A user-friendly method to get automated pollen analysis from environmental samples.

Automated pollen analysis is not yet efficient on environmental samples containing many pollen taxa and debris, which are typical in most pollen-based studies. Contrary to classification, detection remains overlooked although it is the first step from which errors can propagate. Here, we investigated a simple but efficient method to automate pollen detection for environmental samples, optimizing workload and performance.

Rapid diversification underlying the global dominance of a cosmopolitan phytoplankton.

Marine phytoplankton play important roles in the global ecosystem, with a limited number of cosmopolitan keystone species driving their biomass. Recent studies have revealed that many of these phytoplankton are complexes composed of sibling species, but little is known about the evolutionary processes underlying their formation. Gephyrocapsa huxleyi, a widely distributed and abundant unicellular marine planktonic algae, produces calcified scales (coccoliths), thereby significantly affects global biogeochemical cycles via sequestration of inorganic carbon.

Cyclic evolution of phytoplankton forced by changes in tropical seasonality.

Although the role of Earth's orbital variations in driving global climate cycles has long been recognized, their effect on evolution is hitherto unknown. The fossil remains of coccolithophores, a key calcifying phytoplankton group, enable a detailed assessment of the effect of cyclic orbital-scale climate changes on evolution because of their abundance in marine sediments and the preservation of their morphological adaptation to the changing environment. Evolutionary genetic analyses have linked broad changes in Pleistocene fossil coccolith morphology to species radiation events.

Enhanced ocean-atmosphere carbon partitioning via the carbonate counter pump during the last deglacial.

Several synergistic mechanisms were likely involved in the last deglacial atmospheric pCO rise. Leading hypotheses invoke a release of deep-ocean carbon through enhanced convection in the Southern Ocean (SO) and concomitant decreased efficiency of the global soft-tissue pump (STP). However, the temporal evolution of both the STP and the carbonate counter pump (CCP) remains unclear, thus preventing the evaluation of their contributions to the pCO rise.

Authigenic Be/Be ratio signatures of the cosmogenic nuclide production linked to geomagnetic dipole moment variation since the Brunhes/Matuyama boundary.

Geomagnetic dipole moment variations associated with polarity reversals and excursions are expressed by large changes of the cosmogenic nuclide beryllium-10 (Be) production rates. Authigenic Be/Be ratios (proxy of atmospheric Be production) from oceanic cores therefore complete the classical information derived from relative paleointensity (RPI) records. This study presents new authigenic Be/Be ratio results obtained from cores MD05-2920 and MD05-2930 collected in the west equatorial Pacific Ocean.

Why marine phytoplankton calcify.

Calcifying marine phytoplankton-coccolithophores- are some of the most successful yet enigmatic organisms in the ocean and are at risk from global change. To better understand how they will be affected, we need to know "why" coccolithophores calcify. We review coccolithophorid evolutionary history and cell biology as well as insights from recent experiments to provide a critical assessment of the costs and benefits of calcification.

Persistent drying in the tropics linked to natural forcing.

Approximately half of the world's population lives in the tropics, and future changes in the hydrological cycle will impact not just the freshwater supplies but also energy production in areas dependent upon hydroelectric power. It is vital that we understand the mechanisms/processes that affect tropical precipitation and the eventual surface hydrological response to better assess projected future regional precipitation trends and variability. Paleo-climate proxies are well suited for this purpose as they provide long time series that pre-date and complement the present, often short instrumental observations.

Optical measurements to determine the thickness of calcite crystals and the mass of thin carbonate particles such as coccoliths.

We describe a procedure for measuring the thickness and mass of calcite particles that works for most calcite particles <4.5-μm thick. The calcite particles are observed in cross-polarized light, which enables the light transmitted through the calcite particles to be correlated with their thickness.

A NEW HELICOSPHAERA-SYRACOLITHUS COMBINATION COCCOSPHERE (HAPTOPHYTA) FROM THE WESTERN MEDITERRANEAN SEA(1).

A new combination coccosphere of the heterococcolithophore Helicosphaera wallichii (Lohman 1902) Okada and McIntyre 1977 and holococcolithophore Syracolithus ponticuliferus (Kamptner 1941) Kleijne and Jordan 1990 is documented. This combination coccosphere was observed within a rich and diverse assemblage collected during late summer at a 20 m water depth from the NW Mediterranean Sea.

Moisture transport across Central America as a positive feedback on abrupt climatic changes.

Moisture transport from the Atlantic to the Pacific ocean across Central America leads to relatively high salinities in the North Atlantic Ocean and contributes to the formation of North Atlantic Deep Water. This deep water formation varied strongly between Dansgaard/Oeschger interstadials and Heinrich events-millennial-scale abrupt warm and cold events, respectively, during the last glacial period. Increases in the moisture transport across Central America have been proposed to coincide with northerly shifts of the Intertropical Convergence Zone and with Dansgaard/Oeschger interstadials, with opposite changes for Heinrich events.

Stable sea surface temperatures in the western Pacific warm pool over the past 1.75 million years.

About 850,000 years ago, the period of the glacial cycles changed from 41,000 to 100,000 years. This mid-Pleistocene climate transition has been attributed to global cooling, possibly caused by a decrease in atmospheric carbon dioxide concentrations. However, evidence for such cooling is currently restricted to the cool upwelling regions in the eastern equatorial oceans, although the tropical warm pools on the western side of the ocean basins are particularly sensitive to changes in radiative forcing.

Evidence for large methane releases to the atmosphere from deep-sea gas-hydrate dissociation during the last glacial episode.

Past atmospheric methane-concentration oscillations recorded in polar ice cores vary together with rapid global climatic changes during the last glacial episode. In the "clathrate gun hypothesis," massive releases of deep-sea methane from marine gas-hydrate dissociation led to these well known, global, abrupt warmings in the past. If evidence for such releases in the water column exists, however, the mechanism and eventual transfer to the atmosphere has not yet been documented clearly.