(Table 3) Foraminiferal 87Sr/86Sr ratios and ages of ODP Hole 162-986D sediments

Site 986 was drilled to 965 meters below seafloor (mbsf) on the western Svalbard margin to record the onset of glaciations and to date and document the glacial evolution in the Svalbard-Barents Sea region during the Pliocene-Pleistocene. In this paper, results of sedimentological analyses are discussed in light of seismic stratigraphy and new age determinations. The latter were difficult to obtain in the glacial deposits, and datums are sparse. Through combined paleomagnetic data, biostratigraphy, and Sr isotopes, however, an overall chronology for the main evolutionary steps is suggested. The cored sequence at Site 986 is younger than 2.6 Ma, and the lower 60 m of the section contains no evidence of a major glacial influence. An initial glaciation is interpreted to have occurred at ~2.3 Ma, resulting in increased sand deposition from debris flows at Site 986 and forming a prominent seismic reflector, R7. However, glaciers probably did not reach the shelf break until ~1.6-1.7 Ma (Reflector R6), after which the depositional environment was dominated by diamictic debris flows. A gradual change in source area from the Barents Sea to Svalbard is recorded primarily by changes in carbonate and smectite content, ~355 mbsf (Reflector R5), at an interpolated age of 1.4-1.5 Ma. During the last ~1 m.y., Site 986 has undergone more distal deposition as the main depocenters have shifted laterally. This has resulted in less frequent debris flows and more turbidites and hemipelagic deposits, with a slight fining upward of the cored sediments.

Mesocosm experiment on warming and acidification effects on phytoplankton composition and cell size

While the isolated responses of marine phytoplankton to climate warming and to ocean acidification have been studies intensively, studies on the combined effect of both aspects of Global Change are still scarce. Therefore, we performed a mesocosm experiment with a factorial combination of temperature (9 and 15°C) and pCO2 (560 ppm and 1400 ppm) with a natural autumn plankton community from the western Baltic Sea. Temporal trajectories of total biomass and of the biomass of the most important higher taxa followed similar patterns in all treatments. When averaging over the entire time course, phytoplankton biomass decreased with warming and increased with CO2 under warm conditions. The contribution of the two dominant higher phytoplankton taxa (diatoms and cryptophytes) and of the 4 most important species (3 diatoms, 1 cryptophyte) did not respond to the experimental treatments. Taxonomic composition of phytoplankton showed only responses at the level of subdominant and rare species. Phytoplankton cell sizes increased with CO2 addition and decreased with warming. Both effects were stronger for larger species. Warming effects were stronger than CO2 effects and tended to counteract each other. Phytoplankton communities without calcifying species and exposed to short-term variation of COO2 seem to be rather resistant to ocean acidification.