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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.

CO2 Threatens Oceans Regardless of Global Warming

Much of the carbon dioxide (CO2) emissions from fossil fuel burning is absorbed by the oceans. It is elevating ocean acidity threatening many species, especially those like corals, which use calcium carbonate to make their shells or skeletons. A study published in the March 9, 2007, Geophysical Research Letters looks at how both increases in CO2 concentrations and increases in temperatures from climate change could affect ocean acidity. It found that regardless of global warming from carbon dioxide, the greenhouse gas is still a threat to life in the world’s oceans.

Carnegie Institution, 8 March 2007. Press release.

The fate of pelagic CaCO3 production in a high CO2 ocean: A model study

This model study addresses the change in pelagic calcium carbonate production (CaCO3, as calcite in the model) and dissolution in response to rising atmospheric CO2. The parameterization of CaCO3 production includes a dependency on the saturation state of seawater with respect to calcite. It was derived from laboratory and mesocosm studies on particulate organic and inorganic carbon production in Emiliania huxleyi as a function of pCO2. The model predicts values of CaCO3 production and dissolution in line with recent estimates. The effect of rising pCO2 on CaCO3 production and dissolution was quantified by means of model simulations forced with atmospheric CO2 increasing at a rate of 1% per year from 286 ppm to 1144 ppm. The simulation predicts a decrease of CaCO3 production by 27%. The combined change in production and dissolution of CaCO3 yields an excess uptake of CO2 from the atmosphere by the ocean of 5.9 GtC.

M. Gehlen, R. Gangstø, B. Schneider, L. Bopp, O. Aumont, C. Ethe, 2007. The fate of pelagic CaCO3 production in a high CO2 ocean: A model study. Biogeosciences Discussions 4:533-560. Article.

Workshop on the Significance of Changes in Surface CO2 and Ocean pH in Shelf Sea Ecosystems

The ocean is becoming more acidic as increasing atmospheric carbon dioxide (CO2) is absorbed at the surface. It is thought that the pH of the global ocean has fallen by about 0.1 units over the past 200 years and that it could drop by a further 0.5 units by the year 2100 if CO2 emissions are not regulated (Royal Soc, 2005). A recent study of potential change in the North Sea suggests that pH change this century may exceed its natural variability in most of the North Sea. Impacts of acidity change are likely but their exact nature remains largely unknown and may occur across the range of ecosystem processes.  This aspect of climate change is potentially a precursor to the longer-term thermal effects.This workshop will concentrate on shelf sea environments as most previous  work has concentrated on open ocean systems.

Web site.

An ancient carbon mystery

About 55 million years ago, Earth experienced a period of global warming that lasted ~170,000 years (1). This climate event–the Paleocene-Eocene Thermal Maximum (PETM)–may be the best ancient analog for future increases in atmospheric CO2. But how well do we understand this event?

Pagani M., Caldeira K., Archer D., Zachos J. C., 2006. Atmosphere: an ancient carbon mystery. Science 314(5805): 1556. Article.

World experts to gather in kiel, germany to address effects of climate change on marine ecosystems

(Oldendorf/Luhe, Germany, 30 September 2006). Carbon dioxide is now entering the ocean at a rate of ~1 million tons per hour, 10 times the natural rate, and this is changing the acidity of the seas. Geological records indicate that the pH changes that have occurred since the beginning of the Industrial Revolution are unique in the last 650,000 years. These changes have the potential to negatively impact corals, eggs and larvae of some fish species, and those animals with skeletons and shells.

World experts, gathering at the 42nd European Marine Biology Symposium in Kiel, Germany in August 2007 (%20www.embs42.de/), will address these issues in a special symposium: the Effects of Climate Change on Marine Ecosystems (www.ir-symposia.com/Conf_home.asp?ConferenceCode=EMBS%202007).

The Symposium is sponsored by the international journal Climate Research (www.int-res.com/journals/cr/cr-home/), and the Inter-Research Science Center (www.int-res.com). Topics to be covered include the effects of changing temperature, pH and CO2 on marine organisms and ecosystems. Contributed papers are invited and student participation is encouraged (some financial support for students is available).

We invite you to join world-renowned experts to discuss these issues: August 27-31, 2007, at the Auditorium Maximum of Christian-Albrechts-University, Kiel, Germany.

Source: TravelVideo.TV

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