Archive for December, 2006

Responses of calcareous nannofossil assemblages, mineralogy and geochemistry to the environmental perturbations across the Paleocene/Eocene boundary in the Venetian Pre-Alps

Calcareous nannofossil, mineralogical and geochemical data are presented from the expanded Paleocene–Lower Eocene Forada section in the Venetian Pre-Alps. The short-lived Paleocene Eocene Thermal Maximum (PETM) is characterized by profound and temporally constrained changes among calcareous nannoplankton assemblages, triggered by global modifications of the ocean–atmosphere system. The Calcareous Nannofossil Excursion Taxa (CNET) represent transient adaptations to changes in the chemical (nutrients, CO2, pH) and temperature structure of surface waters typifying the PETM. Oligotrophic taxa, such as Sphenolithus, Zygrhablithus, Octolithus and Fasciculithus, exbihit a sharp decrease in abundance, whereas reworked forms show a sharp increase. These changes reflect a response to the modified environmental conditions, characterized by sharp increase in nutrient availability. This increase likely resulted from a huge terrigenous input, suggesting that the siliciclastic pump was intensified by enhanced weathering and runoff. The high correlations between mineralogical/geochemical data and calcareous nannofossil fluctuations is consistent with this scenario. Highly-resolved age estimations are established for several calcareous nannofossil biohorizons based on cyclostratigraphy.

Agnini et al., in press. Responses of calcareous nannofossil assemblages, mineralogy and geochemistry to the environmental perturbations across the Paleocene/Eocene boundary in the Venetian Pre-Alps. Marine Micropaleontology. Article.

Ocean acidification and its consequences

Call for proposals (European Union, Framework program 7)

Temporal and spatial changes of ocean acidification due to increasing CO2 uptake. Quantification of the impacts of the acidification on marine biota and their physiology, and marine ecosystems. Feedback to the carbon and other key element cycles, to climate change and the Earth system over the next decades to centuries. Process and experimental studies and field work should be integrated in biogeochemical, ocean sediment, circulation and climate models.

Cordis, 22 December 2006- Web site

Nannoplankton Extinction and Origination Across the Paleocene-Eocene Thermal Maximum

The Paleocene-Eocene Thermal Maximum (PETM, ~55 million years ago) was an interval of global warming and ocean acidification attributed to rapid release and oxidation of buried carbon. We show that the onset of the PETM coincided with a prominent increase in the origination and extinction of calcareous phytoplankton. Yet major perturbation of the surface-water saturation state across the PETM was not detrimental to the survival of most calcareous nannoplankton taxa and did not impart a calcification or ecological bias to the pattern of evolutionary turnover. Instead, the rate of environmental change appears to have driven turnover, preferentially affecting rare taxa living close to their viable limits.

Gibbs et al., 2006. Nannoplankton Extinction and Origination Across the Paleocene-Eocene Thermal Maximum. Science 314: 1770-1773. Article.

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.

Past global warming suggests massive temperature shift in our future

If past climate change is any indication, Earth could be in store for some significant global warming according to research published in the December 8, 2006, issue of the journal Science. The work suggests that climate change skeptics may be fighting a losing cause.

Mongabay.com, 7 December 2006. Article.

Climate change already affecting UK’s marine life

… Oceans around the world are becoming more acid as a result of the increased concentration of carbon dioxide being absorbed at the sea surface. Computer models suggest that the increased acidity of British coastal waters will surpass the maximum acidity of existing levels.

"The full impacts of acidification remain largely unknown but organisms such as corals, some plankton, shellfish and sea urchins are expected to become less able to produce calcareous parts, such as shells, by the middle of the century," the report says.

The Independent Online, 29 November 2006. Article.


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