Stable carbon and oxygen isotope ratios of planktonic foraminifera from the equatorial Atlantic

Carbon isotopic records of nutrient-depleted surface water place constraints on the past fertility of the oceans and on past atmospheric pCO2 levels. The best records of nutrient-depleted delta13C are obtained from planktonic foraminifera living in the thick mixed layers of the western equatorial and tropical Atlantic Ocean. We have produced a composite, stacked Globigerinoides sacculifer delta13C record from the equatorial Atlantic, which exhibits significant spectral power at the 100,000- and 41,000-year Milankovitch periods, but no power at the 23,000-year period. Similar to the record presented by Shackleton and Pisias [1985], surface-deep ocean Delta delta13C produced with the G. sacculifer record leads the delta18O ice volume record. However, the glacial-interglacial amplitudes of Delta delta13C differ between our record and Shackleton and Pisias [1985] record. Although large changes in Delta delta13C occur in the equatorial Atlantic during early stages of the last three glacial cycles, surface-deep Delta delta13C at glacial maxima (18O stage 2, late stage 6, and late stage 8) was only about 0.2? greater than during the subsequent interglacial. Our results imply that nutrient-driven pCO2 changes account for about one third of the pCO2 decrease observed in ice cores, and consequently, Delta delta13C should not be used as a proxy pCO2 index. Enough variance in the ice core pCO2 records remains to be explained that conclusions about pCO2 and ice volume phase relationships should also be reexamined. As much as 40 ppm pCO2 change still has not been accounted for by models of past physics and chemistry of the ocean.

Abundance of mesozooplankton in the western part of the Black Sea in summer 2005 during Phase 2: Leg1 from the GEF Project

The sampling area was extended to the Western-South area off the Black Sea coast from Kaliakra cape toward the Bosforous. Samples were collected along four transects. The whole dataset is composed of 17 samples (from 10 stations) with data of mesozooplankton species composition abundance and biomass. Sampling for zooplankton was performed from bottom up to the surface at depths depending on water column stratification and the thermocline depth. These data are organized in the "Control of eutrophication, hazardous substances and related measures for rehabilitating the Black Sea ecosystem: Phase 2: Leg I: PIMS 3065". Data Report is not published. Zooplankton samples were collected with vertical closing Juday net,diameter - 36cm, 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 Kremena Stefanova 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 Kremena Stefanova using the relevant taxonomic literature (Mordukhay-Boltovskoy, F.D. (Ed.). 1968, 1969,1972).