(Table 1) Geochemistry of sector-zoned crystal at DSDP Hole 45-395A

Variations in crystal morphologies in pillow basalts and probable sheet flows sampled from the region of the East Pacific Rise drilled during Leg 54 are related both to differences in composition and to an extreme range of cooling rate experienced upon extrusion. The basalts range in composition from olivine-rich tholeiites to tholeiitic ferrobasalts, and include some more alkaline basalts. The kinetics of crystal growth in some samples appears to have been influenced by the amount of initial superheating (or supercooling) of the magma, or possibly by differential retention of volatiles. Olivine in quartznormative ferrobasalts apparently formed metastably at high undercooling. Despite these effects, reliable petrographic criteria are established to distinguish the principal rock types described regardless of the crystallinity and grain size. Microphenocrysts formed prior to pillow formation correspond closely to mineral assemblages inferred from normative plots and variation diagrams to control crystal fractionation at various stages. The details of spherulitic and dendritic growth also provide some clues about composition. Petrographic evidence for magma mixing is scant. Only some Siqueiros fracture zone basalts contain zoned plagioclase phenocrysts with glass inclusions similar to those used to infer mixing among Mid-Atlantic Ridge basalts. All basalts from the summit and flanks of the East Pacific Rise are aphyric. One possible petrographic consequence of mixing between olivine tholeiites and ferrobasalts - formation of clinopyroxene phenocrysts - is not evident in any fracture zone or Rise crest basalt. Highly evolved ferrobasalts with liquidus low-Ca clinopyroxene have not been sampled, nor does textural evidence indicate that any basalts sampled are hybrid compositions between such magmas and less fractionated compositions. Evidently the sampled ferrobasalts are close to the most evolved compositions that occur in any abundance on this portion of the East Pacific Rise.

Contiunous surface water uncorrected and quench-corrected active fluorescence and derived chlorophyll a concentration using calibration by HPLC pigments during POLARSTERN cruise ANT-XXV/1

The relationship between phytoplankton assemblages and the associated optical properties of the water body is important for the further development of algorithms for large-scale remote sensing of phytoplankton biomass and the identification of phytoplankton functional types (PFTs), which are often representative for different biogeochemical export scenarios. Optical in-situ measurements aid in the identification of phytoplankton groups with differing pigment compositions and are widely used to validate remote sensing data. In this study we present results from an interdisciplinary cruise aboard the RV Polarstern along a north-to-south transect in the eastern Atlantic Ocean in November 2008. Phytoplankton community composition was identified using a broad set of in-situ measurements. Water samples from the surface and the depth of maximum chlorophyll concentration were analyzed by high performance liquid chromatography (HPLC), flow cytometry, spectrophotometry and microscopy. Simultaneously, the above- and underwater light field was measured by a set of high spectral resolution (hyperspectral) radiometers. An unsupervised cluster algorithm applied to the measured parameters allowed us to define bio-optical provinces, which we compared to ecological provinces proposed elsewhere in the literature. As could be expected, picophytoplankton was responsible for most of the variability of PFTs in the eastern Atlantic Ocean. Our bio-optical clusters agreed well with established provinces and thus can be used to classify areas of similar biogeography. This method has the potential to become an automated approach where satellite data could be used to identify shifting boundaries of established ecological provinces or to track exceptions from the rule to improve our understanding of the biogeochemical cycles in the ocean.

Pigment concentrations in surface sediments of the Arabian Sea

As part of the large-scale, interdisciplinary deep-sea study "BIGSET", the relationship between the monsoon-induced regional and temporal variability of POC deposition and the small-sized benthic community was investigated at several sites 2316-4420 m deep in the Arabian Sea during four cruises between 1995 and 1998. Vertical and horizontal distribution patterns of chloroplastic pigments (a measure of phytodetritus deposition), readily soluble protein and activity, and biomass parameters of the small-sized benthic community (Electron Transport System Activity (ETSA); bacterial ectoenzymatic activity (FDA turnover) and DNA concentrations) were measured concurrently with the vertical fluxes of POC and chloroplastic pigments. Sediment chlorophyll a (chl. a) profiles were used to calculate chl. a flux rates and to estimate POC flux across the sediment water interface using two different transport reaction models. These estimates were compared with corresponding flux rates determined in sediment traps. Regional variability of primary productivity and POC deposition at the deep-sea floor creates a trophic gradient in the Arabian Basin from the NW to the SE, which is primarily related to the activity of monsoon winds and processes associated with the topography of the Arabian Basin and the vicinity of land masses. Inventories of sediment chloroplastic pigments closely corresponded to this trophic gradient. For ETSA, FDA and DNA, however, no clear coupling was found, although stations WAST (western Arabian Sea) and NAST (northern Arabian Sea) were characterised by high concentrations and activities. These parameters exhibited high spatial and temporal variability, making it impossible to recognise clear mechanisms controlling temporal and spatial community patterns of the small-sized benthic biota. Nevertheless, the entire Arabian Basin was recognised as being affected by monsoonal activity. Comparison of two different transport reaction models indicates that labile chl. a buried in deeper sediment layers may escape rapid degradation in Arabian deep-sea sediments.