(Table 1) Compressional and shear wave velocities and elastic constants of DSDP Hole 83-504B basalts

Compressional and shear wave velocities at confining pressures to 6 kb, densities, and porosities were measured for 32 samples obtained from 836 to 1350 m below seafloor (BSF) in Hole 504B, the section drilled on Leg 83 of the Deep Sea Drilling Project. These data in combination with similar measurements on 28 basalt samples from the section from 274.5 to 836 m, drilled on Legs 69 and 70, provide a comprehensive set of physical property data for over 1000 m of oceanic crust. The velocities, densities, and porosities measured in the laboratory exhibit greater variability in the upper portion of the hole. In general, compressional and shear wave velocities and densities increase with depth, reaching average values at 1 kbar of Vp = 6.45 km/s, Ks = 3.45 km/s and p = 2.94 g/cm3 within the sheeted dike section. Porosities decrease with depth to values generally less than 1% near the bottom of the hole

Data files of figures 1, 2 and 3

We investigated optimal conditions for characterization of bioactivity of lytic compound(s) excreted by Alexandrium tamarense based on a cell-bioassay system. Allelochemical response of the cryptophyte Rhodomonas salina indicated the presence oflytic compound(s) in a reliable and reproducible way and allows for quantification of this lytic effect. The parameters tested were the incubation time of putatively lytic extracts or fractions with the target organism R. salina, different techniques for cell harvest from A. tamarense cultures and the optimal harvest time. A three hour incubation time was found to be optimal to yield a rapid response while accurately estimating effective concentration (ECso) values. Harvest of A. tamarense cultures by filtration resulted in loss of lytic activity in most cases and centrifugation was most efficient in terms of recovery of lytic activity. Maximum yield of extracellular lytic activity of A. tamarense cultures was achieved in the stationary phase. Such optimized bioassay guided fractionation techniques are a valuable asset in the isolation and eventual stmctural elucidation of the unknown lytic substances.

Nd and Sr isotope compositions, REE concentrations and Al/Ca ratios of different phases of surface sediments in the South Pacific

The radiogenic isotope composition of neodymium (Nd) and strontium (Sr) are useful tools to investigate present and past oceanic circulation or input of terrigenous material. We present Nd and Sr isotope compositions extracted from different sedimentary phases, including early diagenetic Fe-Mn coatings, "unclean" foraminiferal shells, fossil fish teeth, and detritus of marine surface sediments (core-tops) covering the entire midlatitude South Pacific. Comparison of detrital Nd isotope compositions to deep water values from the same locations suggests that "boundary exchange" has little influence on the Nd isotope composition of western South Pacific seawater. Concentrations of Rare Earth Elements (REE) and Al/Ca ratios of "unclean" planktonic foraminifera suggest that this phase is a reliable recorder of seawater Nd isotope composition. The signatures obtained from fish teeth and "nondecarbonated" leachates of bulk sediment Fe-Mn oxyhydroxide coatings also agree with "unclean" foraminifera. Direct comparison of Nd isotope compositions extracted using these methods with seawater Nd isotope compositions is complicated by the low accumulation rates yielding radiocarbon ages of up to 24 kyr, thus mixing the signal of different ocean circulation modes. This suggests that different past seawater Nd isotope compositions have been integrated in authigenic sediments from regions with low sedimentation rates. Combined detrital Nd and Sr isotope signatures indicate a dominant role of the Westerly winds transporting lithogenic material from South New Zealand and Southeastern Australia to the open South Pacific. The proportion of this material decreases toward the east, where supply from the Andes increases and contributions from Antarctica cannot be ruled out.