Archive for March, 2007

Rising CO2 levels ‘put shellfish in danger’

Oysters and mussels, two pearls of France’s gastronomic heritage, are in danger of dying out because of rising greenhouse gas levels in seawater, say scientists.

French and Dutch researchers found that rapidly rising concentrations of carbon dioxide in seawater is having potentially devastating effects on the lifecycles of both types of shellfish, slowing down their growth and weakening their shells, leaving them vulnerable to predators.

Daily Telegraph, 21 March 2007. Article.

Study reveals impact of CO2 on shellfish

Ocean acidification resulting from human emissions of carbon dioxide (CO2) is seriously threatening the future of some of the world’s most popular edible shellfish – mussels and oysters – according to a study by Dutch and French researchers.

Cordis web site, 20 March 2007.

Huîtres et moules vont pâtir de l’acidification des océans

La concentration du gaz carbonique (CO2) dans les eaux superficielles des océans augmente, et avec elle l’acidité de ce milieu. Les conséquences de cette acidification pour les organismes marins tels que le corail, le plancton, les algues et nombre de micro-organismes à coquille risquent d’être dévastatrices : le calcaire dont est constitué leur squelette est plus difficile à former lorsque le pH de l’eau baisse.

Pour certains mollusques d’intérêt commercial, telles l’huître ou la moule, l’impact ne sera pas non plus anodin, comme le montre une étude à paraître dans la revue Geophysical Research Letters. En modifiant la concentration en CO2 dans des aquariums abritant des moules comestibles (Mytilus edulis) et des huîtres du Pacifique (Crassostrea gigas), une équipe internationale a constaté que la vitesse de fabrication des coquilles était respectivement diminuée de 25 % et 10 % lorsqu’on atteignait un taux de CO2 correspondant à un scénario moyen prévu pour 2100.

“Il s’agit de mesures à court terme, note Jean-Pierre Gattuso, du laboratoire d’océanographie de Villefranche-sur-Mer (CNRS, université Pierre-et-Marie-Curie), cosignataire de l’article. On ignore si cela conduira à une croissance plus lente, à une coquille plus fragile, ou si cela induira un mécanisme d’adaptation à long terme.”

L’aquaculture des mollusques représente un marché mondial annuel de 7,9 milliards d’euros. Outre leur intérêt commercial, ces animaux jouent un rôle de filtration des eaux. Leur déclin aurait un impact sur l’ensemble des écosystèmes côtiers.

Le Monde, Hervé Morin, 20 Mars 2007. Article (subscription required).

Klimawandel gefährdet Austern

Yerseke/Niederlande (pte/19.03.2007/13:30) – Der Klimawandel bedroht die Zucht von Muscheln und Austern. Ursache dafür ist eine Versauerung der Meere, die durch den Anstieg des Treibhausgases Kohlendioxid (CO2) ausgelöst wird. Dadurch verzögere sich die Bildung einer kalkhaltigen Muschelschale, berichtet ein niederländisch-französisches Forscherteam in der aktuellen Ausgabe der Fachzeitschrift “Geophysical Research Letters”. “Neben wirtschaftlichen Verlusten erwarten wir mit hoher Wahrscheinlichkeit auch negative Folgewirkungen für küstennahe Ökosysteme”, sagt Frederic Gazeau vom Niederländischen Institut für Ökologie im Gespräch mit pressetext.

Pressetext, 19 March 2007. Press release.

Polyp Apocalypse

Some of the ocean’s most colorful inhabitants – including corals, sea snails and many kinds of plankton – will face the risk of extinction over the next century as global warming acidifies the world’s oceans, according to a new assessment by an international committee of scientists convened by the United Nations.

Scienceline, By Morgen E. Peck, posted 19 March 2007. Article.

Elevated Atmospheric CO2 and the Delayed Biotic Recovery from the End-Permian Mass Extinction

Excessive CO2 in the Earth ocean-atmosphere system may have been a significant factor in causing the end-Permian mass extinction. CO2 injected into the atmosphere by the Siberian Traps has been postulated as a major factor leading to the end-Permian mass extinction by facilitating global warming, widespread ocean stratification, and development of anoxic, euxinic and CO2-rich deep waters. A broad incursion of this toxic deep water into the surface ocean may have caused this mass extinction. Although previous studies of the role of excessive CO2 have focused on these “bottom-up” effects emanating from the deep ocean, “top-down” effects of increasing atmosphere CO2 concentrations on ocean-surface waters and biota have not previously been explored. Passive diffusion of atmospheric CO2 into ocean-surface waters decreases the pH and CaCO3 saturation state of seawater, causing a physiological and biocalcification crisis for many marine invertebrates. While both “bottom-up” and “top-down” mechanisms may have contributed to the relatively short-term biotic devastation of the end-Permian mass extinction, such a “top-down” physiological and biocalcification crisis would have had long-term effects and might have contributed to the protracted 5- to 6- million-year-long delay in biotic recovery following this mass extinction. Earth’s Modern marine biota may experience similar “top-down” CO2 stresses if anthropogenic input of atmosphere/ocean CO2 continues to rise.

Fraiser M. I. & Bottjer D. J., 2007. Elevated atmospheric CO2 and the delayed biotic recovery from the end-Permian mass extinction. Palaeogeography, Palaeoclimatology, Palaeoecology 252:164-175. Article.

Technorati Tags: ,

Ocean Acidification Predicted To Harm Shellfish, Aquaculture

In 2100, mussels are expected to calcify their shells 25 percent slower than currently; oysters, 10 percent slower. This will be caused by the continued release and accumulation of carbon dioxide in the air: one third of it will be absorbed by the ocean water, thereby making it more acid. Scientists of the Netherlands Institute of Ecology (NIOO-KNAW) report in Geophysical Research Letters, together with a French colleague, on the potentially major consequences for aquaculture and coastal nature.

Science Daily, 18 March 2007. Article

End-Triassic calcification crisis and blooms of organic-walled ‘disaster species’

The Triassic–Jurassic (T–J) mass-extinction event is marked by isotope anomalies in organic (δ13Corg) and carbonate carbon (δ13Ccarb) reservoirs. These have been attributed to a (rapid) 4-fold rise in pCO2 as a result of massive flood basalt volcanism and/or methane hydrate dissociation. Here we examine the response of marine photosynthetic phytoplankton to the proposed perturbation in the carbon cycle. Our high-resolution micropalaeontological analysis of T–J boundary beds at St Audrie’s Bay in Somerset, UK, provides evidence for a bio-calcification crisis that is characterized by (1) extinction and malformation in calcareous nannoplankton and (2) contemporaneous blooms of organic-walled, green algal ‘disaster’ species which comprise in one case > 70% of the total palynomorph fraction. Blooms of prasinophytes and acritarchs occur at the onset and in association with a prominent negative shift in δ13Corg values close to the first appearance of the Early Jurassic ammonite Psiloceras planorbis. Across the same interval we obtained palaeotemperature and palaeosalinity estimates from oyster low-Mg calcite based on Mg/Ca, Sr/Ca and δ18O records. The results of our palynological and geochemical analyses strongly suggest that shallow marine basins in NW Europe during this period became salinity stratified, inducing anoxic conditions. The T–J boundary event shows similarities with the Permian–Triassic (P–T) mass-extinction event, which was also marked by extensive flood basalt volcanism, negative excursions in carbon isotope records, a bio-calcification crisis, the development of shallow-marine anoxia and mass abundances of acritarchs in the Early Triassic. This leads us to suggest that the proliferation of green algal phytoplankton may be symptomatic of elevated carbon dioxide levels in the atmosphere and oceans during mass-extinction events.

B. van de Schootbrugge, F. Tremolada, Y. Rosenthal, T.R. Bailey, S. Feist-Burkhardt, H. Brinkhuis, J. Pross, D.V. Kent and P.G. Falkowski, 2007. Palaeogeography, Palaeoclimatology, Palaeoecology 244(1-4): 126-141. Article.

Anomalous hopane distributions at the Permian–Triassic boundary, Meishan, China – Evidence for the end-Permian marine ecosystem collapse

Molecular and carbon isotopic geochemistry of hopanes in marine sediments of the Meishan section in Changxing County, Zhejiang Province of China, were studied to reveal biotic and environmental changes across the Permian–Triassic boundary (PTB) and the Wuchiapingian–Changhsingian boundary (WCB). The hopane distribution at the PTB is characterized by high ratios of moretane/hopane, Tm/Ts, Tm/C30 hopane, C31/C32 hopane and hopane/sterane. This hopane distribution is anomalous for these marine sediments, but it is typical of coal measure strata and soils. Two possible genetic mechanisms for such an anomaly are suggested: (1) these hopanes were terrigenous and most probably originated from acidified soil and peat. This mechanism implies that the marine primary production and aerobic bacteria production at the PTB were extremely low. (2) This hopane distribution was possibly caused by freshening and acidification of the upper water column during the end-Permian to Early Triassic marine stagnation and stratification. This hopane anomaly, which coincides with the end-Permian mass extinction and carbon-isotope excursion, may signal the end-Permian mass extinctions and marine and terrigenous ecosystem collapse.

The 13C-enriched hopanes with the fingerprint of typical anoxic marine shales, coupled with an n-C15–n-C17-dominated distribution of n-alkanes, strongly indicate that the organic matter around the WCB at Meishan originated mainly from cyanobacteria. The corresponding positive δ13Ccarbonate, and higher total organic carbon and hydrocarbon index (HI) values, strongly suggest that high marine primary production and marine anoxia caused by intermittent cyanobacterial blooms, resulted in the local mass extinction at Meishan.

Wang C. J., 2007. Anomalous hopane distributions at the Permian–Triassic boundary, Meishan, China – Evidence for the end-Permian marine ecosystem collapse. Organic Geochemistry 38(1): 52-66. Article.

Economy and nature predicted to suffer from more CO2: Ocean acidification harms shellfish

In 2100, mussels and oysters are expected to calcify their shells 25 and 10 % slower than nowadays respectively. This will be caused by the continued release and accumulation of CO2 in the air: one third of it will be absorbed by the ocean water, thereby making it more acid. Scientists of the Netherlands Institute of Ecology (NIOO-KNAW) report in Geophysical Research Letters, together with a French colleague, on the potentially major consequences for aquaculture and coastal nature.
Press release

Subscribe to the RSS feed

Powered by FeedBurner

Follow AnneMarin on Twitter

Blog Stats

  • 1,428,694 hits


Ocean acidification in the IPCC AR5 WG II

OUP book