Absolute abundances (concentrations) of dinoflagellate cysts are often determined through the addition of Lycopodium clavatum marker-grains as a spike to a sample before palynological processing. An interlaboratory calibration exercise was set up in order to test the comparability of results obtained in different laboratories, each using its own preparation method. Each of the 23 laboratories received the same amount of homogenized splits of four Quaternary sediment samples. The samples originate from different localities and consisted of a variety of lithologies. Dinoflagellate cysts were extracted and counted, and relative and absolute abundances were calculated. The relative abundances proved to be fairly reproducible, notwithstanding a need for taxonomic calibration. By contrast, excessive loss of Lycopodium spores during sample preparation resulted in non-reproducibility of absolute abundances. Use of oxidation, KOH, warm acids, acetolysis, mesh sizes larger than 15 µm and long ultrasonication (N 1 min) must be avoided to determine reproducible absolute abundances. The results of this work therefore indicate that the dinoflagellate cyst worker should make a choice between using the proposed standard method which circumvents critical steps, adding Lycopodium tablets at the end of the preparation and using an alternative method.

With an appendix by Bjørn Buchardt: Oxygen isotope palaeotemperatures from the Jurassic in Northwest EuropeThe Jurassic dinoflagellate cyst zonation for the British-Danish area is revised and discussed in relation to palaeoenvironmental factors, in particular, eustatic changes and fluctuations in palaeotemperature. The stepwise evolution of dinoflagellate cyst assemblages as defined by inceptions and apparent extinctions was largely controlled by sea-level change, particularly during intervals with significant short-term eustatic fluctuations. During times characterised by less pronounced, or longer term, sea-level change, fluctuations in oceanic palaeotemperatures appear to have influenced dinoflagellate evolution. Differences in the ranges of certain taxa between Denmark and the United Kingdom may be partly related to differences in palaeotemperature.

Oligocene and Miocene cores from Ocean Drilling Program Leg 151 Holes 907A, 908A, 909C, and 913B in the Norwegian-Greenland Sea were studied palynologically, using a total of 300 samples. Dinoflagellate cysts are present in all samples, allowing age interpretations for all holes. At Site 907 on the Iceland Plateau, the deepest sediments show a Langhian-Serravallian assemblage and the highest section studied (Cores 151-907A-16X to 9H) has an undifferentiated Tortonian to Pliocene assemblage. Oceanic conditions warmer than the present day and poor nutrient conditions are deduced from the taxonomic composition. Sites 908 and 909 in the Fram Strait are less than 50 km apart in very contrasting situations: Site 909 is in 2500 m water depth on the Greenland-Spitsbergen Sill and Site 908 is on the Hovgàrd Ridge, elevated to more than 1000 m above the surrounding seafloor. Organic residues from both sites are dominated by terrestrially derived palynomorphs and plant fragments (many >IOO µm), and dinocyst/pollen ratios are relatively low. This indicates relatively nearshore depositional environments almost to the end of the Miocene. Palynology supports and supplements the plate tectonic model for the origin of the Hovgàrd Ridge as a micro-continental sliver from the Svalbard Platform. At Site 909, dinoflagellates date a near complete Miocene succession with two possible stratigraphic breaks in the Langhian-Serravallian interval. Throughout the Langhian-Serravallian to Messinian-Zanclean? interval, warm-water species indicate temperate conditions. At Site 908, 160 m of late Rupelian-early Chattian sediments are unconformably overlain by late Miocene sediments, leaving a hiatus of 15 to 18 m.y. A series of conspicuous acmes observed within three species at Site 909 could be used to date the truncated Miocene section at Site 908. Cyst reworking in the sediments at Sites 908 and 909 is consistently of late Early Cretaceous and early Paleogene ages and shows a Late Cretaceous gap corresponding to the Albian-Paleogene hiatus observed in the late Mesozoic-Cenozoic formations on Spitsbergen.

Integrated sediment multiproxy studies and modeling were used to reconstruct past changes in the Baltic Sea ecosystem. Results of natural changes over the past 6000 years in the Baltic Sea ecosystem suggest that forecasted climate warming might enhance environmental problems of the Baltic Sea. Integrated modeling and sediment proxy studies reveal increased sea surface temperatures and expanded seafloor anoxia (in deep basins) during earlier natural warm climate phases, such as the Medieval Climate Anomaly. Under future IPCC scenarios of global warming, there is likely no improvement of bottom water conditions in the Baltic Sea. Thus, the measures already designed to produce a healthier Baltic Sea are insufficient in the long term. The interactions between climate change and anthropogenic impacts on the Baltic Sea should be considered in management, implementation of policy strategies in the Baltic Sea environmental issues, and adaptation to future climate change.

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