ13C and δ18O during the PETM based on the relative pH decline (ΔpH) from the preperturbation steady state simulated by a carbon cycle model and the empirical relationships obtained from culture experiments with planktonic foraminifera. The model is configured with Eocene paleogeography and simulates ΔpH for surface, intermediate, and deep water in the major ocean basins in response to various carbon input scenarios (2000 to 5000 Pg C). For an array of scenarios, the modeled ΔpH of the surface ocean ranges from 0.1 to 0.28 units. This suggests that δ13C of planktonic foraminifera may be increased by up to 2.1‰ and δ18O may be increased by up to 0.7‰ (corresponding to over 3°C error in paleotemperature estimate). Under conditions in which the model best simulates the global CaCO3 dissolution pattern, we find marked differences in the deep-sea ΔpH between the Atlantic (−0.4) and Pacific oceans (−0.1). This would imply that the magnitude of the negative δ13C and δ18O excursions of benthic foraminifera in the Atlantic Ocean was dampened by up to 2.8‰ and 0.9‰ at maximum, respectively, relative to a constant pH scenario.
Continue reading ‘Examining possible effects of seawater pH decline on foraminiferal stable isotopes during the Paleocene-Eocene Thermal Maximum’

Rising acidity, a threat to marine species

The increasing acidity of the oceans, which absorb more than a quarter of the carbon dioxide emitted by human activity, could harm corals, molluscs and other marine species, contend specialists on the matter.

At 1,200 kilometres from the North Pole, in the archipelago of Svalbard (Spitzberg), scientists from nine European countries launched a comprehensive investigation to try to understand a well-known phenomenon a little better.

“The cold waters of the Arctic absorb gases faster than warm or moderate ones. Here, in the polar regions, the ocean is becoming corrosive more rapidly, “deems Jean-Pierre Gattuso, an oceanographer from the French Scientific Research Centre (CNRS) and coordinator of the project Age.

Since the beginning of the industrial era, the planet’s oceans have become 30 per cent more acidic, to reach a level unparalleled for 55 million years.

This trend will remain as long as carbon dioxide emissions do not decline (CO2).
Continue reading ‘Rising acidity, a threat to marine species’

Post-Doctoral Fellow – Antarctic ocean acidification

Ocean acidification is a pressing threat to the world’s oceans, and particularly in the cold waters of the Antarctic, with the potential to negatively affect key benthic organisms. We have a significant opportunity for a passionate post doctoral researcher who wants to apply their knowledge and skills in this important area, to take up a two year fellowship with NIWA.

The successful candidate will have a PhD in marine ecology as well as extensive experience in modelling physiological and ecological processes. They will be able to demonstrate a broad knowledge of marine biology and ocean acidification and will already possess a good scientific publication record relative to their experience.

An understanding of bivalve physiological processes in an ecological context, and skills in shell microstructure analyses would be an advantage. This position does not involve any Antarctic field work.

This post doctoral scholarship is funded by Air New Zealand and NIWA, in collaboration with Antarctica New Zealand and WWF-New Zealand.
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Ocean acidification threatens marine life (video)

Our oceans absorb more than one quarter of the CO2 emitted by man. Researchers are concerned over the acidifying affects of rising CO2 levels on our oceans and the consequences for marine life. To study this phenomenon, an international team of scientists has launched project Epoca, an unprecedented experiment in the heart of the Arctic.Duration: 01:37
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What meta-analysis can tell us about vulnerability of marine biodiversity to ocean acidification?

Ocean acidification has been proposed as a major threat for marine biodiversity. Hendriks et al. (2010) proposed an alternative view and suggested, based on a meta-analysis, that marine biota may be far more resistant to ocean acidification than hitherto believed. However, such a meta-analytical approach can mask more subtle features, for example differing sensitivities during the lifecycle of an organism. Using a similar metric on an echinoderm database, we show that key bottlenecks present in the life-cycle (e.g. larvae being more vulnerable than adults) and responsible for driving the whole species response may be hidden in a global meta-analysis. Our data illustrate that any ecological meta-analysis should be hypothesis driven, taking into account the complexity of biological systems, including all life-cycle stages and key biological processes. Available data allow us to conclude that near-future ocean acidification will have negative impact on marine species, including echinoderms, with likely consequences at the ecosystem level.
Continue reading ‘What meta-analysis can tell us about vulnerability of marine biodiversity to ocean acidification?’

Postdoctoral Research Fellow: Ocean acidification: a physiological and environmental challenge for marine calcifiers

Contact. Dr Mary Sewell, Dr Anthony Hickey and Professor Gretchen Hofmann.

Ocean acidification (OA) has been described as “the other CO2 problem”, “global warming’s evil twin” and “a meltdown tinged with acid”. Given that one third of humanity’s emissions of carbon dioxide are absorbed by the world’s oceans, OA will be one of the most important stressors facing marine ecosystems of the future. Under the OA conditions predicted by the Intergovernmental Panel on Climate Change (IPCC 2007), organisms with calcium carbonate skeletons (e.g. coccoliths, corals, molluscs, sea urchins) will suffer significantly from increased costs to the growth and maintenance of skeletal structures, and/or the dissolution of their skeletons.
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Alerte acidité pour les océans (in French; video)

On savait déjà que l’océan se réchauffait. Maintenant, il s’acidifie. Un phénomène qui inquiète les chercheurs, qui redoutent des effets sur les coraux, les mollusques et autres espèces marines.
Continue reading ‘Alerte acidité pour les océans (in French; video)’

Post-doctoral research associate in ocean acidification research

School of Life Sciences, Heriot-Watt University, Edinburgh, Scotland
*Salary: £28,983 – £35,646*

We are looking for a talented and highly motivated postdoctoral scientist for a 3-year research project examining the impacts of ocean acidification on two important marine calcifiers, cold-water corals (Lophelia pertusa) and coralline algae (maerl). This work forms a component of a new benthic research consortium funded through the UK’s £12m Ocean Acidification Research Programme.

The appointee should be prepared to carry out fieldwork and work at sea on ocean-going research cruises. Although desirable, prior experience of ocean acidification and biomineralisation research is not essential.
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IPCC 5th Assessment Report

The list of authors and review editors of IPCC Working Group II, 5th Assessment Report, has just been made public. Marine ecosystems/oceans/coastal systems are very well represented. There are some excellent experts associated with them, many from the ocean acidification field. This includes a number from EPOCA (Jean-Pierre Gattuso, Hans-Otto Pörtner, Daniela Schmidt and Carol Turley) and also some of our international colleagues working in this area.
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Ocean acidification in the IPCC AR5 WG II

OUP book