(Table T2) Biogenic opal in Palmer Deep sediments at ODP Site 178-1098

High-resolution records of sedimentary proxies provide insights into fine-scale geochemical responses to climatic forcing. Gamma-ray attenuation (GRA) bulk-density data and magnetic stratigraphy records from Palmer Deep, Site 1098, show variability close to the same scale as ice cores, making this site ideal for high-resolution geochemical investigations. In conjunction with shipboard geophysical measurements, silica records allow high-resolution evaluation of the frequencies and amplitudes of biogenic variability. This provides investigators additional data sets to evaluate the global extent of climatic events that are presently defined by regional oceanic data sets (e.g., Younger Dryas in the North Atlantic) and to evaluate the potential mechanisms that link biological productivity and climate in the Southern Ocean. In addition, because of the observed links between diatom blooms and export productivity (Michaels and Silver, 1988, doi:10.1016/0198-0149(88)90126-4), biogenic silica may be an indicator of the efficiency of the biological pump (removal of organic carbon from the euphotic zone and burial within the sediments). Because the net removal of CO2 (on short time scales up to millennial, the balance between upwelled CO2, carbon fixation, and the removal of organic carbon from the surface ocean) can determine the atmospheric concentration; proxies that allow us to quantify export production yield insights into carbon cycle responses. In today's ocean, diatoms are integrally linked with new production (production based on the use of nitrate and molecular nitrogen rather than ammonium, which is generated by the microbial degradation of organic carbon) (Dugdale and Goering, 1967). Thus, as with nutrient utilization proxies, biogenic silica may be a good indicator of export production. The difficulties lie in translating the biogenic opal burial records to export production. Numerous factors control the preservation of sedimentary biogenic silica, including depth of the water column, water temperature, trace element chemistry, grazing pressure, bloom structure, and species composition of the diatom assemblage (Nelson et al., 1995, doi:10.1029/95GB01070). In addition, several recent investigations have noted additional complications. Iron limitation increases the uptake of Si relative to carbon (Hutchins et al., 1998, ; Takeda, 1998, doi:10.1038/31674). In the Southern Ocean, iron limitation could produce more robust, and thus better preserved, diatoms; thus, the burial record may be a record of iron limitation rather than of the export of organic carbon (Boyle, 1998). In addition, laboratory experiments show that bacteria accelerate the dissolution of biogenic silica (Bidle and Azam, 1999, doi:10.1038/17351). Both the species composition and temperature seem to influence the amount of dissolution. Evidence of recycling of silicic acid within the photic zone (Brzezinski et al., 1997) suggests that the silica pump (removal from the euphotic zone of silica relative to nitrogen and phosphorus) may work with variable efficiency. This becomes an issue when trying to reconstruct the removal of organic carbon from sedimentary biogenic silica records. In fact, there is a wide range in the Si:Corganic molar ratio in the Southern Ocean (0.18-0.81) (Nelson et al., 1995; Ragueneau et al., 2000, doi:10.1016/S0921-8181(00)00052-7). Thus, the presence (or absence) of biogenic silica alone may tell us little about the export productivity, complicating the interpretation of age-related trends. One recent assessment has added some hope to links between productivity and opal burial in the Southern Ocean (Pondaven et al., 2000). Quantitative comparison of different productivity proxies will greatly aid in this evaluation.

Aerosols over the Arabian Sea

This paper provides an overview of dust transport pathways and concentrations over the Arabian Sea during 1995. Results indicate that the transport and input of dust to the region is complex, being affected by both temporally and spatially important processes. Highest values of dust were found off the Omani coast and in the entrance to the Gulf of Oman. Dust levels were generally lower in summer than the other seasons, although still relatively high compared to other oceanic regions. The Findlater jet, rather than acting as a source of dust from Africa, appears to block the direct transport of dust to the open Arabian Sea from desert dust source regions in the Middle East and Iran/Pakistan. Dust transport aloft, above the jet, rather than at the surface, may be more important during summer. In an opposite pattern to dust, sea salt levels were exceedingly high during the summer monsoon, presumably due to the sustained strong surface winds. The high sea salt aerosols during the summer months may be impacting on the strong aerosol reflectance and absorbance signals over the Arabian Sea that are detected by satellite each year.

Abundance of mesozooplankton in the western part of the Black Sea in 1995 during the Cooperative Marine Science Program for the Black Sea (CoMSBlack)

The "CoMSBlack-95" dataset is based on samples collected in the summer of 1995. The whole dataset is composed of 81 samples (28 stations) with data of zooplankton species composition, abundance and biomass. Samples were collected in discrete layers 0-10, 0-20, 0-50, 10-25, 25-50, 50-100 and from bottom up to the surface at depths depending on water column stratification and the thermocline depth. Zooplankton samples were collected with vertical closing Juday net,diameter - 36 cm, mesh size 150 µm. Tows were performed from surface down to bottom meters depths in discrete layers. Samples were preserved by a 4% formaldehyde sea water buffered solution. Sampling volume was estimated by multiplying the mouth area with the wire length. Mesozooplankton abundance: The collected material was analysed using the method of Domov (1959). Samples were brought to volume of 25-30 ml depending upon zooplankton density and mixed intensively until all organisms were distributed randomly in the sample volume. After that 5 ml of sample was taken and poured in the counting chamber which is a rectangle form for taxomomic identification and count. Large (> 1 mm body length) and not abundant species were calculated in whole sample. Counting and measuring of organisms were made in the Dimov chamber under the stereomicroscope to the lowest taxon possible. Taxonomic identification was done at the Institute of Oceanology by Asen Konsulov and Lyudmila Kamburska using the relevant taxonomic literature (Mordukhay-Boltovskoy, F.D. (Ed.). 1968, 1969,1972). Taxon-specific abundance: The collected material was analysed using the method of Domov (1959). Samples were brought to volume of 25-30 ml depending upon zooplankton density and mixed intensively until all organisms were distributed randomly in the sample volume. After that 5 ml of sample was taken and poured in the counting chamber which is a rectangle form for taxomomic identification and count. Copepods and Cladoceras were identified and enumerated; the other mesozooplankters were identified and enumerated at higher taxonomic level (commonly named as mesozooplankton groups). Large (> 1 mm body length) and not abundant species were calculated in whole sample. Counting and measuring of organisms were made in the Dimov chamber under the stereomicroscope to the lowest taxon possible. Taxonomic identification was done at the Institute of Oceanology by Asen Konsulov and Lyudmila Kamburska using the relevant taxonomic literature (Mordukhay-Boltovskoy, F.D. (Ed.). 1968, 1969,1972).

Palynology on a profile from the Krusné Hory Mountains

Site details: The raised bog Fláje-Kiefern (50°429N, 13°329 E; 760 m a.s.l.; size ca. 500x500 m) lies in the Krusné Hory Mountains (Erzgebirge), Czech Republic, about 10 km from Georgenfelder Moor in Germany. Hejny and Slavík (1988) described the phytogeographic region of the Krusne Hory Mountains as 'a region of mountain flora and vegetation, with thermophilous species largely missing. In the natural forests, conifers, especially spruce (Picea excelsa) prevail. The deforested areas have been converted into meadows and pastures'. The climate is cool with annual average temperatures of about 5°C and annual precipitation of about 900 mm. The bedrock is Precambrian crystallinicum.